Cytopathic hypoxia. Is oxygen use impaired in sepsis as a result of an acquired intrinsic derangement in cellular respiration?

Absent Metabolic Transition from the Early to the Late Period in Non-Survivors Post Cardiac Surgery

After major surgery, longitudinal changes in resting energy expenditure (REE) as well as imbalances in oxygen delivery (DO2) and distribution and processing (VO2) may occur due to dynamic metabolic requirements, an impaired macro- and microcirculatory flow and mitochondrial dysfunction. However, the longitudinal pattern of these parameters in critically ill patients who die during hospitalization remains unknown. Therefore, we analyzed in 566 patients who received a pulmonary artery catheter (PAC) their REE, DO2, VO2 and oxygen extraction ratio (O2ER) continuously in survivors and non-survivors over the first 7 days post cardiac surgery, calculated the percent increase in the measured compared with the calculated REE and investigated the impact of a reduced REE on 30-day, 1-year and 6-year mortality in a uni- and multivariate model. Only in survivors was there a statistically significant transition from a negative to a positive energy balance from day 0 until day 1 (Day 0: −3% (−18, 14) to day 1: 5% (−9, 21); p < 0.001). Furthermore, non-survivors had significantly decreased DO2 during the first 4 days and reduced O2ER from day 2 until day 6. Additionally, a lower REE was significantly associated with a worse survival at 30 days, 1 year and 6 years (p = 0.009, p < 0.0001 and p = 0.012, respectively). Non-survivors seemed to be unable to metabolically adapt from the early (previously called the ‘ebb’) phase to the later ‘flow’ phase. DO2 reduction was more pronounced during the first three days whereas O2ER was markedly lower during the following four days, suggesting a switch from a predominantly limited oxygen supply to prolonged mitochondrial dysfunction. The association between a reduced REE and mortality further emphasizes the importance of REE monitoring.

Influence of Immune Cell Subtypes on Mitochondrial Measurements in Peripheral Blood Mononuclear Cells From Children with Sepsis

INTRODUCTION

Peripheral blood mononuclear cells (PBMCs) are commonly used to compare mitochondrial function in patients with versus without sepsis, but how these measurements in this mixed cell population vary by composition of immune cell subtypes is not known, especially in children. We determined the effect of changing immune cell composition on PBMC mitochondrial respiration and content in children with and without sepsis.

METHODS

PBMC mitochondrial respiration and citrate synthase (CS) activity, a marker of mitochondrial content, were measured in 167 children with sepsis at three timepoints (day 1-2, 3-5, and 8-14) and once in 19 nonseptic controls. The proportion of lymphocytes and monocytes and T, B, and NK cells was measured using flow cytometry. More specific CD4+ and CD8+ T cell subsets were measured from 13 sepsis patients and 6 controls. Spearman's correlation and simple and mixed effects linear regression were used to determine the association of PBMC mitochondrial measures with proportion of immune cell subtypes.

RESULTS

PBMC mitochondrial respiration and CS activity were correlated with proportion of monocytes, lymphocytes, T B, and NK cells in controls, but not in sepsis patients. PBMC mitochondrial respiration was correlated with CD4+ and CD8+ T cell subsets in both groups. After controlling for differences in immune cell composition between groups using linear regression models, PBMC respiration and CS activity remained lower in sepsis patients than controls.

CONCLUSIONS

Mitochondrial measurements from PBMCs varied with changes in immune cell composition in children with and without sepsis. However, differences in PBMC mitochondrial measurements between sepsis patients and controls were at least partially attributable to the effects of sepsis rather than solely an epiphenomena of variable immune cell composition.

Pathophysiology, mechanisms, and managements of tissue hypoxia

Oxygen is needed to generate aerobic adenosine triphosphate and energy that is required to support vital cellular functions. Oxygen delivery (DO₂) to the tissues is determined by convective and diffusive processes. The ability of the body to adjust oxygen extraction (ERO₂) in response to changes in DO₂ is crucial to maintain constant tissue oxygen consumption (VO₂). The capability to increase ERO₂ is the result of the regulation of the circulation and the effects of the simultaneous activation of both central and local factors. The endothelium plays a crucial role in matching tissue oxygen supply to demand in situations of acute drop in tissue oxygenation. Tissue oxygenation is adequate when tissue oxygen demand is met. When DO₂ is severely compromised, a critical DO₂ value is reached below which VO₂ falls and becomes dependent on DO₂, resulting in tissue hypoxia. The different mechanisms of tissue hypoxia are circulatory, anaemic, and hypoxic, characterised by a diminished DO₂ but preserved capacity of increasing ERO₂. Cytopathic hypoxia is another mechanism of tissue hypoxia that is due to impairment in mitochondrial respiration that can be observed in septic conditions with normal overall DO₂. Sepsis induces microcirculatory alterations with decreased functional capillary density, increased number of stopped-flow capillaries, and marked heterogeneity between the areas with large intercapillary distance, resulting in impairment of the tissue to extract oxygen and to satisfy the increased tissue oxygen demand, leading to the development of tissue hypoxia. Different therapeutic approaches exist to increase DO₂ and improve microcirculation, such as fluid therapy, transfusion, vasopressors, inotropes, and vasodilators. However, the effects of these agents on microcirculation are quite variable.

Refining the Pediatric Multiple Organ Dysfunction Syndrome

Since its introduction into the medical literature in the 1970s, the term multiple organ dysfunction syndrome (or some variant) has been applied broadly to any patient with >1 concurrent organ dysfunction. However, the epidemiology, mechanisms, time course, and outcomes among children with multiple organ dysfunction vary substantially. We posit that the term pediatric multiple organ dysfunction syndrome (or MODS) should be reserved for patients with a systemic pathologic state resulting from a common mechanism (or mechanisms) that affects numerous organ systems simultaneously. In contrast, children in whom organ injuries are attributable to distinct mechanisms should be considered to have additive organ system dysfunctions but not the syndrome of MODS. Although such differentiation may not always be possible with current scientific knowledge, we make the case for how attempts to differentiate multiple organ dysfunction from other states of additive organ dysfunctions can help to evolve clinical and research priorities in diagnosis, monitoring, and therapy from largely organ-specific to more holistic strategies.

Comprehensive Review of Biliary Peritonitis

Biliary peritonitis is a growing concern in the canine patient and a thorough understanding of the disease will lead to better treatment outcomes. This article reviews the human and veterinary literature pertaining to biliary peritonitis including both scientific reviews and original publications. Compared to human medicine, biliary peritonitis can be difficult to diagnose preoperatively. Multiple risk factors exist increasing the likelihood of development of biliary peritonitis. Treatment recommendations center on stabilization, surgical cholecystectomy, and postoperative supportive care. Clinically, further studies on treatment and prevention in veterinary medicine are warranted.

