A global perspective on vasoactive agents in shock

Homoisoflavones: Structural diversity, pharmacological activities, and photocatalytic synthesis strategies - A comprehensive review

Homoisoflavones, a rare subclass of flavonoids distinguished from isoflavones by an additional carbon atom in their parent structure, have garnered attention for their significant pharmacological properties. Firstly, this review methodically analyzes the structural diversity of all documented homoisoflavone variants and their pharmacological activities, including antibacterial, antitumor, anti-inflammatory, and other biological effects, based on studies spanning from 1973 to the latest accessible data (March 2025). Secondly, the photo-induced synthesis methodologies for homoisoflavones are meticulously scrutinized and elaborated upon, compared with traditional synthetic approaches, as photo-mediated organic synthesis strategy continue to gain prominence as a valuable tool in medicinal chemistry. Finally, based on the structural features, pharmacological activities, and photo-induced synthesis strategies of homoisoflavones, potential future development prospects are proposed. For the first time, this article analyzes the medicinal chemistry potential of homoisoflavones from the perspective of photocatalysis, highlighting their structural features, pharmacological activities, and innovative synthesis strategies. It is hoped that this review will provide valuable guidance for the development of homoisoflavones in medicinal chemistry.

Bedside clinical prediction tool for mortality in critically ill children

INTRODUCTION

Mortality rates among critically ill pediatric patients remain a persistent challenge. It is imperative to identify patients at higher risk to effectively allocate appropriate resources. Our study aimed to develop a prediction score based on clinical parameters and hemogram to predict pediatric intensive care unit (PICU) mortality.

METHODS

We conducted a retrospective study to develop a clinical prediction score using data from children aged 1 month to 18 years admitted for at least 24 hours to the PICU at Chiang Mai University between January 2018 and December 2022. PICU mortality was defined as death within 28 days of admission. The score was developed using multivariable logistic regression and assessed for calibration and discrimination.

RESULTS

There were 29 deaths in 330 children (8.8%). Our model for predicting 28-day ICU mortality uses four key predictors: male gender, use of vasoactive drugs, red blood cell distribution width (RDW) ≥15.9%, and platelet distribution width (PDW), categorized as follows: <10% (0 points), 10-14.9% (2 points), and ≥15% (4 points). Scores range from 0 to 8, with a cutoff value of 5 to differentiate low-risk (<5) from high-risk (≥5) groups. The tool demonstrates excellent performance with an AuROC curve of 0.86 (95% CI: 0.80-0.91, p<0.001) showing excellent discrimination and calibration, 82.8% sensitivity, and 73.1% specificity, respectively.

CONCLUSIONS

The score, developed from clinical data and hemogram, demonstrated potential in predicting ICU mortality among critically ill children. However, further studies are necessary to externally validate the score before it can be confidentially implemented in clinical practices.

Effect of timing of norepinephrine administration on prognosis of patients with septic shock: A prospective cohort study

Background

Sepsis and septic shock are major healthcare problems worldwide, associated with substantial mortality. Early administration of norepinephrine in septic shock patients has been associated with an increased survival rate, but the timing from septic shock to norepinephrine initiation is controversial. This study examined the associations between the timing of initial norepinephrine administration and clinical outcomes in adult patients with septic shock.

Methods

This prospective cohort study was conducted from September 2021 to June 2022 in an intensive care unit (ICU) of a tertiary general hospital. All enrolled patients were divided into early and late norepinephrine groups according to whether the time from the onset of septic shock to the first application of norepinephrine was >1 h. The primary outcome was 28-day mortality. Secondary outcomes included ICU length of stay (LOS), hospital LOS, time to achieve a mean arterial pressure (MAP) ≥65 mmHg, 24-hour infusion volume, 6-hour Lac clearance, mechanical ventilation days, and continuous renal replacement therapy (CRRT )ratio. Multivariable logistic regression analysis was used to evaluate the independent risk factors for 28-day mortality.

Results

This study enrolled 120 patients, including 42 patients (35.0%) and 78 patients (65.0%) in the early and late norepinephrine groups, respectively. The 28-day mortality was lower in the early group than in the late group (28.6% vs. 47.4%, P=0.045). The median time to achieve MAP ≥65 mmHg was shorter in the early group than in the late group (1.0 h vs. 1.5 h, P=0.010). The median 24-hour intravenous fluids volume in the early group was lower than that in the late group (40.7% vs. 14.9%, P=0.030). The median 6-hour lactate (Lac) clearance rate in the early group was higher than that in the late group (40.7% vs. 14.9%, P=0.009). There were no significant differences between early and late groups by ICU LOS (P=0.748), hospital LOS (P=0.369), mechanical ventilation time (P=0.128), and CRRT ratio (P=0.637). The independent risk factors for 28-day mortality included being male (odds ratio [OR]=3.288, 95% confidence interval [CI]: 1.236 to 8.745, P = 0.017), time to norepinephrine initiation >1 h (OR=4.564, 95% CI: 1.382 to 15.079, P = 0.013), and time to achieve MAP ≥65 mmHg (OR=1.800, 95% CI: 1.171 to 2.767, P = 0.007).

Conclusions

Norepinephrine initiation ≤1 h is associated with lower 28-day mortality in patients with septic shock. Early norepinephrine administration is also associated with a shorter time to achieve MAP ≥65 mmHg, lower 24-hour intravenous fluids volume, and higher 6-hour Lac clearance rate. Being male, time to achieve MAP ≥65 mmHg, and norepinephrine initiation >1 h are independent risk factors for 28-day mortality.Trial registration Chinese Clinical Trial Registry Identifier: ChiCTR2100044071.

Early mobilisation in patients with shock and receiving vasoactive drugs in the intensive care unit: A systematic review and meta-analysis of observational studies

OBJECTIVE

The aim of the study was to assess the feasibility and safety of early mobilisation in patients with shock requiring vasoactive drugs in the intensive care unit (ICU).

DESIGN

Systematic review and meta-analysis.

SETTING

Intensive care unit (ICU).

PATIENTS OR PARTICIPANTS

Adult patients requiring vasoactive drugs who received early mobilisation in the intensive care unit.

INTERVENTIONS

A systematic search was conducted using the databases PubMed, Cochrane Library, Scopus, Medline Ovid, Science Direct, and CINAHL, including observational studies involving adult patients requiring vasoactive drugs who received early mobilisation. A meta-analysis was performed on the proportion of safety events and the proportion of early mobilisation in patients with high, moderate, and low doses of vasoactive drugs.

MAIN VARIABLES OF INTEREST

Feasibility, safety events, and the maximum level of activity achieved during early mobilisation.

RESULTS

The search yielded 1875 studies, of which 8 were included in the systematic review and 5 in the meta-analysis. The results showed that 64% (95% CI: 34%-95%, p<0.05) of patients were mobilised with low doses of vasoactive drugs, 30% (95% CI: 7%-53%, p<0.05) with moderate doses, and 7% (95% CI: 3%-16%, p 0.17) with high doses. The proportion of adverse events was low, at 2% (95% CI: 1%-4%, p<0.05).

CONCLUSIONS

Early mobilisation in patients with shock and the need for vasoactive drugs is feasible and generally safe. However, there is an emphasis on the need for further high-quality research to confirm these findings.

Low-intensity pulsed ultrasound elevates blood pressure for shock

Fluid replacement is the primary treatment for life-threatening shock but is challenging in harsh environments. This study explores low-intensity pulsed ultrasound (LIPUS) as a resuscitation strategy. Cervical LIPUS stimulation effectively elevated blood pressure in shocked rats. It also improved cerebral and multiorgan perfusion. Mechanistically, LIPUS activated pathways related to sympathetic nerve excitation and vascular smooth muscle contraction, increasing plasma catecholamines and stimulating blood pressure-regulating neural nuclei. Partial sympathetic nerve transection reduced LIPUS efficacy, while complete inhibition of these nuclei abolished the response. Preliminary clinical trials demonstrated LIPUS's ability to raise blood pressure in shock patients. The findings suggest that LIPUS enhances sympathetic nerve activity and activates blood pressure-regulating nuclei, offering a noninvasive, neuromodulation-based approach to shock treatment. This method holds potential for improving blood pressure and organ perfusion in shock patients, especially in resource-limited environments.

Development and validation of a clinical prediction model for pneumonia - associated bloodstream infections

Purpose

The aim of this study was to develop a valuable clinical prediction model for pneumonia-associated bloodstream infections (PABSIs).

Patients and methods

The study retrospectively collected clinical data of pneumonia patients at the First Medical Centre of the Chinese People's Liberation Army General Hospital from 2019 to 2024. Patients who met the definition of pneumonia-associated bloodstream infections (PABSIs) were selected as the main research subjects. A prediction model for the probability of bloodstream infections (BSIs) in pneumonia patients was constructed using a combination of LASSO regression and logistic regression. The performance of the model was verified using several indicators, including receiver operating characteristic (ROC) curve, calibration curve, decision curve analysis (DCA) and cross validation.

Results

A total of 423 patients with confirmed pneumonia were included in the study, in accordance with the Inclusion Criteria and Exclusion Criteria. Of the patients included in the study, 73 developed a related bloodstream infection (BSI). A prediction model was constructed based on six predictors: long-term antibiotic use, invasive mechanical ventilation, glucocorticoids, urinary catheterization, vasoactive drugs, and central venous catheter placement. The areas under the curve (AUC) of the training set and validation set were 0.83 and 0.80, respectively, and the calibration curve demonstrated satisfactory agreement between the two.

