Evolution of lactate/pyruvate and arterial ketone body ratios in the early course of catecholamine-treated septic shock

Lactate and Lactate-to-Pyruvate Ratio in Critically Ill COVID-19 Patients: A Pilot Study

A limited number of coronavirus disease-19 (COVID-19) cases may require treatment in an intensive care unit (ICU). Arterial blood lactate levels are routinely measured in the ICU to estimate disease severity, predict poor outcomes, and monitor therapeutic handlings. A number of studies have suggested that, simultaneously with lactate, pyruvate should also be measured, providing augmented prognostic ability, and a better understanding of the underlying metabolic alterations in ICU patients. Hence, the aim of the present study was to elucidate the relationship between lactate levels and the lactate-to-pyruvate (LP) ratio with the clinical outcome in mechanically ventilated COVID-19 patients. Lactate and pyruvate were serially measured during the first 24 h of ICU stay. A group of ICU non-COVID-19 patients was used as a comparison group. The majority of COVID-19 patients (82.5%) had normal lactate levels and a normal LP ratio on ICU admission (normal metabolic pattern). A small, yet significant, percentage of patients had either elevated lactate levels or a high LP ratio (abnormal metabolic pattern); these patients exhibited a significantly higher risk of ICU mortality compared to the patients with a normal metabolic pattern (72.7% vs. 34.6%, p = 0.04). In our critically ill COVID-19 patients, elevated lactate levels or high LP ratios on admission to the ICU could be associated with poor clinical outcome.

Co-Polarized [1-13C]Pyruvate and [1,3-13C2]Acetoacetate Provide a Simultaneous View of Cytosolic and Mitochondrial Redox in a Single Experiment

Cellular redox is intricately linked to energy production and normal cell function. Although the redox states of mitochondria and cytosol are connected by shuttle mechanisms, the redox state of mitochondria may differ from redox in the cytosol in response to stress. However, detecting these differences in functioning tissues is difficult. Here, we employed ¹³C magnetic resonance spectroscopy (MRS) and co-polarized [1-¹³C]pyruvate and [1,3-¹³C₂]acetoacetate ([1,3-¹³C₂]AcAc) to monitor production of hyperpolarized (HP) lactate and β-hydroxybutyrate as indicators of cytosolic and mitochondrial redox, respectively. Isolated rat hearts were examined under normoxic conditions, during low-flow ischemia, and after pretreatment with either aminooxyacetate (AOA) or rotenone. All interventions were associated with an increase in [P_i]/[ATP] measured by ³¹P NMR. In well-oxygenated untreated hearts, rapid conversion of HP [1-¹³C]pyruvate to [1-¹³C]lactate and [1,3-¹³C₂]AcAc to [1,3-¹³C₂]β-hydroxybutyrate ([1,3-¹³C₂]β-HB) was readily detected. A significant increase in HP [1,3-¹³C₂]β-HB but not [1-¹³C]lactate was observed in rotenone-treated and ischemic hearts, consistent with an increase in mitochondrial NADH but not cytosolic NADH. AOA treatments did not alter the productions of HP [1-¹³C]lactate or [1,3-¹³C₂]β-HB. This study demonstrates that biomarkers of mitochondrial and cytosolic redox may be detected simultaneously in functioning tissues using co-polarized [1-¹³C]pyruvate and [1,3-¹³C₂]AcAc and ¹³C MRS and that changes in mitochondrial redox may precede changes in cytosolic redox.

A Systematic Review of Intravenous β-Hydroxybutyrate Use in Humans - A Promising Future Therapy?

Therapeutic ketosis is traditionally induced with dietary modification. However, owing to the time delay involved, this is not a practical approach for treatment of acute conditions such as traumatic brain injury. Intravenous administration of ketones would obviate this problem by rapidly inducing ketosis. This has been confirmed in a number of small animal and human studies. Currently no such commercially available product exists. The aim of this systematic review is to review the safety and efficacy of intravenous beta-hydroxybutyrate. The Web of Science, PubMed and EMBASE databases were searched, and a systematic review undertaken. Thirty-five studies were included. The total beta-hydroxybutyrate dose ranged from 30 to 101 g administered over multiple doses as a short infusion, with most studies using the racemic form. Such dosing achieves a beta-hydroxybutyrate concentration >1 mmol/L within 15 min. Infusions were well tolerated with few adverse events. Blood glucose concentrations occasionally were reduced but remained within the normal reference range for all study participants. Few studies have examined the effect of intravenous beta-hydroxybutyrate in disease states. In patients with heart failure, intravenous beta-hydroxybutyrate increased cardiac output by up to 40%. No studies were conducted in patients with neurological disease. Intravenous beta-hydroxybutyrate has been shown to increase cerebral blood flow and reduce cerebral glucose oxidation. Moreover, beta-hydroxybutyrate reduces protein catabolism and attenuates the production of counter-regulatory hormones during induced hypoglycemia. An intravenous beta-hydroxybutyrate formulation is well tolerated and may provide an alternative treatment option worthy of further research in disease states.

