The pursuit of a high central venous oxygen saturation in sepsis: growing concerns

The Value of Combining Carbon Dioxide Gap and Oxygen-Derived Variables with Lactate Clearance in Predicting Mortality after Resuscitation of Septic Shock Patients

BACKGROUND

Achieving hemodynamic stabilization does not prevent progressive tissue hypoperfusion and organ dysfunction during resuscitation of septic shock patients. Many indicators have been proposed to judge the optimization of oxygen delivery to meet tissue oxygen consumption.

METHODS

A prospective observational study was conducted to evaluate and validate combining CO2 gap and oxygen-derived variables with lactate clearance during early hours of resuscitation of adults presenting with septic shock.

RESULTS

Our study included 456 adults with a mean age of 63.2 ± 6.9 years, with 71.9% being males. Respiratory and urinary infections were the origin of about 75% of sepsis. Mortality occurred in 164 (35.9%) patients. The APACHE II score was 18.2 ± 3.7 versus 34.3 ± 6.8 (p < 0.001), the initial SOFA score was 5.8 ± 3.1 versus 7.3 ± 1.4 (p=0.001), while the SOFA score after 48 hours was 4.2 ± 1.8 versus 9.4 ± 3.1 (p < 0.001) in the survivors and nonsurvivors, respectively. Hospital mortality was independently predicted by hyperlactatemia (OR: 2.47; 95% CI: 1.63-6.82, p=0.004), PvaCO2 gap (OR: 2.62; 95% CI: 1.28-6.74, p=0.026), PvaCO2/CavO2 ratio (OR: 2.16; 95% CI: 1.49-5.74, p=0.006), and increased SOFA score after 48 hours of admission (OR: 1.86; 95% CI: 1.36-8.13, p=0.02). A blood lactate cutoff of 40 mg/dl at the 6th hour of resuscitation (T6) had a 92.7% sensitivity and 75.3% specificity for predicting hospital mortality (AUROC = 0.902) with 81.6% accuracy. Combining the lactate cutoff of 40 mg/dl and PvaCO2/CavO2 ratio cutoff of 1.4 increased the specificity to 93.2% with a sensitivity of 75.6% in predicting mortality and with 86.8% accuracy. Combining the lactate cutoff of 40 mg/dl and PvaCO2 gap of 6 mmHg increased the sensitivity to 93% and increased the specificity to 98% in predicting mortality with 91% accuracy.

CONCLUSION

Combining the carbon dioxide gap and arteriovenous oxygen difference with lactate clearance during early hours of resuscitation of septic shock patients helps to predict hospital mortality more accurately.

Circulatory effects of dexmedetomidine in early sepsis: a randomised controlled experimental study

We designed this experimental study with a view to evaluate the effects of dexmedetomidine (DEX) on cardiac performance and systemic and peripheral hemodynamics in healthy and early-stage endotoxemia swine models. Our study hypothesis was that DEX can ensure hemodynamic stability during the course of endotoxemia. Thirty-two male pigs (25-27 kg) were assigned into four groups: (1) no intervention (group A), (2) DEX 0.8 μg/kg was administered in non-septic animals (group B), (3) sepsis induced by intravenous Escherichia coli endotoxin (group C) and (4) DEX 0.8 μg/kg was administered in septic animals (group D). Hemodynamic parameters such as heart rate, mean blood pressure, central venous pressure, pulmonary artery pressures, pulmonary artery occlusion pressure, pulmonary vascular resistance and cardiac output were continuously recorded. Central venous oxygen saturation was also measured in order to obtain a complete evaluation of cardiovascular response to sepsis. Heart rate was decreased, whilst mean arterial pressure decrease was alleviated after DEX administration in septic animals. In addition, central venous pressure was stable in animals with sepsis after DEX infusion. Sepsis dramatically elevated pulmonary function indicators but DEX succeeded in ameliorating this effect. The important decrease measured in central venous oxygen saturation in both sepsis groups reflected the decreased perfusion of tissues that takes place at the end of early sepsis. Our findings support the hypothesis that DEX has beneficial effects on heart rate and pulmonary artery pressure, whilst reduction in systemic blood pressure occurs at acceptable levels.

Combination of O2 and CO2-derived variables to detect tissue hypoxia in the critically ill patient

Oxygen-derived parameters have been traditionally used to guide resuscitation during shock states. Nevertheless, normalization of venous oxygen saturation does not exclude the persistence of tissue hypoperfusion and tissue hypoxia. Combination of O₂ and CO₂-derived variables has consistently demonstrated to be related with clinical outcomes and its variations could anticipate changes in lactate and also predict fluid responsiveness in terms of oxygen consumption. Here we discuss the potential mechanisms leading to increase the venous-to-arterial CO₂ (Cv-aCO₂) to arterial-to-venous O₂ content difference (Ca-vO₂), i.e., the Cv-aCO₂/Ca-vO₂ ratio, its potential clinical application, limitations and uncertainties. Finally, although biologically plausible, the potential applications of the Cv-aCO₂/Ca-vO₂ ratio in the clinical practice require to be confirmed.

Venoarterial Extracorporeal Membrane Oxygenation Versus Conventional Therapy in Severe Pediatric Septic Shock

OBJECTIVES

The role of venoarterial extracorporeal membrane oxygenation in the treatment of severe pediatric septic shock continues to be intensely debated. Our objective was to determine whether the use of venoarterial extracorporeal membrane oxygenation in severe septic shock was associated with altered patient mortality, morbidity, and/or length of ICU and hospital stay when compared with conventional therapy.

DESIGN

International multicenter, retrospective cohort study using prospectively collected data of children admitted to intensive care with a diagnosis of severe septic shock between the years 2006 and 2014.

SETTING

Tertiary PICUs in Australia, New Zealand, Netherlands, United Kingdom, and United States.