Biochemical markers for clinical monitoring of tissue perfusion

The assessment and monitoring of the tissue perfusion is extremely important in critical conditions involving circulatory shock. There is a wide range of established methods for the assessment of cardiac output as a surrogate of oxygen delivery to the peripheral tissues. However, the evaluation of whether particular oxygen delivery is sufficient to ensure cellular metabolic demands is more challenging. In recent years, specific biochemical parameters have been described to indicate the status between tissue oxygen demands and supply. In this review, the authors summarize the application of some of these biochemical markers, including mixed venous oxygen saturation (S_vO₂), lactate, central venous–arterial carbon dioxide difference (PCO₂ gap), and PCO₂ gap/central arterial-to-venous oxygen difference (C_a–vO₂) for hemodynamic assessment of tissue perfusion. The thorough monitoring of the adequacy of tissue perfusion and oxygen supply in critical conditions is essential for the selection of the most appropriate therapeutic strategy and it is associated with improved clinical outcomes.

In Vivo Assessment of Mitochondrial Oxygen Consumption

The Protoporphyrin IX-Triplet State Lifetime Technique (PpIX-TSLT) has been proposed by us as a potential clinical noninvasive tool for monitoring mitochondrial function. We have been working on the development of mitochondrial respirometry for monitoring mitochondrial oxygen tension (mitoPO2) and mitochondrial oxygen consumption (mitoVO2) in skin. In this work, we describe the principles of the method in small experimental animals.

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

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

Early label-free analysis of mitochondrial redox states by Raman spectroscopy predicts septic outcomes

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Resonance Raman spectroscopy was applied to in vivo detection of the mitochondrial redox state in septic mice for the first time.

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Monitoring mitochondrial redox states using resonance Raman spectroscopy had higher prognostic accuracy for mortality than the lactate level during sepsis and could be a novel diagnostic marker for predicting septic outcomes at an early time point.

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Resonance Raman spectroscopy could detect mitochondrial dysfunction in sepsis and provide a biomarker that can be a specific target of adjunctive treatment.

Background

Sepsis remains an unacceptably high mortality due to the lack of biomarkers for predicting septic outcomes in the early period. Mitochondrial redox states play a pivotal role in this condition and are disturbed early in the development of sepsis. Here, we hypothesized that visualizing mitochondrial redox states via resonance Raman spectroscopy (RRS) could identify septic outcomes at an early time point. Sepsis was induced by cecal ligation and puncture (CLP). We applied RRS analysis at baseline and 30 min, 1 h, 2 h, 4 h, and 6 h after CLP, and the mitochondrial redox states were identified. The levels of blood lactate as a predictor in sepsis were assessed. Our study is the first to reveal the possibility of in vivo detection of the mitochondrial redox state by using RRS in septic mice. The peak area for the Raman reduced mitochondrial fraction, the indicator of mitochondrial redox states, fluctuated significantly at 2 h after CLP. This fluctuation occurred earlier than the change in lactate level. Moreover, this fluctuation had higher prognostic accuracy for mortality than the lactate level during sepsis and could be a novel diagnostic marker for predicting septic outcomes according to the cutoff value of 1.059, which had a sensitivity of 80% and a specificity of 90%.

Objectives

To explore an effective indicator concerning mitochondrial redox states in the early stage of sepsis and to predict septic outcomes accurately in vivo using non-invasive and label-free Resonance Raman spectroscopy (RRS) analysis.

Methods

Mitochondria, primary skeletal muscle cells andex-vivo muscles harvested from gastrocnemius were detected mitochondrial redox states respectively by using RRS. Sepsis was induced by cecal ligation and puncture (CLP). We applied RRS analysis at baseline and 30 min, 1 h, 2 h, 4 h, and 6 h after CLP, and the mitochondrial redox states were identified. The levels of blood lactate as a predictor in sepsis were assessed. The predictive correlation of mitochondrial redox states on mortality, inflammation and organ dysfunction was further assessed.

Results

Mitochondrial redox states were clearly recognized in ex-vivo gastrocnemius muscles as well as purified mitochondria and primary skeletal muscle cells by using RRS. The peak area for the Raman reduced mitochondrial fraction, the indicator of mitochondrial redox states, fluctuated significantly at 2 h after CLP. This fluctuation occurred earlier than the change in lactate level. Moreover, this fluctuation had higher prognostic accuracy for mortality than the lactate level during sepsis and could be a novel diagnostic marker for predicting septic outcomes according to the cutoff value of 1.059, which had a sensitivity of 80% and a specificity of 90%.

Conclusions

This study demonstrated that monitoring mitochondrial redox states using RRS as early as 2 h could indicate outcomes in septic mice. These data may contribute to developing a non-invasive clinical device concerning mitochondrial redox states by using bedside-RRS.

Persistent Mitochondrial Dysfunction Linked to Prolonged Organ Dysfunction in Pediatric Sepsis

OBJECTIVES

Limited data exist about the timing and significance of mitochondrial alterations in children with sepsis. We therefore sought to determine if alterations in mitochondrial respiration and content within circulating peripheral blood mononuclear cells were associated with organ dysfunction in pediatric sepsis.

DESIGN

Prospective observational study SETTING:: Single academic PICU.

PATIENTS

One-hundred sixty-seven children with sepsis/septic shock and 19 PICU controls without sepsis, infection, or organ dysfunction.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Mitochondrial respiration and content were measured in peripheral blood mononuclear cells on days 1-2, 3-5, and 8-14 after sepsis recognition or once for controls. Severity and duration of organ dysfunction were determined using the Pediatric Logistic Organ Dysfunction score and organ failure-free days through day 28. Day 1-2 maximal uncoupled respiration (9.7 ± 7.7 vs 13.7 ± 4.1 pmol O2/s/10 cells; p = 0.02) and spare respiratory capacity (an index of bioenergetic reserve: 6.2 ± 4.3 vs 9.6 ± 3.1; p = 0.005) were lower in sepsis than controls. Mitochondrial content, measured by mitochondrial DNA/nuclear DNA, was higher in sepsis on day 1-2 than controls (p = 0.04) and increased in sepsis patients who had improving spare respiratory capacity over time (p = 0.005). Mitochondrial respiration and content were not associated with day 1-2 Pediatric Logistic Organ Dysfunction score, but low spare respiratory capacity was associated with higher Pediatric Logistic Organ Dysfunction score on day 3-5. Persistently low spare respiratory capacity was predictive of residual organ dysfunction on day 14 (area under the receiver operating characteristic, 0.72; 95% CI, 0.61-0.84) and trended toward fewer organ failure-free days although day 28 (β coefficient, -0.64; 95% CI, -1.35 to 0.06; p = 0.08).

CONCLUSIONS

Mitochondrial respiration was acutely decreased in peripheral blood mononuclear cells in pediatric sepsis despite an increase in mitochondrial content. Over time, a rise in mitochondrial DNA tracked with improved respiration. Although initial mitochondrial alterations in peripheral blood mononuclear cells were unrelated to organ dysfunction, persistently low respiration was associated with slower recovery from organ dysfunction.