Sepsis and the Obesity Paradox: Size Matters in More Than One Way

OBJECTIVES

Multiple studies have demonstrated an obesity paradox such that obese ICU patients have lower mortality and better outcomes. We conducted this study to determine if the mortality benefit conferred by obesity is affected by baseline serum lactate and mean arterial pressure.

DESIGN

Retrospective analysis of prospectively collected clinical data.

SETTING

Five community-based and one academic medical center in the Omaha, NE.

PATIENTS

7,967 adults hospitalized with sepsis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients were categorized by body mass index as underweight, normal weight, overweight, or obese. Multivariable logistic regression models were used to estimate the odds of in-hospital death by body mass index category; two-way interactions between body mass index and each covariate were also evaluated. Subgroup and sensitivity analyses were conducted using an ICU cohort and Acute Physiology and Chronic Health Evaluation III scores, respectively. The overall unadjusted mortality rate was 12.1% and was consistently lower in higher body mass index categories (all comparisons, p < 0.007). The adjusted mortality benefit observed in patients with higher body mass index was smaller in patients with higher lactate levels with no mortality benefit in higher body mass index categories observed at lactate greater than 5 mmol/L. By contrast, the association between lower MAP and higher mortality was constant across body mass index categories. Similar results were observed in the ICU cohort. Finally, the obesity paradox was not observed after including Acute Physiology and Chronic Health Evaluation III scores as a covariate.

CONCLUSIONS

Our retrospective analysis suggests that although patient size (i.e., body mass index) is a predictor of in-hospital death among all-comers with sepsis-providing further evidence to the obesity paradox-it adds that illness severity is critically important whether quantified as higher lactate or by Acute Physiology and Chronic Health Evaluation III score. Our results highlight that the obesity paradox is more than a simple association between body mass index and mortality and reinforces the importance of illness severity.

Validation of a Gas Chromatography-Mass Spectrometry Method for the Measurement of the Redox State Metabolic Ratios Lactate/Pyruvate and β-Hydroxybutyrate/Acetoacetate in Biological Samples

The metabolic ratios lactate/pyruvate and β-hydroxybutyrate/acetoacetate are considered valuable tools to evaluate the in vivo redox cellular state by estimating the free NAD+/NADH in cytoplasm and mitochondria, respectively. The aim of the current study was to validate a gas-chromatography mass spectrometry method for simultaneous determination of the four metabolites in plasma and liver tissue. The procedure included an o-phenylenediamine microwave-assisted derivatization, followed by liquid-liquid extraction with ethyl acetate and silylation with bis(trimethylsilyl)trifluoroacetamide:trimethylchlorosilane 99:1. The calibration curves presented acceptable linearity, with a limit of quantification of 0.001 mM for pyruvate, β-hydroxybutyrate and acetoacetate and of 0.01 mM for lactate. The intra-day and inter-day accuracy and precision were within the European Medicines Agency's Guideline specifications. No significant differences were observed in the slope coefficient of three-point standard metabolite-spiked curves in plasma or liver and water, and acceptable recoveries were obtained in the metabolite-spiked samples. Applicability of the method was tested in precision-cut liver rat slices and also in HepG2 cells incubated under different experimental conditions challenging the redox state. In conclusion, the validated method presented good sensitivity, specificity and reproducibility in the quantification of lactate/pyruvate and β-hydroxybutyrate/acetate metabolites and may be useful in the evaluation of in vivo redox states.

The effect of oral triiodothyronine supplementation on lactate and pyruvate after paediatric cardiac surgery

OBJECTIVE

To determine if triiodothyronine alters lactate, glucose, and pyruvate metabolism, and if serum pyruvate concentration could serve as a predictor of low cardiac output syndrome in children after cardiopulmonary bypass procedures.

METHODS

This study was ancillary to the Oral Triiodothyronine for Infants and Children undergoing Cardiopulmonary bypass (OTICC) trial. Serum pyruvate was measured in the first 48 patients and lactate and glucose were measured in all 208 patients enrolled in the OTICC study on the induction of anaesthesia, 1 and 24 hours post-aortic cross-clamp removal. Patients were also defined as having low cardiac output syndrome according to the OTICC trial protocol.

RESULT

Amongst the designated patient population for pyruvate analysis, 22 received placebo, and 26 received triiodothyronine (T3). Lactate concentrations were nearly 20 times greater than pyruvate. Lactate and pyruvate levels were not significantly different between T3 and placebo group. Glucose levels were significantly higher in the placebo group mainly at 24-hour post-cross-clamp removal. Additionally, lactate and glucose levels peaked at 1-hour post-cross-clamp removal in low cardiac output syndrome and non-low cardiac output syndrome patients, but subsequently decreased at a slower rate in low cardiac output syndrome. Lactate and pyruvate concentrations correlated with glucose only prior to surgery.