PATIENTS

Children greater than 30 days old and less than 18 years old.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 2,452 children with a diagnosis of sepsis or septic shock, 164 patients met the inclusion criteria for severe septic shock. With conventional therapy (n = 120), survival to hospital discharge was 40%. With venoarterial extracorporeal membrane oxygenation (n = 44), survival was 50% (p = 0.25; CI, -0.3 to 0.1). In children who suffered an in-hospital cardiac arrest, survival to hospital discharge was 18% with conventional therapy and 42% with venoarterial extracorporeal membrane oxygenation (Δ = 24%; p = 0.02; CI, 2.5-42%). Survival was significantly higher in patients who received high extracorporeal membrane oxygenation flows of greater than 150 mL/kg/min compared with children who received standard extracorporeal membrane oxygenation flows or no extracorporeal membrane oxygenation (82%, 43%, and 48%; p = 0.03; CI, 0.1-0.7 and p < 0.01; CI, 0.2-0.7, respectively). Lengths of ICU and hospital stay were significantly longer for children who had venoarterial extracorporeal membrane oxygenation.

CONCLUSIONS

The use of venoarterial extracorporeal membrane oxygenation in severe pediatric sepsis is not by itself associated with improved survival. However, venoarterial extracorporeal membrane oxygenation significantly reduces mortality after cardiac arrest due to septic shock. Venoarterial extracorporeal membrane oxygenation flows greater than 150 mL/kg/min are associated with almost twice the survival rate of conventional therapy or standard-flow extracorporeal membrane oxygenation.

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)

Endorsing performance measures is a matter of trust

Healthcare agencies should ensure that performance measures for accreditation or reimbursement are supported by sound scientific evidence and safeguarded from potential commercial influences, argue Peter Eichacker and colleagues

Oxygen extraction and perfusion markers in severe sepsis and septic shock: diagnostic, therapeutic and outcome implications

PURPOSE OF REVIEW

The purpose of this study is to review the recent literature examining the clinical utility of markers of systemic oxygen extraction and perfusion in the diagnosis, treatment and prognosis of severe sepsis and septic shock.

RECENT FINDINGS

When sepsis is accompanied by conditions in which systemic oxygen delivery does not meet tissue oxygen demands, tissue hypoperfusion begins. Tissue hypoperfusion leads to oxygen debt, cellular injury, organ dysfunction and death. Tissue hypoperfusion can be characterized using markers of tissue perfusion (central venous oxygen saturation and lactate), which reflect the interaction between systemic oxygen delivery and demands. For the last two decades, studies and quality initiatives incorporating the early detection and interruption of tissue hypoperfusion have been shown to improve mortality and altered sepsis care. Three recent trials, while confirming an all-time improvement in sepsis mortality, challenged the concept that rapid normalization of markers of perfusion confers outcome benefit. By defining and comparing haemodynamic phenotypes using markers of tissue perfusion, we may better understand which patients are more likely to benefit from early goal-directed haemodynamic optimization.

SUMMARY

The phenotypic haemodynamic characterization of patients using perfusion markers has diagnostic, therapeutic and outcome implications in severe sepsis and septic shock. However, irrespective of haemodynamic phenotype, the outcome reflects the quality of care provided at the point of presentation. Utilizing these principles may allow more objective interpretation of resuscitation trials and translate these findings into current practice.

Early goal-directed therapy in severe sepsis and septic shock: insights and comparisons to ProCESS, ProMISe, and ARISE

Prior to 2001 there was no standard for early management of severe sepsis and septic shock in the emergency department. In the presence of standard or usual care, the prevailing mortality was over 40-50 %. In response, a systems-based approach, similar to that in acute myocardial infarction, stroke and trauma, called early goal-directed therapy was compared to standard care and this clinical trial resulted in a significant mortality reduction. Since the publication of that trial, similar outcome benefits have been reported in over 70 observational and randomized controlled studies comprising over 70,000 patients. As a result, early goal-directed therapy was largely incorporated into the first 6 hours of sepsis management (resuscitation bundle) adopted by the Surviving Sepsis Campaign and disseminated internationally as the standard of care for early sepsis management. Recently a trio of trials (ProCESS, ARISE, and ProMISe), while reporting an all-time low sepsis mortality, question the continued need for all of the elements of early goal-directed therapy or the need for protocolized care for patients with severe and septic shock. A review of the early hemodynamic pathogenesis, historical development, and definition of early goal-directed therapy, comparing trial conduction methodology and the changing landscape of sepsis mortality, are essential for an appropriate interpretation of these trials and their conclusions.

Can venous-to-arterial carbon dioxide differences reflect microcirculatory alterations in patients with septic shock?

Purpose

Septic shock has been associated with microvascular alterations and these in turn with the development of organ dysfunction. Despite advances in video microscopic techniques, evaluation of microcirculation at the bedside is still limited. Venous-to-arterial carbon dioxide difference (Pv-aCO₂) may be increased even when venous O₂ saturation (SvO₂) and cardiac output look normal, which could suggests microvascular derangements. We sought to evaluate whether Pv-aCO₂ can reflect the adequacy of microvascular perfusion during the early stages of resuscitation of septic shock.

Methods

Prospective observational study including 75 patients with septic shock in a 60-bed mixed ICU. Arterial and mixed-venous blood gases and hemodynamic variables were obtained at catheter insertion (T0) and 6 h after (T6). Using a sidestream dark-field device, we simultaneously acquired sublingual microcirculatory images for blinded semiquantitative analysis. Pv-aCO₂ was defined as the difference between mixed-venous and arterial CO₂ partial pressures.

Results

Progressively lower percentages of small perfused vessels (PPV), lower functional capillary density, and higher heterogeneity of microvascular blood flow were observed at higher Pv-aCO₂ values at both T0 and T6. Pv-aCO₂ was significantly correlated to PPV (T0: coefficient −5.35, 95 % CI −6.41 to −4.29, p < 0.001; T6: coefficient, −3.49, 95 % CI −4.43 to −2.55, p < 0.001) and changes in Pv-aCO₂ between T0 and T6 were significantly related to changes in PPV (R² = 0.42, p < 0.001). Absolute values and changes in Pv-aCO₂ were not related to global hemodynamic variables. Good agreement between venous-to-arterial CO₂ and PPV was maintained even after corrections for the Haldane effect.

