The holistic view on perfusion monitoring in septic shock. Curr Opin Crit Care. 2012;18:280-286. [PMID: 22473257 DOI: 10.1097/mcc.0b013e3283532c08]

Point of View: A Holistic Four-Interface Conceptual Model for Personalizing Shock Resuscitation

The resuscitation of a patient in shock is a highly complex endeavor that should go beyond normalizing mean arterial pressure and protocolized fluid loading. We propose a holistic, four-interface conceptual model of shock that we believe can benefit both clinicians at the bedside and researchers. The four circulatory interfaces whose uncoupling results in shock are as follows: the left ventricle to arterial, the arterial to capillary, the capillary to venular, and finally the right ventricle to pulmonary artery. We review the pathophysiology and clinical consequences behind the uncoupling of these interfaces, as well as how to assess them, and propose a strategy for approaching a patient in shock. Bedside assessment of shock may include these critical interfaces in order to avoid hemodynamic incoherence and to focus on microcirculatory restoration rather than simply mean arterial pressure. The purpose of this model is to serve as a mental model for learners as well as a framework for further resuscitation research that incorporates these concepts.

Research Progress on the Measurement Methods and Clinical Significance of Capillary Refill Time

The monitoring of peripheral circulation, as indicated by the capillary refill time, is a sensitive and accurate method of assessing the microcirculatory status of the body. It is a widely used tool for the evaluation of critically ill patients, the guidance of therapeutic interventions, and the assessment of prognosis. In recent years, there has been a growing emphasis on microcirculation monitoring which has led to an increased focus on capillary refill time. The International Sepsis Guidelines, the American Academy of Pediatrics, the World Health Organization, and the American Heart Association all recommend its inclusion in the evaluation of the system in question. Furthermore, the methodology for its measurement has evolved from a traditional manual approach to semiautomatic and fully automatic techniques. This article presents a comprehensive overview of the current research on the measurement of capillary refill time, with a particular focus on its clinical significance. The aim is to provide a valuable reference for clinicians and researchers and further advance the development and application of microcirculation monitoring technology.

Research Progress on Mechanisms and Treatment of Sepsis-Induced Myocardial Dysfunction

Sepsis is a syndrome of organ dysfunction caused by a dysregulated immune response to infection, with high morbidity and mortality. At present, there have been many advances in the study of its pathogenesis, especially the cardiac dysfunction caused by sepsis, namely sepsis-induced myocardial dysfunction, SIMD, which has received widespread attention. The mechanisms of SIMD mainly include excessive release of inflammatory mediators, impaired mitochondrial function, autophagy, apoptosis and myocardial dysfunction. This article reviews the pathogenesis of SIMD and elaborates on the progress in its treatment, aiming to improve the prognosis of patients with SIMD and sepsis.

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.

Using Signal Features of Functional Near-Infrared Spectroscopy for Acute Physiological Score Estimation in ECMO Patients

Extracorporeal membrane oxygenation (ECMO) is a vital emergency procedure providing respiratory and circulatory support to critically ill patients, especially those with compromised cardiopulmonary function. Its use has grown due to technological advances and clinical demand. Prolonged ECMO usage can lead to complications, necessitating the timely assessment of peripheral microcirculation for an accurate physiological evaluation. This study utilizes non-invasive near-infrared spectroscopy (NIRS) to monitor knee-level microcirculation in ECMO patients. After processing oxygenation data, machine learning distinguishes high and low disease severity in the veno-venous (VV-ECMO) and veno-arterial (VA-ECMO) groups, with two clinical parameters enhancing the model performance. Both ECMO modes show promise in the clinical severity diagnosis. The research further explores statistical correlations between the oxygenation data and disease severity in diverse physiological conditions, revealing moderate correlations with the acute physiologic and chronic health evaluation (APACHE II) scores in the VV-ECMO and VA-ECMO groups. NIRS holds the potential for assessing patient condition improvements.

Prognostic value of capillary refill time in adult patients: a systematic review with meta-analysis

PURPOSE

Acute circulatory failure leads to tissue hypoperfusion. Capillary refill time (CRT) has been widely studied, but its predictive value remains debated. We conducted a meta-analysis to assess the ability of CRT to predict death or adverse events in a context at risk or confirmed acute circulatory failure in adults.

METHOD

MEDLINE, EMBASE, and Google scholar databases were screened for relevant studies. The pooled area under the ROC curve (AUC ROC), sensitivity, specificity, threshold, and diagnostic odds ratio using a random-effects model were determined. The primary analysis was the ability of abnormal CRT to predict death in patients with acute circulatory failure. Secondary analysis included the ability of CRT to predict death or adverse events in patients at risk or with confirmed acute circulatory failure, the comparison with lactate, and the identification of explanatory factors associated with better accuracy.

RESULTS

A total of 60,656 patients in 23 studies were included. Concerning the primary analysis, the pooled AUC ROC of 13 studies was 0.66 (95%CI [0.59; 0.76]), and pooled sensitivity was 54% (95%CI [43; 64]). The pooled specificity was 72% (95%CI [55; 84]). The pooled diagnostic odds ratio was 3.4 (95%CI [1.4; 8.3]). Concerning the secondary analysis, the pooled AUC ROC of 23 studies was 0.69 (95%CI [0.65; 0.74]). The prognostic value of CRT compared to lactate was not significantly different. High-quality CRT was associated with a greater accuracy.

CONCLUSION

CRT poorly predicted death and adverse events in patients at risk or established acute circulatory failure. Its accuracy is greater when high-quality CRT measurement is performed.

Hypoperfusion context as a predictor of 28-d all-cause mortality in septic shock patients: A comparative observational study

BACKGROUND

As per the latest Surviving Sepsis Campaign guidelines, fluid resuscitation should be guided by repeated measurements of blood lactate levels until normalization. Nevertheless, raised lactate levels should be interpreted in the clinical context, as there may be other causes of elevated lactate levels. Thus, it may not be the best tool for real-time assessment of the effect of hemodynamic resuscitation, and exploring alternative resuscitation targets should be an essential research priority in sepsis.

AIM

To compare the 28-d mortality in two clinical patterns of septic shock: hyperlactatemic patients with hypoperfusion context and hyperlactatemic patients without hypoperfusion context.

METHODS

This prospective comparative observational study carried out on 135 adult patients with septic shock that met Sepsis-3 definitions compared patients with hyperlactatemia in a hypoperfusion context (Group 1, n = 95) and patients with hyperlactatemia in a non-hypoperfusion context (Group 2, n = 40). Hypoperfusion context was defined by a central venous saturation less than 70%, central venous-arterial PCO2 gradient [P(cv-a)CO2] ≥ 6 mmHg, and capillary refilling time (CRT) ≥ 4 s. The patients were observed for various macro and micro hemodynamic parameters at regular intervals of 0 h, 3 h, and 6 h. All-cause 28-d mortality and all other secondary objective parameters were observed at specified intervals. Nominal categorical data were compared using the χ2 or Fisher's exact test. Non-normally distributed continuous variables were compared using the Mann-Whitney U test. Receiver operating characteristic curve analysis with the Youden index determined the cutoff values of lactate, CRT, and metabolic perfusion parameters to predict the 28-d all-cause mortality. A P value of < 0.05 was considered significant.

RESULTS

Patient demographics, comorbidities, baseline laboratory, vital parameters, source of infection, baseline lactate levels, and lactate clearance at 3 h and 6 h, Sequential Organ Failure scores, need for invasive mechanical ventilation, days on mechanical ventilation, and renal replacement therapy-free days within 28 d, duration of intensive care unit stay, and hospital stay were comparable between the two groups. The stratification of patients into hypoperfusion and non-hypoperfusion context did not result in a significantly different 28-d mortality (24% vs 15%, respectively; P = 0.234). However, the patients within the hypoperfusion context with high P(cv-a)CO2 and CRT (P = 0.022) at baseline had significantly higher mortality than Group 2. The norepinephrine dose was higher in Group 1 but did not achieve statistical significance with a P > 0.05 at all measured intervals. Group 1 had a higher proportion of patients requiring vasopressin and the mean vasopressor-free days out of the total 28 d were lower in patients with hypoperfusion (18.88 ± 9.04 vs 21.08 ± 8.76; P = 0.011). The mean lactate levels and lactate clearance at 3 h and 6 h, CRT, P(cv-a)CO2 at 0 h, 3 h, and 6 h were found to be associated with 28-d mortality in patients with septic shock, with lactate levels at 6 h having the best predictive value (area under the curve lactate at 6 h: 0.845).

