Oxygen transport patterns in patients with sepsis syndrome or septic shock: influence of treatment and relationship to outcome

Main active constituents and mechanism of toxicity of raphides from Arisaema erubescens against Oncomelania hupensis

To find a high-efficiency and environment-friendly biogenic molluscicide against Oncomelania hupensis, and prevent aquatic ecosystem from being contaminated by chemical molluscicides and being toxic. We extracted and purified raphides from the tubers of Arisaema erubescent, and determined the active constituents and molluscicidal activity of the raphides, detoxification enzyme activity, and liver damage. The results showed that the raphides had a strong molluscicidal activity. O. hupensis snails were exposed to the lethal concentration (LC50) of 70.95 mg/L and 44.25 mg/L for treatment with raphides for 48 h and 72 h, respectively. The raphides of molluscicidal activity of the main constituents was as follows: intact raphides > calcium oxalate crystals > AEL (Arisaema erubescens Lectin). The activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) in the snail livers increased significantly at the early stage of treatment (24 h), but decreased sharply in the later stage (120 h), compared with that in the control group. The results indicated that after treatment with 1/2 LC50 raphides for 120 h, the activities of POD, SOD, and CAT in the snail livers decreased by 82.5 %, 62.9 %, and 84.7 %, respectively. In addition, electron micrographs have shown that the raphides were needle-shaped crystals and tended to be sharp at both ends (with a groove down both sides) and some were barbed, which caused damage to the snail livers to different extent. Overall, our results indicate that the mechanism of toxicity of raphides against O. hupensis may be that the calcium oxalate crystals pricked the liver surface of snail and produced mechanical damage; and then the harmful protease AEL in the raphides was injected into the liver, which reduced the activities of detoxification enzymes, produced severe toxic reactions and eventually killed the O. hupensis snails.

Unresponsive Low Mixed Venous Oxygen Saturation During Early Intensive Care Unit Stay is Associated With Increased Risk of Organ Dysfunction After Cardiac Surgery: A Single-Center Retrospective Study

OBJECTIVES

The aim of the study was to determine if unresponsive mixed venous oxygen saturation (SvO2) values during early postoperative hours are associated with postoperative organ dysfunction.

DESIGN

A single-center retrospective observational study.

SETTING

A university hospital.

PARTICIPANTS

A total of 6,282 adult patients requiring cardiac surgery who underwent surgery in a University Hospital from 2007 to 2020.

INTERVENTIONS

A pulmonary artery catheter was used to gather SvO2 samples after surgery at admission to the intensive care unit (ICU) and 4 hours later. For the analysis, patients were divided into 4 groups according to their SvO2 values. The rate of organ dysfunctions categorized according to the SOFA score was then studied among these subgroups.

MEASUREMENTS AND MAIN RESULTS

The crude mortality rate for the cohort at 1 year was 4.3%. Multiple organ dysfunction syndrome (MODS) was present in 33.0% of patients in the early postoperative phase. During the 4-hour initial treatment period, 43% of the 931 patients with low SvO2 on admission responded to goal-directed therapy to increase SvO2 >60%; whereas, in 57% of the 931 patients, the low SvO2 was sustained. According to the adjusted logistic regression analyses, the odds ratio for MODS (4.23 [95% CI 3.41-5.25]), renal- replacement therapy (4.97 [95% CI 3.28-7.52]), time on a ventilator (2.34 [95% CI 2.17-2.52]), and vasoactive-inotropic score >30 (3.62 [95% CI 2.96-4.43]) were the highest in the group with sustained low SvO2.

CONCLUSIONS

Patients with SvO2 <60% at ICU admission and 4 hours later had the greatest risk of postoperative MODS. Responsiveness to a goal-directed therapy protocol targeting maintaining or increasing SvO2 ≥60% at and after ICU admission may be beneficial.

OXYGEN CONSUMPTION AS AN EARLY WARNING SYSTEM IN THE CRITICALLY ILL

ABSTRACT

Introduction: In this study, we assessed whether changes in oxygen consumption (VO 2 ) and other metabolic parameters could be used as an early warning system for detecting clinical deterioration in mechanically ventilated patients. Methods: This was a prospective cohort study of adult patients requiring mechanical ventilation between February 2016 and March 2019. We looked for changes in VO 2 , carbon dioxide production (VCO 2 ), respiratory quotient (RQ), and end-tidal carbon dioxide (EtCO 2 ), occurring prior to clinical deterioration. Clinical deterioration was predefined as a requirement of vasopressor, an increase in serum lactate by 20% where at least one value was above 3 mmol/L, or a decrease in hemoglobin by 20% in the 4 hours prior to clinical deterioration. Results A total of 141 patients were included. There were no detectable changes in VO 2 , VCO 2 , and EtCO 2 within the 4 hours prior to any clinical deterioration. RQ increased significantly within the 4 hours prior to an increase in lactate as compared with no increase in lactate, but there were no detectable changes prior to other clinical deteriorations. Conclusions RQ has the potential to be an early marker of tissue hypoperfusion or mitochondrial dysfunction. However, future studies are necessary to evaluate the use of RQ as a bedside monitor in critical care settings.

Red Blood Cell Transfusion at a Hemoglobin Threshold of Seven g/dL in Critically Ill Patients: A Regression Discontinuity Study

RATIONALE

In critically ill patients, a hemoglobin transfusion threshold of <7.0 G/dl compared to <10.0 G/dl improves organ dysfunction. However, it is unclear if transfusion at a hemoglobin of <7.0 g/dL is superior to no transfusion.

OBJECTIVES

To compare levels of organ dysfunction between transfusion and no transfusion at a hemoglobin threshold of <7.0 G/dl among critically ill patients using quasi-experimental regression discontinuity methods.

METHODS

We performed regression discontinuity analysis using hemoglobin measurements from patients admitted to ICUs in three cohorts (MIMIC-IV, eICU, and Premier Inc.), estimating the change in organ dysfunction (modified sequential organ failure assessment score) in the 24-72-hour window following each hemoglobin measurement. We compared hemoglobin levels just above and below 7.0 g/dL using a 'fuzzy' discontinuity approach, based on the concept that measurement noise pseudorandomizes similar hemoglobin levels on either side of the transfusion threshold.

RESULTS

A total of 11,181, 13,664, and 167,142 patients were included in the MIMIC-IV, eICU, and Premier cohorts, respectively. Patient characteristics below the threshold did not differ from those above the threshold, except that crossing below the threshold resulted in a >20% absolute increase in transfusion rates in all three cohorts. Transfusion was associated with increases in hemoglobin level in the subsequent 24-72 hours (MIMIC-IV 2.4 [95% CI 1.1, 3.6] g/dL; eICU 0.7 [95% CI 0.3, 1.2] g/dL; Premier 1.9 [95% CI 1.5, 2.2] g/dL), but not with improvement in organ dysfunction (MIMIC-IV 4.6 [95% CI -1.2, 10] points; eICU 4.4 [95% CI 0.9, 7.8] points; Premier 1.1 [95% CI -0.2, 2.3] points), compared to no transfusion.