CONCLUSION

Thyroid supplementation does not alter systemic lactate/pyruvate metabolism after cardiopulmonary bypass and reperfusion. Pyruvate levels are not useful for predicting low cardiac output syndrome. Increased blood glucose may be regarded as a response to hypermetabolic stress, seen mostly in patients with low cardiac output syndrome.

Lactate levels and clearance rate in neonates undergoing mechanical ventilation in Tibet

Objective

This study aimed to examine the characteristics of blood lactate in neonates undergoing mechanical ventilation in Tibet.

Methods

We recruited 67 neonates undergoing mechanical ventilation in Naqu People’s Hospital as the plateau observation group and 94 neonates undergoing mechanical ventilation in Shengjing Hospital as the control group. We analyzed the differences in lactate levels between the two groups.

Results

The lactate clearance rates of neonates with asphyxia and those with respiratory distress syndrome were significantly lower in the plateau group than in the control group. Lactate levels in neonates who died in the plateau group were significantly higher and the lactate clearance rate was significantly lower than those in neonates who survived. The cut-off point for the lactate clearance rate at 6 hours for predicting mortality was 6.09% in the plateau group.

Conclusion

The lactate clearance rate of neonates on mechanical ventilation in the plateau area is lower than that in neonates in the non-plateau area. The lactate clearance rate at 6 hours is important for evaluating the prognoses of critical neonates in plateau areas.

Imaging of the Lactate/Pyruvate Ratio Using a Genetically Encoded Förster Resonance Energy Transfer Indicator

The ratio between the cytosolic concentrations of lactate and pyruvate is a direct readout of the balance between glycolysis and mitochondrial oxidative metabolism. Current approaches do not allow detection of the lactate/pyruvate ratio in a single readout with high spatial/temporal resolution in living systems. Using a Förster resonance energy transfer (FRET)-based screening strategy, we found that the orphan transcriptional factor LutR from Bacillus licheniformis is an endogenous sensor of the lactate/pyruvate ratio, suitable for use as a binding moiety to develop a lactate/pyruvate ratio FRET-based genetically encoded indicator, Lapronic. The sensitivity of the indicator to lactate and pyruvate was characterized through changes in the fluorescence FRET ratio and validated with isothermal titration calorimetry. Lapronic was insensitive to physiological pH and temperature and did not respond to structurally related molecules acetate and β-hydroxybutyrate or cofactors NAD⁺ and NADH. Lapronic was expressed in HEK 293 cells showing a homogeneous cytosolic localization and was also targeted to the mitochondrial matrix. A calibration protocol was designed to quantitatively assess the lactate/pyruvate ratio in intact mammalian cells. Purified protein from Escherichia coli showed robust stability over time and was found suitable for lactate/pyruvate ratio detection in biological samples. We envision that Lapronic will be of practical interest for basic and applied research.

Hypoxia-related parameters during septic shock resuscitation: Pathophysiological determinants and potential clinical implications

Background

Assessment of tissue hypoxia at the bedside has yet to be translated into daily clinical practice in septic shock patients. Perfusion markers are surrogates of deeper physiological phenomena. Lactate-to-pyruvate ratio (LPR) and the ratio between veno-arterial PCO₂ difference and Ca–vO₂ (ΔPCO₂/Ca–vO₂) have been proposed as markers of tissue hypoxia, but they have not been compared in the clinical scenario. We studied acute septic shock patients under resuscitation. We wanted to evaluate the relationship of these hypoxia markers with clinical and biochemical markers of hypoperfusion during septic shock resuscitation.

Methods

Secondary analysis of a randomized controlled trial. Septic shock patients were randomized to fluid resuscitation directed to normalization of capillary refill time (CRT) versus normalization or significant lowering of lactate. Multimodal assessment of perfusion was performed at 0, 2, 6 and 24 hours, and included macrohemodynamic and metabolic perfusion variables, CRT, regional flow and hypoxia markers. Patients who attained their pre-specified endpoint at 2-hours were compared to those who did not.

Results

Forty-two patients were recruited, median APACHE-II score was 23 [15–31] and 28-day mortality 23%. LPR and ΔPCO₂/Ca–vO₂ ratio did not correlate during early resuscitation (0–2 h) and the whole study period (24-hours). ΔPCO₂/Ca–vO₂ ratio derangements were more prevalent than LPR ones, either in the whole cohort (52% vs. 23%), and in association with other perfusion abnormalities. In patients who reached their resuscitation endpoints, the proportion of patients with altered ΔPCO₂/Ca-vO₂ ratio decreased significantly (66% to 33%, P=0.045), while LPR did not (14% vs. 25%, P=0.34).

Conclusions

Hypoxia markers did not exhibit correlation during resuscitation in septic shock patients. They probably interrogate different pathophysiological processes and mechanisms of dysoxia during early septic shock. Future studies should better elucidate the interaction and clinical role of hypoxia markers during septic shock resuscitation.