Conclusions

During early phases of resuscitation of septic shock, Pv-aCO₂ could reflect the adequacy of microvascular blood flow.

Electronic supplementary material

The online version of this article (doi:10.1007/s00134-015-4133-2) contains supplementary material, which is available to authorized users.

Combination of arterial lactate levels and venous-arterial CO2 to arterial-venous O 2 content difference ratio as markers of resuscitation in patients with septic shock

PURPOSE

To evaluate the prognostic value of the Cv-aCO2/Da-vO2 ratio combined with lactate levels during the early phases of resuscitation in septic shock.

METHODS

Prospective observational study in a 60-bed mixed ICU. One hundred and thirty-five patients with septic shock were included. The resuscitation protocol targeted mean arterial pressure, pulse pressure variations or central venous pressure, mixed venous oxygen saturation, and lactate levels. Patients were classified into four groups according to lactate levels and Cv-aCO2/Da-vO2 ratio at 6 h of resuscitation (T6): group 1, lactate ≥2.0 mmol/L and Cv-aCO2/Da-vO2 >1.0; group 2, lactate ≥2.0 mmol/L and Cv-aCO2/Da-vO2 ≤1.0; group 3, lactate <2.0 mmol/L and Cv-aCO2/Da-vO2 >1.0; and group 4, lactate <2.0 mmol/L and Cv-aCO2/Da-vO2 ≤1.0.

RESULTS

Combination of hyperlactatemia and high Cv-aCO2/Da-vO2 ratio was associated with the worst SOFA scores and lower survival rates at day 28 [log rank (Mantel-Cox) = 31.39, p < 0.0001]. Normalization of both variables was associated with the best outcomes. Patients with a high Cv-aCO2/Da-vO2 ratio and lactate <2.0 mmol/L had similar outcomes to hyperlactatemic patients with low Cv-aCO2/Da-vO2 ratio. The multivariate analysis revealed that Cv-aCO2/Da-vO2 ratio at both T0 (RR 3.85; 95 % CI 1.60-9.27) and T6 (RR 3.97; 95 % CI 1.54-10.24) was an independent predictor for mortality at day 28, as well as lactate levels at T6 (RR 1.58; 95 % CI 1.13-2.22).

CONCLUSION

Complementing lactate assessment with Cv-aCO2/Da-vO2 ratio during early stages of resuscitation of septic shock can better identify patients at high risk of adverse outcomes. The Cv-aCO2/Da-vO2 ratio may become a potential resuscitation goal in patients with septic shock.

Earliest Bedside Assessment of Hemodynamic Parameters and Cardiac Biomarkers: Their Role as Predictors of Adverse Outcome in Patients with Septic Shock

BACKGROUND

Early assessment and aggressive hemodynamic treatment have been shown to increase the survival of patients in septic shock. Current and past sepsis guidelines recommend a resuscitation protocol including central venous pressure (CVP), mean arterial blood pressure (MAP), urine output and central venous oxygen saturation (ScvO2) for resuscitation within the first six hours. Currently, the established severity score systems like APACHE II score, SOFA score or SAPS II score predict the outcome of critically ill patients on the bases of variables obtained only after the first 24 hours. The present study aims to evaluate the risk of short-term mortality for patients with septic shock by the earliest possible assessment of hemodynamic parameters and cardiac biomarkers as well as their role for the prediction of the adverse outcome.

METHODS

52 consecutive patients treated for septic shock in the intensive care unit of one centre (Marien Hospital Herne, Ruhr University Bochum, Germany) were prospectively enrolled in this study. Hemodynamic parameters (MAP, CVP, ScvO2, left ventricular ejection fraction, Hematocrit) and cardiac biomarkers (Troponin I) at the ICU admission were evaluated in regard to their influence on mortality. The primary endpoint was all-cause mortality within 28 days after the admission.

RESULTS

A total of 52 patients (31 male, 21 female) with a mean age of 71.4±8.5 years and a mean APACHE II score of 37.0±7.6 were enrolled in the study. 28 patients reached the primary endpoint (mortality 54%). Patients presenting with hypotension (MAP <65 mmHg) at ICU admission had significantly higher rates of 28-day mortality as compared with the group of patients without hypotension (28-day mortality rate 74 % vs. 32 %, p<0.01). Furthermore, the patients in the hypotension present group had significantly higher lactate concentration (p=0.002), higher serum creatinin (p=0.04), higher NTproBNP (p=0.03) and after the first 24 hours higher APACHE II scores (p=0.04). A MAP <65 mmHg was the only hemodynamic parameter significantly predicting the primary endpoint (OR: 4.1, CI: 1.1 - 14.8, p=0.008), whereas the remaining hemodynamic variables CVP, ScvO2, Hematocrit, Troponin I and left ventricular ejection fraction (LVEF) seemed to have no influence on survival. Besides, non-survivors had a significantly higher age (74.1±9.0 vs. 68.4±6.9, p=0.01). If hypotension coincided with an age ≥72 years, the 28-day mortality rate escalated to 88%.

CONCLUSIONS

In our study, we identified a risk group with an exceedingly high mortality rate: the patients with an age ≥72 years and presenting with hypotension (MAP <65 mmHg). These data can be easily obtained at the time of the very first patient contact. As a result, an aggressive and a more effective treatment can be initiated within the first minutes of the primary care, possibly reducing organ failure and short-term mortality in this risk group.