CONCLUSION

Septic shock patients fulfilling the hypoperfusion and non-hypoperfusion context exhibited similar 28-d all-cause hospital mortality, although patients with hypoperfusion displayed a more severe circulatory dysfunction. Lactate levels at 6 h had a better predictive value in predicting 28-d mortality than other parameters. Persistently high P(cv-a)CO2 (> 6 mmHg) or increased CRT (> 4 s) at 3 h and 6 h during early resuscitation can be a valuable additional aid for prognostication of septic shock patients.

Exploring the relationship between capillary refill time, skin blood flow and microcirculatory reactivity during early resuscitation of patients with septic shock: a pilot study

Capillary refill time (CRT), a costless and widely available tool, has emerged as a promising target to guide septic shock resuscitation. However, it has yet to gain universal acceptance due to its potential inter-observer variability. Standardization of CRT assessment may minimize this problem, but few studies have compared this approach with techniques that directly assess skin blood flow (SBF). Our objective was to determine if an abnormal CRT is associated with impaired SBF and microvascular reactivity in early septic shock patients. Twelve septic shock patients were subjected to multimodal perfusion and hemodynamic monitoring for 24 h. Three time-points (0, 1, and 24 h) were registered for each patient. SBF was measured by laser doppler. We performed a baseline SBF measurement and two microvascular reactivity tests: one with a thermal challenge at 44 °C and other with a vascular occlusion test. Ten healthy volunteers were evaluated to obtain reference values. The patients (median age 70 years) exhibited a 28-day mortality of 50%. Baseline CRT was 3.3 [2.7-7.3] seconds. In pooled data analysis, abnormal CRT presented a significantly lower SBF when compared to normal CRT [44 (13.3-80.3) vs 193.2 (99.4-285) APU, p = 0.0001]. CRT was strongly associated with SBF (R² 0.76, p < 0.0001). An abnormal CRT also was associated with impaired thermal challenge and vascular occlusion tests. Abnormal CRT values observed during early septic shock resuscitation are associated with impaired skin blood flow, and abnormal skin microvascular reactivity. Future studies should confirm these results.

Effective hemodynamic monitoring

Hemodynamic monitoring is the centerpiece of patient monitoring in acute care settings. Its effectiveness in terms of improved patient outcomes is difficult to quantify. This review focused on effectiveness of monitoring-linked resuscitation strategies from: (1) process-specific monitoring that allows for non-specific prevention of new onset cardiovascular insufficiency (CVI) in perioperative care. Such goal-directed therapy is associated with decreased perioperative complications and length of stay in high-risk surgery patients. (2) Patient-specific personalized resuscitation approaches for CVI. These approaches including dynamic measures to define volume responsiveness and vasomotor tone, limiting less fluid administration and vasopressor duration, reduced length of care. (3) Hemodynamic monitoring to predict future CVI using machine learning approaches. These approaches presently focus on predicting hypotension. Future clinical trials assessing hemodynamic monitoring need to focus on process-specific monitoring based on modifying therapeutic interventions known to improve patient-centered outcomes.

Capillary refill time for the management of acute circulatory failure: a survey among pediatric and adult intensivists

INTRODUCTION

Recent studies have shown the prognostic value of capillary refill time (CRT) and suggested that resuscitation management guided by CRT may reduce morbidity and mortality in patients with septic shock. However, little is known about the current use of CRT in routine clinical practice. This study aimed to assess the modalities of CRT use among French adult and pediatric intensivists.

METHODS

A cross-sectional survey exploring CRT practices in acute circulatory failure was performed. The targeted population was French adult and pediatric intensivists (SFAR and GFRUP networks). An individual invitation letter including a survey of 32 questions was emailed twice. Descriptive and analytical statistics were performed.

RESULTS

Among the 6071 physicians who received the letter, 418 (7%) completed the survey. Among all respondents, 82% reported using CRT in routine clinical practice, mainly to diagnose acute circulatory failure, but 45% did not think CRT had any prognostic value. Perfusion goal-directed therapy based on CRT was viewed as likely to improve patient outcome by 37% of respondents. The measurement of CRT was not standardized as the use of a chronometer was rare (3%) and the average of multiple measurements rarely performed (46%). Compared to adult intensivists, pediatric intensivists used CRT more frequently (99% versus 76%) and were more confident in its diagnostic value and its ability to guide treatment.

CONCLUSION

CRT measurement is widely used by intensivists in patients with acute circulatory failure but most often in a non-standardized way. This may lead to a misunderstanding of CRT reliability and clinical usefulness.

Serum Lactate and Mortality during Pediatric Admissions: Is 2 Really the Magic Number?

The primary objective of this study was to determine if serum lactate level at the time of hospital admission can predict mortality in pediatric patients. A systematic review was conducted to identify studies that assessed the utility of serum lactate at the time of admission to predict mortality in pediatric patients. The areas under the curve from the receiver operator curve analyses were utilized to determine the pooled area under the curve. Additionally, standardized mean difference was compared between those who survived to discharge and those who did not. A total of 12 studies with 2,099 patients were included. Out of these, 357 (17%) experienced mortality. The pooled area under the curve for all patients was 0.74 (0.67-0.80, p  < 0.01). The pooled analyses for all admissions were higher in those who experienced mortality (6.5 vs. 3.3 mmol/L) with a standardized mean difference of 2.60 (1.74-3.51, p  < 0.01). The pooled area under the curve for cardiac surgery patients was 0.63 (0.53-0.72, p  < 0.01). The levels for cardiac surgery patients were higher in those who experienced mortality (5.5 vs. 4.1 mmol/L) with a standardized mean difference of 1.80 (0.05-3.56, p  = 0.04). Serum lactate at the time of admission can be valuable in identifying pediatric patients at greater risk for inpatient mortality. This remained the case when only cardiac surgery patients were included.

Revealing potential diagnostic gene biomarkers of septic shock based on machine learning analysis

Background

Sepsis is an inflammatory response caused by infection with pathogenic microorganisms. The body shock caused by it is called septic shock. In view of this, we aimed to identify potential diagnostic gene biomarkers of the disease.

Material and methods

Firstly, mRNAs expression data sets of septic shock were retrieved and downloaded from the GEO (Gene Expression Omnibus) database for differential expression analysis. Functional enrichment analysis was then used to identify the biological function of DEmRNAs (differentially expressed mRNAs). Machine learning analysis was used to determine the diagnostic gene biomarkers for septic shock. Thirdly, RT-PCR (real-time polymerase chain reaction) verification was performed. Lastly, GSE65682 data set was utilized to further perform diagnostic and prognostic analysis of identified superlative diagnostic gene biomarkers.

Results

A total of 843 DEmRNAs, including 458 up-regulated and 385 down-regulated DEmRNAs were obtained in septic shock. 15 superlative diagnostic gene biomarkers (such as RAB13, KIF1B, CLEC5A, FCER1A, CACNA2D3, DUSP3, HMGN3, MGST1 and ARHGEF18) for septic shock were identified by machine learning analysis. RF (random forests), SVM (support vector machine) and DT (decision tree) models were used to construct classification models. The accuracy of the DT, SVM and RF models were very high. Interestingly, the RF model had the highest accuracy. It is worth mentioning that ARHGEF18 and FCER1A were related to survival. CACNA2D3 and DUSP3 participated in MAPK signaling pathway to regulate septic shock.

Conclusion

Identified diagnostic gene biomarkers may be helpful in the diagnosis and therapy of patients with septic shock.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07056-4.