Conclusion

This study has successfully constructed a prediction model for bloodstream infections associated with pneumonia cases, which has good stability and predictability and can help guide clinical work.

Age Differences in Venoarterial Extracorporeal Membrane Oxygenation for Cardiogenic Shock: Trends in Application and Outcome From the Chinese Extracorporeal Life Support Registry

Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly used for cardiogenic shock (CS) in adults, with age-influencing outcomes. Data from the Chinese Extracorporeal Life Support (CSECLS) Organization registry (January 2017-July 2023) were analyzed to assess in-hospital mortality in VA-ECMO for CS. Patients ≤65 years were categorized as young, and those >65 as elder. The primary outcome was in-hospital mortality, with secondary outcomes including ECMO weaning, 30 day survival, and complications. Of 5,127 patients, the young group (73.4%) had a median age of 51.0 (40.0-58.0) years, and the elder group (26.6%) had a median age of 71.0 (68.0-75.0) years. The in-hospital mortality was lower in the younger group (45.1%) compared with the elder group (52.6%, p < 0.001). The young group also had higher ECMO weaning rates (79.4% vs. 74.8%, p < 0.001) and 30 day survival (59.1% vs. 51.3%, p < 0.001). Bleeding, renal, and pulmonary complications were more frequent in young patients, though not statistically significant. Young patients undergoing VA-ECMO for CS generally have better outcomes than older patients, though careful selection is crucial to manage complications.

Impact of tadalafil on cardiovascular and organ dysfunction induced by experimental sepsis

BACKGROUND

Sepsis is a life-threatening condition that affects the cardiovascular and renal systems. Severe hypotension during sepsis compromises tissue perfusion, which can lead to multiple organ dysfunction and death. Phosphodiesterase 5 (PDE5) degrades intracellular cyclic guanosine monophosphate (cGMP) levels which promotes vasodilatation in specific sites. Our previous studies show that inhibiting cGMP production in early sepsis increases mortality, implying a protective role for cGMP production. Then, we hypothesized that cGMP increased by tadalafil (PDE5 inhibitor) could improve microcirculation and prevent sepsis-induced organ dysfunction.

METHODS

Rats were submitted to cecal ligation and puncture (CLP) sepsis model and treated with tadalafil (2 mg/kg, s.c.) 8 hours after the procedure. Hemodynamic, inflammatory and biochemical assessments were performed 24 hours after sepsis induction. Moreover, the effect of tadalafil on the survival of septic rats was evaluated for 5 days.

RESULTS

Tadalafil treatment improves basal renal blood flow during sepsis and preserves it during noradrenaline infusion. Sepsis induces hypotension, impaired response to noradrenaline, and increased cardiac and renal neutrophil infiltration, in addition to increased levels of plasma nitric oxide and lactate. None of these dysfunctions were changed by tadalafil. Additionally, tadalafil treatment did not increase the survival rate of septic rats.

CONCLUSIONS

Tadalafil improved microcirculation of septic animals; however, no beneficial effects were observed on macrocirculation and inflammation parameters. Then, the potential benefit of tadalafil in the prognosis of sepsis should be evaluated within a therapeutic strategy covering all sepsis injury mechanisms.

Multi-Omics and Network-Based Drug Repurposing for Septic Cardiomyopathy

BACKGROUND/OBJECTIVES

Septic cardiomyopathy (SCM) is a severe cardiac complication of sepsis, characterized by cardiac dysfunction with limited effective treatments. This study aimed to identify repurposable drugs for SCM by integrated multi-omics and network analyses.

METHODS

We generated a mouse model of SCM induced by lipopolysaccharide (LPS) and then obtained comprehensive metabolic and genetic data from SCM mouse hearts using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and RNA sequencing (RNA-seq). Using network proximity analysis, we screened for FDA-approved drugs that interact with SCM-associated pathways. Additionally, we tested the cardioprotective effects of two drug candidates in the SCM mouse model and explored their mechanism-of-action in H9c2 cells.

RESULTS

Network analysis identified 129 drugs associated with SCM, which were refined to 14 drug candidates based on strong network predictions, proven anti-infective effects, suitability for ICU use, and minimal side effects. Among them, acetaminophen and pyridoxal phosphate significantly improved cardiac function in SCM moues, as demonstrated by the increased ejection fraction (EF) and fractional shortening (FS), and the reduced levels of cardiac injury biomarkers: B-type natriuretic peptide (BNP) and cardiac troponin I (cTn-I). In vitro assays revealed that acetaminophen inhibited prostaglandin synthesis, reducing inflammation, while pyridoxal phosphate restored amino acid balance, supporting cellular function. These findings suggest that both drugs possess protective effects against SCM.

CONCLUSIONS

This study provides a robust platform for drug repurposing in SCM, identifying acetaminophen and pyridoxal phosphate as promising candidates for clinical translation, with the potential to improve treatment outcomes in septic patients with cardiac complications.

Comparison of Early and Late Norepinephrine Administration in Patients With Septic Shock: A Systematic Review and Meta-Analysis

BACKGROUND

Vasopressor administration at an appropriate time is crucial, but the optimal timing remains controversial.

RESEARCH QUESTION

Does early vs late norepinephrine administration impact the prognosis of septic shock?

STUDY DESIGN AND METHODS

Searches were conducted in PubMed, EMBASE, the Cochrane Library, and KMbase databases. We included studies of adults with sepsis and categorized patients into an early and late norepinephrine group according to specific time points or differences in norepinephrine use protocols. The primary outcome was overall mortality. The secondary outcomes included length of stay in the ICU, days free from ventilator use, days free from renal replacement therapy, days free from vasopressor use, adverse events, and total fluid volume.

RESULTS

Twelve studies (four randomized controlled trials [RCTs] and eight observational studies) comprising 7,281 patients were analyzed. For overall mortality, no significant difference was found between the early norepinephrine group and late norepinephrine group in RCTs (OR, 0.70; 95% CI, 0.41-1.19) or observational studies (OR, 0.83; 95% CI, 0.54-1.29). In the two RCTs without a restrictive fluid strategy that prioritized vasopressors and lower IV fluid volumes, the early norepinephrine group showed significantly lower mortality than the late norepinephrine group (OR, 0.49; 95%, CI, 0.25-0.96). The early norepinephrine group demonstrated more mechanical ventilator-free days in observational studies (mean difference, 4.06; 95% CI, 2.82-5.30). The incidence of pulmonary edema was lower in the early norepinephrine group in the three RCTs that reported this outcome (OR, 0.43; 95% CI, 0.25-0.74). No differences were found in the other secondary outcomes.

INTERPRETATION

Overall mortality did not differ significantly between early and late norepinephrine administration for septic shock. However, early norepinephrine administration seemed to reduce pulmonary edema incidence, and mortality improvement was observed in studies without fluid restriction interventions, favoring early norepinephrine use.

Association between estimated pulse wave velocity and in-hospital mortality of patients with acute kidney injury: a retrospective cohort analysis of the MIMIC-IV database

BACKGROUND

Estimated pulse wave velocity (ePWV) has been found to be an independent predictor of cardiovascular mortality and kidney injury, which can be estimated noninvasively. This study aimed to investigate the association between ePWV and in-hospital mortality in critically ill patients with acute kidney injury (AKI).

METHODS

This study included 5960 patients with AKI from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. The low and high ePWV groups were compared using a Kaplan-Meier survival curve to evaluate the differences in survival status. Cox proportional hazards models were used to explore the association between ePWV and in-hospital mortality in critically ill patients with AKI. To further examine the dose-response relationship, we used a restricted cubic spline (RCS) model. Stratification analyses were conducted to investigate the effect of ePWV on hospital mortality across various subgroups.

RESULTS

Survival analysis indicated that patients with high ePWV had a lower survival rate than those with low ePWV. Following adjustment, high ePWV demonstrated a statistically significant association with an increased risk of in-hospital mortality among AKI patients (HR = 1.53, 95% CI = 1.36-1.71, p < 0.001). Analysis using the RCS model confirmed a linear increase in the risk of hospital mortality as the ePWV values increased (P for nonlinearity = 0.602).

CONCLUSIONS

A high ePWV was significantly associated with an increased risk of in-hospital mortality among patients with AKI. Furthermore, ePWV was an independent predictor of in-hospital mortality in critically ill patients with AKI.

Crystalloid volume versus catecholamines for management of hemorrhagic shock during esophagectomy: assessment of microcirculatory tissue oxygenation of the gastric conduit in a porcine model using hyperspectral imaging - an experimental study

INTRODUCTION

Oncologic esophagectomy is a two-cavity procedure with considerable morbidity and mortality. Complex anatomy and the proximity to major vessels constitute a risk for massive intraoperative hemorrhage. Currently, there is no conclusive consensus on the ideal anesthesiologic countermeasure in case of such immense blood loss. The objective of this work was to identify the most promising anesthesiologic management in case of intraoperative hemorrhage with regards to tissue perfusion of the gastric conduit during esophagectomy using hyperspectral imaging.