Approach of minimal invasive monitoring and initial treatment of the septic patient in emergency medicine

Sepsis and septic shock constitute a complex disease condition that requires the engagement of several medical specialties. A great number of patients with this disease are constantly admitted to the emergency department, which warrants the need for emergency physicians to lead in the recognition and early management of septic patients. Timely and appropriate interventions may help reduce mortality in a disease with an unacceptably high mortality rate. Poor control of cellular hypoperfusion is one of the most influential mechanisms contributing to the high mortality rate in these patients. This article aims to make an evidence-based approach and an algorithm for the active identification of hypoperfusion in patients with suspicion of severe infection, based on both clinical variables (capillary refill, mottling index, left ventricular function by ultrasound, temperature gradient, etc.) and laboratory-measured variables (lactate, central venous oxygen saturation [ScvO₂], and venous-to-arterial carbon dioxide tension difference [P (v-a) CO₂]). Such variables are feasible to use in the emergency department and would help to explain the cause behind the inadequate oxygen use by cells, thereby guiding treatment at the macrovascular, microvascular, or cellular level.

Clinical use of plasma lactate concentration. Part 1: Physiology, pathophysiology, and measurement

OBJECTIVE

To review the current literature with respect to the physiology, pathophysiology, and measurement of lactate.

DATA SOURCES

Data were sourced from veterinary and human clinical trials, retrospective studies, experimental studies, and review articles. Articles were retrieved without date restrictions and were sourced primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection.

HUMAN AND VETERINARY DATA SYNTHESIS

Lactate is an important energy storage molecule, the production of which preserves cellular energy production and mitigates the acidosis from ATP hydrolysis. Although the most common cause of hyperlactatemia is inadequate tissue oxygen delivery, hyperlactatemia can, and does occur in the face of apparently adequate oxygen supply. At a cellular level, the pathogenesis of hyperlactatemia varies widely depending on the underlying cause. Microcirculatory dysfunction, mitochondrial dysfunction, and epinephrine-mediated stimulation of Na⁺ -K⁺ -ATPase pumps are likely important contributors to hyperlactatemia in critically ill patients. Ultimately, hyperlactatemia is a marker of altered cellular bioenergetics.

CONCLUSION

The etiology of hyperlactatemia is complex and multifactorial. Understanding the relevant pathophysiology is helpful when characterizing hyperlactatemia in clinical patients.

Transcriptomic data from two primary cell models stimulating human monocytes suggest inhibition of oxidative phosphorylation and mitochondrial function by N. meningitidis which is partially up-regulated by IL-10

Background

Biological interpretation of DNA microarray data may differ depending on underlying assumptions and statistical tests of bioinformatics tools used. We used Gene Set Enrichment Analysis (GSEA) and Ingenuity Pathway Analysis (IPA) to analyze previously generated DNA microarray data from human monocytes stimulated with N. meningitidis and IL-10 (“the model system”), and with meningococcal sepsis plasma before and after immunodepletion of IL-10 (“the patient plasma system”). The objectives were to compare if the two bioinformatics methods resulted in similar biological interpretation of the datasets, and to identify whether GSEA provided additional insight compared with IPA about the monocyte host response to meningococcal activation.

Results

In both experimental models, GSEA and IPA identified genes associated with pro-inflammatory innate immune activation, including TNF-signaling, Toll-like receptor signaling, JAK-STAT-signaling, and type I and type II interferon signaling. GSEA identified genes regulated by the presence of IL-10 with similar gene sets in both the model system and the patient plasma system. In the model system, GSEA and IPA in sum identified 170 genes associated with oxidative phosphorylation/mitochondrial function to be down-regulated in monocytes stimulated with meningococci. In the patient plasma system, GSEA and IPA in sum identified 122 genes associated with oxidative phosphorylation/mitochondrial dysfunction to be down-regulated by meningococcal sepsis plasma depleted for IL-10. Using IPA, we identified IL-10 to up-regulate 18 genes associated with oxidative phosphorylation/mitochondrial function that were down-regulated by N. meningitidis.

Conclusions

Biological processes associated with the gene expression changes in the model system of meningococcal sepsis were comparable with the results found in the patient plasma system. By combining GSEA with IPA, we discovered an inhibitory effect of N. meningitidis on genes associated with mitochondrial function and oxidative phosphorylation, and that IL-10 partially reverses this strong inhibitory effect, thereby identifying, to our knowledge, yet another group of genes where IL-10 regulates the effect of LPS. We suggest that relying on a single bioinformatics tool together with an arbitrarily chosen filtering criteria for data analysis may result in overlooking relevant biological processes and signaling pathways associated with genes differentially expressed between compared experimental conditions.

Electronic supplementary material

The online version of this article (10.1186/s12865-017-0229-5) contains supplementary material, which is available to authorized users.

Amelioration of energy metabolism by melatonin in skeletal muscle of rats with LPS induced endotoxemia

In the literature, few studies have investigated the effects of melatonin on energy metabolism in skeletal muscle in endotoxemia. We investigated the effects of melatonin on tissue structure, energy metabolism in skeletal muscle, and antioxidant level of rats with endotoxemia. We divided rats into 4 groups, control, lipopolysaccharide (LPS) (20 mg/kg, i.p., single dose), melatonin (10 mg/kg, i.p., three times), and melatonin + LPS. Melatonin was injected i.p. 30 min before and after the 2nd and 4th hours of LPS injection. Antioxidant status was determined by glutathione (GSH) measurement in the blood. Muscle tissue was stained using modified Gomori trichrome (MGT), succinic dehydrogenase (SDH), and cytochrome oxidase (COX) and histological scored. Also the sections were then stained with hematoxylin and eosin. The stained sections were visualized and photographed. Creatine, creatine phosphate, adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) levels were investigated using high performance liquid chromatography (HPLC) in muscle tissue. In the Melatonin + LPS group, blood GSH levels were increased compared with the LPS group (P<0.01). Melatonin reduced myopathic changes in the LPS group according to the histopathologic findings. In addition, ATP values were increased compared with the LPS group (P<0.05). Our findings showed melatonin treatment prevented muscle damage by increasing ATP and GSH levels in rats with LPS induced endotoxemia.

Pathophysiology of Pediatric Multiple Organ Dysfunction Syndrome

OBJECTIVE

To describe the pathophysiology associated with multiple organ dysfunction syndrome in children.

DATA SOURCES

Literature review, research data, and expert opinion.

STUDY SELECTION

Not applicable.

DATA EXTRACTION

Moderated by an experienced expert from the field, pathophysiologic processes associated with multiple organ dysfunction syndrome in children were described, discussed, and debated with a focus on identifying knowledge gaps and research priorities.

DATA SYNTHESIS

Summary of presentations and discussion supported and supplemented by relevant literature.