The role of peripheral perfusion markers and lactate in septic shock resuscitation

Septic shock leads to progressive hypoperfusion and tissue hypoxia. Unfortunately, numerous uncertainties exist around the best monitoring strategy, as available techniques are mere surrogates for these phenomena. Nevertheless, central venous oxygen saturation (ScvO₂), venous-to-arterial CO₂ gap, and lactate normalization have been fostered as resuscitation targets for septic shock. Moreover, recent evidence has challenged the central role of lactate. Following the ANDROMEDA-SHOCK trial, capillary refill time (CRT) has become a promissory target, considering the observed benefits in mortality, treatment intensity, and organ dysfunction. Interpretation of CRT within a multimodal approach may aid clinicians in guiding resuscitative interventions and stop resuscitation earlier, thus avoiding the risk of morbid fluid overload. Integrative assessment of a patient's perfusion status can be easily performed using bedside clinical tools. Based on its fast kinetics and recent supporting evidence, targeting CRT (within a holistic assessment of perfusion) may improve outcomes in septic shock resuscitation.

Associations between peripheral perfusion disorders, mean arterial pressure and dose of norepinephrine administrated in the early phase of septic shock

The aim of the study was to explore the correlations between peripheral perfusion, mean arterial pressure and the dose-rate of norepinephrine (NE) infused for the treatment of septic shock. The study is retrospective analysis of data acquired prospectively on 57 patients during the first 24 hours after the occurrence of the shock. Clinical and haemodynamic characteristics, skin perfusion parameters (capillary refill time [CRT], mottling score and temperature gradients) and the dose rate of NE infusion were collected. Negative correlations between mean arterial pressure (MAP) and temperature gradients (core-to-toe: P = .03, core-to-index: P = .04) were found and abnormal CRT was associated with lower MAP (P = .02). The dose rate of NE was negatively correlated with temperature gradients (core-to-toe: P = .02, core-to-index: P = .01, forearm-to-index: P = .008) in the overall population. In patients receiving NE for at least 12 hours, the NE dose rate positively was correlated with the mottling score (P = .006), temperature gradients (core-to-toe: P = .04, forearm-to-index: P = .02, core-to-index: P = .005) and CRT (P = .001). The dose of NE administrated was associated with 14-days mortality (odds ration [OR] = 1.21 [1.06-1.38], P = .006) and with 28-days mortality (OR = 1.17 [1.01-1.36], P = 0.04). In conclusion, the study described the presence of correlations between peripheral perfusion and MAP and between peripheral perfusion and the dose rate of NE infusion.

Prolonged Capillary Refilling as a Predictor of Mortality in Patients With Septic Shock

INTRODUCTION

Microcirculatory alterations characterize septic shock; increased blood lactate level has been described as markers of microcirculation alteration in patients with septic shock. Although useful, this serological analysis is not always feasible in all settings worldwide.

OBJECTIVE

To determine if a prolonged capillary refilling is a predictor of mortality in patients with septic shock.

METHODOLOGY

A 10-months prospective cohort study was carried out on 175 patients admitted to the Intensive Care Unit (ICU) with the diagnosis of septic shock. The capillary refilling time (CRT) was evaluated Immediately upon admission and after 6 hours post-resuscitation. Traditional tissue perfusion markers were also used to compare and analyze their predictive value on mortality at 28 days.

RESULTS

The area under the ROC curve (AUC) to estimate mortality in patients with septic shock with CRT at admission was 0.666 (0.584-0.748), while at 6 hours was 0.819 (0.753-0.885), with a cut-off point of 4.5 seconds at admission (PPV 52.87% NPV 72.73%) and 3.5 sec at 6 hours (PPV 95.56% NPV 79.23%). In those with CRT > 3.5 seconds at 6 hours, they had a RR of 4.60, while a CRT > 4.5 seconds at admission had a RR of 1.94, with a non-survivor proportion of 95.56% for a CRT > 3.5 sec at 6 hours vs 20.77% for CRT ≤ 3.5 sec (P value < 0.001). The CRT at 6 hours showed significant differences in the survival curves with P-value < 0.001, where for values > 3.5 sec, survival at 28 days was 4.44% vs 79.20% for values ≤ 3.5 sec.

CONCLUSION

CRT is a strong predictor of mortality in patients with septic shock. Evaluating changes in CRT during resuscitation from septic shock might be used as an important clinical tool to predict mortality; especially in low-resources settings where using other biomarkers might be sometimes difficult.

Effects of capillary refill time-vs. lactate-targeted fluid resuscitation on regional, microcirculatory and hypoxia-related perfusion parameters in septic shock: a randomized controlled trial

Background

Persistent hyperlactatemia has been considered as a signal of tissue hypoperfusion in septic shock patients, but multiple non-hypoperfusion-related pathogenic mechanisms could be involved. Therefore, pursuing lactate normalization may lead to the risk of fluid overload. Peripheral perfusion, assessed by the capillary refill time (CRT), could be an effective alternative resuscitation target as recently demonstrated by the ANDROMEDA-SHOCK trial. We designed the present randomized controlled trial to address the impact of a CRT-targeted (CRT-T) vs. a lactate-targeted (LAC-T) fluid resuscitation strategy on fluid balances within 24 h of septic shock diagnosis. In addition, we compared the effects of both strategies on organ dysfunction, regional and microcirculatory flow, and tissue hypoxia surrogates.

Results

Forty-two fluid-responsive septic shock patients were randomized into CRT-T or LAC-T groups. Fluids were administered until target achievement during the 6 h intervention period, or until safety criteria were met. CRT-T was aimed at CRT normalization (≤ 3 s), whereas in LAC-T the goal was lactate normalization (≤ 2 mmol/L) or a 20% decrease every 2 h. Multimodal perfusion monitoring included sublingual microcirculatory assessment; plasma-disappearance rate of indocyanine green; muscle oxygen saturation; central venous-arterial pCO₂ gradient/ arterial-venous O₂ content difference ratio; and lactate/pyruvate ratio. There was no difference between CRT-T vs. LAC-T in 6 h-fluid boluses (875 [375–2625] vs. 1500 [1000–2000], p = 0.3), or balances (982[249–2833] vs. 15,800 [740–6587, p = 0.2]). CRT-T was associated with a higher achievement of the predefined perfusion target (62 vs. 24, p = 0.03). No significant differences in perfusion-related variables or hypoxia surrogates were observed.

Conclusions

CRT-targeted fluid resuscitation was not superior to a lactate-targeted one on fluid administration or balances. However, it was associated with comparable effects on regional and microcirculatory flow parameters and hypoxia surrogates, and a faster achievement of the predefined resuscitation target. Our data suggest that stopping fluids in patients with CRT ≤ 3 s appears as safe in terms of tissue perfusion.

Clinical Trials: ClinicalTrials.gov Identifier: NCT03762005 (Retrospectively registered on December 3rd 2018)

A lactate-targeted resuscitation strategy may be associated with higher mortality in patients with septic shock and normal capillary refill time: a post hoc analysis of the ANDROMEDA-SHOCK study

Background

Capillary refill time (CRT) may improve more rapidly than lactate in response to increments in systemic flow. Therefore, it can be assessed more frequently during septic shock (SS) resuscitation. Hyperlactatemia, in contrast, exhibits a slower recovery in SS survivors, probably explained by the delayed resolution of non-hypoperfusion-related sources. Thus, targeting lactate normalization may be associated with impaired outcomes. The ANDROMEDA-SHOCK trial compared CRT- versus lactate-targeted resuscitation in early SS. CRT-targeted resuscitation associated with lower mortality and organ dysfunction; mechanisms were not investigated. CRT was assessed every 30 min and lactate every 2 h during the 8-h intervention period, allowing a first comparison between groups at 2 h (T2). Our primary aim was to determine if SS patients evolving with normal CRT at T2 after randomization (T0) exhibited a higher mortality and organ dysfunction when allocated to the LT arm than when randomized to the CRT arm. Our secondary aim was to determine if those patients with normal CRT at T2 had received more therapeutic interventions when randomized to the LT arm. To address these issues, we performed a post hoc analysis of the ANDROMEDA-SHOCK dataset.