CONCLUSIONS

Transfusion was not associated with improved organ dysfunction compared to no transfusion at a hemoglobin threshold of 7.0 g/dL, suggesting that evaluation of transfusion targets other than a hemoglobin threshold of 7.0 G/dl may be warranted.

Sirtuins and Sepsis: Cross Talk between Redox and Epigenetic Pathways

Sepsis and septic shock are the leading causes of death among hospitalized patients in the US. The immune response in sepsis transitions from a pro-inflammatory and pro-oxidant hyper-inflammation to an anti-inflammatory and cytoprotective hypo-inflammatory phase. While 1/3rd sepsis-related deaths occur during hyper-, a vast majority of sepsis-mortality occurs during the hypo-inflammation. Hyper-inflammation is cytotoxic for the immune cells and cannot be sustained. As a compensatory mechanism, the immune cells transition from cytotoxic hyper-inflammation to a cytoprotective hypo-inflammation with anti-inflammatory/immunosuppressive phase. However, the hypo-inflammation is associated with an inability to clear invading pathogens, leaving the host susceptible to secondary infections. Thus, the maladaptive immune response leads to a marked departure from homeostasis during sepsis-phases. The transition from hyper- to hypo-inflammation occurs via epigenetic programming. Sirtuins, a highly conserved family of histone deacetylators and guardians of homeostasis, are integral to the epigenetic programming in sepsis. Through their anti-inflammatory and anti-oxidant properties, the sirtuins modulate the immune response in sepsis. We review the role of sirtuins in orchestrating the interplay between the oxidative stress and epigenetic programming during sepsis.

Energetic dysfunction in sepsis: a narrative review

Background

Growing evidence associates organ dysfunction(s) with impaired metabolism in sepsis. Recent research has increased our understanding of the role of substrate utilization and mitochondrial dysfunction in the pathophysiology of sepsis-related organ dysfunction. The purpose of this review is to present this evidence as a coherent whole and to highlight future research directions.

Main text

Sepsis is characterized by systemic and organ-specific changes in metabolism. Alterations of oxygen consumption, increased levels of circulating substrates, impaired glucose and lipid oxidation, and mitochondrial dysfunction are all associated with organ dysfunction and poor outcomes in both animal models and patients. The pathophysiological relevance of bioenergetics and metabolism in the specific examples of sepsis-related immunodeficiency, cerebral dysfunction, cardiomyopathy, acute kidney injury and diaphragmatic failure is also described.

Conclusions

Recent understandings in substrate utilization and mitochondrial dysfunction may pave the way for new diagnostic and therapeutic approaches. These findings could help physicians to identify distinct subgroups of sepsis and to develop personalized treatment strategies. Implications for their use as bioenergetic targets to identify metabolism- and mitochondria-targeted treatments need to be evaluated in future studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00893-7.

Association Between the Oxygen Consumption: Lactate Ratio and Survival in Critically Ill Patients With Sepsis

INTRODUCTION

Mitochondrial dysfunction leading to impairment of oxygen extraction, referred to as cytopathic hypoxia, contributes to morbidity in sepsis. Oxygen consumption (VO2) may be a useful measure of the severity of cytopathic hypoxia. We monitored VO2 and carbon dioxide production (VCO2) in septic patients and investigated the association with hospital survival.

METHODS

We retrospectively identified adult (≥18 years) septic patients from a larger prospective observational cohort of critically ill patients on mechanical ventilation. A gas-exchange monitor recorded continuous VO2 and VCO2 for up to 48 h. We then tested the association of median VO2, VCO2, respiratory quotient (RQ), and the VO2:lactate ratio with survival.

RESULTS

A total of 46 septic patients were included in the analysis, of whom 28 (61%) survived. Overall median VO2 was not associated with survival (3.72 mL/kg/min [IQR: 3.39, 4.92] in survivors and 3.42 mL/kg/min [IQR: 2.97, 5.26] in non-survivors, P = 0.12). The overall median VCO2 and RQ were also not associated with survival. Adjusting for age and the presence of shock did not change these results. The VO2:lactate ratio was associated with survival (adjusted OR 2.17 [95% CI 1.12, 4.22] per unit increase in ratio, P = 0.03). The percent change in median VCO2 was 11.6% [IQR: -8.2, 28.7] in survivors compared with -8.3% [IQR: -18.0, 4.7] in non-survivors (P = 0.03). The percent changes in median VO2 and RQ were not different between groups.

CONCLUSION

The VO2:lactate ratio was significantly higher in survivors, while there was no association between median VO2 alone and survival. There was a significant difference in change in VCO2 over time between survivors and non-survivors.

Monitoring mitochondrial PO2: the next step

PURPOSE OF REVIEW

To fully exploit the concept of hemodynamic coherence in resuscitating critically ill one should preferably take into account information about the state of parenchymal cells. Monitoring of mitochondrial oxygen tension (mitoPO2) has emerged as a clinical means to assess information of oxygen delivery and oxygen utilization at the mitochondrial level. This review will outline the basics of the technique, summarize its development and describe the rationale of measuring oxygen at the mitochondrial level.

RECENT FINDINGS

Mitochondrial oxygen tension can be measured by means of the protoporphyrin IX-Triplet State Lifetime Technique (PpIX-TSLT). After validation and use in preclinical animal models, the technique has recently become commercially available in the form of a clinical measuring system. This system has now been used in a number of healthy volunteer studies and is currently being evaluated in studies in perioperative and intensive care patients in several European university hospitals.

SUMMARY

PpIX-TSLT is a noninvasive and well tolerated method to assess aspects of mitochondrial function at the bedside. It allows doctors to look beyond the macrocirculation and microcirculation and to take the oxygen balance at the cellular level into account in treatment strategies.

