Second consensus on the assessment of sublingual microcirculation in critically ill patients: results from a task force of the European Society of Intensive Care Medicine

Microcirculation properties of 20 % albumin in sepsis; a randomised controlled trial

INTRODUCTION

Sepsis and septic shock are associated with microcirculatory dysfunction, significantly impacting patient outcomes. This study aimed to evaluate the effects of a 20 % albumin bolus on microcirculation compared to crystalloid resuscitation in fluid-responsive patients (ClinicalTrials.govID:NCT05357339).

METHODS

We conducted a single-centre randomised controlled trial, enrolling 103 patients (Albumin n = 52, Control n = 51). Fluid responsiveness was assessed, and fluid was administered in boluses of 100 ml to clinical effect. Microcirculation was measured using the Side stream Dark Field camera and AVA 4.3 software. Baseline characteristics, macrohaemodynamics, and microcirculation parameters were recorded. Three patients were excluded from analysis.

RESULTS

The final cohort comprised 100 patients, 35 (35 %) females with a mean age of 58 years (range: 18-86). The mean APACHE score was 28 (range: 7-45), and the mean SOFA score was 9.4 (range: 1-17). No significant differences in APACHE (26.24 vs. 29.4, p = 0.069) or SOFA (9.08 vs. 9.78, p = 0.32) scores were found for albumin and control group respectively. The albumin group had worse microcirculation at baseline but demonstrated significant improvements in microvascular density and activity at 15 min and 60 min (p < 0.005), while the control group exhibited no significant changes. Additionally, both groups were fluid responsive, with a mean pulse pressure variability of 17 % at admission. There were no significant differences in overall fluid balances, vasopressor days, length of ICU stay, or mortality between groups.

CONCLUSION

This study demonstrates that a 20 % albumin bolus significantly enhances microcirculation in fluid-responsive patients with septic shock. These findings underscore the potential benefits of targeted microcirculation therapy in critically ill patients.

Intra-operative haemodynamic monitoring and management of adults having noncardiac surgery: A statement from the European Society of Anaesthesiology and Intensive Care

This article was developed by a diverse group of 25 international experts from the European Society of Anaesthesiology and Intensive Care (ESAIC), who formulated recommendations on intra-operative haemodynamic monitoring and management of adults having noncardiac surgery based on a review of the current evidence. We recommend basing intra-operative arterial pressure management on mean arterial pressure and keeping intra-operative mean arterial pressure above 60 mmHg. We further recommend identifying the underlying causes of intra-operative hypotension and addressing them appropriately. We suggest pragmatically treating bradycardia or tachycardia when it leads to profound hypotension or likely results in reduced cardiac output, oxygen delivery or organ perfusion. We suggest monitoring stroke volume or cardiac output in patients with high baseline risk for complications or in patients having high-risk surgery to assess the haemodynamic status and the haemodynamic response to therapeutic interventions. However, we recommend not routinely maximising stroke volume or cardiac output in patients having noncardiac surgery. Instead, we suggest defining stroke volume and cardiac output targets individually for each patient considering the clinical situation and clinical and metabolic signs of tissue perfusion and oxygenation. We recommend not giving fluids simply because a patient is fluid responsive but only if there are clinical or metabolic signs of hypovolaemia or tissue hypoperfusion. We suggest monitoring and optimising the depth of anaesthesia to titrate doses of anaesthetic drugs and reduce their side effects.

Cytokine Hemoadsorption versus Standard Care in Cardiac Surgery Using the Oxiris Membrane: The OXICARD Single-center Randomized Trial

BACKGROUND

Cardiac surgery can lead to dysregulation with a proinflammatory state, resulting in adverse outcomes. Hemadsorption using the AN-69 membrane (Oxiris membrane, Baxter, USA) has the properties to chelate inflammatory cytokines. The authors hypothesized that in patients at high risk of inflammation, the use of the Oxiris membrane could decrease inflammation, preserve endothelial function, and improve postoperative outcomes.

METHODS

The authors conducted a randomized single-center study at Amiens University Hospital (Amiens, France). The study population consisted of adult patients admitted for scheduled cardiac surgery with an expected cardiopulmonary bypass (CPB) time greater than 90 min. The patients were allocated to either the standard group or the Oxiris group. The intervention consisted of using the Oxiris membrane on a Prismaflex device (Baxter, USA) at a blood flow rate of 450 ml/min during CPB. The primary outcome was the assessment of microcirculation on day 1 after surgery by measuring sublingual microcirculation using the microvascular flow index. Microvascular flow index reflects the microcirculation flow type and is graded from 0 to 3 as follows: 0, no flow; 1, intermittent flow; 2, sluggish flow; 3, continuous flow. The secondary outcome was a composite adverse outcome within 30 days after surgery. Cytokines and endothelial biomarkers were measured in all patients at different time points. An intention-to-treat analysis was performed.

RESULTS

From October 2019 to November 2022, the study included 70 patients. Two patients were excluded from the Oxiris group: one patient did not undergo surgery, and one procedure was performed under deep hypothermia. The microvascular flow index did not differ between groups on day 1 from baseline: difference (95% CI) Oxiris minus standard at -0.17 (-0.44 to 0.10); P = 0.2. The occurrence of a composite adverse outcome did not significantly differ between groups (14 [42%] for the Oxiris group vs. 12 [35%] for the standard group; P = 0.7). The overall variation in cytokines and angiopoietins did not significantly differ between groups.

CONCLUSIONS

In patients scheduled for a cardiac surgery with prolonged CPB, the authors could not demonstrate the benefit on microcirculation and major cardiovascular events.

Assisted Fluid Management and Sublingual Microvascular Flow During High-Risk Abdominal Surgery: A Randomized Controlled Trial

BACKGROUND

Implementation of goal-directed fluid therapy (GDFT) protocols remains low. Protocol compliance among anesthesiologists tends to be suboptimal owing to the high workload and the attention required for implementation. The assisted fluid management (AFM) system is a novel decision support tool designed to help clinicians apply GDFT protocols. This system predicts fluid responsiveness better than anesthesia practitioners do and achieves higher stroke volume (SV) and cardiac index values during surgery. We tested the hypothesis that an AFM-guided GDFT strategy would also be associated with better sublingual microvascular flow compared to a standard GDFT strategy.

METHODS

This bicenter, parallel, 2-arm, prospective, randomized controlled, patient and assessor-blinded, superiority study considered for inclusion all consecutive patients undergoing high-risk abdominal surgery who required an arterial catheter and uncalibrated SV monitoring. Patients having standard GDFT received manual titration of fluid challenges to optimize SV while patients having an AFM-guided GDFT strategy received fluid challenges based on recommendations from the AFM software. In all patients, fluid challenges were standardized and titrated per 250 mL and vasopressors were administered to maintain a mean arterial pressure >70 mm Hg. The primary outcome (average of each patient's intraoperative microvascular flow index (MFI) across 4 intraoperative time points) was analyzed using a Mann-Whitney U test and the treatment effect was estimated with a median difference between groups with a 95% confidence interval estimated using the bootstrap percentile method (with 1000 replications). Secondary outcomes included SV, cardiac index, total amount of fluid, other microcirculatory variables, and postoperative lactate.

RESULTS

A total of 86 patients were enrolled over a 7-month period. The primary outcome was significantly higher in patients with AFM (median [Q1-Q3]: 2.89 [2.84-2.94]) versus those having standard GDFT (2.59 [2.38-2.78] points, median difference 0.30; 95% confidence interval [CI], 0.19-0.49; P < .001). Cardiac index and SVI were higher (3.2 ± 0.5 vs 2.7 ± 0.7 l.min -1 .m -2 ; P = .001 and 42 [35-47] vs 36 [32-43] mL.m -2 ; P = .018) and arterial lactate concentration was lower at the end of the surgery in patients having AFM-guided GDFT (2.1 [1.5-3.1] vs 2.9 [2.1-3.9] mmol.L -1 ; P = .026) than patients having standard GDFT strategy. Patients having AFM received a higher fluid volume but 3 times less norepinephrine than those receiving standard GDFT ( P < .001).

CONCLUSIONS

Use of an AFM-guided GDFT strategy resulted in higher sublingual microvascular flow during surgery compared to use of a standard GDFT strategy. Future trials are necessary to make conclusive recommendations that will change clinical practice.

Intraoperative Oxygenation and Microcirculatory Changes Following Off-pump Coronary Artery Bypass Grafting: An Exploratory Secondary Analysis of a Randomized Clinical Trial

OBJECTIVES

The effect of perioperative hyperoxia on microcirculation after cardiac surgery remains inconclusive. We evaluated the relationship between intraoperative fractional inspired oxygen and microcirculation after off-pump coronary artery bypass grafting (OPCAB).

DESIGN

Exploratory secondary analysis of a multicenter cluster-randomized trial.

SETTING

Three teaching hospitals.

PARTICIPANTS

Adult patients who underwent OPCAB.

INTERVENTIONS

Seven postoperative microcirculatory parameters, including De Backer scores and the proportion of perfused vessels via sublingual microscopy (from all and small vessels), and thenar muscle tissue oxygenation, occlusion slope, and recovery slope via the vascular occlusion test, were compared between patients receiving 30% and 80% oxygen intraoperatively. Generalized estimating equations were used to account for intracluster correlation.

MEASUREMENTS AND MAIN RESULTS

The analysis included 52 and 51 patients from the 30% and 80% oxygen groups, respectively, for sublingual microscopy and 59 and 53 patients for the vascular occlusion test. Although all microcirculatory parameters were similar between groups, the 80% oxygen group had higher De Backer scores for all vessels (mean, 9.8 ± 2.9 mm-1 vs. 8.7 ± 2.0 mm-1; p = 0.011) and small vessels (4.0 ± 1.8 mm-1 vs. 3.4 ± 1.1 mm-1; p = 0.024) than the 30% oxygen group at the end of surgery. The 80% oxygen group also exhibited greater thenar muscle tissue oxygenation immediately before vascular occlusion (78.4% ± 10.5 vs. 74.0% ± 9.3; p = 0.031) and a higher recovery score (4.1%·s-1 ± 1.7 vs. 3.2%·s-1 ± 1.4; p = 0.001).

CONCLUSIONS

Patients receiving 80% oxygen during OPCAB had significantly better postoperative microcirculatory profiles than those receiving 30% oxygen. These findings highlight the potential for optimizing perioperative oxygenation to improve or mitigate microcirculatory impairment, thereby reducing postoperative complications.