CONCLUSIONS

Experiment modeling suggests that persistent macrophage activation may be a pathophysiologic basis for multiple organ dysfunction syndrome. Children with multiple organ dysfunction syndrome have 1) reduced cytochrome P450 metabolism inversely proportional to inflammation; 2) increased circulating damage-associated molecular pattern molecules from injured tissues; 3) increased circulating pathogen-associated molecular pattern molecules from infection or endogenous microbiome; and 4) cytokine-driven epithelial, endothelial, mitochondrial, and immune cell dysfunction. Cytochrome P450s metabolize endogenous compounds and xenobiotics, many of which ameliorate inflammation, whereas damage-associated molecular pattern molecules and pathogen-associated molecular pattern molecules alone and together amplify the cytokine production leading to the inflammatory multiple organ dysfunction syndrome response. Genetic and environmental factors can impede inflammation resolution in children with a spectrum of multiple organ dysfunction syndrome pathobiology phenotypes. Thrombocytopenia-associated multiple organ dysfunction syndrome patients have extensive endothelial activation and thrombotic microangiopathy with associated oligogenic deficiencies in inhibitory complement and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13. Sequential multiple organ dysfunction syndrome patients have soluble Fas ligand-Fas-mediated hepatic failure with associated oligogenic deficiencies in perforin and granzyme signaling. Immunoparalysis-associated multiple organ dysfunction syndrome patients have impaired ability to resolve infection and have associated environmental causes of lymphocyte apoptosis. These inflammation phenotypes can lead to macrophage activation syndrome. Resolution of multiple organ dysfunction syndrome requires elimination of the source of inflammation. Full recovery of organ functions is noted 6-18 weeks later when epithelial, endothelial, mitochondrial, and immune cell regeneration and reprogramming is completed.

Serum Procalcitonin and Peripheral Venous Lactate for Predicting Dengue Shock and/or Organ Failure: A Prospective Observational Study

Background

Currently, there are no biomarkers that can predict the incidence of dengue shock and/or organ failure, although the early identification of risk factors is important in determining appropriate management to reduce mortality. Therefore, we sought to determine the factors associated with dengue shock and/or organ failure and to evaluate the prognostic value of serum procalcitonin (PCT) and peripheral venous lactate (PVL) levels as biomarkers of dengue shock and/or organ failure.

Methodology/Principal Findings

A prospective observational study was conducted among adults hospitalized for confirmed viral dengue infection at the Hospital for Tropical Diseases in Bangkok, Thailand between October 2013 and July 2015. Data, including baseline characteristics, clinical parameters, laboratory findings, serum PCT and PVL levels, management, and outcomes, were recorded on pre-defined case report forms. Of 160 patients with dengue, 128 (80.0%) patients had dengue without shock or organ failure, whereas 32 (20.0%) patients developed dengue with shock and/or organ failure. Using a stepwise multivariate logistic regression analysis, PCT ≥0.7 ng/mL (odds ratio [OR]: 4.80; 95% confidence interval [CI]: 1.60–14.45; p = 0.005) and PVL ≥2.5 mmol/L (OR: 27.99, 95% CI: 8.47–92.53; p <0.001) were independently associated with dengue shock and/or organ failure. A combination of PCT ≥0.7 ng/mL and PVL ≥2.5 mmol/L provided good prognostic value for predicting dengue shock and/or organ failure, with an area under the receiver operating characteristics curve of 0.83 (95% CI: 0.74–0.92), a sensitivity of 81.2% (95% CI: 63.6–92.8%), and a specificity of 84.4% (95% CI: 76.9–90.2%). Dengue shock patients with non-clearance of PCT and PVL expired during hospitalization.

Conclusions/Significance

PCT ≥0.7 ng/mL and PVL ≥2.5 mmol/L were independently associated with dengue shock and/or organ failure. The combination of PCT and PVL levels could be used as prognostic biomarkers for the prediction of dengue shock and/or organ failure.

Dengue is a major global health concern, particularly in tropical countries, and affects all age groups. Mortality rates among patients who have been hospitalized with severe dengue are 1.6–10.9%, and death in adults is mainly due to the development of dengue shock and organ dysfunction. In states of poor tissue circulation or shock, lactate is produced. Additionally, procalcitonin is a highly specific biomarker of systemic inflammation. Therefore, we assessed whether procalcitonin and peripheral venous lactate could be used to predict the incidence of dengue shock and/or organ failure in patients with dengue. Our study showed that a combination of serum procalcitonin levels ≥0.7 ng/mL and peripheral venous lactate levels ≥2.5 mmol/L at admission could discriminate between patients who did and did not develop shock and/or organ failure, with high sensitivity and specificity. These parameters may therefore be useful as prognostic biomarkers. Our results suggest that serum procalcitonin is indicative of an extensive early inflammatory response, which may occur during the systemic phase of dengue. Peripheral venous lactate may be produced as a result of the poor tissue circulation that precedes dengue shock. Our findings may help clinicians to predict dengue shock and/or organ failure earlier to reduce in-hospital mortality.

Patterns of central venous oxygen saturation, lactate and veno-arterial CO2 difference in patients with septic shock

BACKGROUND AND AIMS

Tissue hypoperfusion is reflected by metabolic parameters such as lactate, central venous oxygen saturation (ScvO2) and the veno-arterial CO2 (vaCO2) difference. We studied the relation of these parameters over time and with outcome in patients with severe septic shock.

MATERIALS AND METHODS

In this single-center, prospective observational cohort study, adult patients (≥18 years) with circulatory shock were included. Echocardiography and simultaneous arterial and venous blood gases were done on enrolment (0 h) and at 24, 48 and 72 h. The partial pressure of CO2, lactate and ScvO2 were recorded from the central venous blood samples. The vaCO2 was calculated as the difference in CO2 between paired venous and arterial blood gas samples.

RESULTS

Of the 104 patients with circulatory shock, 79 patients (44 males) with septic shock aged 49.8 (standard deviation ± 14.6) years and with sequential organ failure assessment (SOFA) score of 11.0 ± 3.4 were included. 71 patients (89.9%) were ventilated (11.4 ± 12.3 ventilator-free days). The duration of hospitalization was 16.6 ± 12.8 days and hospital mortality 50.6%. Lactate significantly decreased over time with a greater decrement in survivors than nonsurvivors (-0.35 vs. -0.10, P < 0.001). For every l/min increase in cardiac output, vaCO2 decreased by 0.34 mmHg (P = 0.006). There was no association between ScvO2 and mortality (P = 0.930). 0 h SOFA and vaCO2 ≤6 mmHg were strongly associated (P = 0.005, P = 0.018, respectively) with higher odds of mortality. However, this association was evident only in those with ScvO2 >70% and not in ScvO2 ≤70%.

CONCLUSION

In septic shock, vaCO2 ≤6 mmHg is independently associated with mortality, particularly in those with normalized ScvO2 consistent with metabolic microcirculatory abnormalities in these patients.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

How to choose the therapeutic goals to improve tissue perfusion in septic shock

The early recognition and treatment of severe sepsis and septic shock is the key to a successful outcome. The longer the delay in starting treatment, the worse the prognosis due to persistent tissue hypoperfusion and consequent development and worsening of organ dysfunction. One of the main mechanisms responsible for the development of cellular dysfunction is tissue hypoxia. The adjustments necessary for adequate tissue blood flow and therefore of oxygen supply to metabolic demand according to the assessment of the cardiac index and oxygen extraction rate should be performed during resuscitation period, especially in high complexity patients. New technologies, easily handled at the bedside, and new studies that directly assess the impact of macro-hemodynamic parameter optimization on microcirculation and in the clinical outcome of septic patients, are needed.