Metabolic Resuscitation Strategies to Prevent Organ Dysfunction in Sepsis

Significance: Sepsis is the main cause of death among patients admitted to the intensive care unit. As current treatment is limited to antimicrobial therapy and supportive care, mortality remains high, which warrants efforts to find novel therapies. Recent Advances: Mitochondrial dysfunction is emerging as a key process in the induction of organ dysfunction during sepsis, and metabolic resuscitation might reveal to be a novel cornerstone in the treatment of sepsis. Critical Issues: Here, we review novel strategies to maintain organ function in sepsis by precluding mitochondrial dysfunction by lowering energetic demand to allow preservation of adenosine triphosphate-levels, while reducing free radical generation. As the most common strategy to suppress metabolism, that is, cooling, does not reveal unequivocal beneficial effects and may even increase mortality, caloric restriction or modulation of energy-sensing pathways (i.e., sirtuins and AMP-activated protein kinase) may offer safe alternatives. Similar effects may be offered when mimicking hibernation by hydrogen sulfide (H₂S). In addition H₂S may also confer beneficial effects through upregulation of antioxidant mechanisms, similar to the other gasotransmitters nitric oxide and carbon monoxide, which display antioxidant and anti-inflammatory effects in sepsis. In addition, oxidative stress may be averted by systemic or mitochondria-targeted antioxidants, of which a wide range are able to lower inflammation, as well as reduce organ dysfunction and mortality from sepsis. Future Directions: Mitochondrial dysfunction plays a key role in the pathophysiology of sepsis. As a consequence, metabolic resuscitation might reveal to be a novel cornerstone in the treatment of sepsis.

Variability of mitochondrial respiration in relation to sepsis-induced multiple organ dysfunction

Ample experimental evidence suggests that sepsis could interfere with any mitochondrial function; however, the true role of mitochondrial dysfunction in the pathogenesis of sepsis-induced multiple organ dysfunction is still a matter of controversy. This review is primarily focused on mitochondrial oxygen consumption in various animal models of sepsis in relation to human disease and potential sources of variability in experimental results documenting decrease, increase or no change in mitochondrial respiration in various organs and species. To date, at least three possible explanations of sepsis-associated dysfunction of the mitochondrial respiratory system and consequently impaired energy production have been suggested: 1. Mitochondrial dysfunction is secondary to tissue hypoxia. 2. Mitochondria are challenged by various toxins or mediators of inflammation that impair oxygen utilization (cytopathic hypoxia). 3. Compromised mitochondrial respiration could be an active measure of survival strategy resembling stunning or hibernation. To reveal the true role of mitochondria in sepsis, sources of variability of experimental results based on animal species, models of sepsis, organs studied, or analytical approaches should be identified and minimized by the use of appropriate experimental models resembling human sepsis, wider use of larger animal species in preclinical studies, more detailed mapping of interspecies differences and organ-specific features of oxygen utilization in addition to use of complex and standardized protocols evaluating mitochondrial respiration.

A Systematic Review of the Effects of Hyperoxia in Acutely Ill Patients: Should We Aim for Less?

INTRODUCTION

Despite widespread and liberal use of oxygen supplementation, guidelines about rational use of oxygen are scarce. Recent data demonstrates that current protocols lead to hyperoxemia in the majority of the patients and most health care professionals are not aware of the negative effects of hyperoxemia.

METHOD

To investigate the effects of hyperoxemia in acutely ill patients on clinically relevant outcomes, such as neurological and functional status as well as mortality, we performed a literature review using Medline (PubMed) and Embase. We used the following terms: hyperoxemia OR hyperoxemia OR ["oxygen inhalation therapy" AND (mortality OR death OR outcome OR survival)] OR [oxygen AND (mortality OR death OR outcome OR survival)]. Original studies about the clinical effects of hyperoxemia in adult patients suffering from acute or emergency illnesses were included.

RESULTS

37 articles were included, of which 31 could be divided into four large groups: cardiac arrest, traumatic brain injury (TBI), stroke, and sepsis. Although a single study demonstrated a transient protective effect of hyperoxemia after TBI, other studies revealed higher mortality rates after cardiac arrest, stroke, and TBI treated with oxygen supplementation leading to hyperoxemia. Approximately half of the studies showed no association between hyperoxemia and clinically relevant outcomes.

CONCLUSION

Liberal oxygen therapy leads to hyperoxemia in a majority of patients and hyperoxemia may negatively affect survival after acute illness. As a clinical consequence, aiming for normoxemia may limit negative effects of hyperoxemia in patients with acute illness.

Lower mitochondrial dysfunction in survivor septic patients with mitochondrial DNA haplogroup JT

OBJECTIVE

The comparison on mitochondrial function between severe septic patients and healthy control subjects according to mitochondrial deoxyribonucleic acid (mtDNA) haplogroup has not been previously reported; and this was the objective of the current study.

METHODS

Prospective, multicenter, observational study. We obtained blood samples from 198 severe septic patients at days 1, 4 and 8 of severe sepsis diagnosis and from 96 sex- and age-matched healthy controls to determine mtDNA haplogroup and platelet respiratory complex IV (CIV) specific activity. The endpoint of the study was 30-day mortality.

RESULTS

We included 198 severe septic patients (38 with mtDNA haplogroup JT and 160 with mtDNA haplogroup non-JT) and 96 healthy control subjects (16 with mtDNA haplogroup JT and 80 with mtDNA haplogroup non-JT). We have no found statistically significant differences in platelet CIV specific activity between healthy controls and survivor severe septic patients with mtDNA haplogroup JT at days 1, 4 and 8 of severe sepsis diagnosis; and the remaining severe septic patients showed lower platelet CIV specific activity than healthy controls with the same mtDNA haplogroup.

CONCLUSIONS

The new finding of our study was that survivor severe septic patients and healthy controls with mtDNA haplogroup JT showed no different platelet Civ specific activity.

Transfusion of Red Blood Cells to Patients with Sepsis

Sepsis is one of the major causes of death worldwide, and is the host response to infection which renders our organs malfunctioning. Insufficient tissue perfusion and oxygen delivery have been implicated in the pathogenesis of sepsis-related organ dysfunction, making transfusion of packed red blood cells (pRBCs) a reasonable treatment modality. However, clinical trials have generated controversial results. Even the notion that transfused pRBCs increase the oxygen-carrying capacity of blood has been challenged. Meanwhile, during sepsis, the ability of our tissues to utilize oxygen may also be reduced, and the increased blood concentrations of lactate may be the results of strong inflammation and excessive catecholamine release, rather than impaired cell respiration. Leukodepleted pRBCs more consistently demonstrated improvement in microcirculation, and the increase in blood viscosity brought about by pRBC transfusion helps maintain functional capillary density. A restrictive strategy of pRBC transfusion is recommended in treating septic patients.

Risk factors for mortality in patients with low lactate level and septic shock

BACKGROUND

According to the new definition of septic shock, vasopressor therapy and hyperlactatemia are essential for diagnosis. However, there is controversy regarding the cutoff value for lactate, and prognostic factors in patients with septic shock and hypolactatemia. This study evaluated the prognostic significance of the cutoff value for lactate level in septic shock patients.

METHODS

The retrospective observational cohort study enrolled 1043 patients aged ≥18 years who meet the revised definition of septic shock. Clinical outcomes of patients with hyperlactatemia were compared with hypolactatemia.