On the Intensity of the Microvascular Magnetic Field in Normal State and Septic Shock

Background: Capillary tortuosity is a morphological variant of microcirculation. However, the mechanisms by which tortuous vessels meet metabolic requirements in health and disease remain unknown. We recently reported that capillary tortuosity score (CTS) is significantly higher in patients with septic shock than in steady-state individuals, and that CTS is significantly associated with alveolar-to-arterial oxygen (A-a O2) gradient and oxygen debt in septic shock patients. Objective: We aimed to investigate the characteristics of the magnetic fields in the sublingual microcirculation of individuals with normal physiology and patients with septic shock. Methods: Systemic hemodynamics were recorded, and sublingual microcirculation was monitored using sidestream dark field (SDF+) imaging. The number of capillary red blood cells (NRBC), the intensity of the magnetic field of a red blood cell (HRBC), the intensity of the magnetic field of each capillary (HCAP), and the intensity with which the magnetic field of a capillary acts on an RBC (FCAP) were calculated. Results: Significant differences in macro- and microhemodynamic variables were observed between the two groups. Although NRBC was significantly higher in individuals with steady-state physiology [87.4 (87.12) vs. 12.23 (6.9)], HRBC was significantly stronger in patients with septic shock [5.9 × 10-16 (6.9 × 10-16) A m-1 vs. 1.6 × 10-15 (1.4 × 10-15) A m-1]. No significant difference was observed in HCAP [2.16 × 10-14 (2.17 × 10-14) A m-1 vs. 1.34 × 10-14 (1.23 × 10-14) A m-1] and FCAP [1.66 × 10-24 (3.36 × 10-24) A m-1 vs. 6.44 × 10-25 (1.1 × 10-24) A m-1] between the two groups. In patients with septic shock, HRBC was associated with De Backer score (rho = -0.608) and venous-arterial carbon dioxide difference (rho = 0.569). In the same group, HCAP was associated with convective oxygen flow (rho = 0.790) and oxygen extraction ratio (rho = -0.596). Also, FCAP was significantly associated with base deficit (rho = 0.701), A-a O2 gradient (rho = 0.658), and oxygen debt (rho = -0.769). Conclusions: Despite the microcirculatory impairment in patients with septic shock, HRBC was significantly stronger in that group than in steady-state individuals. Also, HCAP and FCAP were comparable between the two groups. Tortuous vessels may function as biomagnetic coils that amplify RBC-induced magnetic fields, enhancing perfusion and oxygenation of adjacent tissues.

EARLY AND CONCOMITANT ADMINISTRATION OF NOREPINEPHRINE AND ILOMEDIN IMPROVES MICROCIRCULATORY PERFUSION WITHOUT IMPAIRING MACROCIRCULATION IN AN INTESTINAL ISCHEMIA-REPERFUSION INJURY SWINE MODEL: A RANDOMIZED EXPERIMENTAL TRIAL

ABSTRACT

Background: Intestinal ischemia-reperfusion injury is associated with both macrocirculatory and microcirculatory failure. Association of a vasoconstrictor in combination with a vasodilator such as ilomedin may improve macrocirculation parameters, microcirculation perfusion and reduce endothelial dysfunction. The primary objective was to demonstrate a difference in mean arterial pressure (MAP) after intestinal reperfusion with the concomitant administration of norepinephrine and ilomedin during ischemia compared with traditional hemodynamic treatment strategies (fluid resuscitation and vasopressors only). Secondary objectives were to demonstrate an improvement in peripheral and intestinal microcirculatory perfusion and endothelial dysfunction after intestinal reperfusion using this association. Methods: We conducted a randomized preclinical trial in 21 large white pigs, in which a 2-h small bowel ischemia was performed using a segmental mesenteric occlusion model, followed by a 2-h reperfusion. Pigs were randomized into the following three groups: goal-directed fluid therapy, early administration of norepinephrine before reperfusion and early administration of ilomedin and norepinephrine before reperfusion. Macrocirculatory (MAP and Cardiac Index (CI), microcirculatory (Sublingual with SideStream Dark Field system and intestinal hemoglobin oxygen saturation with hyperspectral imaging) measurements and biological analysis (biomarkers of endothelial dysfunction) were performed. Results: There were no significant differences in the MAP ( P = 0.499) and the CI ( P = 0.659) between the three groups. Perfused vessel density in sublingual microcirculation was significantly higher immediately after reperfusion and 2 h after reperfusion in the early administration of ilomedin and norepinephrine group compared with the other two groups ( P < 0.05). Hemoglobin oxygen saturation measured at the intestinal level was significantly higher immediately after reperfusion in the early administration of ilomedin and norepinephrine group compared with the other two groups ( P < 0.01). There were no significant differences in biomarkers of endothelial dysfunction between the three groups. Creatinine, AST and alkaline phosphatases increased significantly 2 h after reperfusion in the early administration of ilomedin and norepinephrine group compared with baseline ( P < 0.05). Conclusions: Early administration of norepinephrine and ilomedin during ischemia improved short-term postreperfusion sublingual and intestinal microcirculation without worsening macrocirculatory parameters in an intestinal ischemia-reperfusion injury model. However, use of this strategy seemed to worsen both liver and kidney function.

Characterization of Sublingual Microvascular Tortuosity in Steady-State Physiology and Septic Shock

Background: The characteristics of hemodynamic coherence in healthy states and disease remain unknown. Capillary tortuosity is a morphologic variant of microcirculatory vessels, but its effects have generally not been considered in the assessment of tissue perfusion and oxygenation. We investigated the role of sublingual capillary tortuosity in the hemodynamic coherence of anesthetized adult individuals with steady-state physiology (ASA 1) and patients with septic shock requiring emergency abdominal surgery (ASA 4E and 5E). Methods: Sublingual macro and microcirculatory variables, oxygen transport, metabolic parameters, and the capillary tortuosity score (CTS) were assessed. Results: Mean (SD) CTS was 0.55 (0.76) and 3.31 (0.86) in the steady-state and septic shock group, respectively (p < 0.001). In patients with septic shock, CTS was significantly associated with alveolar-to-arterial oxygen gradient (r = 0.658, p = 0.015) and oxygen debt (r = -0.769, p = 0.002). Significant differences were also observed in Consensus Proportion of Perfused Vessels (PPV; p < 0.001), Consensus PPV (small) (p < 0.001), Microvascular Flow Index (p < 0.001), vessel diameter (p < 0.001) and length (p < 0.001), wall shear stress (p < 0.001), lactate (p < 0.001), oxygen extraction ratio (p = 0.001), arterial oxygen content (p < 0.001), venous oxygen content (p < 0.001), oxygen delivery (p < 0.001), oxygen consumption (p < 0.001), and oxygen debt (p = 0.002) between the two groups. Conclusions: Sublingual tortuosity was essentially absent in individuals with steady-state physiology. In contrast, it was significantly increased and associated with Alveolar-to-arterial oxygen gradient and oxygen debt in critically ill patients with septic shock.

Low-grade hemodilution improves the microcirculatory function in surgical patients

BACKGROUND

Excess fluid in the interstitium can adversely affect the microcirculation. We studied how gradual dilution of the blood plasma by crystalloid fluid influences microcirculatory variables and capillary filtration in 20 patients undergoing surgery.

METHODS

Video recordings of the sublingual mucosal were made on four occasions during the surgery and compared with quasi-measurements of the capillary filtration rate using retrospective volume kinetic data collected over 5-10-minute periods during 262 infusion experiments with crystalloid fluid.

RESULTS

The number of crossings (vessel density) increased up to plasma dilution of 15-20 % whereafter it decreased. The proportion of the vessels that were perfused (PPV) decreased and reached a nadir of -15 % at a dilution of 20-30 %. Changes in the number of crossings and the PPV correlated (r = 0.62, P < 0.001) but the curve was displaced so that crossings showed no change when PPV had decreased by approximately 10 %. However, the PPV of vessels with a thickness of ≤25 μm increased or remained constant in the dilution range of up to 20 %. The volume kinetic analysis showed that the capillary filtration was greater than expected from proportionality with the volume expansion up to a plasma dilution of 15 %, the greatest difference (+89 %) being for plasma dilution up to 5 %.

CONCLUSION

Plasma dilution of up to 15 % increased the vessel density, and the capillary filtration increased by more than suggested by the volume expansion. Dilution >15 % had a negative influence on these variables.

Molecular Mechanisms Underlying Heart Failure and Their Therapeutic Potential

Heart failure (HF) is a prominent fatal cardiovascular disorder afflicting 3.4% of the adult population despite the advancement of treatment options. Therefore, a better understanding of the pathogenesis of HF is essential for exploring novel therapeutic strategies. Hypertrophy and fibrosis are significant characteristics of pathological cardiac remodeling, contributing to HF. The mechanisms involved in the development of cardiac remodeling and consequent HF are multifactorial, and in this review, the key underlying mechanisms are discussed. These have been divided into the following categories thusly: (i) mitochondrial dysfunction, including defective dynamics, energy production, and oxidative stress; (ii) cardiac lipotoxicity; (iii) maladaptive endoplasmic reticulum (ER) stress; (iv) impaired autophagy; (v) cardiac inflammatory responses; (vi) programmed cell death, including apoptosis, pyroptosis, and ferroptosis; (vii) endothelial dysfunction; and (viii) defective cardiac contractility. Preclinical data suggest that there is merit in targeting the identified pathways; however, their clinical implications and outcomes regarding treating HF need further investigation in the future. Herein, we introduce the molecular mechanisms pivotal in the onset and progression of HF, as well as compounds targeting the related mechanisms and their therapeutic potential in preventing or rescuing HF. This, therefore, offers an avenue for the design and discovery of novel therapies for the treatment of HF.

Prevention of ischemia-reperfusion injury on the porcine model of supra-renal aortic clamp by sulodexide

BACKGROUND

The ischemia-reperfusion injury (IRI) is unavoidable in vascular surgery. Damage to the microcirculation and endothelial glycocalyx might set up a shock with loss of circulatory coherence and organ failure. Sulodexide may help to protect endothelial glycocalyx and alleviate the ischemia-reperfusion injury.

METHODS

Twenty female piglets underwent surgery with a 30-min-long suprarenal aortic clamp, followed by two hours of reperfusion. Ten piglets received sulodexide before the clamp, and 10 received normal saline. Blood and urine samples were taken at baseline and in 20-min intervals until the 120th minute to analyze the serum syndecan-1, E-selectin, and thrombomodulin. Albumin and glycosaminoglycans were examined in the urine. The kidney biopsies before and after the protocol were examined by light microscopy with hematoxylin-eosin staining. The sublingual microcirculation was recorded by side-stream dark field imaging at the time as blood and urine.