Central venous oxygenation: when physiology explains apparent discrepancies

Central venous oxygen saturation (ScvO₂) >70% or mixed venous oxygen saturation (SvO₂) >65% is recommended for both septic and non-septic patients. Although it is the task of experts to suggest clear and simple guidelines, there is a risk of reducing critical care to these simple recommendations. This article reviews the basic physiological and pathological features as well as the metrological issues that provide clear evidence that SvO₂ and ScvO₂ are adaptative variables with large inter-patient variability. This variability is exemplified in a modeled population of 1,000 standard ICU patients and in a real population of 100 patients including 15,860 measurements. In these populations, it can be seen how optimizing one to three of the four S(c)vO₂ components homogenized the patients and yields a clear dependency with the fourth one. This explains the discordant results observed in large studies where cardiac output was increased up to predetermined S(c)vO₂ thresholds following arterial oxygen hemoglobin saturation, total body oxygen consumption needs and hemoglobin optimization. Although a systematic S(c)vO₂ goal-oriented protocol can be statistically profitable before ICU admission, appropriate intensive care mandates determination of the best compromise between S(c)vO₂ and its four components, taking into account the specific constraints of each individual patient.

Prevalence of low central venous oxygen saturation in the first hours of intensive care unit admission and associated mortality in septic shock patients: a prospective multicentre study

Introduction

In septic shock patients, the prevalence of low (<70%) central venous oxygen saturation (ScvO2) on admission to the intensive care unit (ICU) and its relationship to outcome are unknown. The objectives of the present study were to estimate the prevalence of low ScvO2 in the first hours of ICU admission and to assess its potential association with mortality in patients with severe sepsis or septic shock.

Methods

This was a prospective, multicentre, observational study conducted over a one-year period in ten French ICUs. Clinicians were asked to include patients with severe sepsis or septic shock preferably within 6 hours of ICU admission and as soon as possible without changing routine practice. ScvO2 was measured at inclusion and 6 hours later (H6), by blood sampling.

Results

We included 363 patients. Initial ScvO2 below 70% was present in 111 patients and the pooled estimate for its prevalence was 27% (95% Confidence interval (95%CI): 18% to 37%). At time of inclusion, among 166 patients with normal lactate concentration (≤2 mmol/L), 55 (33%) had a low initial ScvO2 (<70%), and among 136 patients who had already reached the classic clinical endpoints for mean arterial pressure (≥65 mmHg), central venous pressure (≥8 mmHg), and urine output (≥0.5 mL/Kg of body weight), 43 (32%) had a low initial ScvO2 (<70%). Among them, 49% had lactate below 2 mmol/L. The day-28 mortality was higher in case of low initial ScvO2 (37.8% versus 27.4%; P = 0.049). When adjusted for confounders including the Simplified Acute Physiology Score and initial lactate concentration, a low initial ScvO2 (Odds ratio (OR) = 3.60, 95%CI: 1.76 to 7.36; P = 0.0004) and a low ScvO2 at H6 (OR = 2.18, 95%CI: 1.12 to 4.26; P = 0.022) were associated with day-28 mortality by logistic regression.

Conclusions

Low ScvO2 was common in the first hours of admission to the ICU for severe sepsis or septic shock even when clinical resuscitation endpoints were achieved and even when arterial lactate was normal. A ScvO2 below 70% in the first hours of ICU admission and six hours later was associated with day-28 mortality.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0609-7) contains supplementary material, which is available to authorized users.

Prognostic value of central venous oxygen saturation and blood lactate levels measured simultaneously in the same patients with severe systemic inflammatory response syndrome and severe sepsis

BACKGROUND

Blood lactate levels and central venous oxygen saturation (ScvO(2)) are known to be useful indicators of global tissue hypoxia. However, it is unclear whether ScvO(2) correlates with lactate levels when measured simultaneously and whether changes in ScvO(2) or lactate levels in serial measurements have prognostic value. We investigated the correlation between ScvO(2) and lactate levels measured simultaneously and their association with clinical outcomes.

METHODS

We performed a prospective observational study of patients with severe systemic inflammatory response syndrome (SIRS) and severe sepsis who were admitted to the medical intensive care unit. ScvO(2) and lactate levels were measured simultaneously at the time of study enrollment, every 6 h for 24 h, and then every 24 h until the goal was reached.

RESULTS

Twenty-five patients were enrolled in the study; 13 have died and 12 have survived. There was no correlation between lactate levels and ScvO(2). Neither lactate levels nor ScvO(2) at the time of admission differed between nonsurvivors and survivors. Normalization of lactate levels within 48 h was significantly associated with survival.

CONCLUSIONS

In patients with severe SIRS and severe sepsis, simultaneously measured ScvO(2) and lactate levels showed no correlation, and normalization of lactate levels within 48 h was a predictive factor for survival.

The Surviving Sepsis Campaign's Revised Sepsis Bundles

The Surviving Sepsis Campaign (SSC) sepsis care bundles have recently been revised. The original 6-h resuscitation bundle which included rapid antibiotic administration and hemodynamic support with early goal-directed therapy (EGDT) has been divided into two bundles; one including antibiotic and fluid support to be completed within 3 h, and the other including vasopressor support and measures of central venous pressure and oxygen saturation to be completed within 6 h. The original 24-h management bundle targeting glucose control, administration of corticosteroids and recombinant human activated protein C (rhAPC), and limitation of plateau airway pressures during mechanical ventilation is no longer recommended. Past and recent reports by the SSC and others have suggested that compliance with the original bundles was low and their impact unclear. Examination of the revised bundles in the context of issues and questions arising with the original ones suggest that while compliance with new 3-h bundle will be high, compliance with the 6-h bundle will continue to be low.