RESULTS

Of the 1022 eligible patients, 369 had an arterial lactate level ≤2 mmol/L. More patients in the high lactate group had poor prognosis than in the low lactate group. A high Sequential Organ Failure Assessment score (SOFA) score group was significant (p < 0.001) in predicting lactate levels. On the subgroup analysis of risk factors affecting mortality in the low lactate group, high Acute Physiology And Chronic Health Evaluation Ⅱ (APACHEⅡ) score (p = 0.003), high C-reactive protein (p = 0.034), and chronic heart failure (p = 0.001) were independently associated with 28-day mortality.

CONCLUSION

Arterial lactate is a very reliable diagnostic and prognostic predictor of septic shock. However, despite low arterial lactate, patients with a high APACHEⅡ score, high C-reactive protein levels, and chronic heart failure had a poorer prognosis.

Critical Care Medicine: Major Changes in Dogma of the Past Decade

Critical care medicine is a young specialty that has experienced an expansion of research efforts in the last decade. Many physiologic and therapeutic principles or “dogmas” have been challenged, resulting in major “shifts” and minor “drifts” in thinking. This article reviews the available literature about some of these important and sometimes controversial changes, with emphasis on the practical implications of the concepts. Specific areas discussed include supply-dependent oxygen consumption in critical illness, manipulation of the cytokine cascade in sepsis, ventilation in the acute respiratory distress syndrome (ARDS), blood transfusion in the critically ill, the concept of the multiple organ dysfunction syndrome (MODS), the need for nutritional support in the critically ill, and others. Many of the changes discussed involve the recognition that the host response to a severe insult is exceedingly complex, and the understanding of this response and the effects of it at a tissue and cellular level are incomplete. As a result, the ability to impact the outcome of sepsis and MODS has thus far been disappointing, with the possible exception of “lung-protective” ventilation. The final challenge in critical care medicine is to gain information that will allow the practitioner to better understand, prevent, and treat the complex events that result in organ and cellular dysfunction. Future changes in dogma are welcome if they help achieve these goals.

Advanced Hemodynamic Management in Patients with Septic Shock

In patients with sepsis and septic shock, the hemodynamic management in both early and later phases of these "organ dysfunction syndromes" is a key therapeutic component. It needs, however, to be differentiated between "early goal-directed therapy" (EGDT) as proposed for the first 6 hours of emergency department treatment by Rivers et al. in 2001 and "hemodynamic management" using advanced hemodynamic monitoring in the intensive care unit (ICU). Recent large trials demonstrated that nowadays protocolized EGDT does not seem to be superior to "usual care" in terms of a reduction in mortality in emergency department patients with early identified septic shock who promptly receive antibiotic therapy and fluid resuscitation. "Hemodynamic management" comprises (a) making the diagnosis of septic shock as one differential diagnosis of circulatory shock, (b) assessing the hemodynamic status including the identification of therapeutic conflicts, and (c) guiding therapeutic interventions. We propose two algorithms for hemodynamic management using transpulmonary thermodilution-derived variables aiming to optimize the cardiocirculatory and pulmonary status in adult ICU patients with septic shock. The complexity and heterogeneity of patients with septic shock implies that individualized approaches for hemodynamic management are mandatory. Defining individual hemodynamic target values for patients with septic shock in different phases of the disease must be the focus of future studies.

Hemodynamic management of septic shock: is it time for "individualized goal-directed hemodynamic therapy" and for specifically targeting the microcirculation?

Septic shock is a life-threatening condition in both critically ill medical patients and surgical patients during the perioperative phase. In septic shock, specific alterations in global cardiovascular dynamics (i.e., the macrocirculation) and in the microcirculatory blood flow (i.e., the microcirculation) have been described. However, the presence and degree of microcirculatory failure are in part independent from systemic macrohemodynamic variables. Macrocirculatory and microcirculatory failure can independently induce organ dysfunction. We review current diagnostic and therapeutic approaches for the assessment and optimization of both the macrocirculation and the microcirculation in septic shock. There are various technologies for the determination of macrocirculatory hemodynamic variables. We discuss the data on early goal-directed therapy for the resuscitation of the macrocirculation. In addition, we describe the concept of "individualized goal-directed hemodynamic therapy." Technologies to assess the local microcirculation are also available. However, adequate resuscitation goals for the optimization of the microcirculation still need to be defined. At present, we are not ready to specifically monitor and target the microcirculation in clinical routine outside studies. In the future, concepts for an integrative approach for individualized hemodynamic management of the macrocirculation and in parallel the microcirculation might constitute a huge opportunity to define additional resuscitation end points in septic shock.

Near-infrared spectroscopy: exposing the dark (venous) side of the circulation

The safety of anesthesia has improved greatly in the past three decades. Standard perioperative monitoring, including pulse oximetry, has practically eliminated unrecognized arterial hypoxia as a cause for perioperative injury. However, most anesthesia-related cardiac arrests in children are now cardiovascular in origin, and standard monitoring is unable to detect many circulatory abnormalities. Near-infrared spectroscopy provides noninvasive continuous access to the venous side of regional circulations that can approximate organ-specific and global measures to facilitate the detection of circulatory abnormalities and drive goal-directed interventions to reduce end-organ ischemic injury.

Biomarkers in sepsis

PURPOSE OF REVIEW

This review discusses the current developments in biomarkers for sepsis.

RECENT FINDINGS

With quantum leaps in technology, an array of biomarkers will become available within the next decade as point-of-care tools that will likely revolutionize the management of sepsis. These markers will facilitate early and accurate diagnosis, faster recognition of impending organ dysfunction, optimal selection and titration of appropriate therapies, and more reliable prognostication of risk and outcome. These diagnostics will also enable an improved characterization of the biological phenotype underlying sepsis and thus a better appreciation of the condition.

SUMMARY

The potential for novel biomarkers in sepsis will need to be properly realized with considerable funding, academic-industry collaborations, appropriate investigations and validation in heterogenous populations, but these developments do hold the capacity to transform patient care and outcomes.

Cardiac contractile reserve parameters are related to prognosis in septic shock

INTRODUCTION

Cardiac reserve could be defined as the spontaneous magnitude from basal to maximal cardiac power under stress conditions. The aim of this study was to evaluate the prognostic value of cardiac reserve parameters in resuscitated septic shock patients.

METHODS

Seventy patients with septic shock were included in a prospective and observational study. Prior to inclusion, patients were resuscitated to reach a mean arterial pressure of 65-75 mmHg with an euvolemic status. General, hemodynamic, and cardiac reserve-related parameters (cardiac index, double product, and cardiac power index) were collected at inclusion and at day 1.