Assessment of preload and fluid responsiveness in intensive care unit. How good are we?

Early recognition and treatment of acute circulatory failure and tissue hypoperfusion are paramount for improving the odds of survival in critically ill patients. Fluid volume resuscitation is the mainstay intervention in redistributive and hypovolemic shock. Correct identification of a patient who would benefit from fluid administration allows optimization of hemodynamics and avoids ineffective or even deleterious volume expansion that may result in worsening of gas exchange and pulmonary edema in fluid unresponsive patients, in whom inotropic and/or vasopressor support should preferentially be used. The use of dynamic changes in central venous pressure, pulse pressure, and echocardiography for assessment of inferior vena cava diameter variations during respiration allows prediction of fluid volume responsiveness in hemodynamically unstable patients. The use of these bedside approaches and passive leg raising maneuver, which is a reversible and quick fluid volume challenge, allows timely formulation of treatment strategy in patients with shock.

In vivo assessment of mitochondrial oxygen consumption

The protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT) has been proposed by us as a potential clinical noninvasive tool for monitoring mitochondrial function. We have been working on the development of mitochondrial respirometry for monitoring mitochondrial oxygen tension (mitoPO2) and mitochondrial oxygen consumption (mitoVO2) in skin. In this work we describe the principles of the method in experimental animals.

Left-sided superior vena cava and venous hyperoxia masquerading as inadvertent carotid artery catheterization

BACKGROUND

A persistent left-sided superior vena cava (PLSVC) is a rare, often asymptomatic, venous anomaly that may be first diagnosed during central venous catheterization. During chest radiograph interpretation, a PLSVC can be confused with inadvertent arterial catheterization.

CASE REPORT

We describe the presentation of a 45-year-old man with end-stage liver disease who required central venous catheterization for treatment of septic shock. An aberrantly placed catheter noted on chest radiograph and an elevated central venous oxygen saturation gave the appearance of inadvertent carotid artery catheterization. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: A persistent left-sided superior vena cava can masquerade as an inadvertent cannulation of the carotid artery during central line placement. It is important for emergency physicians to be aware of this possibility when evaluating a chest radiograph with an aberrantly placed catheter. Venous hyperoxia may further complicate attempts to differentiate between arterial and venous catheterization in patients with septic shock. After confirmatory tests, the emergency physician should consider removal of the catheter due to potential complications.

Experimental lung injury promotes alterations in energy metabolism and respiratory mechanics in the lungs of rats: prevention by exercise

In the present study we investigated the effects of lung injury on energy metabolism (succinate dehydrogenase, complex II, cytochrome c oxidase, and ATP levels), respiratory mechanics (dynamic and static compliance, elastance and respiratory system resistance) in the lungs of rats, as well as on phospholipids in bronchoalveolar lavage fluid. The protective effect of physical exercise on the alterations caused by lung injury, including lung edema was also evaluated. Wistar rats were submitted to 2 months of physical exercise. After this period the lung injury was induced by intratracheal instillation of lipopolysaccharide. Adult Wistar rats were submitted to 2 months of physical exercise and after this period the lung injury was induced by intratracheal instillation of lipopolysaccharide in dose 100 μg/100 g body weight. The sham group received isotonic saline instillation. Twelve hours after the injury was performed the respiratory mechanical and after the rats were decapitated and samples were collected. The rats subjected to lung injury presented a decrease in activities of the enzymes of the electron transport chain and ATP levels in lung, as well as the formation of pulmonary edema. A decreased lung dynamic and static compliance, as well as an increase in respiratory system resistance, and a decrease in phospholipids content were observed. Physical exercise was able to totally prevent the decrease in succinate dehydrogenase and complex II activities and the formation of pulmonary edema. It also partially prevented the increase in respiratory system resistance, but did not prevent the decrease in dynamic and static compliance, as well as in phospholipids content. These findings suggest that the mitochondrial dysfunction may be one of the important contributors to lung damage and that physical exercise may be beneficial in this pathology, although it did not prevent all changes present in lung injury.

Do mitochondria limit hot fish hearts? Understanding the role of mitochondrial function with heat stress in Notolabrus celidotus

Hearts are the first organs to fail in animals exposed to heat stress. Predictions of climate change mediated increases in ocean temperatures suggest that the ectothermic heart may place tight constraints on the diversity and distribution of marine species with cardiovascular systems. For many such species, their upper temperature limits (Tmax) and respective heart failure (HF) temperature (T(HF)) are only a few degrees from current environmental temperatures. While the ectothermic cardiovascular system acts as an "ecological thermometer," the exact mechanism that mediates HF remains unresolved. We propose that heat-stressed cardiac mitochondria drive HF. Using a common New Zealand fish, Notolabrus celidotus, we determined the THF (27.5°C). Haemoglobin oxygen saturation appeared to be unaltered in the blood surrounding and within heat stressed hearts. Using high resolution respirometry coupled to fluorimeters, we explored temperature-mediated changes in respiration, ROS and ATP production, and overlaid these changes with T(HF). Even at saturating oxygen levels several mitochondrial components were compromised before T(HF). Importantly, the capacity to efficiently produce ATP in the heart is limited at 25°C, and this is prior to the acute T(HF) for N. celidotus. Membrane leakiness increased significantly at 25°C, as did cytochrome c release and permeability to NADH. Maximal flux rates and the capacity for the electron transport system to uncouple were also altered at 25°C. These data indicate that mitochondrial membrane integrity is lost, depressing ATP synthesis capacity and promoting cytochrome c release, prior to T(HF). Mitochondria can mediate HF in heat stressed hearts in fish and play a significant role in thermal stress tolerance, and perhaps limit species distributions by contributing to HF.

Lactate clearance for death prediction in severe sepsis or septic shock patients during the first 24 hours in Intensive Care Unit: an observational study

Background

This study was design to investigate the prognostic value for death at day-28 of lactate course and lactate clearance during the first 24 hours in Intensive Care Unit (ICU), after initial resuscitation.

Methods

Prospective, observational study in one surgical ICU in a university hospital. Ninety-four patients hospitalized in the ICU for severe sepsis or septic shock were included. In this septic cohort, we measured blood lactate concentration at ICU admission (H0) and at H6, H12, and H24. Lactate clearance was calculated as followed: [(lactate_initial - lactate_delayed)/ lactate_initial] x 100%].