RESULTS

Based on the 2-way ANOVA testing, there was no statistically significant difference in the parameters of sublingual microcirculation. Serum markers of endothelial cell activation and damage (E-selectin and thrombomodulin) did not show any statistically significant difference either. Syndecan-1, a marker of glycocalyx damage, showed statistically significantly higher values based on the 2-way ANOVA testing (p < 0.0001) with the highest difference in the 80th minute: 7.8 (3.9-44) ng/mL in the control group and 1.8 (0.67-2.8) ng/mL in the sulodexide group. In the urine, the albuminuria was higher in the control group, although not statistically significant. Glycosaminoglycans were statistically significantly higher in the sulodexide group based on the mixed-effect analysis due to the intervention itself. Histological analysis of the renal biopsies showed necrosis in both groups after reperfusion.

CONCLUSION

Administering sulodexide significantly reduced the level of endothelial markers of IRI. The study results support further research into using preemptive administration of sulodexide to modulate IRI in clinical medicine.

Dexmedetomidine Improves Microcirculatory Alterations in Patients With Initial Resuscitated Septic Shock

Trial registration: Clinicaltrials.gov NCT02270281. Registered October 16, 2014.

The modulation of endothelial glycocalyx by sulodexide on the porcine model of enzymatic endothelial glycocalyx damage - a pilot study

BackgroundSulodexide is a glycosaminoglycan-based drug prescribed to patients with angiopathy. We performed a pilot study to investigate whether sulodexide positively modulates the endothelial glycocalyx (EG) layer and the microcirculation in a porcine model of EG enzymatic damage. The EG is a sugar-based endothelial lining that is involved in the physiology of the capillary wall and the pathogenesis of many diseases.MethodsEG damage was induced in eight piglets by hyaluronidase III and heparanase I given intravenously. Four animals received sulodexide 600 IU intravenously before the enzymes and four animals after the enzymes were administered. Four animals constituted a control group. Sublingual microcirculation by side-stream dark field imaging and plasmatic concentration of syndecan-1 by ELISA were measured at baseline, 20 min after intervention, and at the 40th, and 60th minute onwards. The statistics were performed with a one-way ANOVA test with Turkey's correction for multiple comparisons testing. Timepoint comparison was performed by Student t-test or Mann-Whitney test.ResultsAt baseline, there were no statistically significant differences between the animal groups. After the intervention, the levels of syndecan-1 were significantly lower in the control group. While there were no differences between the two intervention groups. The sublingual microcirculation analysis showed that the DeBacker score was significantly higher in the control group. At 60 min, there was also a statistically significant difference in DeBacker score between the groups (8.1 ± 1.6 mm-1 in the group with enzymes given first and 11 ± 0.92 mm-1 in the group with sulodexide given first, p = 0.03). The analysis of the proportion of perused vessels did not show any statistically significant differences.ConclusionThe results of the study demonstrated a working model of EG damage but no specific action of sulodexide on EG modulation. In the sublingual microcirculation analysis, the sulodexide reduced the fall in absolute tissue perfusion in 60 min.

Changes in microcirculation variables in an acute endotoxaemic equine model

BACKGROUND

Microcirculation is the essential link between macrocirculation and cellular metabolism.

OBJECTIVES

To test our hypotheses that microcirculation variables will show a heterogeneous flow pattern during experimental endotoxaemia, and that fluid therapy and noradrenaline (NA) infusion will normalise altered microcirculation variables.

STUDY DESIGN

In vivo experiments.

METHODS

Six healthy adult horses were anaesthetised with dexmedetomidine, ketamine, and diazepam and were mechanically ventilated under isoflurane anaesthesia. Endotoxaemia was induced with 30 ng kg-1 Escherichia coli lipopolysaccharide intravenously. One hundred and twenty minutes later fluid bolus and noradrenaline (NA) infusion were administered to produce normotension. Pulse rate (PR) and mean arterial blood pressure (MAP) were measured and microcirculation variables were obtained by side-stream darkfield technique (de Backer density (DBD), perfused de Backer density (PDBD), proportion of perfused vessels, microvascular flow index (MFI), heterogeneity index (HI)), laser Doppler flowmetry (blood flow) and white light spectrometry (tissue oxygen saturation (tSO2)) in sublingual, jejunal and genital area. Measurements were obtained at baseline, after endotoxin, at 60 and 120 min and during the normotensive phase. Data were analysed by mixed model variance analysis and Tukey-Kramer.

RESULTS

The PPV decreased significantly over time by 30% (p < 0.001) at the jejunum. MFI decreased from baseline to ET60 and from baseline to ET120 in sublingual and genital mucosa (2.9 vs. 1.4, p < 0.001 and 2.8 vs. 1.9, p < 0.01), respectively. The sublingual HI increased from baseline to ET60, ET120 and NA (0.1 vs. 0.9, p = 0.02; vs. 0.6, p = 0.01; vs. 0.3, p = 0.01), respectively. The genital HI increased from baseline to ET120 (0.2 vs. 1.1, p ≤ 0.01) and NA (0.16 vs. 0.53, p < 0.05, respectively). Moderate agreement between observers for MFI assessment was present (kappa = 0.4). The PR significantly increased, and MAP significantly decreased from baseline over time.

MAIN LIMITATIONS

The obtained data could be influenced by secretions, pressure artefacts, the experience of the examiner and the sampling location. Blood flow was not quantified and there was no control group.

CONCLUSIONS

Overall, short-term experimental endotoxaemia did negatively alter MFI and HI; however, it did not alter tSO2, blood flow, DBD, PDBD or proportion of perfused vessels. Intravenous fluid therapy and NA did not restore MFI and HI to baseline values.

The association of capillary refill time and return of spontaneous circulation during out-of-hospital cardiac arrest: an observational study

INTRODUCTION

Microcirculatory alterations are predictive of poor outcomes in patients with shock and after cardiac arrest in animal models. However, microcirculatory alterations during human cardiac arrest have not yet been studied.

METHODS

We prospectively included adult patients receiving resuscitation after witnessed out-of-hospital cardiac arrest. Exclusion criteria were hypovolemia, hypo- or hyperthermia (< 34.0 °C, > 37.5 °C), peripheral arterial disease, Raynaud's disease, and logistical issues (e.g., shortage of space). Capillary refill time was measured on the finger (CRT-F) and the earlobe (CRT-E) every other minute until return of spontaneous circulation (any ROSC) or termination of resuscitation. The primary endpoint was any ROSC, secondary endpoints were 30-day-mortality and good neurological outcome (defined as cerebral performance category 1-2). Based on the data structure, CRT-F and CRT-E values were grouped post-hoc into quartiles and tertiles. A cluster-robust standard error logistic regression was performed for the primary outcome. Trend analyses were made for each individual.

RESULTS

After screening of 141 patients, 50 were included in the analysis (median age 75 years, 28% female, any ROSC 32%). The median CRT-F was > 10 [7-> 10] seconds; the median CRT-E was 3 [3-4] seconds. The any ROSC rate for patients in CRT-F quartile 1 (3-5 s) was 71.4%, 31.7% in quartile 2 (6-8 s), 23.1% in quartile 3 (9-10 s), and 10% in quartile 4 (> 10 s). The odds ratio of 0.39 (95% CI 0.20-0.73, p = 0.004) indicated, that with an increase of CRT-F by a quartile, the chance of achieving any ROSC decreased by 61%. Patients with a decreasing CRT-F achieved any ROSC in 70%, whereas patients with constant or increasing CRT-F had any ROSC in only 21% (p = 0.008). In contrast, CRT-E showed no association with any ROSC (T1 [1-2 s.]: 16.7%, T2 [3 s.]: 27.5%, T3 [4-> 10 s.]: 22.4%, OR by tertiles: 1.18, 95% CI 0.58-2.44, p = 0.646).

CONCLUSION

During out-of-hospital cardiac arrest, shorter CRT-F, but not CRT-E, is associated with a higher chance of any ROSC.

TRIAL REGISTRATION

This trial was pre-registered on clinicaltrials.gov with the number: NCT04791995 on March 2nd, 2021.

Visualizing hemodynamics: innovative graphical displays and imaging techniques in anesthesia and critical care

The advancements in cardiovascular imaging over the past two decades have been significant. The miniaturization of ultrasound devices has greatly contributed to their widespread adoption in operating rooms and intensive care units. The integration of AI-enabled tools has further transformed the field by simplifying echocardiographic evaluations and enhancing the reproducibility of hemodynamic measurements, even for less experienced operators. Speckle tracking echocardiography offers a direct, visual, and quantitative assessment of myocardial shortening, serving as a compelling alternative to traditional methods for evaluating right and left ventricular systolic function. In critically ill patients, sublingual microcirculation imaging has revealed a high prevalence of microvascular alterations, which are markers of disease severity. The use of handheld vital microscopes enables the quantification of several key parameters, including vessel density, perfusion, red blood cell velocity, and the perfused vascular density. Such metrics are useful for evaluating microcirculatory health. The development of automated software marks a significant advance toward real-time bedside microvascular assessment. These advancements could eventually allow shock resuscitation to be tailored based on microvascular responses. In parallel with imaging advances, cardiac output monitors have evolved significantly. Once cumbersome devices displaying basic numerical data in tabular form, they now feature sleek, touch-screen interfaces integrated with visual decision-support tools. These tools synthesize hemodynamic data into intuitive graphical formats, allowing clinicians to quickly grasp the determinants of circulatory shock. This visual clarity supports more efficient and accurate decision-making, which may ultimately lead to improved patient care and outcomes.