RESULTS

Seventy patients were included with 28-day mortality at 38.5%. Ten of the 70 patients died during the first day. In multivariate analysis, independent predictors of death were SAPS II ≥ 58 (OR: 3.36 [1.11-10.17]; P = 0.032), a high double product at inclusion (OR [95% IC]: 1.20 [1.00-1.45] per 10(3) mmHg · min; P = 0.047), and at day 1, a decrease in cardiac index (1.30 [1.08-1.56] per 0.5 L/min/m(2); P = 0.007) or cardiac power index (1.84 [1.18-2.87] per 0.1 W/m(2), P = 0.008).

CONCLUSION

In the first 24 hours, parameters related to cardiac reserve, such as double product and cardiac index evolution, provide crucial and easy to achieve hemodynamic physiological information, which may impact the outcome.

The evolving concepts of haemodynamic support: from pulmonary artery catheter to echocardiography and theragnostics

Echocardiography is a non-invasive tool, aimed towards the anatomical and functional characterization of the heart. In Intensive Care it is considered nowadays as a necessary tool for patient evaluation. However, the information obtained using echocardiography is not the same as provided by other means, namely the invasive ones. In recent years there has been a significant evolution in the general concepts of haemodynamic support for the critically ill patient. In this new environment, echocardiography has gained particular relevance. In this text the new positioning of echocardiography in the light of the new concepts for hemodynamic support is described, as well as, the need for a specific formative program directed towards Intensive Care physicians. A new generation of biomarkers can also add relevant information and start a new era in haemodynamic support. They may help to further characterize the disease process, identifying patients at risk, as well as, characterize specific organ failure as well as monitoring therapy.

Systemic and microcirculatory effects of dobutamine in patients with septic shock

PURPOSE

The aim of this study was to characterize the cardiovascular responses to dobutamine and their predictors. Our hypotheses were that dobutamine mainly produces tachycardia and vasodilation and fails to improve the microcirculation of patients with septic shock.

MATERIALS AND METHODS

Systemic hemodynamics and sublingual microcirculation were evaluated with dobutamine (0, 2.5, 5.0, and 10.0 μg kg(-1) min(-1)) in 23 patients with septic shock.

RESULTS

Dobutamine increased heart rate, cardiac index, and stroke volume index (SVI). Mean blood pressure was unchanged, and systemic vascular resistance decreased. Individual responses were heterogeneous. Stroke volume index increased in 52% of the patients. These patients showed lower changes in mean blood pressure (3 ± 16 mm Hg vs -10 ± 6 mm Hg, P < .05) and higher increases in cardiac index (1.47 ± 0.93 L m(-1) m(-2) vs 0.20 ± 0.5 L m(-1) m(-2)) than did nonresponders. Changes in SVI significantly correlated with echocardiographic left ventricular ejection fraction (r = 0.55). In the whole group, perfused capillary density remained unchanged (14.0 ± 4.3 mm/mm(2) vs 14.8 ± 3.7 mm/mm(2)), but improved if basal values were 12 mm/mm(2) or less (9.1 ± 4.3 mm/mm(2) vs 12.5 ± 4.8 mm/mm(2)).

CONCLUSIONS

Dobutamine produced variable hemodynamic effects. Systolic dysfunction was the only variable associated with increases in SVI. Finally, dobutamine only improved sublingual microcirculation when severe alterations were found at baseline.

Bench-to-bedside review: sepsis - from the redox point of view

The pathogenesis of sepsis and its progression to multiple organ dysfunction syndrome and septic shock have been the subject of investigations for nearly half a century. Controversies still exist with regard to understanding the molecular pathophysiology of sepsis in relation to the complex roles played by reactive oxygen species, nitric oxide, complements and cytokines. In the present review we categorise the key turning points in sepsis development and outline the most probable sequence of events leading to cellular dysfunction and organ failure under septic conditions. We have applied an integrative approach in order to fuse current state-of-the-art knowledge about redox processes involving hydrogen peroxide, nitric oxide, superoxide, peroxynitrite and hydroxyl radical, which lead to mitochondrial respiratory dysfunction. Finally, from this point of view, the potential of redox therapy targeting sepsis is discussed.

Platelet cytochrome c oxidase activity and quantity in septic patients

OBJECTIVE

The cytopathic hypoxia theory proposes that there is an impaired cellular oxygen utilization during sepsis. Respiratory complex IV, or cytochrome c oxidase, was only previously studied in muscle biopsies of 16 surviving and 12 nonsurviving septic patients. We hypothesized that higher activities and quantities of this enzyme complex could be associated with septic patient survival. The objective was to evaluate the relationship between cytochrome c oxidase activities and quantities and 6-month survival in a larger series of septic patients using a less invasive method (circulating platelets).

DESIGN

Prospective, multicenter, observational study.

SETTING

The study was carried out in six Spanish intensive care units.

PATIENTS

We included 96 septic patients.

INTERVENTIONS

We determined the cytochrome c oxidase activity per citrate synthase activity ratio and cytochrome c oxidase quantity per citrate synthase activity ratio in circulating platelets at the time of diagnosis and related them to 6-month survival. The written informed consent from the family members was obtained.

MEASUREMENTS AND MAIN RESULTS

Survivor patients (n = 54) showed higher cytochrome c oxidase activity per citrate synthase activity ratio (p = .04) and cytochrome c oxidase quantity per citrate synthase activity ratio (p = .006) than nonsurvivors (n = 42). Logistic regression analyses confirmed that the cytochrome c oxidase activity per citrate synthase activity ratio (p = .04) and cytochrome c oxidase quantity per citrate synthase activity ratio (p = .02) were independent predictors of 6-month survival. The area under the curve to predict 6-month survival was 0.62 (95% confidence interval 0.51-0.74; p = .04) for the cytochrome c oxidase activity per citrate synthase activity ratio and 0.67 (95% confidence interval 0.56-0.76; p = .003) for the cytochrome c oxidase quantity per citrate synthase activity ratio. A negative correlation was found between the cytochrome c oxidase quantity per citrate synthase activity ratio and Sepsis-Related Organ Failure Assessment score (p = .04).

CONCLUSIONS

Platelet cytochrome c oxidase activity and quantity were independent predictors of 6-month survival and could be used as biomarkers of sepsis mortality. This is a rapid, easy, and less invasive protocol to assess mitochondrial function. Patients with lower cytochrome c oxidase activity and quantity could benefit from drugs that improve mitochondrial function.

Should we use early less invasive hemodynamic monitoring in unstable ICU patients?

In the previous issue of Critical Care, Takala and colleagues presented the results of a multicenter study to investigate whether the early presence of less invasive hemodynamic monitoring improves outcome in patients admitted with hemodynamic instability to the intensive care unit. The authors' results suggest that it makes no difference. We discuss these findings and compare them to the literature on early goal-directed therapy in which monitors are used early but with a protocol.

Pulmonary artery catheters

BACKGROUND

After its introduction in 1970, the use of the pulmonary artery catheter became a central part of the management of critically ill patients in adult and pediatric intensive care units. However, because it was introduced as a class II device, efficacy for its safety and clinical benefit did not exist during the early years of use. This review describes the pulmonary artery catheter and reviews the literature supporting its use.