Results

The mean time between severe sepsis diagnosis and H0 (ICU admission) was 8.0 ± 4.5 hours. Forty-two (45%) patients died at day 28. Lactate clearance was higher in survivors than in nonsurvivors patients for H0-H6 period (13 ± 38% and −13 ± 7% respectively, p = 0.021) and for the H0-H24 period (42 ± 33% and −17 ± 76% respectively, p < 0.001). The best predictor of death at day 28 was lactate clearance for the H0-H24 period (AUC = 0.791; 95% CI 0.6-0.85). Logistic regression found that H0-H24 lactate clearance was independently correlated to a survival status with a p = 0.047 [odds ratio = 0.35 (95% CI 0.01-0.76)].

Conclusions

During the first 24 hr in the ICU, lactate clearance was the best parameter associated with 28-day mortality rate in septic patients. Protocol of lactate clearance-directed therapy should be considered in septic patients, even after the golden hours.

Perioperative acute kidney injury

Acute kidney injury (AKI) is a serious complication in the perioperative period, and is consistently associated with increased rates of mortality and morbidity. Two major consensus definitions have been developed in the last decade that allow for easier comparison of trial evidence. Risk factors have been identified in both cardiac and general surgery and there is an evolving role for novel biomarkers. Despite this, there has been no real change in outcomes and the mainstay of treatment remains preventive with no clear evidence supporting any therapeutic intervention as yet. This review focuses on definition, risk factors, the emerging role of biomarkers and subsequent management of AKI in the perioperative period, taking into account new and emerging strategies.

Near infrared spectroscopy (NIRS) of the thenar eminence in anesthesia and intensive care

Near infrared spectroscopy of the thenar eminence (NIRS_th) is a noninvasive bedside method for assessing tissue oxygenation. The NIRS probe emits light with several wavelengths in the 700- to 850-nm interval and measures the reflected light mainly from a predefined depth. Complex physical models then allow the measurement of the relative concentrations of oxy and deoxyhemoglobin, and thus tissue saturation (StO₂), as well as an approximation of the tissue hemoglobin, given as tissue hemoglobin index.

Here we review of current knowledge of the application of NIRS_th in anesthesia and intensive care.

We performed an analytical and descriptive review of the literature using the terms “near-infrared spectroscopy” combined with “anesthesia,” “anesthesiology,” “intensive care,” “critical care,” “sepsis,” “bleeding,” “hemorrhage,” “surgery,” and “trauma” with particular focus on all NIRS studies involving measurement at the thenar eminence.

We found that NIRS_th has been applied as clinical research tool to perform both static and dynamic assessment of StO₂. Specifically, a vascular occlusion test (VOT) with a pressure cuff can be used to provide a dynamic assessment of the tissue oxygenation response to ischemia. StO₂ changes during such induced ischemia-reperfusion yield information on oxygen consumption and microvasculatory reactivity. Some evidence suggests that StO₂ during VOT can detect fluid responsiveness during surgery. In hypovolemic shock, StO₂ can help to predict outcome, but not in septic shock. In contrast, NIRS parameters during VOT increase the diagnostic and prognostic accuracy in both hypovolemic and septic shock. Minimal data are available on static or dynamic StO₂ used to guide therapy.

Although the available data are promising, further studies are necessary before NIRS_th can become part of routine clinical practice.

The use of recombinant human activated protein C (drotrecogin alpha) in solid organ transplant recipients: case series and review of the literature

Septic shock occurs frequently in solid organ transplant (SOT) recipients. Standard therapy includes fluid resuscitation, the administration of antimicrobials, and source control of the infection. Adjunctive therapy with recombinant human activated protein C (rhaPC), also called drotrecogin alpha, is another treatment that is used in patients but has not been studied in SOT patients. Concerns regarding the use of this drug in this patient population include the risk of bleeding and the potential to adversely affect graft survival. Here we report the largest case series of SOT recipients with septic shock who received rhaPC. This was a retrospective chart review that looked at the impact of this drug in the SOT population. In this single-center study, we identified 17 patients with a SOT and septic shock who received rhaPC. Six of the patients underwent kidney transplants, 5 received lung transplants, 4 received cadaveric liver transplants, and 2 received combined kidney/pancreas transplants. The average APACHE II score was 26.6 ± 5.5; all patients were undergoing mechanical ventilation and receiving vasopressors at the time of rhaPC administration. Overall mortality in the group was 23.5% (4/17) at 28 days post infusion. All of the deaths were due to complications of septic shock. Allograft survival was present in 13/17 (76.5%) of the patients at 28 days. Bleeding occurred in 17.6% of patients (3/17). The use of rhaPC appears to be associated with a favorable effect on mortality, with the potential for increased risk of bleeding. Clinicians must balance this risk with the potential benefit of this drug until further research can be conducted.

Current concepts in resuscitation

Early recognition and differentiation of shock, as well as goal-directed resuscitation, are fundamental principles in the care of the critically ill or injured patient. Substantial progress has been made over the last decade in the understanding of both shock and resuscitation. Specific areas of advancement, particularly pertaining to hemorrhagic shock, include a heightened appreciation of dynamic measurements of preload responsiveness (e.g., respiratory-induced pulse pressure and venous diameter variability), an improved awareness of the detrimental effects of blood product transfusion, and better recognition of the complications of overzealous volume expansion. However, several areas of controversy remain regarding the optimal resuscitation strategy. These include the optimal targets for perfusion pressure and oxygen delivery, endpoints of resuscitation, resuscitative fluid, and transfusion strategies for packed red blood cells and blood products. This article reviews the diagnosis and differentiation of shock, measurements of tissue perfusion, current evidence regarding various resuscitative techniques, and complications of resuscitation.

Protective effects of glutamine preconditioning on ischemia-reperfusion injury in rats

BACKGROUND

Hepatic ischemia-reperfusion injury is a common phenomenon in hepatic surgical procedures and can result in further severe damage. This study aimed to investigate the protective effects of glutamine preconditioning on hepatic ischemia-reperfusion injury in rats and its dose-dependency.

METHODS

Thirty-two healthy male Wistar rats were randomly divided into four groups (n=8 per group). One group received 0.9% NaCl (control) and the other three received glutamine (Gln groups) 4 hours before ischemia. The Gln groups were named GL, GM, and GH according to the glutamine dose. The liver was subjected to 1 hour of ischemia and 2 hours of reperfusion. Two hours later, the levels of alanine aminotransferase (ALT), intracellular free calcium (Ca2+), and activity of Na+/K+ adenosine triphosphatase (ATPase) and superoxide dismutase (SOD) were assessed, and liver tissue sections were examined under a microscope.

RESULTS

The Gln and control groups differed in the concentration of intracellular free calcium (P<0.05), and the activity of Na+/K+ ATPase and SOD in the Gln groups was higher than in the control group (P<0.05). The ALT level was lower in the GM and GH groups than in the control group (P<0.05). The levels of Na+/K+ ATPase and SOD rose gradually with increasing glutamine dose (P<0.05), and the concentration of Ca2+ declined gradually with increasing glutamine dose (P<0.05). The degree of hepatocyte injury was milder in the Gln groups than in the control group.