MATERIAL AND METHODS

An established live porcine model ( n =32) for esophagectomy was used with gastric conduit formation and simulation of a linear stapled side-to-side esophagogastrostomy. After a standardized procedure of controlled blood loss of about 1 l per pig, the four experimental groups ( n =8 each) differed in anesthesiologic intervention, that is, (I) permissive hypotension, (II) catecholamine therapy using noradrenaline, (III) crystalloid volume supplementation, and (IV) combined crystalloid volume supplementation with noradrenaline therapy. Hyperspectral imaging tissue oxygenation (StO 2 ) of the gastric conduit was evaluated and correlated with systemic perfusion parameters. Measurements were conducted before (T0) and after (T1) laparotomy, after hemorrhage (T2), and 60 min (T3) and 120 min (T4) after anesthesiologic intervention.

RESULTS

StO 2 values of the gastric conduit showed significantly different results between the four experimental groups, with 63.3% (±7.6%) after permissive hypotension (I), 45.9% (±6.4%) after catecholamine therapy (II), 70.5% (±6.1%) after crystalloid volume supplementation (III), and 69.0% (±3.7%) after combined therapy (IV). StO 2 values correlated strongly with systemic lactate values (r=-0.67; CI -0.77 to -0.54), which is an established prognostic factor.

CONCLUSION

Crystalloid volume supplementation (III) yields the highest StO 2 values and lowest systemic lactate values and therefore appears to be the superior primary treatment strategy after hemorrhage during esophagectomy with regards to microcirculatory tissue oxygenation of the gastric conduit.

The Association Between Vasopressin and Adverse Kidney Outcomes in Children and Young Adults Requiring Vasopressors on Continuous Renal Replacement Therapy

OBJECTIVES

Continuous renal replacement therapy (CRRT) and shock are both associated with high morbidity and mortality in the ICU. Adult data suggest renoprotective effects of vasopressin vs. catecholamines (norepinephrine and epinephrine). We aimed to determine whether vasopressin use during CRRT was associated with improved kidney outcomes in children and young adults.

DESIGN

Secondary analysis of Worldwide Exploration of Renal Replacement Outcomes Collaborative in Kidney Disease (WE-ROCK), a multicenter, retrospective cohort study.

SETTING

Neonatal, cardiac, PICUs at 34 centers internationally from January 1, 2015, to December 31, 2021.

PATIENTS/SUBJECTS

Patients younger than 25 years receiving CRRT for acute kidney injury and/or fluid overload and requiring vasopressors. Patients receiving vasopressin were compared with patients receiving only norepinephrine/epinephrine. The impact of timing of vasopressin relative to CRRT start was assessed by categorizing patients as: early (on or before day 0), intermediate (days 1-2), and late (days 3-7).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 1016 patients, 665 (65%) required vasopressors in the first week of CRRT. Of 665, 248 (37%) received vasopressin, 473 (71%) experienced Major Adverse Kidney Events at 90 days (MAKE-90) (death, renal replacement therapy dependence, and/or > 125% increase in serum creatinine from baseline 90 days from CRRT initiation), and 195 (29%) liberated from CRRT on the first attempt within 28 days. Receipt of vasopressin was associated with higher odds of MAKE-90 (adjusted odds ratio [aOR], 1.80; 95% CI, 1.20-2.71; p = 0.005) but not liberation success. In the vasopressin group, intermediate/late initiation was associated with higher odds of MAKE-90 (aOR, 2.67; 95% CI, 1.17-6.11; p = 0.02) compared with early initiation.

CONCLUSIONS

Nearly two-thirds of children and young adults receiving CRRT required vasopressors, including over one-third who received vasopressin. Receipt of vasopressin was associated with more MAKE-90, although earlier initiation in those who received it appears beneficial. Prospective studies are needed to understand the appropriate timing, dose, and subpopulation for use of vasopressin.

BILL Strategy: Points to Consider During the Performance and Interpretation of Critical Care Echocardiography

The growing utilization of critical care echocardiography (CCE) by clinicians necessitates a meticulous review of clinical conditions in critically ill patients, both before and during the examination. The reviewing process of clinical conditions minimizes the risk of overlooking or misinterpreting crucial findings. This article proposes a comprehensive strategy, namely BILL strategy, to integrate into the CCE protocol, where "B" represents baseline respiratory and hemodynamic support, "I" signifies information gleaned from invasive monitoring, including central venous pressure and thermodilution-derived cardiac output, the first "L" denotes laboratory results such as central venous oxygen saturation, troponin, and brain natriuretic peptide, and the second "L" refers to lung ultrasound data. Combining the BILL strategy with CCE can enhance comprehensive understanding of critical conditions, potentially leading to improved diagnostic accuracy and patient outcomes.

Clinical Effect of Norepinephrine Combined with Esmolol Treatment in Patients with Septic Shock and Its Impact on Prognosis

Objective

To unveil the influence of norepinephrine (NE) combined with esmolol treatment on cardiac function, hemodynamics, inflammatory factor levels, and prognosis in patients with septic shock.

Methods

Ninety-six patients with septic shock admitted to our hospital from January 2021 to June 2023 were retrospectively analyzed and divided into the control and observation groups according to the different treatment methods. The control group was treated with standard anti-infection and fluid resuscitation, followed by NE administration [with an infusion rate of 0.1-0.5 μg/(kg-min)]. The observation group was treated with esmolol [starting pumping rate of 50 μg/(kg-min) and adjusting the pumping rate according to the target heart rate] in combination with the control group. Changes in hemodynamic parameters, including heart rate, mean arterial pressure, central venous pressure, cardiac index, stroke volume index, and systemic vascular resistance index, were monitored by pulse-indicating continuous cardiac output monitors before treatment (T0), 24h after treatment (T1), and 72h after treatment (T2); changes in cardiac function before and after 72h of treatment, indicators of inflammatory factors before and after treatment, and indicators of oxygenation metabolism were assessed; and adverse drug reactions during treatment were recorded in both groups.

Results

NE combined with esmolol treatment improved the efficacy of patients with septic shock; was beneficial for the enhancement of blood perfusion in patients; improved the patient's cardiac function, reduced myocardial injury, and suppressed the inflammatory response in patients; improved the oxygenation metabolism and the prognosis of patients; did not significantly increase the adverse drug reactions of patients and had a better safety profile.

Conclusion

NE combined with esmolol treatment can improve the efficacy of patients with septic shock, improve their cardiac function and hemodynamic indices, reduce myocardial injury and inflammatory response, and have a better safety profile, which is conducive to improving patient prognosis and reducing mortality.

Blood pressure response index and clinical outcomes in patients with septic shock: a multicenter cohort study

BACKGROUND

Sepsis is a leading cause of mortality in intensive care units and vasoactive drugs are widely used in septic patients. The cardiovascular response of septic shock patients during resuscitation therapies and the relationship of the cardiovascular response and clinical outcome has not been clearly described.

METHODS

We included adult patients admitted to the ICU with sepsis from Peking Union Medical College Hospital (internal), Medical Information Mart for Intensive Care IV (MIMIC-IV) and eICU Collaborative Research Database (eICU-CRD). The Blood Pressure Response Index (BPRI) was defined as the ratio between the mean arterial pressure and the vasoactive-inotropic score. BRRI was compared with existing risk scores on predicting in-hospital death. The relationship between BPRI and in-hospital mortality was calculated. A XGBoost's machine learning model identified the features that influence short-term changes in BPRI.

FINDINGS

There were 2139, 9455, and 4202 patients in the internal, MIMIC-IV and eICU-CRD cohorts, respectively. BPRI had a better AUROC for predicting in-hospital mortality than SOFA (0.78 vs. 0.73, p = 0.01) and APS (0.78 vs. 0.74, p = 0.03) in the internal cohort. The estimated odds ratio for death per unit decrease in BPRI was 1.32 (95% CI 1.20-1.45) when BPRI was below 7.1 vs. 0.99 (95% CI 0.97-1.01) when BPRI was above 7.1 in the internal cohort; similar relationships were found in MIMIC-IV and eICU-CRD. Respiratory support and latest cumulative 12-h fluid balance were intervention-related features influencing BPRI.

INTERPRETATION

BPRI is an easy, rapid, precise indicator of the response of patients with septic shock to vasoactive drugs. It is a comparable and even better predictor of prognosis than SOFA and APS in sepsis and it is simpler and more convenient in use. The application of BPRI could help clinicians identify potentially at-risk patients and provide clues for treatment.

FUNDING

Fundings for the Beijing Municipal Natural Science Foundation; the National High Level Hospital Clinical Research Funding; the CAMS Innovation Fund for Medical Sciences (CIFMS) from Chinese Academy of Medical Sciences and the National Key R&D Program of China, Ministry of Science and Technology of the People's Republic of China.

Catecholamine treatment induces reversible heart injury and cardiomyocyte gene expression

BACKGROUND

Catecholamines are commonly used as therapeutic drugs in intensive care medicine to maintain sufficient organ perfusion during shock. However, excessive or sustained adrenergic activation drives detrimental cardiac remodeling and may lead to heart failure. Whether catecholamine treatment in absence of heart failure causes persistent cardiac injury, is uncertain. In this experimental study, we assessed the course of cardiac remodeling and recovery during and after prolonged catecholamine treatment and investigated the molecular mechanisms involved.