METHODOLOGY

A search of MEDLINE, PubMed, and the Cochrane Database was made to find literature about pulmonary artery catheter use. Literature for both adult and pediatric patients was reviewed. Guidelines published by the Society for Critical Care Medicine and the American Heart Association were reviewed, including further review of references cited.

RESULTS AND CONCLUSIONS

The evidence supporting the use of the pulmonary artery catheter is mostly limited to level IV (nonrandomized, historical controls, and expert opinion) and level V (case series, uncontrolled studies, and expert opinion). A higher level of evidence supports the use of the pulmonary artery catheter in selected pediatric patients, especially those with pulmonary arterial hypertension and shock refractory to standard fluid resuscitation and vasoactive agents. There are no data to suggest that use of the pulmonary artery catheter increases mortality in children.

Temporal changes in tissue cardiorespiratory function during faecal peritonitis

PURPOSE

Sepsis affects both macro- and micro-circulatory transport of oxygen to tissues, causing regional hypoxia. However, this relationship is poorly characterized with respect to inter-organ variability, disease severity and the evolution to organ dysfunction. We hypothesized that an early circulatory insult precedes the development of organ dysfunction, and is more severe in predicted non-survivors. Consequently, we assessed temporal changes in myocardial function and regional tissue oxygenation in peripheral and deep organs in a rat model of faecal peritonitis. We also examined the utility of a dynamic oxygen challenge test to assess the microcirculation.

METHODS

Awake, tethered, fluid-resuscitated male Wistar rats were randomized to receive intraperitoneal injection of faecal slurry, or to act as controls. At either 6 or 24 h post insult, rats were anaesthetized and underwent echocardiography, arterial cannulation and placement of tissue oxygen probes in peripheral (muscle, bladder) and deep (liver and renal cortex) organ beds. Measurements were repeated during fluid loading and an oxygen challenge test (administration of high oxygen concentrations).

RESULTS

Early sepsis (6 h) was characterized by a fall in global oxygen delivery with concurrent decreases in muscle, renal cortical and, especially, liver tissue PO2. By contrast, during established sepsis (24 h), myocardial and circulatory function had largely recovered despite increasing clinical unwellness, hyperlactataemia and biochemical evidence of organ failure. O2 challenge revealed an early depression of response that, by 24 h, had improved in all organ beds bar the kidney.

CONCLUSIONS

This long-term septic model exhibited an early decline in tissue oxygenation, the degree of which related to predicted mortality. Clinical and biochemical deterioration, however, progressed despite cardiovascular recovery. Early circulatory dysfunction may thus be an important trigger for downstream processes that result in multi-organ failure. Furthermore, the utility of tissue PO2 monitoring to highlight the local oxygen supply-demand balance, and dynamic O2 challenge testing to assess microcirculatory function merit further investigation.

Sepsis and the heart

Septic shock, the most severe complication of sepsis, accounts for approximately 10% of all admissions to intensive care. Our understanding of its complex pathophysiology remains incomplete but clearly involves stimulation of the immune system with subsequent inflammation and microvascular dysfunction. Cardiovascular dysfunction is pronounced and characterized by elements of hypovolaemic, cytotoxic, and distributive shock. In addition, significant myocardial depression is commonly observed. This septic cardiomyopathy is characterized by biventricular impairment of intrinsic myocardial contractility, with a subsequent reduction in left ventricular (LV) ejection fraction and LV stroke work index. This review details the myocardial dysfunction observed in adult septic shock, and discusses the underlying pathophysiology. The utility of using the regulatory protein troponin for the detection of myocardial dysfunction is also considered. Finally, options for the management of sepsis-induced LV hypokinesia are discussed, including the use of levosimendan.

Pharmacological optimization of tissue perfusion

After fluid resuscitation, vasoactive drug treatment represents the major cornerstone for correcting any major impairment of the circulation. However, debate still rages as to the choice of agent, dose, timing, targets, and monitoring modalities that should optimally be used to benefit the patient yet, at the same time, minimize harm. This review highlights these areas and some new pharmacological agents that broaden our therapeutic options.

Sepsis induces brain mitochondrial dysfunction

OBJECTIVE

Mitochondrial dysfunctions have been associated with the pathogenesis of sepsis. A systematic survey of mitochondrial function in brain tissues during sepsis is lacking. In the present work, we investigate brain mitochondrial function in a septic mouse model.

DESIGN

Prospective animal study.

SETTING

University research laboratory.

SUBJECTS

Male Swiss mice, aged 6-8 wks.

INTERVENTIONS

Mice were subjected to cecal ligation and perforation (sepsis group) with saline resuscitation or to sham operation (control group).

MEASUREMENTS AND MAIN RESULTS

Oxygen consumption was measured polarographically in an oximeter. Brain homogenates from septic animals presented higher oxygen consumption in the absence of adenosine 5'-diphosphate (state 4) compared with control animals. The increase in state 4 respiration in animals in the cecal ligation and perforation group resulted in a drastic decrease in both respiratory control and adenosine 5'-diphosphate/oxygen ratios, indicating a reduction in the oxidative phosphorylation efficiency. Septic animals presented a significant increase in the recovery time of mitochondrial membrane potential on adenosine 5'-diphosphate addition compared with control animals, suggesting a proton leak through the inner mitochondrial membrane. The septic group presented a general reduction in the content of cytochromes. Moreover, the activity of cytochrome c oxidase was specifically and significantly decreased in the brain during sepsis. Hydrogen peroxide generation by brain mitochondria from septic mice did not respond to substrates of electron transport chain or to adenosine 5'-diphosphate, showing that mitochondrial function may be compromised in a critical level in the brain during sepsis.

CONCLUSIONS

The mitochondrial dysfunctions demonstrated here indicate that uncoupling of oxidative phosphorylation takes place in the brain of septic mice, compromising tissue bioenergetic efficiency.

Fluid therapy in resuscitated sepsis: less is more

Fluid infusion may be lifesaving in patients with severe sepsis, especially in the earliest phases of treatment. Following initial resuscitation, however, fluid boluses often fail to augment perfusion and may be harmful. In this review, we seek to compare and contrast the impact of fluids in early and later sepsis; show that much fluid therapy is clinically ineffective in patients with severe sepsis; explore the detrimental aspects of excessive volume infusion; examine how clinicians assess the intravascular volume state; appraise the potential for dynamic indexes to predict fluid responsiveness; and recommend a clinical approach.