CONCLUSIONS

Glutamine preconditioning protected effectively against hepatic ischemia-reperfusion injury. These protective effects were related to the dose of glutamine and due to the reduction of intracellular calcium overload and the improvements in the activity of Na+/K+ ATPase and SOD.

Mitochondrial injury underlies hyporeactivity of arterial smooth muscle in severe shock

BACKGROUND

Our previous data showed membrane hyperpolarization of arteriolar smooth muscle cells (ASMCs) caused by adenosine triphosphate (ATP)-sensitive potassium channels (K(ATP)) activation contributed to vascular hyporeactivity in shock. Despite supply of oxygen and nutrients, vascular hyporeactivity to vasoconstrictor agents still remains, which may result from low ATP level. The study was designed to investigate shock-induced mitochondrial changes of rat ASMCs in the genesis and treatment of hypotension in severe shock.

METHODS

The animals were divided into four groups: controls, hemorrhagic shock, CsA+shock (preadministration of cyclosporin A before bleeding), and ATR+CsA+shock (preadministration of atractyloside, followed by CsA and bleeding). ASMCs were isolated and the ultrastructure and function of ASMC mitochondria and the vasoresponsiveness to norepinephrine (NE) was measured on microcirculatory preparations.

RESULTS

Ultrastructurally, the hemorrhagic shock group showed swollen mitochondria with poorly defined cristae. In this group, the number of ASMCs with low mitochondrial membrane potential (Δψ(m)) was increased by 49.7%, and the intracellular ATP level was reduced by 82.1%, which led to activation of K(ATP) plasma membrane channels with resultant ASMC hyperpolarization and low vasoreactivity. These changes were reduced in the CsA+shock group. When mitochondrial damage was aggravated by ATR in the ATR+CsA+shock group, the CsA did not protect. Compared to the shock group, vasoresponsiveness to NE was much improved in the CsA+shock group.

CONCLUSIONS

Mitochondrial ASMC dysfunction is involved in the genesis of reduced vasoreactivity in severe shock. Mitochondrial protection may therefore be a new approach in the treatment of shock-induced hypotension.

Mitochondrial dysfunction and resuscitation in sepsis

Sepsis is among the most common causes of death in patients in intensive care units in North America and Europe. In the United States, it accounts for upwards of 250,000 deaths each year. Investigations into the pathobiology of sepsis have most recently focused on common cellular and subcellular processes. One possibility would be a defect in the production of energy, which translates to an abnormality in the production of adenosine triphosphate and therefore in the function of mitochondria. This article presents a clear role for mitochondrial dysfunction in the pathogenesis and pathophysiology of sepsis. What is less clear is the teleology underlying this response. Prolonged mitochondrial dysfunction and impaired biogenesis clearly are detrimental. However, early inhibition of mitochondrial function may be adaptive.

Oxygen consumption is depressed in patients with lactic acidosis due to biguanide intoxication

INTRODUCTION

Lactic acidosis can develop during biguanide (metformin and phenformin) intoxication, possibly as a consequence of mitochondrial dysfunction. To verify this hypothesis, we investigated whether body oxygen consumption (VO2), that primarily depends on mitochondrial respiration, is depressed in patients with biguanide intoxication.

METHODS

Multicentre retrospective analysis of data collected from 24 patients with lactic acidosis (pH 6.93 +/- 0.20; lactate 18 +/- 6 mM at hospital admission) due to metformin (n = 23) or phenformin (n = 1) intoxication. In 11 patients, VO2 was computed as the product of simultaneously recorded arterio-venous difference in O2 content [C(a-v)O2] and cardiac index (CI). In 13 additional cases, C(a-v)O2, but not CI, was available.

RESULTS

On day 1, VO2 was markedly depressed (67 +/- 28 ml/min/m2) despite a normal CI (3.4 +/- 1.2 L/min/m2). C(a-v)O2 was abnormally low in both patients either with (2.0 +/- 1.0 ml O2/100 ml) or without (2.5 +/- 1.1 ml O2/100 ml) CI (and VO2) monitoring. Clearance of the accumulated drug was associated with the resolution of lactic acidosis and a parallel increase in VO2 (P < 0.001) and C(a-v)O2 (P < 0.05). Plasma lactate and VO2 were inversely correlated (R2 0.43; P < 0.001, n = 32).

CONCLUSIONS

VO2 is abnormally low in patients with lactic acidosis due to biguanide intoxication. This finding is in line with the hypothesis of inhibited mitochondrial respiration and consequent hyperlactatemia.

Techniques for assessment of intravascular volume in critically ill patients

Fluid replacement is considered the cornerstone of resuscitation in the ICU.However, only about 50% of critically ill hemodynamically unstable patients are fluid responsive; furthermore, both under-resuscitation and overzealous fluid administration adversely affect outcome Consequently, the resuscitation of critically ill patients requires an accurate assessment of the patients' intravascular volume status and their volume responsiveness. This paper reviews the evolution and accuracy of methods for assessing fluid responsiveness in critically ill patients.

Caffeine restores myocardial cytochrome oxidase activity and improves cardiac function during sepsis

OBJECTIVE

Impaired mitochondrial function is a potential cause of sepsis-associated myocardial depression. Cytochrome oxidase (CcOX), the terminal oxidase of the electron transport chain, is inhibited in the septic heart. Caffeine increases CcOX activity by increasing cyclic adenosine monophosphate and protein kinase A activity. We hypothesized that caffeine will restore myocardial CcOX activity, increase cardiac function, and improve survival during sepsis.

DESIGN

Prospective randomized controlled study.

SETTING

University hospital-based laboratory.

SUBJECTS

One hundred twenty Sprague-Dawley male rats.

INTERVENTIONS

Sprague-Dawley male rats underwent cecal ligation and puncture (CLP) or sham operation. At 24 and 48 hours, rats underwent intraperitoneal injection of either caffeine (7.5 mg/kg, the equivalent of 1-1.5 cups of coffee) or equal volume of saline.

MEASUREMENTS AND MAIN RESULTS

One hour following the 48-hour injection, steady-state CcOX kinetic activity was measured in isolated mitochondria and normalized to citrate synthase activity. Cardiac function was assessed using an isolated rat heart preparation and survival was tracked to 96 hours. CLP significantly decreased myocardial CcOX activity, oxygen consumption, left ventricular pressure, and pressure developed during isovolumic contraction (+dP/dt) and relaxation (-dP/dt). Caffeine restored CcOX activity and increased left ventricular pressure and +/-dP/dt toward sham values following CLP. Survival significantly improved following CLP in caffeine-injected animals compared with saline injection.

CONCLUSION

Caffeine may be a novel therapy to treat sepsis-associated myocardial depression.