Results

Patients randomized to the lactate arm at T0, evolving with normal CRT at T2 exhibited significantly higher mortality than patients with normal CRT at T2 initially allocated to CRT (40 vs 23%, p = 0.009). These results replicated at T8 and T24. LT arm received significantly more resuscitative interventions (fluid boluses: 1000[500–2000] vs. 500[0–1500], p = 0.004; norepinephrine test in previously hypertensive patients: 43 (35) vs. 19 (19), p = 0.001; and inodilators: 16 (13) vs. 3 (3), p = 0.003). A multivariate logistic regression of patients with normal CRT at T2, including APACHE-II, baseline lactate, cumulative fluids administered since emergency admission, source of infection, and randomization group) confirmed that allocation to LT group was a statistically significant determinant of 28-day mortality (OR 3.3; 95%CI[1.5–7.1]); p = 0.003).

Conclusions

Septic shock patients with normal CRT at baseline received more therapeutic interventions and presented more organ dysfunction when allocated to the lactate group. This could associate with worse outcomes.

Optimal target in septic shock resuscitation

Septic shock presents a high risk of morbidity and mortality. Through therapeutic strategies, such as fluid administration and vasoactive agents, clinicians intend to rapidly restore tissue perfusion. Nonetheless, these interventions have narrow therapeutic margins. Adequate perfusion monitoring is paramount to avoid progressive hypoperfusion or detrimental over-resuscitation. During early stages of septic shock, macrohemodynamic derangements, such as hypovolemia and decreased cardiac output (CO) tend to predominate. However, during late septic shock, endothelial and coagulation dysfunction induce severe alterations of the microcirculation, making it more difficult to achieve tissue reperfusion. Multiple perfusion variables have been described in the literature, from bedside clinical examination to complex laboratory tests. Moreover, all of them present inherent flaws and limitations. After the ANDROMEDA-SHOCK trial, there is evidence that capillary refill time (CRT) is an interesting resuscitation target, due to its rapid kinetics and correlation with deep hypoperfusion markers. New concepts such as hemodynamic coherence and flow responsiveness may be used at the bedside to select the best treatment strategies at any time-point. A multimodal perfusion monitoring and an integrated analysis with macrohemodynamic parameters is mandatory to optimize the resuscitation of septic shock patients.

Tissue oxygen saturation changes and postoperative complications in cardiac surgery: a prospective observational study

Background

Cardiac surgery with extracorporeal circulation (ECC) can induce microvascular dysfunction and tissue hypoperfusion. We hypothesized that the alterations in near-infrared spectroscopy (NIRS)-derived parameters would be associated with post-operative complications in cardiac surgery patients.

Methods

Prospective observational study performed at two University Hospitals. Ninety patients undergoing cardiac surgery with ECC were enrolled. The NIRS sensor was applied on the thenar eminence. A vascular occlusion test (VOT, 3-min ischemia) was performed at baseline (t0), at Intensive Care Unit (ICU) admission (t1), 3 (t2) and 6 (t3) hours later. Baseline tissue oxygen saturation (StO₂), oxygen extraction rate and microvascular reactivity indices were calculated.

Results

In the first hours after cardiac surgery, StO₂ tended to increase (86% [80–89] at T3 versus 82% [79–86] at T0, p = ns), while both tissue oxygen extraction and microvascular reactivity tended to decrease, as indicated by increasing occlusion slope (− 8.1%/min [− 11.2 to − 7] at T3 versus − 11.2%/min [− 13.9 to − 7.9] at T0, p = ns) and decreasing recovery slope (1.9%/sec [1.1–2.9] at T3 versus 3.1%/sec [2.3–3.9] at T0, p = ns). No substantial differences were found in NIRS-derived variables and their changes over time between patients with complications and those without complications.

Conclusions

Peripheral tissue oxygen extraction and microvascular reactivity were reduced during the first hours after cardiac surgery. NIRS-derived parameters were not able to predict complications in this population of cardiac surgery patients.

The Role of ALDH2 in Sepsis and the To-Be-Discovered Mechanisms

Sepsis, defined as life-threatening tissue damage and organ dysfunction caused by a dysregulated host response to infection, is a critical disease which imposes global health burden. Sepsis-induced organ dysfunction, including circulatory and cardiac dysfunction, hepatic dysfunction, renal dysfunction, etc., contributes to high mortality and long-term disability of sepsis patients. Altered inflammatory response, ROS and reactive aldehyde stress, mitochondrial dysfunction, and programmed cell death pathways (necrosis, apoptosis, and autophagy) have been demonstrated to play crucial roles in septic organ dysfunction. Unfortunately, except for infection control and supportive therapies, no specific therapy exists for sepsis. New specific therapeutic targets are highly warranted. Emerging studies suggested a role of potential therapeutic target of ALDH2, a tetrameric enzyme located in mitochondria to detoxify aldehydes, in septic organ dysfunction. In this article, we will review the presentations and pathophysiology of septic organ dysfunction, as well as summarize and discuss the recent insights regarding ALDH2 in sepsis.

Capillary refill time variation induced by passive leg raising predicts capillary refill time response to volume expansion

BACKGROUND

A peripheral perfusion-targeted resuscitation during early septic shock has shown encouraging results. Capillary refill time, which has a prognostic value, was used. Adding accuracy and predictability on capillary refill time (CRT) measurement, if feasible, would benefit to peripheral perfusion-targeted resuscitation. We assessed whether a reduction of capillary refill time during passive leg raising (ΔCRT-PLR) predicted volume-induced peripheral perfusion improvement defined as a significant decrease of capillary refill time following volume expansion.

METHODS

Thirty-four patients with acute circulatory failure were selected. Haemodynamic variables, metabolic variables (PCO2gap), and four capillary refill time measurements were recorded before and during a passive leg raising test and after a 500-mL volume expansion over 20 min. Receiver operating characteristic curves were built, and areas under the curves were calculated (ROCAUC). Confidence intervals (CI) were performed using a bootstrap analysis. We recorded mortality at day 90.

RESULTS

The least significant change in the capillary refill time was 25% [95% CI, 18-30]. We defined CRT responders as patients showing a reduction of at least 25% of capillary refill time after volume expansion. A decrease of 27% in ΔCRT-PLR predicted peripheral perfusion improvement with a sensitivity of 87% [95% CI, 73-100] and a specificity of 100% [95% CI, 74-100]. The ROCAUC of ΔCRT-PLR was 0.94 [95% CI, 0.87-1.0]. The ROCAUC of baseline capillary refill time was 0.73 [95% CI, 0.54-0.90] and of baseline PCO2gap was 0.79 [0.61-0.93]. Capillary refill time was significantly longer in non-survivors than in survivors at day 90.

CONCLUSION

ΔCRT-PLR predicted peripheral perfusion response following volume expansion. This simple low-cost and non-invasive diagnostic method could be used in peripheral perfusion-targeted resuscitation protocols.

TRIAL REGISTRATION

CPP Lyon Sud-Est II ANSM: 2014-A01034-43 Clinicaltrial.gov, NCT02248025 , registered 13th of September 2014.

Alterations of complex IV in the tissues of a septic mouse model

OBJECTIVES

To characterize the mitochondrial respiratory chain complex IV(complex IV) activity and protein expression during polymicrobial sepsis.

MATERIAL AND METHODS

Polymicrobial peritonitis, a clinically relevant mouse model of sepsis, was generated by cecum ligation and puncture (CLP) in Sprague- Dawley rats. The rats were randomly divided into 3 groups as follows: the sepsis without resuscitation (S), sepsis and fluid resuscitated (R) group, and a control (C) group. Twelve hours after the sepsis model was established, tissue specimens were obtained from the myocardium, liver and skeletal muscle. Mitochondrial respiratory chain complex IV activity of all tissue specimens was detected by spectrophotometry. Western blot was used to measure the liver mitochondrial respiratory chain complex IV protein content. The ultrastructure changes of mitochondria were detected by transmission electron microscopy.

RESULTS

In myocardial cells, complex IV activity decreased significantly in the S and R groups as compared to the C group. There were no differences in complex IV activity between groups in skeletal muscle cells while in liver cells, complex IV activity and content was significantly decreased for the S group but no differences were observed between the C and R groups. Increased matrix volume and reduced density with generalized disruption of the normal cristae pattern was most extensive in the liver, followed by cardiac muscle cells with that in skeletal muscle cells been relatively mild in the S group. Mitochondrial fusion/fission and mitochondrial autophagy was also observed in the S group by transmission electron microscopy. Mitochondrial ultrastructure was preserved in the R-group and was similar to that seen in the C-group.