How much is too much?: A retrospective causal analysis of the 7-day fluid balance for septic critical care patients

Many studies have provided significant evidence to suggest that early aggressive fluid resuscitation strategies are acutely beneficial in patients with sepsis. However, most of these studies did not follow up to determine the long-term impacts on patients' fluid and electrolyte balance after high-volume resuscitation strategies. This study sought to investigate the results of the aggressive fluid resuscitation measures used on patients with sepsis over the course of 7 days following resuscitation. An initial 3528 adult patients with sepsis who met inclusion criteria from the Medical Information Mart for Intensive Care IV database were collected. The total 7-day fluid balance of each patient was calculated and categorized into quartiles. Univariate Cox regression, lasso regression, backward stepwise elimination, and multivariate Cox regression were performed to search for variables related to survival during hospitalization. To determine the critical point of patients' fluid balance over 7 days, a restricted cubic spline regression model with 4 knots was performed. In addition, an inverse probability of treatment weighting analysis was conducted to confirm our findings. The median 7-day fluid balance is 5321.4 (interquartile range, 848.5-10,404.0) mL. The observed 28-day mortality in this cohort was 21.6%. Both before and after the inverse probability of treatment weighting analysis, the first 7-day fluid balance in the intensive care unit was significantly related to mortality during hospitalization (P < .001). A restricted cubic spline regression analysis indicated when the 7-day fluid balance was equal to 5243.3ml, the heart rate value was ≈1. A 7-day fluid balance < 5243.3 mL was considered a protective factor, while a balance > 5243.3 mL was considered a risk factor for patient mortality. To be clear, this study does not advocate against aggressive fluid resuscitation in patients with sepsis. However, clinicians walk a fine line with the extent of the resuscitation volume given to patients with sepsis. As a result of this study, it is highly advised that fluid resuscitation in patients with sepsis be limited to ≈5200-mL 7-day fluid balance for optimal clinical benefit.

Use of extracorporeal blood purification therapies in sepsis: the current paradigm, available evidence, and future perspectives

BACKGROUND

Sepsis is the result of a dysregulated immune response to infection and is associated with acute organ dysfunction. The syndrome's complexity is contingent upon the underlying pathology and individual patient characteristics, including their immune response. The involvement of multiple organs and physiological functions adds complexity, with "organ cross-talk" emerging as a pivotal pathophysiological and clinical aspect. This narrative review to evaluate the rationale and available clinical evidence supporting the use of extracorporeal blood purification therapies as adjunctive therapy in patients with sepsis and septic shock.

MAIN BODY

A search of the PubMed, Embase, Web of Science and Scopus databases for relevant literature from August 2002 to May 2024 has been conducted. The search was performed using the terms: 1) "blood purification" or "hemadsorption" or "plasma exchange" AND 2) "sepsis" or "septic shock". Therefore the authors have focused our discussion on several key areas such as conducting well-designed trials, developing more personalized protocols, ensuring optimal management and monitoring.

CONCLUSIONS

Given the heterogeneity of patients with sepsis, conducting traditional randomized clinical trials in this domain can be a daunting task. However, statistical techniques such as Bayesian methods, propensity score analysis, and emulated clinical trials using clinical databases hold promise for enhancing comparability between the study groups. Indeed, to comprehend the clinical efficacy of extracorporeal blood purification techniques in patients with sepsis, it is imperative to assemble homogeneous groups of patients receiving uniform treatments. Clinical strategies should be individualized, signaling the end of the "one size fits all" approach in sepsis therapy and the need for personalized treatments.

Effect of fluid and driving pressure on cyclical "on-off" flow of pulmonary microcirculation during mechanical ventilation

OBJECTIVES

This study aimed to identify the cyclical "on-off" flow of pulmonary microcirculation during inspiration and expiration by sidestream dark field imaging (SDF) technology in vivo and investigate the effects of volume status and driving pressure on cyclical "on-off" flow of microcirculation.

METHODS

24 ARDS-modeled rabbits were randomly divided into high-driving pressure group (HDP group) and low-driving pressure group (LDP group). Lung microcirculation measurements were performed using the SDF microscope at two timepoints (T1 CVP 2-4 mmHg, T2 CVP 8-10 mmHg). From T1 to T2, 10 ml/kg saline was infused to increase CVP. The cyclical "on-off" pulmonary microcirculation was quantitatively assessed by the change of microcirculation between expiration and inspiration.

RESULTS

Proportion of perfused vessels (PPV), microvascular flow index (MFI), perfused vessel density (PVD), and total vessel density (TVD) at expiration were significantly higher than inspiration in the HDP group. The HDP group has a higher ΔPPV and ΔPVD. After fluid loading, ΔPPV and ΔMFI decreased. TNF-α, IL-6, Ang-2, and vWF levels in the HDP group were higher. The HDP group also has a higher lung wet-weight/body weight ratio, lung wet-to-dry weight ratio, and more severe damage of pulmonary capillaries than the LDP group.

CONCLUSIONS

The difference in alveolar perfused microcirculation between inspiration and expiration defined as cyclical "on-off flow" can be detected. High driving pressure can enhance the cyclical "on-off" flow, and fluid loading can relieve it. High driving pressure can potentially cause injury to pulmonary capillaries due to the phenomenon of "on-off" flow, thereby exacerbating ARDS.

The microcirculation in cardiogenic shock

Cardiogenic shock is a life-threatening condition characterized by inadequate cardiac output, leading to end-organ hypoperfusion and associated mortality rates ranging between 40 and 50%. The critical role of microcirculatory impairments in the progression of organ failure during shock has been highlighted in several studies. Traditional therapies have often focused on stabilizing macrocirculation, neglecting microcirculatory dysfunction, which can result in persistent tissue hypoxia and poor outcomes. This review highlights the importance of assessing microcirculation in cardiogenic shock, including parameters such as skin perfusion, sublingual microcirculation, and lactate dynamics. Integrating microcirculatory assessments into clinical practice remains challenging due to the complexity of the methods and limited therapeutic options targeting microvascular perfusion. While advances in microcirculation-guided therapies hold promise for improving outcomes in cardiogenic shock, further research is needed to establish effective protocols.

Nailfold videocapillaroscopy - a novel method for the assessment of hemodynamic incoherence on the ICU

BACKGROUND

Loss of hemodynamic coherence is a phenomenon in critically ill patients. Due to inflammatory events and endothelial remodeling, macro- and microhemodynamics are decoupled from each other, resulting in microcirculatory disturbances and end organ ischemia despite adequate vital parameters. So far, quantification of perfusion of vessels with < 100 μm diameter on the intensive care unit (ICU) was regularly performed with incident darkfield (IDF) microscopy. Nailfold videocapillaroscopy (NVC), however, is an established and easy method for visualization of the microcirculation in chronic diseases. We here evaluated NVC in critically ill patients and compared its use with consensus microcirculatory assessment of IDF-microscopy.

METHODS

A new score, the capillary microcirculation (CapMic) score summarizing the microcirculation of the nail fold at four regions of digitus III, IV and V in a number between 0 (= no microcirculation) and 1 (= completely preserved microcirculation) was first established in 10 healthy volunteers and compared to the Microangiopathy Evolution Score (MES) standardized for NVC in chronic diseases. Then, n = 60 critically ill patients were recruited from a surgical ICU. Consensus-defined IDF scores and NCV data were compared at a single time point.

RESULTS

Evaluation of the CapMic score in 10 healthy volunteers at rest and under iatrogenic limb ischemia showed robust changes (0.80 ± 0.03 vs. 0.51 ± 0.12, p < 0.001). In critically ill patients, the IDF microscopy parameters "proportion of perfused vessels" (PPV) and "microvascular flow index" (MFI) inversely correlated with the MES (Spearman's R = -0.590, p < 0.001; Spearman's R = -0.585, p < 0.001). There was a positive correlation between PPV and the CapMic score (Spearman's R = 0.714, p < 0.001) and between MFI and the CapMic score (Spearman's R = 0.711, p < 0.001) and an inverse correlation between MES and the CapMic score (Spearman's R = -0.610, p < 0.001). Both sublingual and nailfold microcirculation deteriorated under rising norepinephrine- and crystalloid volume-requirements.

CONCLUSION

NVC-imaging provides comparable information on the microcirculation in critically ill patients compared to sublingual IDF microscopy. NCV could represent a new, additional method for diagnosing microcirculatory parameters on the ICU.

Cardiac arrest and microcirculatory dysfunction: a narrative review

PURPOSE OF REVIEW

This review provides an overview of the role of microcirculation in cardiac arrest and postcardiac arrest syndrome through handheld intravital microscopy and biomarkers. It highlights the importance of microcirculatory dysfunction in postcardiac arrest outcomes and explores potential therapeutic targets.

RECENT FINDINGS

Sublingual microcirculation is impaired in the early stage of postarrest and is potentially associated with increased mortality. Recent work suggests that the proportion of perfused small vessels is predictive of mortality. Microcirculatory impairment is consistently found to be independent of macrohemodynamic parameters. Biomarkers of endothelial cell injury and endothelial glycocalyx degradation are elevated in postarrest settings and may predict mortality and clinical outcomes, warranting further studies. Recent studies of exploratory therapies targeting microcirculation have shown some promise in animal models but still require significant research.

SUMMARY

Although research continues to suggest the important role that microcirculation may play in postcardiac arrest syndrome and cardiac arrest outcomes, the existing studies are still limited to draw any definitive conclusions. Further research is needed to better understand microcirculatory changes and their significance to improve cardiac arrest care and outcomes.

Prognostic Value of Sublingual Microcirculation in Sepsis: A Systematic Review and Meta-analysis

Objectives: To investigate the relationship between sublingual microcirculation and the prognosis of sepsis. Data sources: The PubMed, Web of Science, Embase, and China National Knowledge Infrastructure (CNKI) databases were searched to identify studies published from January 2003 to November 2023. Study selection: Clinical studies examining sublingual microcirculation and the prognosis of sepsis were included. Data extraction: Sublingual microcirculation indices included the microvascular blood index (MFI), total vascular density (TVD), perfusion vascular density (PVD), perfusion vascular vessel (PPV), and heterogeneity index (HI). Prognostic outcomes included mortality and severity. Funnel plots and Egger's test were used to detect publication bias. The ability of the small vessel PPV (PPVs) to predict sepsis-related mortality was analyzed based on the summary receiver operating characteristic (SROC) curve, pooled sensitivity, and pooled specificity. Data synthesis: Twenty-five studies involving 1750 subjects were included. The TVD (95% CI 0.11-0.39), PVD (95% CI 0.42-0.88), PPV (95% CI 6.63-13.83), and MFI (95% CI 0.13-0.6) of the survival group were greater than those of the nonsurvival group. The HI in the survival group was lower than that in the nonsurvival group (95% CI -0.49 to -0.03). The TVD (95% CI 0.41-0.83), PVD (95% CI 0.83-1.17), PPV (95% CI 14.49-24.9), and MFI (95% CI 0.25-0.66) of the nonsevere group were greater than those of the severe group. Subgroup analysis revealed no significant difference in TVD between the survival group and the nonsurvival group in the small vessel subgroup. The area under the SROC curve (AUC) was 0.88. Conclusions: Sublingual microcirculation was worse among patients who died and patients with severe sepsis than among patients who survived and patients with nonsevere sepsis. PPV has a good predictive value for the mortality of sepsis patients. This study was recorded in PROSPERO (registration number: CRD42023486349).