Sepsis: Clinical Approach, Evidence-Based at the Bedside

Sepsis is a common disease in intensive care medicine representing almost one third of patient admissions. Its incidence has substantially increased over the past decades and overall mortality has declined during this period of time. It was reported that sepsis incidence increased from 82.7 to 240.4 per 100,000 population between 1979–2000. At the same time, sepsis global mortality decreased from 27.8 to 17.9% [1–3]. However, the absolute number of deaths significantly increased from 21.9 to 43.9 per 100,000 population. Male gender, some chronic diseases like diabetes, immunosuppressive states, human immunodeficiency virus infections, and malignancies are factors that increase the risk for sepsis. Some particular conditions like progressive number of organ dysfunctions, in-hospital-acquired infections and increasing age are associated with higher risk of death [1,4]. On the other hand, septic shock mortality only diminished from 61.6 to 53.1% [5]. This slight decline in mortality observed during recent decades could be attributable to improvements in supportive care and/or avoidance of iatrogenic complications. For example, the instrumentation of early goal resuscitation protocols not aiming at supranormal targets for cardiac output and oxygen delivery, and the use of lung protective strategies could explain at least in part this favorable change. Other strategies directed to treat the pathophysiological mechanisms involved in the septic process like recombinant human-activated protein-C (rhAPC), have also contributed to improve survival. However, mortality remains unacceptably high and further improvement in sepsis management is needed.

Molecular events in the cardiomyopathy of sepsis

Septic cardiomyopathy is a well-described complication of severe sepsis and septic shock. However, the interplay of its underlying mechanisms remains enigmatic. Consequently, we constantly add to our pathophysiological understanding of septic cardiomyopathy. Various cardiosuppressive mediators have been discovered, as have multiple molecular mechanisms (alterations of myocardial calcium homeostasis, mitochondrial dysfunction, and myocardial apoptosis) that may be involved in myocardial dysfunction during sepsis. Finally, the detrimental roles of nitric oxide and peroxynitrite have been unraveled. Here, we describe our present understanding of systemic, supracellular, and cellular molecular mechanisms involved in sepsis-induced myocardial suppression.

Central venous-to-arterial carbon dioxide difference: an additional target for goal-directed therapy in septic shock?

OBJECTIVE

To test the hypothesis that, in resuscitated septic shock patients, central venous-to-arterial carbon dioxide difference [P(cv-a)CO(2)] may serve as a global index of tissue perfusion when the central venous oxygen saturation (ScvO(2)) goal value has already been reached.

DESIGN

Prospective observational study.

SETTING

A 22-bed intensive care unit (ICU).

PATIENTS

After early resuscitation in the emergency unit, 50 consecutive septic shock patients with ScvO(2) > 70% were included immediately after their admission into the ICU (T0). Patients were separated in Low P(cv-a)CO(2) group (Low gap; n = 26) and High P(cv-a)CO(2) group (High gap; n = 24) according to a threshold of 6 mmHg at T0.

MEASUREMENTS

Measurements were performed every 6 h over 12 h (T0, T6, T12).

RESULTS

At T0, there was a significant difference between Low gap patients and High gap patients for cardiac index (CI) (4.3 +/- 1.6 vs. 2.7 +/- 0.8 l/min/m(2), P < 0.0001) but not for ScvO(2) values (78 +/- 5 vs. 75 +/- 5%, P = 0.07). From T0 to T12, the clearance of lactate was significantly larger for the Low gap group than for the High gap group (P < 0.05) as well as the decrease of SOFA score at T24 (P < 0.01). At T0, T6 and T12, CI and P(cv-a)CO(2) values were inversely correlated (P < 0.0001).

CONCLUSION

In ICU-resuscitated patients, targeting only ScvO(2) may not be sufficient to guide therapy. When the 70% ScvO(2) goal-value is reached, the presence of a P(cv-a)CO(2) larger than 6 mmHg might be a useful tool to identify patients who still remain inadequately resuscitated.

Exogenous cytochrome C restores myocardial cytochrome oxidase activity into the late phase of sepsis

Mitochondrial dysfunction is thought to play a role in the pathogenesis of a variety of disease states, including sepsis. An acquired defect in oxidative phosphorylation potentially causes sepsis-induced organ dysfunction. Cytochrome oxidase (CcOX), the terminal oxidase of the respiratory chain, is competitively inhibited early in sepsis and progresses, becoming noncompetitive during the late phase. We have previously demonstrated that exogenous cytochrome c can overcome myocardial CcOX competitive inhibition and improve cardiac function during murine sepsis at the 24-h point. Here, we evaluate the effect of exogenous cytochrome c on CcOX activity and survival in mice at the later time points. Exogenous cytochrome c (800 microg) or saline was intravenously injected 24 h after cecal ligation and puncture (CLP) or sham operation. Steady-state mitochondrial cytochrome c levels and heme c content increased significantly 48 h post-CLP and remained elevated at 72 h in cytochrome c-injected mice compared with saline injection. Cecal ligation and puncture inhibited CcOX at 48 h in saline-injected mice. However, cytochrome c injection abrogated this inhibition and restored CcOX kinetic activity to sham values at 48 h. Survival after CLP to 96 h after cytochrome c injection approached 50% compared with only 15% after saline injection. Thus, a single injection of exogenous cytochrome c 24 h post-CLP repletes mitochondrial substrate levels for up to 72 h, restores myocardial COX activity, and significantly improves survival.

Longitudinal increases in mitochondrial DNA levels in blood cells are associated with survival in critically ill patients

Background

Mitochondrial dysfunction may be causally related to the pathogenesis of organ failure in critically ill patients. Decreased mitochondrial DNA (mtDNA) levels have been associated with mitochondrial dysfunction and were investigated here in relation to short-term (31-day) survival.

Methods

This was a prospective longitudinal cohort study of 28 mechanically ventilated critically ill adults admitted to a single center tertiary care intensive care unit (ICU) with hypotension secondary to cardiogenic (N = 13), septic (N = 14) or hypovolemic (N = 1) disease processes. Clinical data and blood were collected at baseline and patients were followed until they expired or left the ICU. Blood was collected every Monday, Wednesday and Friday, and the buffycoat relative mtDNA/nuclear DNA (nDNA) ratio was determined. An archived pool of healthy controls was also studied.

Results

At baseline, the patients' mtDNA/nDNA ratio was 30% lower than a pool of 24 healthy controls (0.76 versus 1.09) and was not different between short-term survivors and non-survivors (0.74 ± 0.05 (N = 16) versus 0.79 ± 0.06 (N = 12), p = 0.49). By day 4, the percent mtDNA/nDNA change from baseline in survivors was significantly different from that in non-survivors (+29.5% versus -5.7%, p = 0.03). It also tended to be higher in survivors at last measurement (+38.4% versus +7.1%, p = 0.06). There was a weak correlation between within patient mtDNA/nDNA and platelet count (r = 0.20, p = 0.03) but not with Sequential Organ Failure Assessment (SOFA) scores (r = 0.12, p = 0.23). The mtDNA associations remained after adjustment for platelet.

Conclusion

Blood mtDNA levels appeared initially low, increased over time in patients who ultimately survived, and remained low in those who did not. This is consistent with mitochondrial recovery being associated with survival and warrants further investigation as a marker of mitochondrial alterations and outcome in critical illness.