RESULTS

C57BL/6N wild-type mice were assigned to 14 days catecholamine treatment with isoprenaline and phenylephrine (IsoPE), treatment with IsoPE and subsequent recovery, or healthy control groups. IsoPE improved left ventricular contractility but caused substantial cardiac fibrosis and hypertrophy. However, after discontinuation of catecholamine treatment, these alterations were largely reversible. To uncover the molecular mechanisms involved, we performed RNA sequencing from isolated cardiomyocyte nuclei. IsoPE treatment resulted in a transient upregulation of genes related to extracellular matrix formation and transforming growth factor signaling. While components of adrenergic receptor signaling were downregulated during catecholamine treatment, we observed an upregulation of endothelin-1 and its receptors in cardiomyocytes, indicating crosstalk between both signaling pathways. To follow this finding, we treated mice with endothelin-1. Compared to IsoPE, treatment with endothelin-1 induced minor but longer lasting changes in cardiomyocyte gene expression. DNA methylation-guided analysis of enhancer regions identified immediate early transcription factors such as AP-1 family members Jun and Fos as key drivers of pathological gene expression following catecholamine treatment.

CONCLUSIONS

The results from this study show that prolonged catecholamine exposure induces adverse cardiac remodeling and gene expression before the onset of left ventricular dysfunction which has implications for clinical practice. The observed changes depend on the type of stimulus and are largely reversible after discontinuation of catecholamine treatment. Crosstalk with endothelin signaling and the downstream transcription factors identified in this study provide new opportunities for more targeted therapeutic approaches that may help to separate desired from undesired effects of catecholamine treatment.

Effect of Norepinephrine on Peripheral Perfusion Index and Its Association With the Prognosis of Patients With Sepsis

Background: To evaluate whether the use of norepinephrine during the management of patients with sepsis affects the perfusion index (PI) and patient outcomes. Methods: We retrospectively studied patients with septic shock between January 2014 and December 2018 who had undergone Pulse index Continuous Cardiac Output-Plus cardiac output monitoring and received norepinephrine during the management. We collected data regarding basic clinical characteristics. Hemodynamic parameters, including lactate, PI, and norepinephrine dose at T0 and 24 h after Pulse index Continuous Cardiac Output catheterization (T24) were obtained. Results: The PI of the nonsurvivor group (n  =  44) was significantly lower than that of the survivor group (n  =  144) at T24, and the lactate level of the nonsurvivor group was significantly higher than that of the survivor group. The multiple logistic regression analysis suggested that the norepinephrine dose and PI were the most independent risk and protective factors, respectively, for intensive care unit mortality. The area under the curve for a poor prognosis was 0.847 (95% confidence interval, 0.782-0.912). The optimal cutoff value of the PI at T24 to predict intensive care unit mortality was 0.6, with a sensitivity of 77.1% and a specificity of 80%. Based on this optimal cutoff value, we divided patients into groups with PI ≥ 0.6 (n  =  125) and PI < 0.6 (n  =  59). The lactate level of the PI < 0.6 group was higher than that of the PI ≥ 0.6 group at T24. The PI < 0.6 group showed a significantly higher sublingual dose of norepinephrine indicators than the PI ≥ 0.6 group. The PI showed a strong negative correlation with norepinephrine dose (r  =  -0.344, P < .001) and lactate (r  =  -0.291, P < .001). Conclusions: A higher PI is a protective factor, and a higher dose of norepinephrine is a risk factor for the prognosis of critically ill patients with septic shock. A lower PI was associated with a higher dose of norepinephrine.

Role of toll-like receptor-mediated pyroptosis in sepsis-induced cardiomyopathy

Sepsis, a life-threatening dysregulated status of the host response to infection, can cause multiorgan dysfunction and mortality. Sepsis places a heavy burden on the cardiovascular system due to the pathological imbalance of hyperinflammation and immune suppression. Myocardial injury and cardiac dysfunction caused by the aberrant host responses to pathogens can lead to cardiomyopathy, one of the most critical complications of sepsis. However, many questions about the specific mechanisms and characteristics of this complication remain to be answered. The causes of sepsis-induced cardiac dysfunction include abnormal cardiac perfusion, myocardial inhibitory substances, autonomic dysfunction, mitochondrial dysfunction, and calcium homeostasis dysregulation. The fight between the host and pathogens acts as the trigger for sepsis-induced cardiomyopathy. Pyroptosis, a form of programmed cell death, plays a critical role in the progress of sepsis. Toll-like receptors (TLRs) act as pattern recognition receptors and participate in innate immune pathways that recognize damage-associated molecular patterns as well as pathogen-associated molecular patterns to mediate pyroptosis. Notably, pyroptosis is tightly associated with cardiac dysfunction in sepsis and septic shock. In line with these observations, induction of TLR-mediated pyroptosis may be a promising therapeutic approach to treat sepsis-induced cardiomyopathy. This review focuses on the potential roles of TLR-mediated pyroptosis in sepsis-induced cardiomyopathy, to shed light on this promising therapeutic approach, thus helping to prevent and control septic shock caused by cardiovascular disorders and improve the prognosis of sepsis patients.

Postoperative norepinephrine versus dopamine in patients undergoing noncardiac surgery: a propensity-matched analysis using a nationwide intensive care database

BACKGROUND

Choosing catecholamines, such as norepinephrine and dopamine, for perioperative blood pressure control is essential for anesthesiologists and intensivists. However, studies specific to noncardiac surgery are limited. Therefore, we aimed to evaluate the effects of postoperative norepinephrine and dopamine on clinical outcomes in adult noncardiac surgery patients by analyzing a nationwide intensive care patient database.

METHODS

The Japanese Intensive care PAtient Database (JIPAD) was used for this multicenter retrospective study. Adult patients in the JIPAD who received norepinephrine or dopamine within 24 h after noncardiac surgery in 2018-2020 were included. We compared the norepinephrine and dopamine groups using a one-to-one propensity score matching analysis. The primary outcome was in-hospital mortality. Secondary outcomes were intensive care unit (ICU) mortality, hospital length of stay, and ICU length of stay.

RESULTS

A total of 6,236 eligible patients from 69 ICUs were allocated to the norepinephrine (n = 4,652) or dopamine (n = 1,584) group. Propensity score matching was used to create a matched cohort of 1,230 pairs. No differences in the in-hospital mortality was found between the two propensity score matched groups (risk difference: 0.41%, 95% CI [-1.15, 1.96], P = 0.608). Among the secondary outcomes, only the ICU length of stay was significantly shorter in the norepinephrine group than in the dopamine group (median length: 3 vs. 4 days, respectively; P < 0.001).

CONCLUSIONS

In adult patients after noncardiac surgery, norepinephrine was not associated with decreased mortality but was associated with a shorter ICU length of stay than dopamine.

Echocardiographic profiles and hemodynamic response after vasopressin initiation in septic shock: A cross-sectional study

PURPOSE

Vasopressin, used as a catecholamine adjunct, is a vasoconstrictor that may be detrimental in some hemodynamic profiles, particularly left ventricular (LV) systolic dysfunction. This study tested the hypothesis that echocardiographic parameters differ between patients with a hemodynamic response after vasopressin initiation and those without a response.

METHODS

This retrospective, single-center, cross-sectional study included adults with septic shock receiving catecholamines and vasopressin with an echocardiogram performed after shock onset but before vasopressin initiation. Patients were grouped by hemodynamic response, defined as decreased catecholamine dosage with mean arterial pressure ≥ 65 mmHg six hours after vasopressin initiation, with echocardiographic parameters compared. LV systolic dysfunction was defined as LV ejection fraction (LVEF) <45%.

RESULTS

Of 129 included patients, 72 (56%) were hemodynamic responders. Hemodynamic responders, versus non-responders, had higher LVEF (61% [55%,68%] vs. 55% [40%,65%]; p = 0.02) and less-frequent LV systolic dysfunction (absolute difference  -16%; 95% CI -30%,-2%). Higher LVEF was associated with higher odds of hemodynamic response (for each LVEF 10%, response OR 1.32; 95% CI 1.04-1.68). Patients with LV systolic dysfunction, versus without LV systolic dysfunction, had higher mortality risk (HR(t) = e[0.81-0.1*t]; at t = 0, HR 2.24; 95% CI 1.08-4.64).

CONCLUSIONS

Pre-drug echocardiographic profiles differed in hemodynamic responders after vasopressin initiation versus non-responders.

Severe fluctuation in mean perfusion pressure is associated with increased risk of in-hospital mortality in critically ill patients with central venous pressure monitoring: A retrospective observational study

BACKGROUND

The mean perfusion pressure (MPP) was recently proposed to personalize tissue perfusion pressure management in critically ill patients. Severe fluctuation in MPP may be associated with adverse outcomes. We sought to determine if higher MPP variability was correlated with increased mortality in critically ill patients with CVP monitoring.

METHODS

We designed a retrospective observational study and analyzed data stored in the eICU Collaborative Research Database. Validation test was conducted in MIMIC-III database. The exposure was the coefficient of variation (CV) of MPP in the primary analyses, using the first 24 hours MPP data recorded within 72 hours in the first ICU stay. Primary endpoint was in-hospital mortality.

RESULTS

A total of 6,111 patients were included. The in-hospital mortality of 17.6% and the median MPP-CV was 12.3%. Non-survivors had significantly higher MPP-CV than survivors (13.0% vs 12.2%, p<0.001). After accounting for confounders, the highest MPP-CV in decile (CV > 19.2%) were associated with increased risk of hospital mortality compared with those in the fifth and sixth decile (adjusted OR: 1.38, 95% Cl: 1.07-1.78). These relationships remained remarkable in the multiple sensitivity analyses. The validation test with 4,153 individuals also confirmed the results when MPP-CV > 21.3% (adjusted OR: 1.46, 95% Cl: 1.05-2.03).