Effect of high-volume hemofiltration on children with sepsis

BACKGROUND

Sepsis has always been a challenge in pediatric intensive care unit (PICU) with poor prognosis. In order to evaluate the effect between routine continuous renal replacement therapy (CRRT) and high-volume hemofiltration (HVHF) in children with sepsis, we performed out this prospective, randomized, controlled, open-label trial.

METHODS

Forty-seven children with sepsis were enrolled from January 2015 to December 2016. Twenty-two patients in Control group received routine CRRT and 25 patients in HVHF group received HVHF within 6 hours after the diagnosis of sepsis. The oxygenation index, serum creatinine, urea, lactate, inflammatory cytokines (IL-6, IL-10, and TNF-α), pediatric risk of mortality III (PRISM III) and 28-day mortality rate were collected and compared.

RESULTS

The oxygenation index in HVHF group and Control group was significantly increased at 48 hours (P<0.01) and 72 hours after treatment (P<0.05). The same result of arterial lactate was observed. Serum creatinine, urea, IL-6, IL-10, TNF-α and PRISM III score were significantly ameliorated after 72 hours treatment in HVHF group (P<0.01), while there was no significant difference in Control group. After 72 hours of treatment, the oxygenation index, lactate, serum creatinine, urea, TNF-α, IL-6, IL-10 and PRISM III score in HVHF group were significantly improved compared with Control group (P<0.01). There is no significant difference on 28-day mortality between the two groups (P>0.05).

CONCLUSIONS

HVHF might be an effective treatment for children with sepsis.

Cardiogenic Shock: Reflections at the Crossroad Between Perfusion, Tissue Hypoxia, and Mitochondrial Function

Cardiogenic shock is classically defined by systemic hypotension with evidence of hypoperfusion and end organ dysfunction. In modern practice, however, these metrics often incompletely describe cardiogenic shock because patients present with more advanced cardiovascular disease and greater degrees of multiorgan dysfunction. Understanding how perfusion, congestion, and end organ dysfunction contribute to hypoxia at the cellular level are central to the diagnosis and management of cardiogenic shock. Although, in clinical practice, increased lactate level is often equated with hypoxia, several other factors might contribute to an elevated lactate level including mitochondrial dysfunction, impaired hepatic and renal clearance, as well as epinephrine use. To this end, we present the evidence underlying the value of lactate to pyruvate ratio as a potential discriminator of cellular hypoxia. We will then discuss the physiological implications of hypoxia and congestion on hepatic, intestinal, and renal physiology. Organ-specific susceptibility to hypoxia is presented in the context of their functional architecture. We discuss how the concepts of contractile reserve, fluid responsiveness, tissue oxygenation, and cardiopulmonary interactions can help personalize the management of cardiogenic shock. Finally, we highlight the limitations of using lactate for tailoring therapy in cardiogenic shock.

Metabolic Acidosis in Critically Ill Cirrhotic Patients with Acute Kidney Injury

Background and Aims: The metabolic acid-base disorders have a high incidence of acute kidney injury (AKI) in critically ill cirrhotic patients (CICPs). The aims of our study were to ascertain the composition of metabolic acidosis of CICPs with AKI and explore its relationship with hospital mortality. Methods: Three-hundred and eighty consecutive CICPs with AKI were eligible for the cohort study. Demographic, clinical and laboratory parameters were recorded and arterial acid-base state was analyzed by the Stewart and Gilfix methodology. Results: Net metabolic acidosis, lactic acidosis, acidosis owing to unmeasured anions, acidemia, and dilutional acidosis were less frequent in the non-survival group compared to the survival group of CICPs. The presence of acidemia, acidosis owing to unmeasured anions, and lactic acidosis were independently associated with increased risk of intensive care unit 30-day mortality, with hazard ratios of 2.11 (95% confidence interval (CI): 1.43-3.12), 3.38 (95% CI: 2.36-4.84), and 2.16 (95% CI: 1.47-3.35), respectively. After full adjustment for confounders, the relationship between acidosis owing to unmeasured anions with hospital mortality was still significant, with hazard ratio of 2.29 (95% CI: 1.22-4.30). Furthermore, arterial lactate concentration in combination with chronic liver failure-sequential organ failure assessment and BE_UMA had the strongest ability to differentiate 30-day mortality (area under the receiver operating characteristic curve: 0.79, 95% CI: 0.74-0.83). Conclusions: CICPs with AKI exhibit a complex metabolic acidosis during intensive care unit admission. Lactic acidosis and BE_UMA, novel markers of acid-base disorders, show promise in predicting mortality rate of CICPs with AKI.

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.