CONCLUSIONS

Changes in complex IV activity and mitochondrial ultrastructure, a manifestation of the mitochondrial dysfunction varied depending on cell type. These changes are partly reversed by fluid therapy. Therapies aimed at mitochondrial resuscitation should be explored.

Monitoring peripheral perfusion and microcirculation

PURPOSE OF REVIEW

Microcirculatory alterations play a major role in the pathogenesis of shock. Monitoring tissue perfusion might be a relevant goal for shock resuscitation. The goal of this review was to revise the evidence supporting the monitoring of peripheral perfusion and microcirculation as goals of resuscitation. For this purpose, we mainly focused on skin perfusion and sublingual microcirculation.

RECENT FINDINGS

Although there are controversies about the reproducibility of capillary refill time in monitoring peripheral perfusion, it is a sound physiological variable and suitable for the ICU settings. In addition, observational studies showed its strong ability to predict outcome. Moreover, a preliminary study suggested that it might be a valuable goal for resuscitation. These results should be confirmed by the ongoing ANDROMEDA-SHOCK randomized controlled trial. On the other hand, the monitoring of sublingual microcirculation might also provide relevant physiological and prognostic information. On the contrary, methodological drawbacks mainly related to video assessment hamper its clinical implementation at the present time.

SUMMARY

Measurements of peripheral perfusion might be useful as goal of resuscitation. The results of the ANDROMEDA-SHOCK will clarify the role of skin perfusion as a guide for the treatment of shock. In contrast, the assessment of sublingual microcirculation mainly remains as a research tool.

Transient hyperlactatemia during intravenous administration of glycerol: a prospective observational study

Background

Intravenous glycerol treatment, usually administered in the form of a 5% fructose solution, can be used to reduce intracranial pressure. The administered fructose theoretically influences blood lactate levels, although little is known regarding whether intravenous glycerol treatment causes transient hyperlactatemia. This study aimed to evaluate blood lactate levels in patients who received intravenous glycerol or mannitol.

Methods

This single-center prospective observational study was performed at a 14-bed general intensive care unit between August 2016 and January 2018. Patients were excluded if they were < 20 years old or had pre-existing hyperlactatemia (blood lactate > 2.0 mmol/L). The included patients received intravenous glycerol or mannitol to reduce intracranial pressure and provided blood samples for lactate testing before and after the drug infusion (before the infusion and after 15 min, 30 min, 45 min, 60 min, 90 min, 120 min, and 150 min).

Results

Among the 33 included patients, 13 patients received 200 mL of glycerol over 30 min, 13 patients received 200 mL of glycerol over 60 min, and 7 patients received 300 mL of mannitol over 60 min. Both groups of patients who received glycerol had significantly higher lactate levels than the mannitol group (2.8 mmol/L vs. 2.2 mmol/L vs. 1.6 mmol/L, P < 0.0001), with the magnitude of the increase in lactate levels corresponding to the glycerol infusion time. There were no significant inter-group differences in cardiac index, stroke volume, or stroke volume variation. In the group that received the 30-min glycerol infusion, blood lactate levels did not return to the normal range until after 120 min.

Conclusions

Intravenous administration of glycerol leads to higher blood lactate levels that persist for up to 120 min. Although hyperlactatemia is an essential indicator of sepsis and/or impaired tissue perfusion, physicians should be aware of this phenomenon when assessing the blood lactate levels.

Statistical analysis plan for early goal-directed therapy using a physiological holistic view - the ANDROMEDA-SHOCK: a randomized controlled trial

Background

ANDROMEDA-SHOCK is an international, multicenter, randomized controlled trial comparing peripheral perfusion-targeted resuscitation to lactate-targeted resuscitation in patients with septic shock in order to test the hypothesis that resuscitation targeting peripheral perfusion will be associated with lower morbidity and mortality.

Objective

To report the statistical analysis plan for the ANDROMEDA-SHOCK trial.

Methods

We describe the trial design, primary and secondary objectives, patients, methods of randomization, interventions, outcomes, and sample size. We describe our planned statistical analysis for the primary, secondary and tertiary outcomes. We also describe the subgroup and sensitivity analyses. Finally, we provide details for presenting our results, including mock tables showing baseline characteristics, the evolution of hemodynamic and perfusion variables, and the effects of treatments on outcomes.

Conclusion

According to the best trial practice, we report our statistical analysis plan and data management plan prior to locking the database and initiating the analyses. We anticipate that this procedure will prevent analysis bias and enhance the utility of the reported results.

Early goal-directed therapy using a physiological holistic view: the ANDROMEDA-SHOCK-a randomized controlled trial

Background

Septic shock is a highly lethal condition. Early recognition of tissue hypoperfusion and its reversion are key factors for limiting progression to multiple organ dysfunction and death. Lactate-targeted resuscitation is the gold-standard under current guidelines, although it has several pitfalls including that non-hypoxic sources of lactate might predominate in an unknown proportion of patients. Peripheral perfusion-targeted resuscitation might provide a real-time response to increases in flow that could lead to a more timely decision to stop resuscitation, thus avoiding fluid overload and the risks of over-resuscitation. This article reports the rationale, study design and analysis plan of the ANDROMEDA-SHOCK Study.

Methods

ANDROMEDA-SHOCK is a randomized controlled trial which aims to determine if a peripheral perfusion-targeted resuscitation is associated with lower 28-day mortality compared to a lactate-targeted resuscitation in patients with septic shock with less than 4 h of diagnosis. Both groups will be treated with the same sequential approach during the 8-hour study period pursuing normalization of capillary refill time versus normalization or a decrease of more than 20% of lactate every 2 h. The common protocol starts with fluid responsiveness assessment and fluid loading in responders, followed by a vasopressor and an inodilator test if necessary. The primary outcome is 28-day mortality, and the secondary outcomes are: free days of mechanical ventilation, renal replacement therapy and vasopressor support during the first 28 days after randomization; multiple organ dysfunction during the first 72 h after randomization; intensive care unit and hospital lengths of stay; and all-cause mortality at 90-day. A sample size of 422 patients was calculated to detect a 15% absolute reduction in mortality in the peripheral perfusion group with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle.

Conclusions

If peripheral perfusion-targeted resuscitation improves 28-day mortality, this could lead to simplified algorithms, assessing almost in real-time the reperfusion process, and pursuing more physiologically sound objectives. At the end, it might prevent the risk of over-resuscitation and lead to a better utilization of intensive care unit resources.

Trial registration ClinicalTrials.gov Identifier: NCT03078712 (registered retrospectively March 13th, 2017)

Septic Shock

For more than 20 years, sepsis has been defined as symptoms associated with the response to microorganism infection, which was more specifically called systemic inflammatory response syndrome (SIRS). With the evidence of organ failure, it was called severe sepsis, and this could lead to hypotension (septic shock). However, with the deep understanding of the pathophysiology of sepsis, sepsis has been known as both inflammatory and anti-inflammatory. Additionally, the classic use of SIRS could lead to overestimation of sepsis. For example, usual common cold could be identified as sepsis in classic definition. With this background, new sepsis definition, Sepsis 3, was introduced and sepsis was defined as a “life-threatening organ dysfunction caused by a dysregulated host response to infection.” The management of sepsis has been changed dramatically, with the development of Surviving Sepsis Campaign, which substantially increased the survival of sepsis. However, this is not with the help of a new drug, but the implementation of a treatment system. Unfortunately, no specific drug for sepsis has survived in clinical use even though many candidate drugs have been successfully investigated in preclinical setting, and this leads to the new approach to the sepsis.