CONCLUSIONS

Severe fluctuation in MPP was associated with increased short-term mortality in critically ill patients with CVP monitoring.

Tendency of dynamic vasoactive and inotropic medications data as a robust predictor of mortality in patients with septic shock: An analysis of the MIMIC-IV database

Background

Septic shock patients fundamentally require delicate vasoactive and inotropic agent administration, which could be quantitatively and objectively evaluated by the vasoactive–inotropic score (VIS); however, whether the dynamic trends of high-time-resolution VIS alter the clinical outcomes remains unclear. Thus, this study proposes the term VIS Reduction Rate (VRR) to generalise the tendency of dynamic VIS, to explore the association of VRR and mortality for patients with septic shock.

Methods

We applied dynamic and static VIS data to predict ICU mortality by two models: the long short-term memory (LSTM) deep learning model, and the extreme gradient boosting (XGBoost), respectively. The specific target cohort was extracted from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database by the sophisticated structured query language (SQL). Enrolled patients were divided into four groups by VRR value: ≥50%, 0 ~ 50%, −50% ~ 0, and &lt; −50%. Statistical approaches included pairwise propensity score matching (PSM), Cox proportional hazards regression, and two doubly robust estimation models to ensure the robustness of the results. The primary and secondary outcomes were ICU mortality and in-hospital mortality, respectively.

Results

VRR simplifies the dosing trends of vasoactive and inotropic agents represented by dynamic VIS data while requiring fewer data. In total, 8,887 septic shock patients were included. Compared with the VRR ≥50% group, the 0 ~ 50%, −50% ~ 0, and &lt; −50% groups had significantly higher ICU mortality [hazard ratio (HR) 1.32, 95% confidence interval (CI) 1.17–1.50, p &lt; 0.001; HR 1.79, 95% CI 1.44–2.22, p &lt; 0.001; HR 2.07, 95% CI 1.61–2.66, p &lt; 0.001, respectively] and in-hospital mortality [HR 1.43, 95% CI 1.28–1.60, p &lt; 0.001; HR 1.75, 95% CI 1.45–2.11, p &lt; 0.001; HR 2.00, 95% CI 1.61–2.49, p &lt; 0.001, respectively]. Similar findings were observed in two doubly robust estimation models.

Conclusion

The trends of dynamic VIS in ICU might help intensivists to stratify the prognosis of adult patients with septic shock. A lower decline of VIS was remarkably associated with higher ICU and in-hospital mortality among septic shock patients receiving vasoactive–inotropic therapy for more than 24 h.

Evaluating the effects of Esmolol on cardiac function in patients with Septic cardiomyopathy by Speck-tracking echocardiography-a randomized controlled trial

BACKGROUND

Esmolol as one treatment of sepsis induced cardiomyopathy (SIC) is still controversial. The objective of this study is to evaluate cardiac function after reducing heart rate by Esmolol in patients with SIC using speck-tracking echocardiography.

METHODS

This study was a single-center, prospective, and randomized controlled study. A total of 100 SIC patients with a heart rate more than 100/min, admitted to the Intensive Care Department of Tianjin Third Central Hospital from March 1, 2020 to September 30, 2021, were selected as the research subjects. They were randomly divided into the Esmolol group (Group E) and the conventional treatment group (Group C), each with 50 cases. The target heart rate of patients in Group E was controlled between 80/min and 100/min. Speck-tracking echocardiography (STE) and pulse indicating continuous cardiac output monitoring (PICCO) were performed in both groups at 1 h, 24 h, 48 h, 72 h, 96 h and 7 d after admission, with data concerning left ventricular global longitudinal strain (GLS), left ventricular ejection fraction (LVEF) and global ejection fraction (GEF), left ventricular systolic force index (dP/dtmx) were obtained, respectively. Hemodynamics and other safety indicators were monitored throughout the whole process. These subjects were followed up to 90 d, with their mortality recorded at Day 28 and Day 90, respectively. Statistical analyses were performed using SPSS version 21.

RESULTS

With 24 h of Esmolol, all patients in Group E achieved the target heart rate, and there was no deterioration of GLS, or adverse events. However, compared with those in Group C, their GLS, GEF and dP/dtmx were increased, and the difference was statistically significant (P > 0.05). Compared with patients in Group C, those in Group E had lower short-term mortality, and logistic regression analysis also suggested that Esmolol improved patient outcomes.

CONCLUSION

In SIC patients, the application of Esmolol to lower heart rate decreased their short-term mortality while not making any impairment on the myocardial contractility.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR2100047513. Registered June 20, 2021- Retrospectively registered, http://www.chictr.org.cn/index.aspx . The study protocol followed the CONSORT guidelines. The study protocol was performed in the relevant guidelines.

Identification of Bioactive Peptides from a Laminaria digitata Protein Hydrolysate Using In Silico and In Vitro Methods to Identify Angiotensin-1-Converting Enzyme (ACE-1) Inhibitory Peptides

Bioactive peptides range in size from 2-30 amino acids and may be derived from any protein-containing biomass using hydrolysis, fermentation or high-pressure processing. Pro-peptides or cryptides result in shorter peptide sequences following digestion and may have enhanced bioactivity. Previously, we identified a protein hydrolysate generated from Laminaria digitata that inhibited ACE-1 in vitro and had an ACE-1 IC50 value of 590 µg/mL compared to an ACE-1 IC50 value of 500 µg/mL (~2.3 µM) observed for the anti-hypertensive drug Captopril©. A number of peptide sequences (130 in total) were identified using mass spectrometry from a 3 kDa permeate of this hydrolysate. Predicted bioactivities for these peptides were determined using an in silico strategy previously published by this group utilizing available databases including Expasy peptide cutter, BIOPEP and Peptide Ranker. Peptide sequences YIGNNPAKGGLF and IGNNPAKGGLF had Peptide Ranker scores of 0.81 and 0.80, respectively, and were chemically synthesized. Synthesized peptides were evaluated for ACE-1 inhibitory activity in vitro and were found to inhibit ACE-1 by 80 ± 8% and 91 ± 16%, respectively. The observed ACE-1 IC50 values for IGNNPAKGGLF and YIGNNPAKGGLF were determined as 174.4 µg/mL and 133.1 µg/mL. Both peptides produced sequences following simulated digestion with the potential to inhibit Dipeptidyl peptidase IV (DPP-IV).

Dobutamine promotes the clearance of erythrocytes from the brain to cervical lymph nodes after subarachnoid hemorrhage in mice

Background: Erythrocytes and their breakdown products in the subarachnoid space (SAS) are the main contributors to the pathogenesis of subarachnoid hemorrhage (SAH). Dobutamine is a potent β₁-adrenoreceptor agonist that can increase cardiac output, thus improving blood perfusion and arterial pulsation in the brain. In this study, we investigated whether the administration of dobutamine promoted the clearance of red blood cells (RBCs) and their degraded products via meningeal lymphatic vessels (mLVs), thus alleviating neurological deficits in the early stage post-SAH. Materials and methods: Experimental SAH was induced by injecting autologous arterial blood into the prechiasmatic cistern in male C57BL/6 mice. Evans blue was injected into the cisterna magna, and dobutamine was administered by inserting a femoral venous catheter. RBCs in the deep cervical lymphatic nodes (dCLNs) were evaluated by hematoxylin-eosin staining, and the hemoglobin content in dCLNs was detected by Drabkin's reagent. The accumulation of RBCs in the dura mater was examined by immunofluorescence staining, neuronal death was evaluated by Nissl staining, and apoptotic cell death was evaluated by TUNEL staining. The Morris water maze test was used to examine the cognitive function of mice after SAH. Results: RBCs appeared in dCLNs as early as 3 h post-SAH, and the hemoglobin in dCLNs peaked at 12 h after SAH. Dobutamine significantly promoted cerebrospinal fluid (CSF) drainage from the SAS to dCLNs and obviously reduced the RBC residue in mLVs, leading to a decrease in neuronal death and an improvement in cognitive function after SAH. Conclusion: Dobutamine administration significantly promoted RBC drainage from cerebrospinal fluid in the SAS via mLVs into dCLNs, ultimately relieving neuronal death and improving cognitive function.

Multimodal strategy to counteract vasodilation in septic shock

Early initiation of a multimodal treatment strategy in the management of vasopressors during septic shock has been advocated to reduce delays in restoring adequate organ perfusion and to mitigate side effects associated with the administration of high-dose catecholamines. We provide a review that summarises the pathophysiology of vasodilation, the physiologic response to the vascular response, and the different drugs used in this situation, focusing on the need to combine early different vasopressors. Fluid loading being insufficient for counteracting vasoplegia, norepinephrine is usually the first-line vasopressor used to restore hemodynamics. Norepinephrine sparing is discussed in further detail through the concomitant use of adrenergic, vasopressinergic, and renin-angiotensin systems and the optimisation of endothelial reactivity with methylene blue. A blueprint for the construction of new studies is outlined to address the question of vasopressor selection and timing in septic shock.

Intraoperative Diastolic Hypotension-Prolonged Postoperative Hospital Stay in Patients with Gastric Cancer: A Retrospective Cohort Study with Propensity Score Matching

Purpose

In patients undergoing surgical resection for gastric cancer, perioperative hemodynamic fluctuations may affect organ perfusion, increase the incidence of postoperative complications, and prolong hospital stay.