Central venous oxygen saturation under non-protocolized resuscitation is not related to survival in severe sepsis or septic shock

Protocolized hemodynamic resuscitation in severe sepsis or septic shock is not universally applied in all emergency departments and general hospital wards around the world. It is unknown whether ScvO2 levels are associated with the clinical outcome of severe sepsis or septic shock under nonprotocolized resuscitation. In this prospective study, we enrolled 124 noncirrhotic patients who were admitted to intensive care units for severe sepsis or septic shock. The average Acute Physiology and Chronic Health Evaluation II score was 25.3 (SD, 7.6). According to ScvO2 levels after initial resuscitation before intensive care unit admission, patients were divided into high (ScvO2 ≥ 70%, n = 63) and low (ScvO2 < 70%, n = 61) ScvO2 groups. Compared with high ScvO2 groups, low ScvO2 groups showed no significant differences in 28-day mortality (25.4% vs. 24.6%; P = 0.943) or hospital mortality (30.2% vs. 31.1%; P = 0.794). Multivariate logistic regression models showed that low mean arterial pressure (hazard ratio, 0.967; 95% confidence interval, 0.940-0.994; P = 0.019) and high central venous pressure (hazard ratio, 1.150; 95% confidence interval, 1.057-1.251; P = 0.001) after initial resuscitation were associated with higher 28-day mortality. On the contrary, ScvO2 levels after resuscitation were not related to 28-day or hospital mortality. In conclusion, our results showed that mean arterial pressure and central venous pressure were still the most important hemodynamic variables in initial hemodynamic resuscitation. Low postresuscitation ScvO2 was not associated with a worse outcome. It is possible that ScvO2 less than 70% might not necessarily be associated with tissue hypoxia, and critical ScvO2 levels require to be determined by further studies.

Does lactate measurement performed on admission predict clinical outcome on the intensive care unit? A concise systematic review

Background

There is a need for practical, efficient and effective prognostic markers for patients admitted to the intensive care unit (ICU) with sepsis, to identify patients at highest risk and guide and monitor treatment. Although many biomarkers and scoring systems have been advocated, none have yet achieved this elusive combination. Most ICUs already use blood lactate concentrations to monitor patients but the evidence base for this application is unclear.

Methods

A systematic review of the last five years of evidence of effectiveness of lactate measurement in prediction of outcome in ICUs was performed.

Results

It was found that there is a lack of high-quality evidence, and no specific studies of prognostic accuracy. d- or l-Lactate concentrations measured in plasma, serum, whole blood or colonic washings were raised at admission in almost all patient groups, and were higher in patient groups who had the worst outcomes (in-hospital mortality, sequential organ failure). However, there was significant overlap in individual concentrations measured in those who died within 28 days of admission, or who developed multiple organ failure, and those who did not. For serum l-lactate concentrations, no specific cut-off value capable of predicting in-hospital mortality or sequential organ failure could be recommended.

Conclusions

The evidence reviewed suggested that whole blood, plasma or serum lactate measurement could not provide specific prognostic information for individual patients. There may be a role for monitoring for normalization of serum d- or l-lactate concentrations during goal-directed therapy in the ICU but further good-quality studies are needed. Measurement of the d-lactate stereoisomer shows promise, such that further studies are warranted.

Prognostic value and agreement of achieving lactate clearance or central venous oxygen saturation goals during early sepsis resuscitation

OBJECTIVES

Lactate clearance (LC) and central venous oxygen saturation (ScvO(2)) have been proposed as goals of early sepsis resuscitation. The authors sought to determine the agreement and prognostic value of achieving ScvO(2) or LC goals in septic shock patients undergoing emergency department (ED)-based early resuscitation.

METHODS

This was a preplanned analysis of a multicenter ED randomized controlled trial of early sepsis resuscitation targeting three variables: central venous pressure, mean arterial pressure, and either ScvO(2) or LC. Inclusion criteria included suspected infection, two or more systemic inflammation criteria, and either systolic blood pressure of <90 mm Hg after intravenous fluid bolus or lactate level of >4 mmol/L. Both ScvO(2) and LC were measured simultaneously. The ScvO(2) goal was defined as ≥70%. Lactate was measured at enrollment and every 2 hours until the goal was reached or up to 6 hours. LC goal was defined as a decrease of ≥10% from initial measurement. The primary outcome was in-hospital mortality.

RESULTS

A total of 203 subjects were included, with an overall mortality of 19.7%. Achievement of the ScvO(2) goal only was associated with a mortality rate of 41% (9/22), while achievement of the LC goal only was associated with a mortality rate of 8% (2/25; proportion difference = 33%; 95% confidence interval [CI] = 9% to 55%). No agreement was found between goal achievement (κ = -0.02), and exact test for matched pairs demonstrated no significant difference between discordant pairs (p = 0.78).

CONCLUSIONS

No agreement was found between LC and ScvO(2) goal achievement in early sepsis resuscitation. Achievement of a ScvO(2) ≥ 70% without LC ≥ 10% was more strongly associated with mortality than achievement of LC ≥ 10% with failure to achieve ScvO(2) ≥ 70%.

Clinical review: use of venous oxygen saturations as a goal - a yet unfinished puzzle

Shock is defined as global tissue hypoxia secondary to an imbalance between systemic oxygen delivery and oxygen demand. Venous oxygen saturations represent this relationship between oxygen delivery and oxygen demand and can therefore be used as an additional parameter to detect an impaired cardiorespiratory reserve. Before appropriate use of venous oxygen saturations, however, one should be aware of the physiology. Although venous oxygen saturation has been the subject of research for many years, increasing interest arose especially in the past decade for its use as a therapeutic goal in critically ill patients and during the perioperative period. Also, there has been debate on differences between mixed and central venous oxygen saturation and their interchangeability. Both mixed and central venous oxygen saturation are clinically useful but both variables should be used with insightful knowledge and caution. In general, low values warn the clinician about cardiocirculatory or metabolic impairment and should urge further diagnostics and appropriate action, whereas normal or high values do not rule out persistent tissue hypoxia. The use of venous oxygen saturations seems especially useful in the early phase of disease or injury. Whether venous oxygen saturations should be measured continuously remains unclear. Especially, continuous measurement of central venous oxygen saturation as part of the treatment protocol has been shown a valuable strategy in the emergency department and in cardiac surgery. In clinical practice, venous oxygen saturations should always be used in combination with vital signs and other relevant endpoints.