Heliox ventilation in elderly, hypertensive ICU patients improves microcirculation: A randomized controlled study

BACKGROUND

Conventional mechanical ventilation has adverse impacts on the hemodynamics of elderly, hypertensive ICU patients. Limited studies have addressed ways to ameliorate these negative effects. This study aimed to determine whether heliox ventilation could improve the hemodynamics, especially microcirculation, of elderly, hypertensive patients undergoing mechanical ventilation.

METHODS

Thirty-eight patients, over the age of 65 with essential hypertension who underwent invasive mechanical ventilation treatment, were divided into two groups: a control group of nitrogen‑oxygen ventilation (n = 19) and an experimental group of heliox ventilation (n = 19). The control group received conventional room air ventilation and the experimental group adopted the innovative, closed heliox ventilation technique. Changes in blood pressure, heart rate (HR), peripheral oxygen saturation (SpO2), central venous oxygen saturation (ScvO2), regional cerebral oxygen saturation (rSO2), lactic acid (Lac) and airway pressure were measured at 0,1,2,3 h under volume-controlled ventilation (VCV) mode throughout the study. Sublingual microcirculation parameters were additionally measured at 0 h and 3 h of ventilation treatment.

RESULTS

SpO2 in both groups increased after 1 h of ventilation compared with 0 h (p < 0.001), subsequently remaining stable. Compared with the control group, the experimental group showed a decrease in airway pressure and Lac, while blood pressure, ScvO2, and rSO2 increased (p < 0.05). Moreover, the sublingual microcirculation indexes in the experimental group improved compared with the control group (p < 0.05).

CONCLUSIONS

Heliox ventilation improves blood pressure and microcirculation in elderly hypertensive patients and may resolve the limitations of traditional nitrogen‑oxygen ventilation.

TRIAL REGISTRATION

This trial was registered. The Chinese trial registration number is ChiCTR2100043945. The date of registration is 6-3-2021.

Microcirculation: Current Perspective in Diagnostics, Imaging, and Clinical Applications

This review discusses the pivotal role of microcirculation in maintaining tissue oxygenation and waste removal and highlights its significance in various pathological conditions. It delves into the cellular mechanisms underlying hemodynamic coherence, elucidating the roles of the endothelium, glycocalyx, and erythrocytes in sustaining microcirculatory integrity. Furthermore, the review gives comprehensive information about microcirculatory changes observed in cardiac surgery, sepsis, shock, and COVID-19 disease. Through comprehensive exploration, the review underscores the intricate relationship between microcirculation, disease states, and clinical outcomes, emphasizing the importance of understanding and monitoring microvascular dynamics in critical care settings.

Association between cytokines, nitric oxide, hemodynamic and microcirculation in a porcine model of sepsis

Systemic inflammation and hemodynamic or microvascular alterations are a hallmark of sepsis and play a role in organs hypoperfusion and dysfunction. Pimobendan, an inodilator agent, could be an interesting option for inotropic support and microcirculation preservation during shock. The objectives of this study were to evaluate effect of pimobendan on cytokine and nitric oxide (NO) release and investigate whether changes of macro and microcirculation parameters are associated with the release of cytokines and NO in pigs sepsis model. After circulatory failure, induced by intravenous inoculation of live Pseudomonas aeruginosa, eight animals were treated with pimobendan and eight with placebo. Pimobendan did not affect cytokines secretion (TNF-α, IL-6 and IL-10), but decreased time-dependently NO release. Data of macro and microcirculation parameters, NO and TNF- α recorded at the time of circulatory failure (Thypotension) and the time maximum of production cytokines was used for analyses. A positive correlation was observed between TNF-α and cardiac index (r = 0.55, p = 0.03) and a negative with systemic vascular resistance (r = -0.52, p = 0.04). Positive correlations were seen both between IL-10, 30 min after resuscitation (T30min), and systolic arterial pressure (r = 0.57, p = 0.03) and cardiac index (r = 0.67, p = 0.01), and also between IL-6, taken 2 h after resuscitation and systolic arterial pressure (r = 0.53, p = 0.04). Negative correlations were found between IL-10 and lactate, measured resuscitation time (r = -0.58, p = 0.03). Regarding microcirculation parameters, we observed a positive correlation between IL-6 and IL-10 with the microvascular flow index (r = 0.52, p = 0.05; r = 0.84, p = 0.0003) and a negative correlation with the heterogeneity index with TNF-α and IL-10 (r = -0.51, p = 0.05; r = -0.74, p = 0.003) respectively. NO derivatives showed a positive correlation with temperature gradient (r = 0.54, p = 0.04). Pimobendan did not show anti-inflammatory effects in cytokines release. Our results also, suggest changes of macro- and microcirculation are associated mainly with low levels of IL-10 in sepsis.

Quantification of Video Sequences of the Microcirculation: A Comparison Between Automated Analysis Using Analysis Manager and Manual Analysis Using Capillary Mapper

OBJECTIVE

Microcirculatory disturbances can contribute to organ dysfunction in patients undergoing major surgeries and critical illness. Incident dark field imaging (CytoCam, Braedius Medical BV, Huizen, Netherlands) provides direct visualization of the microcirculation. To utilize this method in daily clinical practice, automated image analysis is essential. This study aims to compare the automated analysis of recorded microcirculation video sequences using CytoCamTools V2 Analysis Manager (Braedius Medical BV) with established manual analysis using Capillary Mapper (Version 1.4.5, University Hospital Münster, Germany) as reference method.

METHODS

Sublingual microcirculation video sequences were recorded in patients undergoing laparotomy at four time points (before surgery, 2 and 6 h after surgery, and on the first postoperative day) using incident dark field imaging. Agreement between automated and manual analysis of total vessel density (TVD), perfused vessel density (PVD), and proportion of perfused vessels (PPV) was compared using intraclass correlation (ICC) and Bland-Altman method.

RESULTS

A total of 336 videos from 30 patients were analyzed. The ICC between the two measurement methods was 0.13 for TVD, 0.14 for PVD, and 0.16 for PPV. Bland-Altman analysis showed mean differences (95% limits of agreement) of 10.46 mm/mm2 (-1.73-22.65 mm/mm2) for TVD, 8.25 mm/mm2 (-9.88-26.39 mm/mm2) for PVD, and - 3.96% (-59.58%-51.65%) for PPV.

DISCUSSION

Automated microcirculatory analysis using the Analysis Manager did not show clinically acceptable agreement with manual analysis using Capillary Mapper. Consequently, automated video analysis using the Analysis Manager does not appear to be a suitable approach.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: DRKS00020264.

DETECTION AND QUANTIFICATION OF MICROCIRCULATORY DYSFUNCTION IN SEVERE COVID-19 NOT REQUIRING MECHANICAL VENTILATION: A THREE-ARM COHORT STUDY

ABSTRACT

Aim: To identify and describe microcirculatory dysfunction (MD) in severe COVID-19 cases. Methods: This prospective, cohort study evaluated microvascular function in COVID-19 patients with acute respiratory failure not requiring mechanical ventilation and compared it with that of non-COVID-19 intensive care unit (ICU)-matched controls. A validation cohort included healthy, comorbidity-free patients. The primary outcome compared tissue oxygen resaturation slope (rStO 2 ) in COVID-19 patients and non-COVID ICU controls. rStO 2 was measured post a 3-min vaso-occlusive test during post-occlusive reactive hyperemia (PORH). Additionally, microvascular reactivity was assessed using perfusion index (PI) during PORH and laser speckle contrast imaging post iontophoresis with acetylcholine (ACH), sodium nitroprusside (SNP), and sublingual microcirculation. Results: Overall, 75 patients (25 per cohort) were included. COVID-19 patients exhibited greater severity than ICU controls, as indicated by their SOFA scores (4.0 [3.0; 4.0] vs. 1.0 [0; 1.0], P < 0.001) and PaO 2 /FiO 2 ratios (113 [82; 150] vs. 443 [348; 533], P < 0.001). No significant difference was observed in rStO 2 between the groups. COVID-19 patients showed longer time in reaching peak PI ( P = 0.025), reduced vasodilation with ACH and SNP ( P = 0.010 and P = 0.018, respectively), and increased microvascular density ( P = 0.019) compared to non-COVID-19 ICU controls. Conclusion: We observed evidence of MD in COVID-19 patients through various microcirculatory parameters. This study's reproducible multimodal approach facilitates acute MD detection across multiple clinical applications. Limitations included the observational design, limited statistical power, single-time microvascular measurements, varying illness severity among groups, and possible influences of treatments and vaccinations on MD. Trial registration : Clinical-Trials.gov (NCT04773899).

Microcirculatory Perfusion Disturbances During Veno-Arterial Extracorporeal Membrane Oxygenation: A Systematic Review

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is used in case of potentially reversible cardiac failure and restores systemic hemodynamics. However, whether this is followed by improvement of microcirculatory perfusion is unknown. Moreover, critically ill patients have possible pre-existing microcirculatory perfusion disturbances. Therefore, this review provides an overview of alterations in sublingual microcirculatory perfusion in critically ill adult patients receiving VA-ECMO support. Pubmed, Embase (Ovid), Cochrane Central Register of Controlled Trials, and Web of Science were systematically searched according to PRISMA guidelines. Studies reporting sublingual microcirculatory perfusion measurements in adult patients supported by VA-ECMO were included. Outcome parameters included small vessel density (SVD), perfused vessel density (PVD), perfused small vessel density (PSVD), proportion of perfused vessels (PPV), microvascular flow index (MFI) and the heterogeneity index (HI). The protocol was registered at PROSPERO (CRD42021243930). The search identified 1215 studies of which 11 were included. Cardiogenic shock was the most common indication for VA-ECMO (n=8). Three studies report increased PSVD, PPV, and MFI 24 hours after initiation of ECMO compared to pre-ECMO. Nonetheless, microcirculatory perfusion stabilized thereafter. Four out of four studies showed higher PSVD and PPV in survivors compared to non-survivors. Over time, survivors showed recovery of microcirculatory perfusion within hours of initiation of ECMO, whereas this was absent in non-survivors. Notwithstanding the limited sample, VA-ECMO seems to improve microcirculatory perfusion shortly after initiation of ECMO, especially in survivors. Further research in larger cohorts is needed to clarify the longitudinal effects of ECMO on microcirculatory perfusion.