Inflammasomes: Pandora's box for sepsis

Sepsis was known to ancient Greeks since the time of great physician Hippocrates (460-377 BC) without exact information regarding its pathogenesis. With time and medical advances, it is now considered as a condition associated with organ dysfunction occurring in the presence of systemic infection as a result of dysregulation of the immune response. Still with this advancement, we are struggling for the development of target-based therapeutic approach for the management of sepsis. The advancement in understanding the immune system and its working has led to novel discoveries in the last 50 years, including different pattern recognition receptors. Inflammasomes are also part of these novel discoveries in the field of immunology which are <20 years old in terms of their first identification. They serve as important cytosolic pattern recognition receptors required for recognizing cytosolic pathogens, and their pathogen-associated molecular patterns play an important role in the pathogenesis of sepsis. The activation of both canonical and non-canonical inflammasome signaling pathways is involved in mounting a proinflammatory immune response via regulating the generation of IL-1β, IL-18, IL-33 cytokines and pyroptosis. In addition to pathogens and their pathogen-associated molecular patterns, death/damage-associated molecular patterns and other proinflammatory molecules involved in the pathogenesis of sepsis affect inflammasomes and vice versa. Thus, the present review is mainly focused on the inflammasomes, their role in the regulation of immune response associated with sepsis, and their targeting as a novel therapeutic approach.

Serum lactate level accurately predicts mortality in critically ill patients with cirrhosis with acute kidney injury

BACKGROUND AND AIM

Serum lactate levels are routinely measured in critically ill patients with cirrhosis, and hyperlactatemia is a common finding, but its prognostic value remains controversial. Our aim was to examine whether serum lactate level could be used as a predictor of outcome in critically ill patients with cirrhosis (CICP) with acute kidney injury (AKI).

PATIENTS AND METHODS

In this study, we included 480 consecutive patients with cirrhosis admitted to ICU, complicated with AKI, and were followed up for 365 days. Patients were divided into four groups (Q1-Q4) by serum lactate quartiles: Q1≤1.8 mg/dl, Q2=1.9-2.4 mg/dl, Q3=2.5-4.0 mg/dl, and Q4≥4.1 mg/dl. The hazard ratio (HR) and 95% confidence intervals (CIs) for hospital mortality were calculated across each quartile of serum lactate, using the Q1 as reference, and four models were built to adjust for the HR of mortality.

RESULTS

Compared with patients in the survival group, nonsurvivors had higher serum lactate levels. Mortality rate increased progressively as the serum lactate level increased (Q1: 56.06%, Q2: 62.16%, Q3: 72.73% and Q4: 75.86%), and this relationship remained statistically significant after rigorous control of confounding factors in Q2, Q3, and Q4 with HRs of 1.03 (95% CI: 0.73-1.46), 1.40 (95% CI: 1.01-1.95), and 1.84 (95% CI: 1.28-2.64), respectively.

CONCLUSION

Our study brings a new perspective to the role of lactate monitoring in CICP with AKI. Elevated serum lactate levels are associated with a higher mortality rate in CICP with AKI. Elevated serum lactate levels should be part of rapid diagnosis and initiation of therapy to improve clinical outcome.

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.

Lactate Parameters Predict Clinical Outcomes in Patients with Nonvariceal Upper Gastrointestinal Bleeding

The predictive role of lactate in patients with nonvariceal upper gastrointestinal bleeding (NVUGIB) has been suggested. This study evaluated several lactate parameters in terms of predicting outcomes of bleeding patients and sought to establish a new scoring model by combining lactate parameters and the AIMS65 score. A total of 114 patients with NVUGIB who underwent serum lactate level testing at least twice and endoscopic hemostasis within 24 hours after admission were retrospectively analyzed. The associations between five lactate parameters and clinical outcomes were evaluated and the predictive power of lactate parameter combined AIMS65s (L-AIMS65s) and AIMS56 scoring was compared. The most common cause of bleeding was gastric ulcer (48.2%). Lactate clearance rate (LCR) was associated with 30-day rebleeding (odds ratio [OR], 0.931; 95% confidence interval [CI], 0.872-0.994; P = 0.033). Initial lactate (OR, 1.313; 95% CI, 1.050-1.643; P = 0.017), maximal lactate (OR, 1.277; 95% CI, 1.037-1.573; P = 0.021), and average lactate (OR, 1.535; 95% CI, 1.137-2.072; P = 0.005) levels were associated with 30-day mortality. Initial lactate (OR, 1.213; 95% CI, 1.027-1.432; P = 0.023), maximal lactate (OR, 1.271; 95% CI, 1.074-1.504; P = 0.005), and average lactate (OR, 1.501; 95% CI, 1.150-1.959; P = 0.003) levels were associated with admission over 7 days. Although L-AIMS65s showed the highest area under the curve for prediction of each outcome, differences between L-AIMS65s and AIMS65 did not reach statistical significance. In conclusion, lactate parameters have a prognostic role in patients with NVUGIB. However, they do not increase the predictive power of AIMS65 when combined.

Which one is a better predictor of ICU mortality in septic patients? Comparison between serial serum lactate concentrations and its removal rate

PURPOSE

To predict 28-day mortality with serum lactate and oxygenation profile in sepsis.

METHODS

82 patients were admitted to the ICU with sepsis. Comorbid disease, hemodynamic and oxygenation parameters were recorded. Serum lactate was measured at T0, T6, T12 and T24 hours of admission. Arterial and venous oxygen saturation levels were also measured. Regression and ROC analyses were used to predict death within 28days.