Sepsis-induced tissue hypoperfusion

The understanding of sepsis is continuously evolving. An overview of sepsis-induced tissue hypoperfusion has been provided herein. It is of critical importance that the clinician understands the pathophysiology of this emergent condition and is able to synthesize the available data in a rapid fashion so that tissue hypoperfusion is readily detected. Once detected, aggressive and endpoint-directed resuscitation should be implemented to reverse the hypoperfusion and to prevent further deterioration, organ dysfunction, and death.

Surviving sepsis: going beyond the guidelines

The Surviving Sepsis Campaign is a global effort to improve the care of patients with severe sepsis and septic shock. The first Surviving Sepsis Campaign Guidelines were published in 2004 with an updated version published in 2008. These guidelines have been endorsed by many professional organizations throughout the world and come regarded as the standard of care for the management of patients with severe sepsis. Unfortunately, most of the recommendations of these guidelines are not evidence-based. Furthermore, the major components of the 6-hour bundle are based on a single-center study whose validity has been recently under increasing scrutiny. This paper reviews the validity of the Surviving Sepsis Campaign 6-hour bundle and provides a more evidence-based approach to the initial resuscitation of patients with severe sepsis.

Haplotype association mapping of acute lung injury in mice implicates activin a receptor, type 1

RATIONALE

Because acute lung injury is a sporadic disease produced by heterogeneous precipitating factors, previous genetic analyses are mainly limited to candidate gene case-control studies.

OBJECTIVES

To develop a genome-wide strategy in which single nucleotide polymorphism associations are assessed for functional consequences to survival during acute lung injury in mice.

METHODS

To identify genes associated with acute lung injury, 40 inbred strains were exposed to acrolein and haplotype association mapping, microarray, and DNA-protein binding were assessed.

MEASUREMENTS AND MAIN RESULTS

The mean survival time varied among mouse strains with polar strains differing approximately 2.5-fold. Associations were identified on chromosomes 1, 2, 4, 11, and 12. Seven genes (Acvr1, Cacnb4, Ccdc148, Galnt13, Rfwd2, Rpap2, and Tgfbr3) had single nucleotide polymorphism (SNP) associations within the gene. Because SNP associations may encompass "blocks" of associated variants, functional assessment was performed in 91 genes within ± 1 Mbp of each SNP association. Using 10% or greater allelic frequency and 10% or greater phenotype explained as threshold criteria, 16 genes were assessed by microarray and reverse real-time polymerase chain reaction. Microarray revealed several enriched pathways including transforming growth factor-β signaling. Transcripts for Acvr1, Arhgap15, Cacybp, Rfwd2, and Tgfbr3 differed between the strains with exposure and contained SNPs that could eliminate putative transcriptional factor recognition sites. Ccdc148, Fancl, and Tnn had sequence differences that could produce an amino acid substitution. Mycn and Mgat4a had a promoter SNP or 3'untranslated region SNPs, respectively. Several genes were related and encoded receptors (ACVR1, TGFBR3), transcription factors (MYCN, possibly CCDC148), and ubiquitin-proteasome (RFWD2, FANCL, CACYBP) proteins that can modulate cell signaling. An Acvr1 SNP eliminated a putative ELK1 binding site and diminished DNA-protein binding.

CONCLUSIONS

Assessment of genetic associations can be strengthened using a genetic/genomic approach. This approach identified several candidate genes, including Acvr1, associated with increased susceptibility to acute lung injury in mice.

ANGPT2 genetic variant is associated with trauma-associated acute lung injury and altered plasma angiopoietin-2 isoform ratio

RATIONALE

Acute lung injury (ALI) acts as a complex genetic trait, yet its genetic risk factors remain incompletely understood. Large-scale genotyping has not previously been reported for ALI.

OBJECTIVES

To identify ALI risk variants after major trauma using a large-scale candidate gene approach.

METHODS

We performed a two-stage genetic association study. We derived findings in an African American cohort (n = 222) using a cardiopulmonary disease-centric 50K single nucleotide polymorphism (SNP) array. Genotype and haplotype distributions were compared between subjects with ALI and without ALI, with adjustment for clinical factors. Top performing SNPs (P < 10(-4)) were tested in a multicenter European American trauma-associated ALI case-control population (n = 600 ALI; n = 2,266 population-based control subjects) for replication. The ALI-associated genomic region was sequenced, analyzed for in silico prediction of function, and plasma was assayed by ELISA and immunoblot.

MEASUREMENTS AND MAIN RESULTS

Five SNPs demonstrated a significant association with ALI after adjustment for covariates in Stage I. Two SNPs in ANGPT2 (rs1868554 and rs2442598) replicated their significant association with ALI in Stage II. rs1868554 was robust to multiple comparison correction: odds ratio 1.22 (1.06-1.40), P = 0.0047. Resequencing identified predicted novel splice sites in linkage disequilibrium with rs1868554, and immunoblots showed higher proportion of variant angiopoietin-2 (ANG2) isoform associated with rs1868554T (0.81 vs. 0.48; P = 0.038).

CONCLUSIONS

An ANGPT2 region is associated with both ALI and variation in plasma angiopoietin-2 isoforms. Characterization of the variant isoform and its genetic regulation may yield important insights about ALI pathogenesis and susceptibility.

Optimizing hemodynamic support in septic shock using central and mixed venous oxygen saturation

Global tissue hypoxia is one of the most important factors in the development of multisystem organ dysfunction. In hemodynamically unstable critically ill patients, central venous oxygen saturation (Scvo(2)) and mixed venous oxygen saturation (Svo(2)) monitoring has been shown to be a better indicator of global tissue hypoxia than vital signs and other clinical parameters alone. Svo(2) is probably more representative of global tissue oxygenation, whereas Scvo(2), is less invasive. Svo(2) and Scvo(2) monitoring can have diagnostic and therapeutic uses in understanding the efficacy of interventions in treating critically ill, hemodynamically unstable patients.

Early goal-directed therapy: on terminal life support?