Capillary refill time during fluid resuscitation in patients with sepsis-related hyperlactatemia at the emergency department is related to mortality

INTRODUCTION

Acute circulatory dysfunction in patients with sepsis can evolve rapidly into a progressive stage associated with high mortality. Early recognition and adequate resuscitation could improve outcome. However, since the spectrum of clinical presentation is quite variable, signs of hypoperfusion are frequently unrecognized in patients just admitted to the emergency department (ED). Hyperlactatemia is considered a key parameter to disclose tissue hypoxia but it is not universally available and getting timely results can be challenging in low resource settings. In addition, non-hypoxic sources can be involved in hyperlactatemia, and a misinterpretation could lead to over-resuscitation in an unknown number of cases. Capillary refill time (CRT) is a marker of peripheral perfusion that worsens during circulatory failure. An abnormal CRT in septic shock patients after ICU-based resuscitation has been associated with poor outcome. The aim of this study was to determine the prevalence of abnormal CRT in patients with sepsis-related hyperlactatemia in the early phase after ED admission, and its relationship with outcome.

METHODS

We performed a prospective observational study. Septic patients with hyperlactemia at ED admission subjected to an initial fluid resuscitation (FR) were included. CRT and other parameters were assessed before and after FR. CRT-normal or CRT-abnormal subgroups were defined according to the status of CRT following initial FR, and major outcomes were registered.

RESULTS

Ninety-five hyperlactatemic septic patients were included. Thirty-one percent had abnormal CRT at ED arrival. After FR, 87 patients exhibited normal CRT, and 8 an abnormal one. Patients with abnormal CRT had an increased risk of adverse outcomes (88% vs. 20% p<0.001; RR 4.4 [2.7-7.4]), and hospital mortality (63% vs. 9% p<0.001; RR 6.7 [2.9-16]) as compared to those with normal CRT after FR. Specifically, CRT-normal patients required less frequently mechanical ventilation, renal replacement therapy, and ICU admission, and exhibited a lower hospital mortality.

CONCLUSIONS

Hyperlactatemic sepsis patients with abnormal CRT after initial fluid resuscitation exhibit higher mortality and worse clinical outcomes than patients with normal CRT.

Modified model for end-stage liver disease improves short-term prognosis of hepatitis B virus-related acute-on-chronic liver failure

AIM

To investigate whether the short-term prognosis of hepatitis B virus (HBV)-related acute-on-chronic liver failure (ACLF) could be improved by using a modified model for end-stage liver disease (MELD) including serum lactate.

METHODS

This clinical study was conducted at the First Affiliated Hospital, Fujian Medicine University, China. From 2009 to 2015, 236 patients diagnosed with HBV-related ACLF at our center were recruited for this 3-month follow-up study. Demographic data and serum lactate levels were collected from the patients. The MELD scores with or without serum lactate levels from survival and non-survival groups were recorded and compared.

RESULTS

Two hundred and thirty-six patients with HBV-ACLF were divided into two groups: survival group (S) and non-survival group (NS). Compared with the NS group, the patients in survival the S group had a significantly lower level of serum lactate (3.11 ± 1.98 vs 4.67 ± 2.43, t = 5.43, P < 0.001) and MELD score (23.33 ± 5.42 vs 30.37 ± 6.58, t = 9.01, P = 0.023). Furthermore, serum lactate level was positively correlated with MELD score (r = 0.315, P < 0.001). Therefore, a modified MELD including serum lactate was developed by logistic regression analysis (0.314 × lactate + 0.172 × MELD - 5.923). In predicting 3-month mortality using the MELD-LAC model, the patients from the S group had significantly lower baseline scores (-0.930 ± 1.34) when compared with those from the NS group (0.771 ± 1.32, t = 9.735, P < 0.001). The area under the receiver operating characteristic curve (AUROC) was 0.859 calculated by using the MELD-LAC model, which was significantly higher than that calculated by using the lactate level (0.790) or MELD alone (0.818). When the cutoff value was set at -0.4741, the sensitivity, specificity, positive predictive value and negative predictive value for predicting short-term mortality were 91.5%, 80.10%, 94.34% and 74.62%, respectively. When the MELD-LAC scores at baseline level were set at -0.5561 and 0.6879, the corresponding mortality rates within three months were 75% and 90%, respectively.

CONCLUSION

The short-term prognosis of HBV-related ACLF was improved by using a modified MELD including serum lactate from the present 6-year clinical study.

A hypoperfusion context may aid to interpret hyperlactatemia in sepsis-3 septic shock patients: a proof-of-concept study

Background

Persistent hyperlactatemia is particularly difficult to interpret in septic shock. Besides hypoperfusion, adrenergic-driven lactate production and impaired lactate clearance are important contributors. However, clinical recognition of different sources of hyperlactatemia is unfortunately not a common practice and patients are treated with the same strategy despite the risk of over-resuscitation in some. Indeed, pursuing additional resuscitation in non-hypoperfusion-related cases might lead to the toxicity of fluid overload and vasoactive drugs. We hypothesized that two different clinical patterns can be recognized in septic shock patients through a multimodal perfusion monitoring. Hyperlactatemic patients with a hypoperfusion context probably represent a more severe acute circulatory dysfunction, and the absence of a hypoperfusion context is eventually associated with a good outcome. We performed a retrospective analysis of a database of septic shock patients with persistent hyperlactatemia after initial resuscitation.

Results

We defined hypoperfusion context by the presence of a ScvO₂ < 70%, or a P(cv-a)CO₂ ≥6 mmHg, or a CRT ≥4 s together with hyperlactatemia. Ninety patients were included, of whom seventy exhibited a hypoperfusion-related pattern and 20 did not. Although lactate values were comparable at baseline (4.8 ± 2.8 vs. 4.7 ± 3.7 mmol/L), patients with a hypoperfusion context exhibited a more severe circulatory dysfunction with higher vasopressor requirements, and a trend to longer mechanical ventilation days, ICU stay, and more rescue therapies. Only one of the 20 hyperlactatemic patients without a hypoperfusion context died (5%) compared to 11 of the 70 with hypoperfusion-related hyperlactatemia (16%).

Conclusions

Two different clinical patterns among hyperlactatemic septic shock patients may be identified according to hypoperfusion context. Patients with hyperlactatemia plus low ScvO₂, or high P(cv-a)CO₂, or high CRT values exhibited a more severe circulatory dysfunction. This provides a starting point to launch further prospective studies to confirm if this approach can lead to a more selective resuscitation strategy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-017-0253-x) contains supplementary material, which is available to authorized users.

Effects of dexmedetomidine and esmolol on systemic hemodynamics and exogenous lactate clearance in early experimental septic shock

BACKGROUND

Persistent hyperlactatemia during septic shock is multifactorial. Hypoperfusion-related anaerobic production and adrenergic-driven aerobic generation together with impaired lactate clearance have been implicated. An excessive adrenergic response could contribute to persistent hyperlactatemia and adrenergic modulation might be beneficial. We assessed the effects of dexmedetomidine and esmolol on hemodynamics, lactate generation, and exogenous lactate clearance during endotoxin-induced septic shock.

METHODS

Eighteen anesthetized and mechanically ventilated sheep were subjected to a multimodal hemodynamic/perfusion assessment including hepatic and portal vein catheterizations, total hepatic blood flow, and muscle microdialysis. After monitoring, all received a bolus and continuous infusion of endotoxin. After 1 h they were volume resuscitated, and then randomized to endotoxin-control, endotoxin-dexmedetomidine (sequential doses of 0.5 and 1.0 μg/k/h) or endotoxin-esmolol (titrated to decrease basal heart rate by 20 %) groups. Samples were taken at four time points, and exogenous lactate clearance using an intravenous administration of sodium L-lactate (1 mmol/kg) was performed at the end of the experiments.

RESULTS

Dexmedetomidine and esmolol were hemodynamically well tolerated. The dexmedetomidine group exhibited lower epinephrine levels, but no difference in muscle lactate. Despite progressive hypotension in all groups, both dexmedetomidine and esmolol were associated with lower arterial and portal vein lactate levels. Exogenous lactate clearance was significantly higher in the dexmedetomidine and esmolol groups.

CONCLUSIONS

Dexmedetomidine and esmolol were associated with lower arterial and portal lactate levels, and less impairment of exogenous lactate clearance in a model of septic shock. The use of dexmedetomidine and esmolol appears to be associated with beneficial effects on gut lactate generation and lactate clearance and exhibits no negative impact on systemic hemodynamics.