Assessment of Microcirculatory Dysfunction by Measuring Subcutaneous Tissue Oxygen Saturation Using Near-Infrared Spectroscopy in Patients with Circulatory Failure

BACKGROUND

Patients with circulatory failure have high mortality rates and require prompt assessment of microcirculation. Despite the improvement in hemodynamic parameters, microcirculatory dysfunction persists. We measured subcutaneous regional tissue oxygen saturation (rSO2) with near-infrared spectroscopy (NIRS), which can assess microcirculation in patients with circulatory failure.

METHODS

A finger-worn oximeter with NIRS measured rSO2 in the forehead, thenar eminence, thumb, and knees. First, the rSO2 was measured in healthy adult volunteers (n = 10). Circulatory failure was defined as a systolic blood pressure ≤ 90 mmHg and lactate ≥ 2 mmol/L. The study included 35 patients without circulatory failure and SOFA score of 0 at ICU admission and 38 patients with circulatory failure at ICU admission. Both groups included a single-center prospective study of patients who were transported to the ICU of the Nihon University Hospital. The rSO2 was measured only on ICU admission in the non-circulatory failure group and later in the circulatory failure group.

RESULTS

In the volunteer group, rSO2 at each site was approximately 58%. The rSO2 was significantly lower in the circulatory failure group than in the non-circulatory failure group (knee, p < 0.01). In the circulatory failure group, knee rSO2 showed a significant negative correlation with SOFA score (Day 0, ρ = -0.37, p = 0.02; Day 1, ρ = -0.53, p < 0.01; Day 2, ρ = -0.60, p < 0.01).

CONCLUSIONS

Subcutaneous knee rSO2 was associated with SOFA score and was considered an indicator of microcirculatory dysfunction and organ damage.

[Relationship between cardiac output, heart rate and microcirculation in patients with multiorgan dysfunction syndrome]

BACKGROUND

Multiple organ dysfunction syndrome (MODS) is one of the main causes of death in intensive care units. There is evidence that microcirculation in sepsis and coronary shock is regulated separately from hemodynamics. This study investigates the relationship between heart rate (HR), cardiac output (CO) and microcirculation in patients with MODS.

METHODS

This is a partial analysis of the "MODIFY study" (Reducing Elevated Heart Rate in Patients With Multiple Organ Dysfunction Syndrome [MODS] by Ivabradine). During the period 05/2010-09/2011, the microcirculation of 46 patients with septic and coronary MODS was measured using the sidestream dark field technique on the day of inclusion and 96 h later. Patients were randomized into a control and ivabradine treatment group.

RESULTS

Overall, there is a relevant improvement in microcirculation over time small perfused vessels, SPV [%] on day 0, d0:56.5 ± 34.2/d4:73.2 ± 22.1 (p = 0.03); perfused vessel density, PVDsmall [1/mm2] d0:7.5 ± 5.0/d4:9.8 ± 3.4 (p = 0.04); proportion of perfused vessels, PPVsmall [%] d0:51.6 ± 31.6/d4:66.7 ± 21.8 (p = 0.04); microcirculatory flow index, MFI d0:1.7 ± 1.0/d4:2.2 ± 0.7 (p = 0.05). Administration of ivabradine shows no effect. In patients with coronary MODS, there is a relevant correlation between microcirculatory parameters and cardiac output (SPV [%]: r = 0.98, p = 0.004). Patients with coronary MODS show better microcirculation values at high heart rates (> 100 bpm), while patients with septic MODS show an opposite relationship.

CONCLUSION

The results indicate that in critically ill patients, depending on the genesis of the MODS, there are different relationships between HF or CO values, on the one hand, and the parameters of the microcirculation, on the other.

Intraoperative haemodynamic monitoring and management of adults having non-cardiac surgery: Guidelines of the German Society of Anaesthesiology and Intensive Care Medicine in collaboration with the German Association of the Scientific Medical Societies

Haemodynamic monitoring and management are cornerstones of perioperative care. The goal of haemodynamic management is to maintain organ function by ensuring adequate perfusion pressure, blood flow, and oxygen delivery. We here present guidelines on "Intraoperative haemodynamic monitoring and management of adults having non-cardiac surgery" that were prepared by 18 experts on behalf of the German Society of Anaesthesiology and Intensive Care Medicine (Deutsche Gesellschaft für Anästhesiologie und lntensivmedizin; DGAI).

Association between the lactate-albumin ratio and microcirculation changes in Pediatric Septic patients

A lactate/albumin ratio (LAR) greater than 0.5 measured early in the course of pediatric critical illness is associated with greater mortality. Whether the elevated LAR can be explained by microcirculation disorders in children with sepsis is not known. In this longitudinal retrospective study (January 2021-January 2024), serum albumin and lactate were measured on admission to the pediatric intensive care unit (PICU), with sublingual video microscopy performed simultaneously to measure microcirculation. A total of 178 children were included, 37% of whom had septic shock measured with the Phoenix Sepsis Score. Patients with remote sepsis had greater odds of an elevated LAR (aOR 6.87: 95% CI 1.98-23.73; p < 0.01). Children with an elevated LAR had more microvascular blood flow abnormalities (aOR 1.31 95% CI 1.08-1.58; p < 0.01), lower 4-6-micron capillary density (aOR 1.03 95% CI 1.01-1.05; p < 0.01) and greater odds of dying (aOR 3.55 95% CI 1.21-10.38; p = 0.02) compared to those with a low LAR. We found no association between LAR and endothelial glycocalyx degradation. A normal LAR is associated with less risk of microcirculatory injury (aOR 0.77 95% CI 0.65-0.93; p < 0.01). In children with sepsis, an elevated LAR is associated with microcirculation abnormalities (microvascular density and flow). The lactate/albumin ratio is a potentially useful biomarker for microcirculatory injury in sepsis.

Nitroglycerin challenge identifies microcirculatory target for improved resuscitation in patients with circulatory shock

BACKGROUND

Circulatory shock and multi-organ failure remain major contributors to morbidity and mortality in critically ill patients and are associated with insufficient oxygen availability in the tissue. Intrinsic mechanisms to improve tissue perfusion, such as up-regulation of functional capillary density (FCD) and red blood cell velocity (RBCv), have been identified as maneuvers to improve oxygen extraction by the tissues; however, their role in circulatory shock and potential use as resuscitation targets remains unknown. To fill this gap, we examined the baseline and maximum recruitable FCD and RBCv in response to a topical nitroglycerin stimulus (FCDNG, RBCvNG) in patients with and without circulatory shock to test whether this may be a method to identify the presence and magnitude of a microcirculatory reserve capacity important for identifying a resuscitation target.

METHODS

Sublingual handheld vital microscopy was performed after initial resuscitation in mechanically ventilated patients consecutively admitted to a tertiary medical ICU. FCD and RBCv were quantified using an automated computer vision algorithm (MicroTools). Patients with circulatory shock were retrospectively identified via standardized hemodynamic and clinical criteria and compared to patients without circulatory shock.

RESULTS

54 patients (57 ± 14y, BMI 26.3 ± 4.9 kg/m2, SAPS 56 ± 19, 65% male) were included, 13 of whom presented with circulatory shock. Both groups had similar cardiac index, mean arterial pressure, RBCv, and RBCvNG. Heart rate (p < 0.001), central venous pressure (p = 0.02), lactate (p < 0.001), capillary refill time (p < 0.01), and Mottling score (p < 0.001) were higher in circulatory shock after initial resuscitation, while FCD and FCDNG were 10% lower (16.9 ± 4.2 and 18.9 ± 3.2, p < 0.01; 19.3 ± 3.1 and 21.3 ± 2.9, p = 0.03). Nitroglycerin response was similar in both groups, and circulatory shock patients reached FCDNG similar to baseline FCD found in patients without shock.

CONCLUSION

Critically ill patients suffering from circulatory shock were found to present with a lower sublingual FCD. The preserved nitroglycerin response suggests a dysfunction of intrinsic regulation mechanisms to increase the microcirculatory oxygen extraction capacity associated with circulatory shock and identifies a potential resuscitation target. These differences in microcirculatory hemodynamic function between patients with and without circulatory shock were not reflected in blood pressure or cardiac index.

Plasma as endothelial rescue in septic shock: A randomized, phase 2a pilot trial

BACKGROUND

Septic shock is associated with high morbidity and mortality, the endothelium plays an important role. Crystalloids is standard of care to maintain intravascular volume. Plasma is associated with improved endothelial integrity and restoration of the glycocalyx layer. We evaluated the efficacy and safety aspects of cell-free and pathogen inactivated pooled plasma (OctaplasLG®) as resuscitation in septic shock patients.

STUDY DESIGN AND METHODS

This randomized, investigator-initiated phase IIa trial ran at a Danish single center intensive care unit, from 2017 to 2019. Patients were 18 years of age or older with septic shock and randomized to fluid optimization with OctaplasLG® or Ringer-acetate in the first 24 h. The primary endpoints were changes in biomarkers indicative of endothelial activation, damage, and microvascular perfusion from baseline to 24 h. Safety events and mortality were assessed during 90 days.

RESULTS

Forty-four patients were randomized, 20 to OctaplasLG versus 24 to Ringer-acetate. The median age was 69, and 55% were men. Median Sequential Organ Failure Assessment score was 13. Baseline differences favoring the Ringer-acetate group were observed. The OctaplasLG® group was resuscitated with 740 mL plasma and the Ringer-acetate group with 841 mL crystalloids. There was no significant change in the microvascular perfusion or five biomarkers except VEGFR1 change, which was higher in patients receiving OctaplasLG® 0.12(SD 0.37) versus Ringer-acetate -0.24 (SD 0.39), with mean difference 0.36 (95% CI, 0.13-0.59, p = .003) in favor of Ringer-acetate.

DISCUSSION

This study found that fluid resuscitation with OctaplasLG® in critically ill septic shock patients is feasible. Baseline confounding prevented assessment of the potential effect of OctaplasLG®.