Early goal-directed therapy (EGDT) has become regarded as the standard of care for the management of patients with severe sepsis and septic shock. The elements of EGDT have been bundled together as the "Sepsis Bundle," and compliance with the elements of the bundle is frequently used as an indicator of the quality of care delivered. The major elements of EGDT include fluid resuscitation to achieve a central venous pressure of 8 to 12 cm of water, followed by the transfusion of packed red cells or an inotropic agent to maintain the central venous oxygen saturation higher than 70%. Although the concept of early resuscitation is a scientifically sound concept, we believe that the major elements of the sepsis bundle are fatally flawed.

Bundled care for septic shock: an analysis of clinical trials

CONTEXT

Sepsis bundles have been developed to improve patient outcomes by combining component therapies. Valid bundles require effective components with additive benefits. Proponents encourage evaluation of bundles, both as a whole and based on the performance of each component.

OBJECTIVE

Assess the association between outcome and the utilization of component therapies in studies of sepsis bundles.

DATA SOURCE

Database searches (January 1980 to July 2008) of PubMed, Embase, and the Cochrane Library, using the terms sepsis, bundles, guidelines, and early goal directed therapy.

DATA EXTRACTION

Inclusion required comparison of septic adults who received bundled care vs. nonprotocolized care. Survival and use rates for individual interventions were abstracted.

MAIN RESULTS

Eight unblinded trials, one randomized and seven with historical controls, were identified. Sepsis bundles were associated with a consistent (I2 = 0%, p = .87) and significant increase in survival (odds ratio, 1.91; 95% confidence interval, 1.49-2.45; p < .0001). For all studies reporting such data, there were consistent (I2 = 0%, p > or = .64) decreases in time to antibiotics, and increases in the appropriateness of antibiotics (p < or = .0002 for both). In contrast, significant heterogeneity was seen across trials for all other treatments (antibiotic use within a specified time period; administration of fluids, vasopressors, inotropes, and packed red blood cells titrated to hemodynamic goals; corticosteroids and human recombinant activated protein C use) (all I2 > or = 67%, p < .002). Except for antibiotics, sepsis bundle components are still being investigated for efficacy in randomized controlled trials.

CONCLUSION

Bundle use was associated with consistent and significant improvement in survival and antibiotic use. Use of other bundle components changed heterogeneously across studies, making their impact on survival uncertain. However, this analysis should be interpreted cautiously as these studies were unblinded, and only one was randomized.

Year in review 2008: Critical Care--cardiology

We review key research papers in cardiology and intensive care published during 2008 in Critical Care. We quote studies on the same subject published in other journals if appropriate. Papers have been grouped into three categories: (a) cardiovascular biomarkers in critical illness, (b) haemodynamic management of septic shock, and (c) haemodynamic monitoring.

Venous oxygen saturation and lactate gradient from superior vena cava to pulmonary artery in patients with septic shock

Monitoring of central venous oxygen saturation (ScvO2) is considered comparable with mixed venous oxygen saturation (SvO2) in the initial resuscitation phase of septic shock. Our aim was to assess their agreement in septic shock in the intensive care unit setting and the effect of a potential difference in a computed parameter, namely, oxygen consumption (VO2). In addition, we sought for a central venous to pulmonary artery (PA) lactate gradient. We enrolled 37 patients with septic shock who were receiving noradrenaline infusions, and their attending physicians had placed a PA catheter for fluid management. Blood samples were drawn in succession from the superior vena cava, right atrium (RA), right ventricle, and PA. Hemodynamic and treatment parameters were monitored, and data were compared by correlation and Bland-Altman analysis. Mixed venous oxygen saturation was lower than ScvO2 (70.2% +/- 11.4% vs. 78.6% +/- 10.2%; P < 0.001), with a bias of -8.45% and 95% limits of agreement ranging from -20.23% to 3.33%. This difference correlated significantly to the noradrenaline infusion rate and the oxygen consumption and extraction ratio. These lower SvO2 values resulted in computed VO2v higher than the VO2cv (P < 0.001), with a bias of 104.97 mL min(-1) and 95% limits of agreement from -4.12 to 214.07 mL min(-1). Finally, lactate concentration was higher in the superior vena cava and RA than in the PA (2.42 +/- 3.15 and 2.35 +/- 3.16 vs. 2.17 +/- 3.19 mM; P < 0.01 for both comparisons). Thus, our data suggest that ScvO2 and SvO2 are not equivalent in intensive care unit patients with septic shock. Additionally, the substitution of ScvO2 for SvO2 in the calculation of VO2 produces unacceptably large errors. Finally, the decrease in lactate between RA and PA may support the hypothesis that the mixing of RA and coronary sinus blood is at least partially responsible for the difference between ScvO2 and SvO2.

Central venous oxygen saturation and emergency intubation--another piece in the puzzle?

A recent multicentre observational study examined the effect of emergency intubation on central venous oxygen saturation (SCVo2) in critically ill patients. The main finding was that SCVo2 significantly increases 15 minutes after emergency intubation and institution of mechanical ventilation with 100% oxygen, especially in those patients with pre-intubation SCVo2 values <70%, regardless of whether these patients suffered from severe sepsis. However, in only one-quarter of this subgroup was the SCVo2 normalized to > or =70% solely by this intervention. In contrast, in patients with pre-intubation SCVo2 > or =70%, the SCVo2 failed to increase after intubation. A rise in SCVo2 can be expected when whole body oxygen extraction remains unchanged after intubation and ventilation with pure oxygen.

Impact of emergency intubation on central venous oxygen saturation in critically ill patients: a multicenter observational study

INTRODUCTION

Central venous oxygen saturation (ScvO2) has emerged as an important resuscitation goal for critically ill patients. Nevertheless, growing concerns about its limitations as a perfusion parameter have been expressed recently, including the uncommon finding of low ScvO2 values in patients in the intensive care unit (ICU). Emergency intubation may induce strong and eventually divergent effects on the physiologic determinants of oxygen transport (DO2) and oxygen consumption (VO2) and, thus, on ScvO2. Therefore, we conducted a study to determine the impact of emergency intubation on ScvO2.