Cardiovascular response to dobutamine stress predicts outcome in severe sepsis and septic shock

Introduction

During septic shock, resistance to the haemodynamic effects of catecholamine vasopressors and inotropes is a well-recognised marker of mortality risk. However, the specific cardiovascular or metabolic response elements that are most closely associated with outcome have not been well defined. The objective of this study was to assess cardiovascular and metabolic responses to dobutamine as correlates of outcome in patients with severe sepsis or septic shock.

Methods

A prospective, non-randomised, non-blinded interventional study of graded dobutamine challenge (0, 5, 10, and 15 μg/kg/min) in adult patients who had undergone pulmonary artery catheterisation within 48 hours of onset of severe sepsis or septic shock (8 survivors/15 non-survivors) was performed. Radionuclide cineangiography during graded infusion was used to determine biventricular ejection fractions at each increment of dobutamine.

Results

In univariate analysis, a variety of cardiovascular or haemodynamic and oxygen transport or metabolic variables (at the point of maximum cardiac index response for a given subject) were associated with survival including: increased stroke volume index (p = 0.0003); right ventricular end-diastolic volume index (p = 0.0047); left ventricular stroke work index (p = 0.0054); oxygen delivery index (p = 0.0084); cardiac index (p = 0.0093); systolic blood pressure/left ventricular end-systolic volume index ratio (p = 0.0188); left ventricular ejection fraction (p = 0.0160); venous oxygen content (p = 0.0208); mixed venous oxygen saturation (p = 0.0234); pulse pressure (p = 0.0403); decreased pulmonary artery diastolic pressure (p = 0.0133); systemic vascular resistance index (p = 0.0154); extraction ratio (p = 0.0160); and pulmonary vascular resistance index (p = 0.0390). Increases of stroke volume index of greater than or less than 8.5 mL/m² were concordant with survival or death in 21 of 23 cases. Multivariate profile construction showed stroke volume index as the dominant discriminating variable for survival with the systolic blood pressure/left ventricular end-systolic volume index ratio alone among all other variables significantly improving the model.

Conclusion

Survivors maintain cardiac responsiveness to catecholamine stimulation during septic shock. Survival from severe sepsis or septic shock is associated with increased cardiac performance and contractility indices during dobutamine infusion. Further studies are required to determine whether these parameters are predictive of outcome in a larger severe sepsis/septic shock population.

Bench-to-bedside review: potential strategies to protect or reverse mitochondrial dysfunction in sepsis-induced organ failure

The pathogenesis of sepsis-induced multiple organ failure may crucially depend on the development of mitochondrial dysfunction and consequent cellular energetic failure. According to this hypothesis, interventions aimed at preventing or reversing mitochondrial damage may have major clinical relevance, although the timing of such interventions will be critical to both ensuring benefit and avoiding harm. Early correction of tissue hypoxia, strict control of glycaemia, and modulation of oxidative and nitrosative stress may afford protection during the initial, acute systemic inflammatory response. The regulated induction of a hypometabolic state resembling hibernation may protect the cells from dying once energy failure has developed, allowing the possibility of functional recovery. Repair of damaged organelles through stimulation of mitochondrial biogenesis and reactivation of cellular metabolism may accelerate resolution of the multiple organ failure syndrome.

The inflammatory response to surgery and trauma

PURPOSE OF REVIEW

The inflammatory or stress response to injury has evolved to ensure survival. This review will examine this response in otherwise healthy patients. Additionally, the impact of several common comorbid conditions on the inflammatory response will be considered. What will become evident is that the stress response may be exaggerated in some conditions and suppressed in others. Rapid identification of both an abnormal response and its cause will allow clinicians to maximize a patient's healing potential.

RECENT FINDINGS

Recent work has shown that an altered inflammatory response has marked effects on both immune competence and the endocrine system. Investigations are ongoing to delineate the mechanism of lymphocyte dysfunction. With regard to critical care endocrinopathies, the effects of insulin and hyperglycemia on inflammation and wound healing are being investigated.

SUMMARY

An understanding of the stress response will aid the clinician in preparing for expected responses, recognizing and perhaps correcting deviations from the norm and accounting for potential complications that arise in the face of preexisting disease. Deviations from the normal time course may represent the effects of preexisting medical illness, treatment or postoperative/injury complications.

Carbamoyl phosphate synthase-1: a marker of mitochondrial damage and depletion in the liver during sepsis

OBJECTIVE

Mitochondrial damage and dysfunction are thought to play an important role in the pathogenesis of sepsis-induced organ failures. Unfortunately, specific markers of mitochondrial damage in vital organs do not currently exist. Recently, carbomyl phosphate synthase (CPS)-1, a protein primarily localized to liver mitochondria, was found to be present in high concentrations in the plasma of septic humans. Thus, we hypothesized that the circulatory release of CPS-1 would correlate with mitochondrial damage or impaired mitochondrial function in the liver in a clinically relevant model of sepsis.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University medical center research laboratory.

SUBJECTS

Male, Balb/C mice, aged 10-12 wks.

INTERVENTIONS

Animals were assigned to receive cecal ligation and puncture (CLP sepsis) or sham operation and compared with untreated controls. Plasma CPS-1 levels and liver mitochondrial variables, including morphology, respiratory activity, mass (i.e., cardiolipin content), and protein carbonylation, were assessed at various time points (8, 24, and 48 hrs and 6 days) after surgery.

MEASUREMENTS AND MAIN RESULTS

Oxidant stress (i.e., carbonylation) was detected within 8 hrs of CLP and persisted through 48 hrs. Plasma CPS-1 levels increased dramatically at 24 hrs, remained significantly elevated at 48 hrs, and normalized by 6 days in the sepsis group. Abnormalities of liver mitochondrial morphology and function coincided with increased plasma CPS-1 levels. Mitochondrial depletion in the liver was not due to cell death but was associated with increased lysosomal clearance. Increased expression of mitochondrial biogenesis factors preceded restoration of mitochondrial variables and normalization of CPS-1 levels by day 6.

CONCLUSIONS

Circulating CPS-1 is a marker of mitochondrial damage and depletion in the liver during the subacute phase of CLP sepsis. From a mechanistic standpoint, mitochondrial depletion is not due to cell death but is apparently related to the removal of damaged mitochondria by lysosomes (i.e., autophagy), followed by repletion of mitochondrial populations. Further studies are needed to determine the clinical utility of CPS-1 as a marker of sepsis severity.

Hemodynamic and metabolic effects of selective beta1 adrenergic blockade during sepsis

BACKGROUND

Selective beta adrenergic antagonists are commonly used to reduce myocardial demise in patients at risk for cardiac-related death. The purpose of this study was to examine the hemodynamic and metabolic effects of cardiac selective beta adrenergic blockade in patients.

METHODS

Muscle protein kinetics were quantified using isotopic tracer methodology in 6 moderately septic, mechanically ventilated patients with pneumonia before and then at the conclusion of a 3-hour infusion of esmolol of sufficient dose to reduce heart rate by 20% from baseline. A battery of hemodynamic measurements as facilitated by a thermodilution pulmonary artery catheter and indirect calorimetry were also measured before and after the 3-hour selective beta adrenergic blockade.