Blood pressure measurement and assessment of arterial structure and function: an expert group position paper

Measuring blood pressure (BP) and investigating arterial hemodynamics are essential in understanding cardiovascular disease and assessing cardiovascular risk. Several methods are used to measure BP in the doctor's office, at home, or over 24 h under ambulatory conditions. Similarly, several noninvasive methods have been introduced for assessing arterial structure and function; these methods differ for the large arteries, the small ones, and the capillaries. Consequently, when studying arterial hemodynamics, the clinician is faced with a multitude of assessment methods whose technical details, advantages, and limitations are sometimes unclear. Moreover, the conditions and procedures for their optimal implementation, and/or the reference normality values for the parameters they yield are not always taken into sufficient consideration. Therefore, a practice guideline summarizing the main methods and their use in clinical practice is needed. This expert group position paper was developed by an international group of scientists after a two-day meeting during which each of the most used methods and techniques for blood pressure measurement and arterial function and structure evaluation were presented and discussed, focusing on their advantages, limitations, indications, normal values, and their pragmatic clinical application.

Transitions from Aerobic to Anaerobic Metabolism and Oxygen Debt during Elective Major and Emergency Non-Cardiac Surgery

INTRODUCTION

Intraoperative hemodynamic and metabolic optimization of both the high-risk surgical patients and critically ill patients remains challenging. Reductions in oxygen delivery or increases in oxygen consumption can initiate complex cellular processes precipitating oxygen debt (OXD).

METHODS

This study tested the hypothesis that intraoperative changes in sublingual microcirculatory flow reflect clinically relevant transitions from aerobic to anaerobic metabolism (TRANAM). We included patients undergoing elective major and emergency non-cardiac surgery. Macro- and microcirculatory variables, oxygen extraction, and transitions of metabolism were assessed in both cohorts.

RESULTS

In the elective group, OXD was progressively increased over time, with an estimated 2.24 unit increase every 30 min (adjusted p < 0.001). Also, OXD was negatively correlated with central venous pressure (ρ = -0.247, adjusted p = 0.006) and positively correlated with stroke volume variation (ρ = 0.185, adjusted p = 0.041). However, it was not significantly correlated with sublingual microcirculation variables. In the emergency surgery group, OXD increased during the first two intraoperative hours and then gradually decreased until the end of surgery. In that cohort, OXD was positively correlated with diastolic arterial pressure (ρ = 0.338, adjpatients and the critically ill patients remains challengingsted p = 0.015). Also, OXD was negatively correlated with cardiac index (ρ = -0.352, adjusted p = 0.003), Consensus Proportion of Perfused Vessels (PPV) (ρ = -0.438, adjusted p < 0.001), and Consensus PPV (small) (ρ = -0.434, adjusted p < 0.001).

CONCLUSIONS

TRANAM were evident in both the elective major and emergency non-cardiac surgery cohorts independent of underlying alterations in the sublingual microcirculation.

Predictive value of microcirculation for pediatric extracorporeal membrane oxygenation weaning test: A monocentric prospective observational study

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is widely used for children treated for refractory respiratory failures or refractory cardiogenic shock. Its duration depends on organ functions recovery. Weaning is decided using macro-circulatory tools, but microcirculation is not well evaluated. Sidestream dark-field video imaging is used to assess the perfusion of the sublingual microvascular vessels. The aim of this study was to assess the predictive value of microcirculatory indices in ECMO weaning.

METHODS

This prospective monocentric study examined pediatric patients at Trousseau Hospital between March 2017 and December 2020. The study included all patients from 35 weeks of gestational age to 18 years old who were treated with ECMO. Children were divided into two groups: one with stability after weaning and the other with instability after weaning. We collected clinical and biological data, ventilation parameters, extracorporeal membrane oxygenation parameters, and drugs used at admission and after the weaning test. Microcirculations videos were taken after weaning trials with echocardiography and blood gas monitoring.

RESULTS

The study included 30 patients with a median age of 29 days (range: 1-770 days) at admission, including 18 patients who received venoarterial ECMO (60%). There were 19 children in the stability group and 11 in the instability group. Macrocirculatory and microcirculatory indices showed no differences between groups. The microvascular flow index was subnormal in both groups (2.3 (1.8-2.4) and 2.3 (2.3-2.6), respectively; p = 0.24). The microvascular indices were similar between cases of venovenous and venoarterial ECMO and between age groups.

CONCLUSION

Microcirculation monitoring at the weaning phase did not predict the failure of ECMO weaning.

Anaerobic Lactate Production Is Associated With Decreased Microcirculatory Blood Flow and Decreased Mitochondrial Respiration Following Cardiovascular Surgery With Cardiopulmonary Bypass

OBJECTIVES

Quantify the relationship between perioperative anaerobic lactate production, microcirculatory blood flow, and mitochondrial respiration in patients after cardiovascular surgery with cardiopulmonary bypass.

DESIGN

Serial measurements of lactate-pyruvate ratio (LPR), microcirculatory blood flow, plasma tricarboxylic acid cycle cycle intermediates, and mitochondrial respiration were compared between patients with a normal peak lactate (≤ 2 mmol/L) and a high peak lactate (≥ 4 mmol/L) in the first 6 hours after surgery. Regression analysis was performed to quantify the relationship between clinically relevant hemodynamic variables, lactate, LPR, and microcirculatory blood flow.

SETTING

This was a single-center, prospective observational study conducted in an academic cardiovascular ICU.

PATIENTS

One hundred thirty-two patients undergoing elective cardiovascular surgery with cardiopulmonary bypass.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients with a high postoperative lactate were found to have a higher LPR compared with patients with a normal postoperative lactate (14.4 ± 2.5 vs. 11.7 ± 3.4; p = 0.005). Linear regression analysis found a significant, negative relationship between LPR and microcirculatory flow index ( r = -0.225; β = -0.037; p = 0.001 and proportion of perfused vessels: r = -0.17; β = -0.468; p = 0.009). There was not a significant relationship between absolute plasma lactate and microcirculation variables. Last, mitochondrial complex I and complex II oxidative phosphorylation were reduced in patients with high postoperative lactate levels compared with patients with normal lactate (22.6 ± 6.2 vs. 14.5 ± 7.4 pmol O 2 /s/10 6 cells; p = 0.002).

CONCLUSIONS

Increased anaerobic lactate production, estimated by LPR, has a negative relationship with microcirculatory blood flow after cardiovascular surgery. This relationship does not persist when measuring lactate alone. In addition, decreased mitochondrial respiration is associated with increased lactate after cardiovascular surgery. These findings suggest that high lactate levels after cardiovascular surgery, even in the setting of normal hemodynamics, are not simply a type B phenomenon as previously suggested.

Noninvasive assessment of human microvascular function in health and disease using incident dark-field microscopy

Reduced peripheral microvascular reactivity is associated with an increased risk for major adverse cardiac events (MACEs). Tools for noninvasive assessment of peripheral microvascular function are limited, and existing technology is poorly validated in both healthy populations and patients with cardiovascular disease (CVD). Here, we used a handheld incident dark-field imaging tool (CytoCam) to test the hypothesis that, compared with healthy individuals (no risk factors for CVD), subjects formally diagnosed with coronary artery disease (CAD) or those with ≥2 risk factors for CAD (at risk) would exhibit impaired peripheral microvascular reactivity. A total of 17 participants (11 healthy, 6 at risk) were included in this pilot study. CytoCam was used to measure sublingual microvascular total vessel density (TVD), perfused vessel density (PVD), and microvascular flow index (MFI) in response to the topical application of acetylcholine (ACh) and sublingual administration of nitroglycerin (NTG). Baseline MFI and PVD were significantly reduced in the at-risk cohort compared with healthy individuals. Surprisingly, following the application of acetylcholine and nitroglycerin, both groups showed a significant improvement in all three microvascular perfusion parameters. These results suggest that, despite baseline reductions in both microvascular density and perfusion, human in vivo peripheral microvascular reactivity to both endothelial-dependent and -independent vasoactive agents remains intact in individuals with CAD or multiple risk factors for disease.NEW & NOTEWORTHY To our knowledge, this is the first study to comprehensively characterize in vivo sublingual microvascular structure and function (endothelium-dependent and -independent) in healthy patients and those with CVD. Importantly, we used an easy-to-use handheld device that can be easily translated to clinical settings. Our results indicate that baseline microvascular impairments in structure and function can be detected using the CytoCam technology, although reactivity to acetylcholine may be maintained even during disease in the peripheral microcirculation.

A multimodal tissue perfusion measurement approach for the evaluation of the effect of pimobendan, an inodilator, in a porcine sepsis model

Sepsis is associated with hypoperfusion and organ failure. The aims of the study were: 1) to assess the effect of pimobendan on macrocirculation and perfusion and 2) to describe a multimodal approach to the assessment of perfusion in sepsis and compare the evolution of the perfusion parameters. Eighteen anaesthetized female piglets were equipped for macrocirculation monitoring. Sepsis was induced by an infusion of Pseudomonas aeruginosa. After the occurrence of hypotension, animals were resuscitated. Nine pigs received pimobendan at the start of resuscitation maneuvers, the others received saline. Tissue perfusion was assessed using temperature gradients measured with infrared thermography (TG = core temperature - tarsus temperature), urethral perfusion index (uPI) derived from photoplethysmography and sublingual microcirculation (Sidestream dark field imaging device): De Backer score (DBs), proportion of perfused vessels (PPV), microvascular flow index (MFI) and heterogeneity index (HI). Arterial lactate and ScvO2 were also measured. Pimobendan did not improve tissue perfusion nor macrocirculation. It did not allow a reduction in the amount of noradrenaline and fluids administered. Sepsis was associated with tissue perfusion disorders: there were a significant decrease in uPI, PPV and ScvO2 and a significant rise in TG. TG could significantly predict an increase in lactate. Resuscitation was associated with a significant increase in uPI, DBs, MFI, lactate and ScvO2. There were fair correlations between the different perfusion parameters. In this model, pimobendan did not show any benefit. The multimodal approach allowed the detection of tissue perfusion alteration but only temperature gradients predicted the increase in lactatemia.

Relationship between the mixed venous-to-arterial carbon dioxide gradient and the cardiac index in acute pulmonary embolism

AIMS

Among patients with acute pulmonary embolism (PE) undergoing mechanical thrombectomy, the cardiac index (CI) is frequently reduced even among those without a clinically apparent shock. The purpose of this study is to describe the mixed venous-to-arterial carbon dioxide gradient (CO2 gap), a surrogate of perfusion adequacy, among patients with acute PE undergoing mechanical thrombectomy.