Patients and Methods

We retrospectively identified patients who underwent resection for gastric cancer at our institution from April 1, 2015 to October 30, 2018. Demographic information, perioperative data, and information on postoperative recovery were recorded. The primary outcome was length of postoperative hospital stay; the secondary outcome was incidence of postoperative complications. Propensity score matching was performed. The associations between perioperative factors and postoperative hospital stay were analyzed using multivariable logistic regression models in the full and matched cohorts.

Results

In total, 933 patients were included; of these, 676 had diastolic hypotension (defined as diastolic blood pressure <60 mmHg for >10 min). In both cohorts, patients with diastolic hypotension had statistically significantly longer postoperative hospital stay (full: mean 14.5 ± standard deviation 10.2 vs 11.6 ± 6.5 days, P < 0.001; matched: 13.7 ± 9.9 vs 11.7 ± 6.6 days, P = 0.009) and a higher incidence of postoperative complications (full: 170 [25.1%] vs 27 [10.5%] cases, P < 0.001; matched: 60 [24.4%] vs 33 [13.4%] cases, P = 0.003), compared with patients without diastolic hypotension. After correction for confounding factors, intraoperative diastolic hypotension was associated with longer postoperative hospital stay in both the full and the matched cohort (full: HR, 1.535 [95% CI, 1.115-2.114], P = 0.009; matched: HR, 1.532 [95% CI, 1.032-2.273], P = 0.034).

Conclusion

For patients with gastric cancer, intraoperative diastolic hypotension may increase the incidence of postoperative complications and prolong postoperative hospital stay.

Mobilisation of critically ill patients receiving norepinephrine: a retrospective cohort study

BACKGROUND

Mobilisation and exercise intervention in general are safe and feasible in critically ill patients. For patients requiring catecholamines, however, doses of norepinephrine safe for mobilisation in the intensive care unit (ICU) are not defined. This study aimed to describe mobilisation practice in our hospital and identify doses of norepinephrine that allowed a safe mobilisation.

METHODS

We conducted a retrospective single-centre cohort study of 16 ICUs at a university hospital in Germany with patients admitted between March 2018 and November 2021. Data were collected from our patient data management system. We analysed the effect of norepinephrine on level (ICU Mobility Scale) and frequency (units per day) of mobilisation, early mobilisation (within 72 h of ICU admission), mortality, and rate of adverse events. Data were extracted from free-text mobilisation entries using supervised machine learning (support vector machine). Statistical analyses were done using (generalised) linear (mixed-effect) models, as well as chi-square tests and ANOVAs.

RESULTS

A total of 12,462 patients were analysed in this study. They received a total of 59,415 mobilisation units. Of these patients, 842 (6.8%) received mobilisation under continuous norepinephrine administration. Norepinephrine administration was negatively associated with the frequency of mobilisation (adjusted difference -0.07 mobilisations per day; 95% CI - 0.09, - 0.05; p ≤ 0.001) and early mobilisation (adjusted OR 0.83; 95% CI 0.76, 0.90; p ≤ 0.001), while a higher norepinephrine dose corresponded to a lower chance to be mobilised out-of-bed (adjusted OR 0.01; 95% CI 0.00, 0.04; p ≤ 0.001). Mobilisation with norepinephrine did not significantly affect mortality (p > 0.1). Higher compared to lower doses of norepinephrine did not lead to a significant increase in adverse events in our practice (p > 0.1). We identified that mobilisation was safe with up to 0.20 µg/kg/min norepinephrine for out-of-bed (IMS ≥ 2) and 0.33 µg/kg/min for in-bed (IMS 0-1) mobilisation.

CONCLUSIONS

Mobilisation with norepinephrine can be done safely when considering the status of the patient and safety guidelines. We demonstrated that safe mobilisation was possible with norepinephrine doses up to 0.20 µg/kg/min for out-of-bed (IMS ≥ 2) and 0.33 µg/kg/min for in-bed (IMS 0-1) mobilisation.

The Association of Norepinephrine Utilization With Mortality Risk in Trauma Patients

INTRODUCTION

While the pillars of trauma resuscitation are surgical hemostasis and blood product administration, norepinephrine (NE) can be used as an adjunct. The goal of this study was to evaluate the relationship between the maximum dose of NE, timing of NE administration, and mortality in trauma patients.

METHODS

Patients admitted between January 2013 and January 2021 treated with NE were reviewed. Univariate and multivariate logistic regression were used to assess whether maximum NE dose was independently associated with mortality. Optimal dosage rates for NE were determined via Youden Index. Subgroup analyses comparing those who received NE within versus after the first 24 h of admission were conducted.

RESULTS

Three hundred fifty-first trauma patients were included, with 217 (62%) surviving. Patients who died received an average maximum dose of 16.7 mcg/min compared to 9.1 mcg/min in survivors (P = 0.0003). Mortality rate increased with dosage (P < 0.0001), with doses greater than 20 mcg/min having 79% mortality. Those who received NE within the first 24 h had an inflection point in mortality at 16 mcg/min (Youden = 0.45) (OR 1.06; 95% CI 1.03-1.10). For patients who received NE after the first 24 h, an inflection point in mortality was at 10 mcg/min (Youden = 0.34) (OR 1.09; 95% CI 1.04-1.14).

CONCLUSIONS

Higher maximum doses of NE were associated with increased mortality. Patients initiated on NE more than 24 h into their admission displayed an inflection point at a lower dose than those initiated later. This suggests that trauma patients initiated on NE after 24 h from injury may have a dire prognosis.

Second- and Third-Tier Therapies for Severe Traumatic Brain Injury

Intracranial hypertension is a common finding in patients with severe traumatic brain injury. These patients need treatment in the intensive care unit, where intracranial pressure monitoring and, whenever possible, multimodal neuromonitoring can be applied. A three-tier approach is suggested in current recommendations, in which higher-tier therapies have more significant side effects. In this review, we explain the rationale for this approach, and analyze the benefits and risks of each therapeutic modality. Finally, we discuss, based on the most recent recommendations, how this approach can be adapted in low- and middle-income countries, where available resources are limited.

The effect of continuous intravenous norepinephrine infusion on systemic hemodynamics in a telemetrically-monitored mouse model of sepsis

Sepsis, a life-threatening organ dysfunction, results from dysregulated host responses to infection and still has a high incidence and mortality. Although administration of vasopressors to treat septic shock is standard of care, the benefits are not well established. We evaluated the effect of continuous intravenous norepinephrine infusion in a septic cecal ligation and puncture (CLP) mouse model, evaluating systemic hemodynamics and body temperature post-hoc. CLP surgery significantly decreased mean arterial blood pressure (MAP), heart rate, and body temperature within six hours. Continuous norepinephrine infusion (NE+, n = 12) started at the time of CLP surgery significantly increased MAP at 24 and 30 hours and heart rate at 6, 18, 24, and 30 hours after CLP vs CLP alone (NE-, n = 12). However, addition of norepinephrine did not improve survival rate (NE+ n = 34, NE- n = 31). Early (6 hours or earlier, when the animal became visibly sick) MAP did not predict 7-day mortality. However, heart rates at 3 and at 6 hours after CLP/norepinephrine (NE+) were highly predictive of mortality, as also been found in one clinical study. We conclude that limited hemodynamic support can be provided in a mouse sepsis model. We propose that heart rate can be used to stratify severity of illness in rodent preclinical studies of sepsis therapeutics.

6-NitroDopamine is an endogenous modulator of rat heart chronotropism

6-Nitrodopamine (6-ND) is released by rat vas deferens and exerts a potent contractile response that is antagonized by tricyclic antidepressants and α₁-, β₁- and β₁/β₂-adrenoceptor antagonists. The release of 6-ND, noradrenaline, adrenaline and dopamine from rat isolated right atria was assessed by tandem mass spectrometry. The effects of the catecholamines were evaluated in both rat isolated right atria and in anaesthetized rats. 6-ND was the major catecholamine released from the isolated atria and the release was significantly reduced in nitric oxide synthase inhibitor L-NAME pre-treated atria or in atria obtained from L-NAME chronically treated animals, but unaffected by tetrodotoxin. 6-ND (1 pM) significantly increased the atrial frequency, being 100 times more potent than noradrenaline and adrenaline. Selective β₁-blockers reduced the atrial frequency only at concentrations that prevented the increases in atrial frequency induced by 6-ND 1pM. Conversely, β₁-blockade did not affect dopamine (10 nM), noradrenaline (100 pM) or adrenaline (100 pM) effect. The reductions in atrial frequency induced by the β₁-adrenoceptor antagonists were absent in L-NAME pre-treated atria and in atria obtained from chronic L-NAME-treated animals. Tetrodotoxin did not prevent the reduction in atrial frequency induced by L-NAME or by β₁-blockers treated preparations. In anaesthetized rats, at 1 pmol/kg, only 6-ND caused a significant increase in heart rate. Inhibition of 6-ND synthesis by chronic L-NAME treatment reduced both atrial frequency and heart rate. The results indicate that 6-ND is a major modulator of rat heart chronotropism and the reduction in heart rate caused by β₁-blockers are due to selective blockade of 6-ND receptor.

Current practice and evolving concepts in septic shock resuscitation

Clinical and pathophysiological understanding of septic shock has progressed exponentially in the previous decades, translating into a steady decrease in septic shock-related morbidity and mortality. Even though large randomized, controlled trials have addressed fundamental aspects of septic shock resuscitation, many questions still exist. In this review, we will describe the current standards of septic shock resuscitation, but the emphasis will be placed on evolving concepts in different domains such as clinical resuscitation targets, adequate use of fluids and vasoactive drugs, refractory shock, and the use of extracorporeal therapies. Multiple research opportunities remain open, and collaborative endeavors should be performed to fill in these gaps.