RESULTS

Selective beta adrenergic blockade was associated with the 20% reduction in heart rate and a comparable decrease in cardiac output. Esmolol administration failed to affect systemic or pulmonary vascular resistance, oxygen consumption, hepatic or leg blood flow, energy expenditure, or ATP availability/energy charge within muscle. Esmolol infuse did incite a shift in fuel oxidation toward an increase in palmitate oxidation and with a decrease in the oxidation of glucose. There was no demonstrable influence beta1 adrenergic blockade on muscle protein kinetics.

CONCLUSIONS

Cardiac selective beta adrenergic blockade with esmolol reduces cardiac output in proportion to the percentage decreases in heart rate in moderately severe septic patients without adversely affecting oxygen utilization or hepatic, peripheral blood flow.

Propofol improves endothelial dysfunction and attenuates vascular superoxide production in septic rats

OBJECTIVE

To determine the effects of propofol on vascular functions, plasma and endothelium-derived nitric oxide (EDNO), vascular NO, and cyclic guanosine monophosphate (cGMP), as well as vascular production of superoxide anion (O2*-), in septic animals.

DESIGN

Prospective, multiexperimental, randomized, controlled studies.

SETTING

University research laboratory.

SUBJECTS

Male adult Sprague-Dawley rats weighing 350-400 g.

INTERVENTIONS

Cecal ligation and puncture (CLP), with and without propofol (25 mg/kg/hr) infusion, after sham or CLP (24 hrs postsurgery).

MEASUREMENTS AND MAIN RESULTS

Plasma NOx, basal aortic NOx, and cGMP concentrations all increased, whereas acetylcholine-induced endothelium-dependent relaxation (EDR), contractile response, and EDNO all decreased in CLP vs. sham rats (p < .001). Acetylcholine stimulated aortic NOx and cGMP significantly in sham and CLP-propofol (p < .01) but not CLP rats. Thus, propofol ameliorated the CLP-induced increases in plasma NOx, basal aortic NOx, and cGMP. It restored the CLP-induced impairment of EDR, EDNO, and acetylcholine-stimulated aortic NOx and cGMP levels. More O2*- production (measured by lucigenin-enhanced chemiluminescence) was noted in carotid arteries from CLP vs. sham rats (p < .001). Nicotinamide adenine dinucleotide (NADH; 1 mM) stimulated O2*- production in all rings, with significantly more increase in CLP vs. sham (p < .001). Propofol attenuated the excessive increase in O2*- production of CLP rings.

CONCLUSIONS

Propofol treatment attenuated the overproduction of NO and O2*-, thus restoring the acetylcholine-responsive NO-cGMP pathway in CLP-induced sepsis. It also significantly improved the CLP-impaired EDR and EDNO in a parallel manner. These beneficial effects of propofol could be accounted for by improvement of the disturbed NO/O2*- balance in sepsis.

Red blood cell 2,3-diphosphoglycerate concentration and in vivo P50 during early critical illness

OBJECTIVE

To measure red blood cell 2,3-diphosphoglycerate (RBC 2,3-DPG) concentrations in early critical illness; to investigate factors associated with high or low RBC 2,3-DPG levels; to calculate in vivo P50 in patients with early critical illness; and to explore the relationship between RBC 2,3-DPG and intensive care mortality.

DESIGN

Prospective cohort study.

SETTING

General medical-surgical intensive care unit (ICU) of a major Scottish teaching hospital.

PATIENTS

One-hundred eleven critically ill patients during the first 24 hrs in the ICU with no history of chronic hematologic disorders or RBC transfusion within 24 hrs and 34 age- and sex-matched healthy reference subjects.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We measured RBC 2,3-DPG concentration, plasma biochemistry values, and arterial blood gas parameters. On average, RBC 2,3-DPG was lower among critically ill patients than controls (mean [sd], 14.1 [6.3] vs. 16.7 [3.7] mumol/g hemoglobin; p = .004) and had a wider range of values (patients, 3.2-32.5 mumol/g hemoglobin; reference group, 9.1-24.3). Regression analysis indicated a strong independent association between plasma pH and RBC 2,3-DPG (B, 32.15 [95% confidence interval, 19.07-46.22], p < .001) and a weak association with plasma chloride (B, -0.196 [95% confidence interval, -0.39 to -0.01], p = .044) but not with hemoglobin or other measured biochemical parameters. The mean calculated in vivo P50 level was normal (3.8 kPa) but varied widely among patients (range, 2.0-5.5 kPa). RBC 2,3-DPG concentration was similar for ICU survivors and nonsurvivors.

CONCLUSIONS

RBC 2,3-DPG concentrations vary widely among critically ill patients. Acidosis is associated with lower RBC 2,3-DPG concentrations, but anemia is not associated with a compensatory increase in RBC 2,3-DPG early in critical illness. Lower RBC 2,3-DPG concentrations during the first 24 hrs of intensive care are not associated with higher ICU mortality.

Time course of endothelial damage in septic shock: prediction of outcome

Introduction

Endothelial damage accounts greatly for the high mortality in septic shock. Higher expression of mediators (IL-6, IL-8, soluble intercellular adhesion molecule 1 [sICAM-1], soluble endothelial-linked adhesion molecule 1 [sELAM-1]) have been described for non-survivors in comparison with survivors. We investigated the predictive value of the mediators IL-6, IL-8, sELAM-1 and sICAM-1 and their time course in intensive care unit patients who developed septic shock with respect to outcome.

Materials and methods

We measured serum levels of IL-6, IL-8, sELAM-1 and sICAM-1 in 40 intensive care unit patients who developed septic shock. Measurements were performed until death or until resolution of septic shock. Clinical and laboratory data were also recorded.

Results

After 48 hours the levels of sELAM-1 and sICAM-1 increased in non-survivors and decreased in survivors. sELAM-1 was predictive for outcome on the third day (P = 0.02) and the fourth day (P = 0.02) after diagnosis of septic shock. This difference in the time course between survivors and non-survivors occurred 7 days before death of the patients (median, 10 days). sICAM-1 levels increased significantly in non-survivors over the study period (P < 0.001). sELAM-1 (P = 0.04), IL-6 (P = 0.04) and IL-8 (P = 0.008) were significantly higher in non-survivors over the whole study period. The age and norepinephrine dose >0.5 μg/kg/min were significantly different between the groups.

Conclusion

sELAM-1 showed a markedly opposing course after 48 hours of septic shock. This adhesion molecule may be a useful early predictor of disease severity in the course of septic shock after early initial treatment of the patients, and might suggest considering endothelial-restoring therapy.