Prognostic Value of Lactate and Central Venous Oxygen Saturation after Early Resuscitation in Sepsis Patients

The objective of this study was to evaluate the prognostic value of static and dynamic variables of central venous oxygen saturation (ScvO₂) and lactate in patients with severe sepsis or septic shock who underwent early quantitative resuscitation. We also investigated whether ScvO₂ measured after initial resuscitation could provide additive prognostic value to that of lactate. We analyzed the sepsis registry for patients presenting to the emergency department and included patients with simultaneous measurements of lactate and ScvO₂ at the time of presentation (H0) and 6 hours (H6) after resuscitation. The primary outcome was 28-day mortality and multivariable logistic analysis was used to adjust for confounders. A total of 363 patients were included, and the overall 28-day mortality was 18%. The area under the receiver operator characteristic curve for predicting 28-day mortality was as follows: lactate (H6), 0.81; lactate (H0), 0.73; relative lactate change, 0.67; ScvO₂ (H6), 0.65; relative ScvO₂ change 0.59; ScvO₂ (H0), 0.58. Patients with lactate normalization showed significantly lower 28-day mortality compared to patients without lactate normalization (3% vs. 28%, P<0.01). However, in those who achieved ScvO₂ (H6) ≥70%, there was a significant difference in 28-mortality only in patients without lactate normalization (21% vs. 39%, P<0.01) but no difference in those with lactate normalization (4% vs. 3%, P = 0.71). In multivariable analysis, lactate normalization was significantly associated with 28-day mortality (adjusted odds ratio [OR] for 28-day mortality, 0.20; 95% confidence interval [CI], 0.07–0.54; P <0.01), but ScvO₂ (H6) ≥70% showed only a marginal association (the adjusted OR for 28-day mortality, 0.51; 95% CI, 0.26–1.01; P = 0.05). ScvO₂ (H6) ≥70% was associated with 28-day mortality only in cases without lactate normalization in subgroup analysis (adjusted OR 0.37, 95% CI, 0.18–0.79; P = 0.01). Six-hour lactate was the strongest predictor of 28-day mortality in patients with severe sepsis or septic shock. Six-hour ScvO₂ provided additional prognostic value only in cases where lactate values were not normalized after resuscitation.

Non-invasive monitoring of mitochondrial oxygenation and respiration in critical illness using a novel technique

Introduction

Although mitochondrial dysfunction is proposed to be involved in the pathophysiology of sepsis, conflicting results are reported. Variation in methods used to assess mitochondrial function might contribute to this controversy. A non-invasive method for monitoring mitochondrial function might help overcome this limitation. Therefore, this study explores the possibility of in vivo monitoring of mitochondrial oxygen tension (mitoPO₂) and local mitochondrial oxygen consumptionin in an endotoxin-induced septic animal model.

Methods

Animals (rats n = 28) were assigned to a control group (no treatment), or to receive lipopolysaccharide without fluid resuscitation (LPS-NR) or lipopolysaccharide plus fluid resuscitation (LPS-FR). Sepsis was induced by intravenous LPS injection (1.6 mg/kg during 10 min), fluid resuscitation was performed by continuous infusion of a colloid solution, 7 ml kg⁻¹ h⁻¹ and a 2-ml bolus of the same colloid solution. MitoPO₂ and ODR were measured by means of the protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT). Kinetic aspects of the drop in mitoPO₂ were recorded during 60s of skin compression. ODR was derived from the slope of the mitoPO₂ oxygen disappearance curve. Measurements were made before and 3 h after induction of sepsis.

Results

At baseline (t0) all rats were hemodynamically stable. After LPS induction (t1), significant (p < 0.05) hemodynamic changes were observed in both LPS groups. At t0, mitoPO₂ and ODR were 59 ± 1 mmHg, 64 ± 3 mmHg, 68 ± 4 mmHg and 5.0 ± 0.3 mmHg s⁻¹, 5.3 ± 0.5 mmHg s⁻¹, 5.7 ± 0.5 mmHg s⁻¹ in the control, LPS-FR and LPS-NR groups, respectively; at t1 these values were 58 ± 5 mmHg, 50 ± 2.3 mmHg, 30 ± 3.3 mmHg and 4.5 ± 0.5 mmHg s⁻¹, 3.3 ± 0.3 mmHg s⁻¹, 1.8 ± 0.3 mmHg s⁻¹, respectively. At t1, only mitoPO₂ showed a significant difference between the controls and LPS-NR. In contrast, at t1 both LPS groups showed a significantly lower ODR compared to controls.

Conclusion

These data show the feasibility to monitor alterations in mitochondrial oxygen consumption in vivo by PpIX-TSLT in a septic rat model. These results may contribute to the development of a clinical device to monitor mitochondrial function in the critically ill.

Impairment of exogenous lactate clearance in experimental hyperdynamic septic shock is not related to total liver hypoperfusion

Introduction

Although the prognostic value of persistent hyperlactatemia in septic shock is unequivocal, its physiological determinants are controversial. Particularly, the role of impaired hepatic clearance has been underestimated and is only considered relevant in patients with liver ischemia or cirrhosis. Our objectives were to establish whether endotoxemia impairs whole body net lactate clearance, and to explore a potential role for total liver hypoperfusion during the early phase of septic shock.

Methods

After anesthesia, 12 sheep were subjected to hemodynamic/perfusion monitoring including hepatic and portal catheterization, and a hepatic ultrasound flow probe. After stabilization (point A), sheep were alternatively assigned to lipopolysaccharide (LPS) (5 mcg/kg bolus followed by 4 mcg/kg/h) or sham for a three-hour study period. After 60 minutes of shock, animals were fluid resuscitated to normalize mean arterial pressure. Repeated series of measurements were performed immediately after fluid resuscitation (point B), and one (point C) and two hours later (point D). Monitoring included systemic and regional hemodynamics, blood gases and lactate measurements, and ex-vivo hepatic mitochondrial respiration at point D. Parallel exogenous lactate and sorbitol clearances were performed at points B and D. Both groups included an intravenous bolus followed by serial blood sampling to draw a curve using the least squares method.

Results

Significant hyperlactatemia was already present in LPS as compared to sham animals at point B (4.7 (3.1 to 6.7) versus 1.8 (1.5 to 3.7) mmol/L), increasing to 10.2 (7.8 to 12.3) mmol/L at point D. A significant increase in portal and hepatic lactate levels in LPS animals was also observed. No within-group difference in hepatic DO₂, VO₂ or O₂ extraction, total hepatic blood flow (point D: 915 (773 to 1,046) versus 655 (593 to 1,175) ml/min), mitochondrial respiration, liver enzymes or sorbitol clearance was found. However, there was a highly significant decrease in lactate clearance in LPS animals (point B: 46 (30 to 180) versus 1,212 (743 to 2,116) ml/min, P <0.01; point D: 113 (65 to 322) versus 944 (363 to 1,235) ml/min, P <0.01).

Conclusions

Endotoxemia induces an early and severe impairment in lactate clearance that is not related to total liver hypoperfusion.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0928-3) contains supplementary material, which is available to authorized users.

New directions for sepsis and septic shock research

BACKGROUND

Septic shock is a frequent complication in intensive care unit that can result in multiple organ failure and death. In addition, recent data suggested that severe sepsis and septic shock represent an economic burden. Therefore, septic shock is an important public health problem.

METHOD

In this review, we will focus on the recent evidences concerning the stages of septic shock, the complex macrocirculation and microcirculation relationship, and the importance of those evidences for future resuscitation goals and therapeutic strategies during late septic shock.

RESULT

Recently, two stages of septic shock are suggested. In early stage, hypovolemia is the main contributing factor. During this stage, macrocirculatory and microcirculatory changes run parallel, and fluid resuscitation seems to be effective in restoring the hemodynamic parameters. Late stage of septic shock is characterized by complex microcirculation and macrocirculation relationship.