Chlorpromazine Efficiently Treats the Crisis of Pheochromocytoma: Four Case Reports and Literature Review

Pheochromocytoma multisystem crisis (PMC) is a potentially lethal emergency due to catecholamine secretion. The condition manifests as severe hypertension to intractable cardiogenic shock and has a high mortality rate. This study explored the efficacy and safety of applying chlorpromazine on PMC patients. The study included seven patients (median age, 42 years; range, 14–57 years) diagnosed with pheochromocytoma. Four consecutive PMC patients were admitted to our critical care unit between 2016 and 2020 due to abdominal or waist pain, nausea, and vomiting. Their blood pressure (BP) fluctuated between 200–330/120–200 and 40–70/30–50 mmHg. Chlorpromazine (25 or 50 mg) was injected intramuscularly, followed by continuous intravenous infusion (2–8 mg/h). The patients' BP decreased to 100–150/60–100 mmHg within 1–3 h and stabilized within 3–5 days. Two weeks later, surgical tumor resection was successfully performed in all four patients. Similar clinical outcomes were also obtained in three patients with sporadic PMC reported in the literature who received chlorpromazine treatment, which reduced their BP readings from >200/100 mmHg to 120/70 mmHg. Our observations, combined with sporadic reports, showed that chlorpromazine efficiently controlled PMC. Thus, future studies on the use of chlorpromazine are warranted.

Hyperspectral Imaging for the Evaluation of Microcirculatory Tissue Oxygenation and Perfusion Quality in Haemorrhagic Shock: A Porcine Study

BACKGROUND

The ultimate goal of haemodynamic therapy is to improve microcirculatory tissue and organ perfusion. Hyperspectral imaging (HSI) has the potential to enable noninvasive microcirculatory monitoring at bedside.

METHODS

HSI (Tivita® Tissue System) measurements of tissue oxygenation, haemoglobin, and water content in the skin (ear) and kidney were evaluated in a double-hit porcine model of major abdominal surgery and haemorrhagic shock. Animals of the control group (n = 7) did not receive any resuscitation regime. The interventional groups were treated exclusively with either crystalloid (n = 8) or continuous norepinephrine infusion (n = 7).

RESULTS

Haemorrhagic shock led to a drop in tissue oxygenation parameters in all groups. These correlated with established indirect markers of tissue oxygenation. Fluid therapy restored tissue oxygenation parameters. Skin and kidney measurements correlated well. High dose norepinephrine therapy deteriorated tissue oxygenation. Tissue water content increased both in the skin and the kidney in response to fluid therapy.

CONCLUSIONS

HSI detected dynamic changes in tissue oxygenation and perfusion quality during shock and was able to indicate resuscitation effectivity. The observed correlation between HSI skin and kidney measurements may offer an estimation of organ oxygenation impairment from skin monitoring. HSI microcirculatory monitoring could open up new opportunities for the guidance of haemodynamic management.

Beyond the bundle: Clinical controversies in the management of sepsis in emergency medicine patients

Sepsis is a condition characterized by life-threatening organ dysfunction caused by a dysregulated host response to infection. The emergency department (ED) serves as a crucial entry point for patients presenting with sepsis. Given the heterogeneous presentation and high mortality rate associated with sepsis and septic shock, several clinical controversies have emerged in the management of sepsis. These include the use of novel therapeutic agents like angiotensin II, hydrocortisone, ascorbic acid, thiamine ("HAT") therapy, and levosimendan, Additionally, controversies with current treatments in vasopressor dosing, and the use of and balanced or unbalanced crystalloid are crucial to consider. The purpose of this review is to discuss clinical controversies in the management of septic patients, including the use of novel medications and dosing strategies, to assist providers in appropriately determining what treatment strategy is best suited for patients.

Potential role of herbal medicines as a novel approach in sepsis treatment

The growing number of deaths related to sepsis has become a major concern for past few years. Sepsis is a complex pathological reactions that is explained by series of host response to microbial insult. The resulted systemic reactions are manifested by early appearance of proinflammatory cytokines leading to hyperinflammatory phase which is followed by septic shock and death of the patient. The present study has revealed that antibiotics are not self-sufficient to control the complex mechanism of sepsis. Moreover prolonged and unnecessary administration of antibiotics may lead to antibiotic resistance to pathogens. In addition to this, immunosuppressive medications are selective and have targeted approach to certain study population. Drugs from herbal origin have shown to possess a mammoth of immunomodulatory potential by suppressing proinflammatory and anti-inflammatory cytokines exhibiting no or minimal unwanted secondary responses. Concomitantly, herbal plants tend to modulate oxidative stress level and haematological imbalance during inflammatory diseased conditions. Natural compounds have gained much attention for the treatment of several clinical complications. Considering the promising responses of medicinal plants with less/no side effects and easy procurement, comprehensive research on herbal plants to treat sepsis should be contemplated.

Norepinephrine potentiates the efficacy of volume expansion on mean systemic pressure in septic shock

Background

Through venous contraction, norepinephrine (NE) increases stressed blood volume and mean systemic pressure (Pms) and exerts a “fluid-like” effect. When both fluid and NE are administered, Pms may not only result from the sum of the effects of both drugs. Indeed, norepinephrine may enhance the effects of volume expansion: because fluid dilutes into a more constricted, smaller, venous network, fluid may increase Pms to a larger extent at a higher than at a lower dose of NE. We tested this hypothesis, by mimicking the effects of fluid by passive leg raising (PLR).

Methods

In 30 septic shock patients, norepinephrine was decreased to reach a predefined target of mean arterial pressure (65–70 mmHg by default, 80–85 mmHg in previously hypertensive patients). We measured the PLR-induced increase in Pms (heart–lung interactions method) under high and low doses of norepinephrine. Preload responsiveness was defined by a PLR-induced increase in cardiac index ≥ 10%.

Results

Norepinephrine was decreased from 0.32 [0.18–0.62] to 0.26 [0.13–0.50] µg/kg/min (p < 0.0001). This significantly decreased the mean arterial pressure by 10 [7–20]% and Pms by 9 [4–19]%. The increase in Pms (∆Pms) induced by PLR was 13 [9–19]% at the higher dose of norepinephrine and 11 [6–16]% at the lower dose (p < 0.0001). Pms reached during PLR at the high dose of NE was higher than expected by the sum of Pms at baseline at low dose, ∆Pms induced by changing the norepinephrine dose and ∆Pms induced by PLR at low dose of NE (35.6 [11.2] mmHg vs. 33.6 [10.9] mmHg, respectively, p < 0.01). The number of preload responders was 8 (27%) at the high dose of NE and 15 (50%) at the low dose.

Conclusions

Norepinephrine enhances the Pms increase induced by PLR. These results suggest that a bolus of fluid of the same volume has a greater haemodynamic effect at a high dose than at a low dose of norepinephrine during septic shock.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03711-5.

[Pharmacological therapy of circulatory shock]

Circulatory shock requires treatment of the underlying pathology in addition to supportive pharmacological therapy that is guided by hemodynamic monitoring. Based on the evaluation of the patient's volume, perfusion and cardiac status, the following therapeutic goals should be achieved: (1) Normalization of the intra- and extravascular fluid volume. (2) Provision of sufficient perfusion pressure and organ perfusion. (3) Optimization of cardiac function including protecting an ischemic and exhausted myocardium from overload. The most important therapeutic substances are balanced electrolyte solutions and the vasopressor noradrenaline. Because there is little scientific evidence for the use of alternative drugs, these should only be given if there is a good pathophysiologic rationale and if their effect is continuously monitored and re-evaluated.

Vasopressors in Trauma: A Never Event?

Vasopressor use in severely injured trauma patients is discouraged due to concerns that vasoconstriction will worsen organ perfusion and result in increased mortality and organ failure in hypotensive trauma patients. Hypotensive resuscitation is advocated based on limited data that lower systolic blood pressure and mean arterial pressure will result in improved mortality. It is classically taught that hypotension and hypovolemia in trauma are associated with peripheral vasoconstriction. However, the pathophysiology of traumatic shock is complex and involves multiple neurohormonal interactions that are ultimately manifested by an initial sympathoexcitatory phase that attempts to compensate for acute blood loss and is characterized by vasoconstriction, tachycardia, and preserved mean arterial blood pressure. The subsequent hypotension observed in hemorrhagic shock reflects a sympathoinhibitory vasodilation phase. The objectives of hemodynamic resuscitation in hypotensive trauma patients are restoring adequate intravascular volume with a balanced ratio of blood products, correcting pathologic coagulopathy, and maintaining organ perfusion. Persistent hypotension and hypoperfusion are associated with worse coagulopathy and organ function. The practice of hypotensive resuscitation would appear counterintuitive to the goals of traumatic shock resuscitation and is not supported by consistent clinical data. In addition, excessive volume resuscitation is associated with adverse clinical outcomes. Therefore, in the resuscitation of traumatic shock, it is necessary to target an appropriate balance with intravascular volume and vascular tone. It would appear logical that vasopressors may be useful in traumatic shock resuscitation to counteract vasodilation in hemorrhage as well as other clinical conditions such as traumatic brain injury, spinal cord injury, multiple organ dysfunction syndrome, and vasodilation of general anesthetics. The purpose of this article is to discuss the controversy of vasopressors in hypotensive trauma patients and advocate for a nuanced approach to vasopressor administration in the resuscitation of traumatic shock.