RESULTS

Out of 82 patients, 32 died within 28days of ICU admission. Non-survivors differed from survivors in having higher serum lactate concentrations on admission (0.6mmol/L; P=0.033), requiring more norepinephrine (14μg/min; P<0.001), higher frequency of acute kidney injury, prolonged mechanical ventilation (5-days; P<0.001) and ICU stay (1-day; P=0.029). Saturation of oxygen in arterial (a), central venous blood (cv) and (a-cv) were similar between the survivors and non-survivors. T24 level of lactate was the best predictor of 28-day mortality with 78% sensitivity and 90% specificity (AUC=0.912±0.033).

CONCLUSION

Serial measurements of serum lactate with special emphasis on its concentration at 24hour after admission remains the most predictive of short-term mortality in the ICU. Other predictors of mortality are relatively inferior and must be used collectively in context to better predict the clinical outcome of sepsis.

The effects of acute renal denervation on kidney perfusion and metabolism in experimental septic shock

BACKGROUND

Perfusion deficits likely play an important role in the development of renal dysfunction in sepsis. Renal denervation may improve kidney perfusion and metabolism.

METHODS

We randomized 14 female sheep to undergo bilateral surgical renal denervation (n = 7) or sham procedure (n = 7) prior to induction of sepsis. Renal blood flow (RBF) was measured with a pre-calibrated flowprobe. Laser Doppler probes were implanted to measure cortical and medullary perfusion. Cortical glucose, lactate and pyruvate levels were measured using the microdialysis technique. Creatinine clearance was determined. Sepsis was induced by peritonitis and fluid resuscitation was provided to avoid hypovolemia.

RESULTS

RBF and cortical perfusion were higher in the denervated group during the first 6 h after induction of sepsis (P < 0.001 and P < 0.05, respectively), while medullary perfusion decreased similarly in both groups. After hypotension developed, RBF decreased to similar levels in both groups. Cortical pyruvate and lactate levels were lower in the denervated animals (P < 0.001 and P < 0.001, respectively). There were no differences between groups in creatinine clearance, urine output or time to oliguria.

CONCLUSION

Denervation thus caused an early increase in RBF that was distributed towards the kidney cortex. Although associated with an attenuation of early cortical metabolic alterations, denervation failed to prevent the deterioration in renal function.

Lactate clearance as the predictor of outcome in pediatric septic shock

CONTEXT

Septic shock can rapidly evolve into multiple system organ failure and death. In the recent years, hyperlactatemia has been found to be a risk factor for mortality in critically ill adults.

AIMS

To evaluate the predictive value of lactate clearance and to determine the optimal cut-off value for predicting outcome in children with septic shock.

SETTINGS AND DESIGN

A prospective observational study was performed on children with septic shock admitted to pediatric Intensive Care Unit (PICU).

SUBJECTS AND METHODS

Serial lactate levels were measured at PICU admission, 24 and 48 h later. Lactate clearance, percent decrease in lactate level in 24 h, was calculated. The primary outcome measure was survival or nonsurvival at the end of hospital stay. We performed receiver operating characteristic analyses to calculate optimal cut-off values.

RESULTS

The mean lactate levels at admission were significantly higher in the nonsurvivors than survivors, 5.12 ± 3.51 versus 3.13 ± 1.71 mmol/L (P = 0.0001). The cut-off for lactate level at admission for the best prediction of mortality was determined as ≥4 mmol/L (odds ratio 5.4; 95% confidence interval [CI] =2.45-12.09). Mean lactate clearance was significantly higher in survivors than nonsurvivors (17.9 ± 39.9 vs. -23.2 ± 62.7; P < 0.0001). A lactate clearance rate of <10% at 24 h had a sensitivity and specificity of 78.7% and 72.2%, respectively and a positive predictive value of 83.1% for death. Failure to achieve a lactate clearance of more than 10% was associated with greater risk of mortality (likelihood ratio + 2.83; 95% CI = 1.82-4.41).

CONCLUSIONS

Serial lactate levels can be used to predict outcome in pediatric septic shock. A 24 h lactate clearance cut-off of <10% is a predictor of in-hospital mortality in such patients.

A Valuable Tool in Predicting Poor Outcome due to Sepsis in Pediatric Intensive Care Unit: Tp-e/QT Ratio

OBJECTIVE

To assess the feasibility of 12-lead electrocardiographic (ECG) measures such as P wave dispersion (PWd), QT interval, QT dispersion (QTd), Tp-e interval, Tp-e/QT and Tp-e/QTc ratio in predicting poor outcome in patients diagnosed with sepsis in pediatric intensive care unit (PICU).

METHODS

Ninety-three patients diagnosed with sepsis, severe sepsis or septic shock and 103 age- and sex-matched healthy children were enrolled into the study. PWd, QT interval, QTd, Tp-e interval and Tp-e/QT, Tp-e/QTc ratios were obtained from a 12-lead electrocardiogram.