CONCLUSIONS

Although early goal-directed therapy is a stepwise approach in the treatment of septic shock, tissue perfusion remains an important factor that contributes to septic shock outcome. Because appropriate monitoring of tissue perfusion is a matter of debt, the ideal therapeutic strategy remains a controversial issue that needs further investigations.

When to stop septic shock resuscitation: clues from a dynamic perfusion monitoring

BACKGROUND

The decision of when to stop septic shock resuscitation is a critical but yet a relatively unexplored aspect of care. This is especially relevant since the risks of over-resuscitation with fluid overload or inotropes have been highlighted in recent years. A recent guideline has proposed normalization of central venous oxygen saturation and/or lactate as therapeutic end-points, assuming that these variables are equivalent or interchangeable. However, since the physiological determinants of both are totally different, it is legitimate to challenge the rationale of this proposal. We designed this study to gain more insights into the most appropriate resuscitation goal from a dynamic point of view. Our objective was to compare the normalization rates of these and other potential perfusion-related targets in a cohort of septic shock survivors.

METHODS

We designed a prospective, observational clinical study. One hundred and four septic shock patients with hyperlactatemia were included and followed until hospital discharge. The 84 hospital-survivors were kept for final analysis. A multimodal perfusion assessment was performed at baseline, 2, 6, and 24 h of ICU treatment.

RESULTS

Some variables such as central venous oxygen saturation, central venous-arterial pCO2 gradient, and capillary refill time were already normal in more than 70% of survivors at 6 h. Lactate presented a much slower normalization rate decreasing significantly at 6 h compared to that of baseline (4.0 [3.0 to 4.9] vs. 2.7 [2.2 to 3.9] mmol/L; p < 0.01) but with only 52% of patients achieving normality at 24 h. Sublingual microcirculatory variables exhibited the slowest recovery rate with persistent derangements still present in almost 80% of patients at 24 h.

CONCLUSIONS

Perfusion-related variables exhibit very different normalization rates in septic shock survivors, most of them exhibiting a biphasic response with an initial rapid improvement, followed by a much slower trend thereafter. This fact should be taken into account to determine the most appropriate criteria to stop resuscitation opportunely and avoid the risk of over-resuscitation.

Prospective evaluation of intravascular volume status in critically ill patients: does inferior vena cava collapsibility correlate with central venous pressure?

BACKGROUND

In search of a standardized noninvasive assessment of intravascular volume status, we prospectively compared the sonographic inferior vena cava collapsibility index (IVC-CI) and central venous pressures (CVPs). Our goals included the determination of CVP behavior across clinically relevant IVC-CI ranges, examination of unitary behavior of IVC-CI with changes in CVP, and estimation of the effect of positive end-expiratory pressure (PEEP) on the IVC-CI/CVP relationship.

METHODS

Prospective, observational study was performed in surgical/medical intensive care unit patients between October 2009 and July 2013. Patients underwent repeated sonographic evaluations of IVC-CI. Demographics, illness severity, ventilatory support, CVP, and patient positioning were recorded. Correlations were made between CVP groupings (<7, 7-12, 12-18, 19+) and IVC-CI ranges (<25, 25-49, 50-74, 75+). Comparison of CVP (2-unit quanta) and IVC-CI (5-unit quanta) was performed, followed by assessment of per-unit ΔIVC-CI/ΔCVP behavior as well as examination of the effect of PEEP on the IVC-CI/CVP relationship.

RESULTS

We analyzed 320 IVC-CI/CVP measurement pairs from 79 patients (mean [SD] age, 55.8 [16.8] years; 64.6% male; mean [SD] Acute Physiology and Chronic Health Evaluation II, 11.7 [6.21]). Continuous data for IVC-CI/CVP correlated poorly (R = 0.177, p < 0.01) and were inversely proportional, with CVP less than 7 noted in approximately 10% of the patients for IVC-CIs less than 25% and CVP less than 7 observed in approximately 85% of patients for IVC-CIs greater than or equal to 75%. Median ΔIVC-CI per unit CVP was 3.25%. Most measurements (361 of 320) were collected in mechanically ventilated patients (mean [SD] PEEP, 7.76 [4.11] cm H2O). PEEP-related CVP increase was approximately 2 mm Hg to 2.5 mm Hg for IVC-CIs greater than 60% and approximately 3 mm Hg to 3.5 mm Hg for IVC-CIs less than 30%. PEEP also resulted in lower IVC-CIs at low CVPs, which reversed with increasing CVPs. When IVC-CI was examined across increasing PEEP ranges, we noted an inverse relationship between the two variables, but this failed to reach statistical significance.

CONCLUSION

IVC-CI and CVP correlate inversely, with each 1 mm Hg of CVP corresponding to 3.3% median ΔIVC-CI. Low IVC-CI (<25%) is consistent with euvolemia/hypervolemia, while IVC-CI greater than 75% suggests intravascular volume depletion. The presence of PEEP results in 2 mm Hg to 3.5 mm Hg of CVP increase across the IVC-CI spectrum and lower collapsibility at low CVPs. Although IVC-CI decreased with increasing degrees of PEEP, this failed to reach statistical significance. While this study represents a step forward in the area of intravascular volume estimation using IVC-CI, our findings must be applied with caution owing to some methodologic limitations.

LEVEL OF EVIDENCE

Diagnostic study, level III. Prognostic study, level III.

Effects of dobutamine on systemic, regional and microcirculatory perfusion parameters in septic shock: a randomized, placebo-controlled, double-blind, crossover study

PURPOSE

The role of dobutamine during septic shock resuscitation is still controversial since most clinical studies have been uncontrolled and no physiological study has unequivocally demonstrated a beneficial effect on tissue perfusion. Our objective was to determine the potential benefits of dobutamine on hemodynamic, metabolic, peripheral, hepatosplanchnic and microcirculatory perfusion parameters during early septic shock resuscitation.

METHODS

We designed a randomized, controlled, double-blind, crossover study comparing the effects of 2.5-h infusion of dobutamine (5 mcg/kg/min fixed-dose) or placebo in 20 septic shock patients with cardiac index ≥2.5 l/min/m(2) and hyperlactatemia. Primary outcome was sublingual perfused microvascular density.

RESULTS

Despite an increasing cardiac index, heart rate and left ventricular ejection fraction, dobutamine had no effect on sublingual perfused vessel density [9.0 (7.9-10.1) vs. 9.1 n/mm (7.9-9.9); p = 0.24] or microvascular flow index [2.1 (1.8-2.5) vs. 2.1 (1.9-2.5); p = 0.73] compared to placebo. No differences between dobutamine and placebo were found for the lactate levels, mixed venous-arterial pCO2 gradient, thenar muscle oxygen saturation, capillary refill time or gastric-to-arterial pCO2 gradient. The indocyanine green plasma disappearance rate [14.4 (9.5-25.6) vs. 18.8 %/min (11.7-24.6); p = 0.03] and the recovery slope of thenar muscle oxygen saturation after a vascular occlusion test [2.1 (1.1-3.1) vs. 2.5 %/s (1.2-3.4); p = 0.01] were worse with dobutamine compared to placebo.

CONCLUSIONS

Dobutamine failed to improve sublingual microcirculatory, metabolic, hepatosplanchnic or peripheral perfusion parameters despite inducing a significant increase in systemic hemodynamic variables in septic shock patients without low cardiac output but with persistent hypoperfusion.

Clinical use of lactate monitoring in critically ill patients

Increased blood lactate levels (hyperlactataemia) are common in critically ill patients. Although frequently used to diagnose inadequate tissue oxygenation, other processes not related to tissue oxygenation may increase lactate levels. Especially in critically ill patients, increased glycolysis may be an important cause of hyperlactataemia. Nevertheless, the presence of increased lactate levels has important implications for the morbidity and mortality of the hyperlactataemic patients. Although the term lactic acidosis is frequently used, a significant relationship between lactate and pH only exists at higher lactate levels. The term lactate associated acidosis is therefore more appropriate. Two recent studies have underscored the importance of monitoring lactate levels and adjust treatment to the change in lactate levels in early resuscitation. As lactate levels can be measured rapidly at the bedside from various sources, structured lactate measurements should be incorporated in resuscitation protocols.