Impella RP Versus Pharmacologic Vasoactive Treatment in Profound Cardiogenic Shock due to Right Ventricular Failure

The aim was to translationally compare a pharmacologic strategy versus treatment with the Impella RP in profound RV cardiogenic shock (CS). The pigs were allocated to either vasoactive therapy with norepinephrine (0.10 μg/kg/min) for the first 30 min, supplemented by an infusion of milrinone (0.4 μg/kg/min) for additional 150 min, or treatment with the Impella RP device for 180 min. Total RV workload (Pressure-volume-area × heart rate*10³(mmHg/min)) remained unaffected upon treatment with the Impella RP and increased in the vasoactive group (CS 179[147;228] to norepinephrine 268[247;306](p = 0.002 compared to Impella RP) and norepinephrine + milrinone 366[329;422] (p = 0.002 compared to Impella RP). A trend towards higher venous cerebral oxygen saturation was observed with norepinephrine than Impella RP (Impella RP 51[47;61]% vs norepinephrine 62[57;71]%; p = 0.07), which became significantly higher with the addition of milrinone (Impella RP 45[32;63]% vs norepinephrine + milrinone 73[66;81]%; p = 0.002). The Impella RP unloaded the failing RV. In contrast, vasoactive treatment led to enhanced cerebral venous oxygen saturation.

Hitting the Vasopressor Ceiling: Finding Norepinephrine Associated Mortality in the Critically Ill

BACKGROUND

There is no consensus on what dose of norepinephrine corresponds with futility. The purpose of this study was to investigate the maximum infusion and cumulative doses of norepinephrine associated with survival for patients in medical and surgical intensive care units (MICU and SICU).

MATERIALS AND METHODS

A retrospective review was conducted of 661 critically ill patients admitted to a large academic medical center who received norepinephrine. Univariate, multivariate, and area under the curve analyses with optimal cut offs for maximum infusion rate and cumulative dosage were determined by Youden Index.

RESULTS

The population was 54.9% male, 75.8% white, and 58.7 ± 16.1 y old with 384 (69.8%) admitted to the MICU and 166 (30.2%) admitted to the SICU, including 38 trauma patients. Inflection points in mortality were seen at 18 mcg/min and 17.6 mg. The inflection point was higher in MICU patients at 21 mcg/min and lower in SICU patients at 11 mcg/min. MICU patients also had a higher maximum cumulative dosage of 30.7 mg, compared to 2.7 mg in SICU patients. In trauma patients, norepinephrine infusions up to 5 mcg/min were associated with a 41.7% mortality rate.

CONCLUSION

A maximum rate of 18 mcg/min and cumulative dose of 17.6 mg were the inflection points for mortality risk in ICU patients, with SICU patients tolerating lower doses. In trauma patients, even low doses of norepinephrine were associated with higher mortality. These data suggest that MICU, SICU, and trauma patients differ in need for, response to, and outcome from escalating norepinephrine doses.

Hemodynamic support in septic shock

PURPOSE OF REVIEW

The current article reviews recent findings on the monitoring and hemodynamic support of septic shock patients.

RECENT FINDINGS

The ultimate goal of hemodynamic resuscitation is to restore tissue oxygenation. A multimodal approach combining global and regional markers of tissue hypoxia seems appropriate to guide resuscitation. Several multicenter clinical trials have provided evidence against an aggressive fluid resuscitation strategy. Fluid administration should be personalized and based on the evidence of fluid responsiveness. Dynamic indices have proven to be highly predictive of responsiveness. Recent data suggest that balanced crystalloids may be associated with less renal failure. When fluid therapy is insufficient, a multimode approach with different types of vasopressors has been suggested as an initial approach. Dobutamine remains the firs inotropic option in patients with persistent hypotension and decrease ventricular systolic function. Calcium sensitizer and phosphodiesterase inhibitors may be considered, but evidence is still limited. Veno-arterial extracorporeal membrane oxygenation may be considered in selected unresponsive patients, particularly with myocardial depression, and in a highly experienced center.

SUMMARY

Resuscitation should be personalized and based on global and regional markers of tissue hypoxia as well as the fluid responsiveness indices. The beneficial effect of multimode approach with different types of vasopressors, remains to be determined.

Echocardiographic measure of dynamic arterial elastance predict pressure response during norepinephrine weaning: an observational study

The purpose of this study was to determine whether dynamic elastance E_Adyn derived from echocardiographic measurements of stroke volume variations can predict the success of a one-step decrease of norepinephrine dose. In this prospective single-center study, 39 patients with vasoplegic syndrome treated with norepinephrine and for whom the attending physician had decided to decrease norepinephrine dose and monitored by thermodilution were analyzed. E_Adyn is the ratio of pulse pressure variation to stroke volume variation and was calculated from echocardiography stroke volume variations and from transpulmonary thermodilution. Pulse pressure variation was obtained from invasive arterial monitoring. Responders were defined by a decrease in mean arterial pressure (MAP) > 10% following norepinephrine decrease. The median decrease in norepinephrine was of 0.04 [0.03-0.05] µg kg^-1 min^-1. Twelve patients (31%) were classified as pressure responders with a median decrease in MAP of 13% [12-15%]. E_Adyn was lower in pressure responders (0.40 [0.24-0.57] vs 0.95 [0.77-1.09], p < 0.01). E_Adyn was able to discriminate between pressure responders and non-responders with an area under the curve of 0.86 (CI_95% [0.71 to1.0], p < 0.05). The optimal cut-off was 0.8. E_Adyn calculated from the echocardiographic estimation of the stroke volume variation and the invasive arterial pulse pressure variation can be used to discriminate pressure response to norepinephrine weaning. Agreement between E_Adyn calculated from echocardiography and thermodilution was poor. Echocardiographic E_Adyn might be used at bedside to optimize hemodynamic treatment.

Current use of inotropes in circulatory shock

BACKGROUND

Treatment decisions on critically ill patients with circulatory shock lack consensus. In an international survey, we aimed to evaluate the indications, current practice, and therapeutic goals of inotrope therapy in the treatment of patients with circulatory shock.

METHODS

From November 2016 to April 2017, an anonymous web-based survey on the use of cardiovascular drugs was accessible to members of the European Society of Intensive Care Medicine (ESICM). A total of 14 questions focused on the profile of respondents, the triggering factors, first-line choice, dosing, timing, targets, additional treatment strategy, and suggested effect of inotropes. In addition, a group of 42 international ESICM experts was asked to formulate recommendations for the use of inotropes based on 11 questions.

RESULTS

A total of 839 physicians from 82 countries responded. Dobutamine was the first-line inotrope in critically ill patients with acute heart failure for 84% of respondents. Two-thirds of respondents (66%) stated to use inotropes when there were persistent clinical signs of hypoperfusion or persistent hyperlactatemia despite a supposed adequate use of fluids and vasopressors, with (44%) or without (22%) the context of low left ventricular ejection fraction. Nearly half (44%) of respondents stated an adequate cardiac output as target for inotropic treatment. The experts agreed on 11 strong recommendations, all of which were based on excellent (> 90%) or good (81-90%) agreement. Recommendations include the indications for inotropes (septic and cardiogenic shock), the choice of drugs (dobutamine, not dopamine), the triggers (low cardiac output and clinical signs of hypoperfusion) and targets (adequate cardiac output) and stopping criteria (adverse effects and clinical improvement).

CONCLUSION

Inotrope use in critically ill patients is quite heterogeneous as self-reported by individual caregivers. Eleven strong recommendations on the indications, choice, triggers and targets for the use of inotropes are given by international experts. Future studies should focus on consistent indications for inotrope use and implementation into a guideline for circulatory shock that encompasses individualized targets and outcomes.

The Hippo Signaling Pathway in Drug Resistance in Cancer

Simple Summary

Although great breakthroughs have been made in cancer treatment following the development of targeted therapy and immune therapy, resistance against anti-cancer drugs remains one of the most challenging conundrums. Considerable effort has been made to discover the underlying mechanisms through which malignant tumor cells acquire or develop resistance to anti-cancer treatment. The Hippo signaling pathway appears to play an important role in this process. This review focuses on how components in the human Hippo signaling pathway contribute to drug resistance in a variety of cancer types. This article also summarizes current pharmacological interventions that are able to target the Hippo signaling pathway and serve as potential anti-cancer therapeutics.

Abstract

Chemotherapy represents one of the most efficacious strategies to treat cancer patients, bringing advantageous changes at least temporarily even to those patients with incurable malignancies. However, most patients respond poorly after a certain number of cycles of treatment due to the development of drug resistance. Resistance to drugs administrated to cancer patients greatly limits the benefits that patients can achieve and continues to be a severe clinical difficulty. Among the mechanisms which have been uncovered to mediate anti-cancer drug resistance, the Hippo signaling pathway is gaining increasing attention due to the remarkable oncogenic activities of its components (for example, YAP and TAZ) and their druggable properties. This review will highlight current understanding of how the Hippo signaling pathway regulates anti-cancer drug resistance in tumor cells, and currently available pharmacological interventions targeting the Hippo pathway to eradicate malignant cells and potentially treat cancer patients.

Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function

Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.