RESULTS

PWd, QTd, Tp-e interval and Tp-e/QT, Tp-e/QTc ratios were significantly higher in septic patients compared with the controls. During the study period, 41 patients had died. In multivariate logistic regression analyses, only Tp-e/QT ratio was found to be an independent predictor of mortality.

CONCLUSION

The ECG measurements can predict the poor outcome in patients with sepsis. The Tp-e/QT ratio may be a valuable tool in predicting mortality for patients with sepsis in the PICU.

Lactic Acidosis in Sepsis: It's Not All Anaerobic: Implications for Diagnosis and Management

Increased blood lactate concentration (hyperlactatemia) and lactic acidosis (hyperlactatemia and serum pH < 7.35) are common in patients with severe sepsis or septic shock and are associated with significant morbidity and mortality. In some patients, most of the lactate that is produced in shock states is due to inadequate oxygen delivery resulting in tissue hypoxia and causing anaerobic glycolysis. However, lactate formation during sepsis is not entirely related to tissue hypoxia or reversible by increasing oxygen delivery. In this review, we initially outline the metabolism of lactate and etiology of lactic acidosis; we then address the pathophysiology of lactic acidosis in sepsis. We discuss the clinical implications of serum lactate measurement in diagnosis, monitoring, and prognostication in acute and intensive care settings. Finally, we explore treatment of lactic acidosis and its impact on clinical outcome.

[The role of biomarkers in the diagnostics of acute mesenteric ischemia]

Acute mesenteric ischemia is a severe and challenging disease. Unspecific symptoms in the initial phase make a fast diagnosis difficult although it is of major importance to protect patients from irreversible ischemia, extended bowel resection, sepsis and death in the late phase. In contrast to troponin as an early biomarker for cardiac ischemia, a reliable biomarker for acute intestinal ischemia has not yet been identified in the current literature and clinical practice. This would allow the early identification of these critically ill patients in the initial reversible phase of acute intestinal ischemia.This review highlights the pathophysiology, epidemiology and clinical findings of acute mesenteric ischemia and gives an overview of biomarkers which have been investigated in mesenteric ischemia with a special focus on lactate, which is the only parameter routinely used in the diagnostic setting of acute mesenteric ischemia.

Pharmacometabolomics of l-carnitine treatment response phenotypes in patients with septic shock

RATIONALE

Sepsis therapeutics have a poor history of success in clinical trials, due in part to the heterogeneity of enrolled patients. Pharmacometabolomics could differentiate drug response phenotypes and permit a precision medicine approach to sepsis.

OBJECTIVES

To use existing serum samples from the phase 1 clinical trial of l-carnitine treatment for severe sepsis to metabolically phenotype l-carnitine responders and nonresponders.

METHODS

Serum samples collected before (T0) and after completion of the infusion (T24, T48) from patients randomized to either l-carnitine (12 g) or placebo for the treatment of vasopressor-dependent septic shock were assayed by untargeted (1)H-nuclear magnetic resonance metabolomics. The normalized, quantified metabolite data sets of l-carnitine- and placebo-treated patients at each time point were compared by analysis of variance with post-hoc testing for multiple comparisons. Pathway analysis was performed to statistically rank metabolic networks.

MEASUREMENTS AND MAIN RESULTS

Thirty-eight metabolites were identified in all samples. Concentrations of 3-hydroxybutyrate, acetoacetate, and 3-hydroxyisovalerate were different at T0 and over time in l-carnitine-treated survivors versus nonsurvivors. Pathway analysis of pretreatment metabolites revealed that synthesis and degradation of ketone bodies had the greatest impact in differentiating l-carnitine treatment response. Analysis of all patients based on pretreatment 3-hydroxybutyrate concentration yielded distinct phenotypes. Using the T0 median 3-hydroxybutyrate level (153 μM), patients were categorized as either high or low ketone. l-Carnitine-treated low-ketone patients had greater use of carnitine as evidenced by lower post-treatment l-carnitine levels. The l-carnitine responders also had faster resolution of vasopressor requirement and a trend toward a greater improvement in mortality at 1 year (P = 0.038) compared with patients with higher 3-hydroxybutyrate.

CONCLUSIONS

The results of this preliminary study, which were not readily apparent from the parent clinical trial, show a unique metabolite profile of l-carnitine responders and introduce pharmacometabolomics as a viable strategy for informing l-carnitine responsiveness. The approach taken in this study represents a concrete example for the application of precision medicine to sepsis therapeutics that warrants further study.

Predictive Role of Admission Lactate Level in Critically Ill Patients with Acute Upper Gastrointestinal Bleeding

BACKGROUND

The predictive role of lactate in critically ill patients with acute upper gastrointestinal bleeding (UGIB) remains to be elucidated.