METHODS AND RESULTS

This was a single-centre retrospective study of consecutive patients with PE undergoing mechanical thrombectomy and simultaneous pulmonary artery catheterization over a 3-year period. Of 107 patients, 97 had simultaneous mixed venous and arterial blood gas measurements available. The CO2 gap was elevated (>6 mmHg) in 51% of the cohort and in 49% of patients with intermediate-risk PE. A reduced CI (≤2.2 L/min/m2) was associated with an increased odds [odds ratio = 7.9; 95% confidence interval (CI) 3.49-18.1, P < 0.001] for an elevated CO2 gap. There was an inverse relationship between the CI and the CO2 gap. For every 1 L/min/m2 decrease in the CI, the CO2 gap increased by 1.3 mmHg (P = 0.001). Among patients with an elevated baseline CO2 gap >6 mmHg, thrombectomy improved the CO2 gap, CI, and mixed venous oxygen saturation. When the CO2 gap was dichotomized above and below 6, there was no difference in the in-hospital mortality rate (9 vs. 0%; P = 0.10; hazard ratio: 1.24; 95% CI 0.97-1.60; P = 0.085).

CONCLUSION

Among patients with acute PE undergoing mechanical thrombectomy, the CO2 gap is abnormal in nearly 50% of patients and inversely related to the CI. Further studies should examine the relationship between markers of perfusion and outcomes in this population to refine risk stratification.

The Sublingual Microcirculation in Critically Ill Children with Septic Shock Undergoing Hemoadsorption: A Pilot Study

Background: The importance of perfusion-guided resuscitation in septic shock has recently emerged. We explored whether the use of hemoadsorption led to a potential beneficial role in microvascular alterations in this clinical setting. Methods: A pre-planned secondary analysis of a Phase-II interventional single-arm pilot study (NCT05658588) was carried out, where 17 consecutive septic shock children admitted into PICU were treated with continuous renal replacement therapy (CRRT) and CytoSorb. Thirteen patients were eligible to be investigated with sublingual microcirculation at baseline, 24, 48, 72 and 96 h from the onset of blood purification. Patients achieving a microvascular flow index (MFI) ≥ 2.5 and/or proportion of perfused vessels (PPV) exceeding 90% by 96 h were defined as responders. Results: In 10/13 (77%), there was a significant improvement in MFIs (p = 0.01) and PPVs% (p = 0.04) between baseline and 24 h from the end of treatment. Eight patients displayed a high heterogenicity index (HI > 0.5) during blood purification and among these, five showed an improvement by the end of treatment (HI < 0.5). Conclusions: In this pilot study, we have found a potential association between CytoSorb hemoadsorption and a microcirculation improvement in pediatric patients with septic shock, particularly when this observation has been associated with hemodynamic improvement.

Effects of remote ischemic preconditioning on early markers of intestinal injury in experimental hemorrhage in rats

The maintenance of intestinal integrity and barrier function under conditions of restricted oxygen availability is crucial to avoid bacterial translocation and local inflammation. Both lead to secondary diseases after hemorrhagic shock and might increase morbidity and mortality after surviving the initial event. Monitoring of the intestinal integrity especially in the early course of critical illness remains challenging. Since microcirculation and mitochondrial respiration are main components of the terminal stretch of tissue oxygenation, the evaluation of microcirculatory and mitochondrial variables could identify tissues at risk during hypoxic challenges, indicate an increase of intestinal injury, and improve our understanding of regional pathophysiology during acute hemorrhage. Furthermore, improving intestinal microcirculation or mitochondrial respiration, e.g. by remote ischemic preconditioning (RIPC) that was reported to exert a sufficient tissue protection in various tissues and was linked to mediators with vasoactive properties could maintain intestinal integrity. In this study, postcapillary oxygen saturation (µHbO2), microvascular flow index (MFI) and plasmatic D-lactate concentration revealed to be early markers of intestinal injury in a rodent model of experimental hemorrhagic shock. Mitochondrial function was not impaired in this experimental model of acute hemorrhage. Remote ischemic preconditioning (RIPC) failed to improve intestinal microcirculation and intestinal damage during hemorrhagic shock.

Resuscitating the macro- vs. microcirculation in septic shock

PURPOSE OF REVIEW

This review summarizes current literature about the relationships between macro and microcirculation and their practical clinical implications in children with septic shock.

RECENT FINDINGS

Current evidence from experimental and clinical observational studies in children and adults with septic shock reveals that the response to treatment and resuscitation is widely variable. Furthermore, there is a loss of hemodynamic coherence, as resuscitation-induced improvement in macrocirculation (systemic hemodynamic parameters) does not necessarily result in a parallel improvement in the microcirculation. Therefore, patient-tailored monitoring is essential in order to adjust treatment requirements during resuscitation in septic shock. Optimal monitoring must integrate macrocirculation (heart rate, blood pressure, cardiac output, and ultrasound images), microcirculation (videomicroscopy parameters and capillary refill time) and cellular metabolism (lactic acid, central venous blood oxygen saturation, and difference of central venous to arterial carbon dioxide partial pressure).

SUMMARY

There is a dire need for high-quality studies to assess the relationships between macrocirculation, microcirculation and tissue metabolism in children with septic shock. The development of reliable and readily available microcirculation and tissue perfusion biomarkers (other than lactic acid) is also necessary to improve monitoring and treatment adjustment in such patients.

Sedation with propofol and isoflurane differs in terms of microcirculatory parameters: A randomized animal study using dorsal skinfold chamber mouse model

OBJECTIVE

This study aimed to explore the effects of sedative doses of propofol and isoflurane on microcirculation in septic mice compared to controls. Isoflurane, known for its potential as a sedation drug in bedside applications, lacks clarity regarding its impact on the microcirculation system. The hypothesis was that propofol would exert a more pronounced influence on the microvascular flow index, particularly amplified in septic conditions.

MATERIAL AND METHODS

Randomized study was conducted from December 2020 to October 2021 involved 60 BALB/c mice, with 52 mice analyzed. Dorsal skinfold chambers were implanted, followed by intraperitoneal injections of either sterile 0.9 % saline or lipopolysaccharide for the control and sepsis groups, respectively. Both groups received propofol or isoflurane treatment for 120 min. Microcirculatory parameters were obtained via incident dark-field microscopy videos, along with the mean blood pressure and heart rate at three time points: before sedation (T0), 30 min after sedation (T30), and 120 min after sedation (T120). Endothelial glycocalyx thickness and syndecan-1 concentration were also analyzed.

RESULTS

In healthy controls, both anesthetics reduced blood pressure. However, propofol maintained microvascular flow, differing significantly from isoflurane at T120 (propofol, 2.8 ± 0.3 vs. isoflurane, 1.6 ± 0.9; P < 0.001). In the sepsis group, a similar pattern occurred at T120 without statistical significance (propofol, 1.8 ± 1.1 vs. isoflurane, 1.2 ± 0.7; P = 0.023). Syndecan-1 levels did not differ between agents, but glycocalyx thickness index was significantly lower in the isoflurane-sepsis group than propofol (P = 0.001).

CONCLUSIONS

Propofol potentially offers protective action against microvascular flow deterioration compared to isoflurane, observed in control mice. Furthermore, a lower degree of sepsis-induced glycocalyx degradation was evident with propofol compared to isoflurane.

Optimization of cardiopulmonary bypass prime fluid to preserve microcirculatory perfusion during on-pump coronary artery bypass graft surgery: PRIME study protocol for a double-blind randomized trial

BACKGROUND

Acute microcirculatory perfusion disturbances and organ edema are important factors leading to organ dysfunction during cardiac surgery with cardiopulmonary bypass (CPB). Priming of the CPB system with crystalloid or colloid fluids, which inevitably leads to hemodilution, could contribute to this effect. However, there is yet no optimal evidence-based strategy for this type of priming. Hence, we will investigate different priming strategies to reduce hemodilution and preserve microcirculatory perfusion.

METHODS

The PRIME study is a single-center double-blind randomized trial. Patients undergoing elective coronary artery bypass graft surgery with CPB will be randomized into three groups of prime fluid strategy: (1) gelofusine with crystalloid, (2) albumin with crystalloid, or (3) crystalloid and retrograde autologous priming. We aim to include 30 patients, 10 patients in each arm. The primary outcome is the change in microcirculatory perfusion. Secondary outcomes include colloid oncotic pressure; albumin; hematocrit; electrolytes; fluid balance and requirements; transfusion rates; and endothelial-, glycocalyx-, inflammatory- and renal injury markers. Sublingual microcirculatory perfusion will be measured using non-invasive sidestream dark field video microscopy. Microcirculatory and blood measurements will be performed at five consecutive time points during surgery up to 24 h after admission to the intensive care unit.

DISCUSSION

PRIME is the first study to assess the effect of different prime fluid strategies on microcirculatory perfusion in cardiac surgery with CPB. If the results suggest that a specific crystalloid or colloid prime fluid strategy better preserves microcirculatory perfusion during on-pump cardiac surgery, the current study may help to find the optimal pump priming in cardiac surgery.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05647057. Registered on 04/25/2023.

CLINICALTRIALS

gov PRS: Record Summary NCT05647057, all items can be found in the protocol.

Microcirculation-driven mitochondrion dysfunction during the progression of experimental sepsis

Sepsis is accompanied by a less-known mismatch between hemodynamics and mitochondrial respiration. We aimed to characterize the relationship and time dependency of microcirculatory and mitochondrial functions in a rodent model of intraabdominal sepsis. Fecal peritonitis was induced in rats, and multi-organ failure (MOF) was evaluated 12, 16, 20, 24 or 28 h later (n = 8/group, each) using rat-specific organ failure assessment (ROFA) scores. Ileal microcirculation (proportion of perfused microvessels (PPV), microvascular flow index (MFI) and heterogeneity index (HI)) was monitored by intravital video microscopy, and mitochondrial respiration (OxPhos) and outer membrane (mtOM) damage were measured with high-resolution respirometry. MOF progression was evidenced by increased ROFA scores; microcirculatory parameters followed a parallel time course from the 16th to 28th h. Mitochondrial dysfunction commenced with a 4-h time lag with signs of mtOM damage, which correlated significantly with PPV, while no correlation was found between HI and OxPhos. High diagnostic value was demonstrated for PPV, mtOM damage and lactate levels for predicting MOF. Our findings indicate insufficient splanchnic microcirculation to be a possible predictor for MOF that develops before the start of mitochondrial dysfunction. The adequate subcellular compensatory capacity suggests the presence of mitochondrial subpopulations with differing sensitivity to septic insults.