METHODS

In this prospective multicenter observational study, we included 103 septic and non-septic patients with a central venous catheter in place and in whom emergency intubation was required. A common intubation protocol was used and we evaluated several parameters including ScvO2 before and 15 minutes after emergency intubation. Statistical analysis included chi-square test and t test.

RESULTS

ScvO2 increased from 61.8 +/- 12.6% to 68.9 +/- 12.2%, with no difference between septic and non-septic patients. ScvO2 increased in 84 patients (81.6%) without correlation to changes in arterial oxygen saturation (SaO2). Seventy eight (75.7%) patients were intubated with ScvO2 less than 70% and 21 (26.9%) normalized the parameter after the intervention. Only patients with pre-intubation ScvO2 more than 70% failed to increase the parameter after intubation.

CONCLUSIONS

ScvO2 increases significantly in response to emergency intubation in the majority of septic and non-septic patients. When interpreting ScvO2 during early resuscitation, it is crucial to consider whether the patient has been recently intubated or is spontaneously breathing.

Gastric tonometry versus cardiac index as resuscitation goals in septic shock: a multicenter, randomized, controlled trial

INTRODUCTION

Resuscitation goals for septic shock remain controversial. Despite the normalization of systemic hemodynamic variables, tissue hypoperfusion can still persist. Indeed, lactate or oxygen venous saturation may be difficult to interpret. Our hypothesis was that a gastric intramucosal pH-guided resuscitation protocol might improve the outcome of septic shock compared with a standard approach aimed at normalizing systemic parameters such as cardiac index (CI).

METHODS

The 130 septic-shock patients were randomized to two different resuscitation goals: CI >or= 3.0 L/min/m2 (CI group: 66 patients) or intramucosal pH (pHi) >or= 7.32 (pHi group: 64 patients). After correcting basic physiologic parameters, additional resuscitation consisting of more fluids and dobutamine was started if specific goals for each group had not been reached. Several clinical data were registered at baseline and during evolution. Hemodynamic data and pHi values were registered every 6 hours during the protocol. Primary end point was 28 days' mortality.

RESULTS

Both groups were comparable at baseline. The most frequent sources of infection were abdominal sepsis and pneumonia. Twenty-eight day mortality (30.3 vs. 28.1%), peak Therapeutic Intervention Scoring System scores (32.6 +/- 6.5 vs. 33.2 +/- 4.7) and ICU length of stay (12.6 +/- 8.2 vs. 16 +/- 12.4 days) were comparable. A higher proportion of patients exhibited values below the specific target at baseline in the pHi group compared with the CI group (50% vs. 10.9%; P < 0.001). Of 32 patients with a pHi < 7.32 at baseline, only 7 (22%) normalized this parameter after resuscitation. Areas under the receiver operator characteristic curves to predict mortality at baseline, and at 24 and 48 hours were 0.55, 0.61, and 0.47, and 0.70, 0.90, and 0.75, for CI and pHi, respectively.

CONCLUSIONS

Our study failed to demonstrate any survival benefit of using pHi compared with CI as resuscitation goal in septic-shock patients. Nevertheless, a normalization of pHi within 24 hours of resuscitation is a strong signal of therapeutic success, and in contrast, a persistent low pHi despite treatment is associated with a very bad prognosis in septic-shock patients.

Recent advances in genetic predisposition to clinical acute lung injury

It has been well established that acute lung injury (ALI), and the more severe presentation of acute respiratory distress syndrome (ARDS), constitute complex traits characterized by a multigenic and multifactorial etiology. Identification and validation of genetic variants contributing to disease susceptibility and severity has been hampered by the profound heterogeneity of the clinical phenotype and the role of environmental factors, which includes treatment, on outcome. The critical nature of ALI and ARDS, compounded by the impact of phenotypic heterogeneity, has rendered the amassing of sufficiently powered studies especially challenging. Nevertheless, progress has been made in the identification of genetic variants in select candidate genes, which has enhanced our understanding of the specific pathways involved in disease manifestation. Identification of novel candidate genes for which genetic association studies have confirmed a role in disease has been greatly aided by the powerful tool of high-throughput expression profiling. This article will review these studies to date, summarizing candidate genes associated with ALI and ARDS, acknowledging those that have been replicated in independent populations, with a special focus on the specific pathways for which candidate genes identified so far can be clustered.

Year in review 2007: Critical Care--cardiology

This review summarises key research papers in the fields of cardiology and intensive care published during 2007 in Critical Care. To create a context and for comparison with the papers described in the review, we cite studies on the same subject published in other journals. The papers have been grouped into four categories: venous oximetry, cardiac surgery, perioperative fluid optimisation, and haemodynamic monitoring.

Bench-to-bedside review: the initial hemodynamic resuscitation of the septic patient according to Surviving Sepsis Campaign guidelines--does one size fit all?

The Surviving Sepsis Campaign guidelines for the management of severe sepsis and septic shock recommend that the initial hemodynamic resuscitation be done according to the protocol used by Rivers and colleagues in their well-known early goal-directed therapy (EGDT) study. However, it may well be that their patients were much sicker on admission than many other septic patients. Compared with other populations of septic patients, the patients of Rivers and colleagues had a higher incidence of severe comorbidities, a more severe hemodynamic status on admission (excessively low central venous oxygen saturation [ScvO₂], low central venous pressure [CVP], and high lactate), and higher mortality rates. Therefore, it may well be that these patients arrived to the hospital in late untreated hypovolemic sepsis, which may have been due, in part at least, to low socioeconomic status and reduced access to health care. The EGDT protocol uses target values for CVP and ScvO₂ to guide hemodynamic management. However, filling pressures do not reliably predict the response to fluid administration, while the ScvO₂ of septic patients is characteristically high due to decreased oxygen extraction. For all these reasons, it seems that the hemodynamic component of the Surviving Sepsis Campaign guidelines cannot be applied to all septic patients, particularly those who develop sepsis during their hospital stay.