OBJECTIVE

The primary objective of this study was to assess the value of lactate level on admission to predict in-hospital death in patients with UGIB admitted to the intensive care unit (ICU). The secondary objective was to assess whether lactate level adds predictive value to the clinical Rockall score in these patients.

METHODS

This was a retrospective cohort study that included 133 patients with acute UGIB admitted to the ICU. Inclusion criteria were age > 18 years and presence of UGIB on admission to the ICU.

RESULTS

Mean age was 55.4 years old and 64.7% were male. The most common cause of gastrointestinal bleeding was peptic ulcer disease, followed by erosive esophagitis/gastritis. The in-hospital mortality was 22.6%. Median lactate level in survivors and nonsurvivors was 2.0 (interquartile range [IQR] 1.2-4.2 mmol/L) and 8.8 (IQR 3.4-13.3 mmol/L; p < 0.01), respectively. The receiver operating characteristic (ROC) area to predict in-hospital death for clinical Rockall score and lactate level (0.82) was significantly higher than the ROC area for the clinical Rockall score alone (0.69) (p < 0.01).

CONCLUSIONS

In patients admitted to the ICU with acute UGIB, lactate level on admission has a high sensitivity but low specificity for predicting in-hospital death. Lactate level adds to the predictive value of the clinical Rockall score. Given its high sensitivity, lactate level can be used in addition to other prediction tools to predict outcomes in patients with UGIB.

Capillary lactate as a tool for the triage nurse among patients with SIRS at emergency department presentation: a preliminary report

Background

The triage nurse is involved in the early identification of the most severe patients at emergency department (ED) presentation. However, clinical criteria alone may be insufficient to identify them correctly. Measurement of capillary lactate concentration at ED presentation may help to discriminate these patients. The primary objective of this study was to identify the prognostic value of capillary lactate concentration measured by the triage nurse among patients presenting to the ED.

Methods

This was a prospective observational study, performed in the ED of a university hospital. At ED presentation, capillary lactate measurement was performed by the triage nurse among patients presenting with a clinical criteria of systemic inflammatory response syndrome (SIRS). Clinical variables usually used to determine severity were collected at presentation. Twenty-eight-day mortality and MEDS score were recorded.

Results

One hundred seventy-six patients with clinical SIRS presented to the ED. Median age was 72 years, and 28-day mortality was 16%. Capillary lactate at ED presentation was significantly higher among 28-day non-survivors than among survivors (5.7 mmol.L⁻¹ [3.2 to 7.4] vs 2.9 mmol.L⁻¹ [1.9 to 5.2], p = 0.003). A score based on mottling and capillary lactate concentration >3.6 mmol.L⁻¹ was significantly associated with 28-day mortality (area under curve, AUC = 0.75), independently of the MEDS score (AUC = 0.79) for the prediction of 28-day mortality (AUC global model 0.87).

Conclusions

A high capillary lactate concentration measured by the triage nurse among patients presenting to the ED with clinical SIRS is associated with a high risk of death. A score calculated by the triage nurse, based on mottling and capillary lactate concentration, appears to be useful for identifying the most severe patients.

Early prediction of norepinephrine dependency and refractory septic shock with a multimodal approach of vascular failure

PURPOSE

The purpose of the study is to improve our ability to detect catecholamine dependency and refractory septic shock.

METHODS

Fifty-one patients with septic shock were studied within the first 4 hours of norepinephrine administration. Patients were divided into 2 groups according to their evolution in the intensive care unit, namely, group A, shock reversal, and group B, no shock reversal. Reversal of shock was defined as the maintenance of a systolic blood pressure greater than or equal to 90 mm Hg without vasopressor support for 24 hours or more. Vascular reactivity was tested using incremental doses of phenylephrine. Muscle tissue oxygen saturation and its changes during a vascular occlusion test were measured.

RESULTS

Group B patients had a higher Sequential Organ Failure Assessment (SOFA) score and lactate level and more frequently received norepinephrine and renal replacement. Overall mortality was 100% in group B (16/16) and 20% (7/35) in group A. Phenylephrine increased mean arterial pressure in a dose-dependent manner more significantly in group A patients than in group B (P = .0004). Basal tissue oxygen saturation and the recovery slope after vascular occlusion test were lower in group B. In multivariate analysis, 4 parameters remained independently associated with mortality: the increase in mean arterial pressure at phenylephrine 6 μg/kg per minute, the recovery slope, SOFA score, and norepinephrine doses at H0.

CONCLUSIONS

The intensity of septic shock-induced vascular hyporesponsiveness to vasopressor is tightly linked to septic shock severity and evolution and may potentially be identified early with simple to obtain parameters such as near-infrared spectroscopy value, SOFA score, or norepinephrine dose.

Sepsis-associated hyperlactatemia

There is overwhelming evidence that sepsis and septic shock are associated with hyperlactatemia (sepsis-associated hyperlactatemia (SAHL)). SAHL is a strong independent predictor of mortality and its presence and progression are widely appreciated by clinicians to define a very high-risk population. Until recently, the dominant paradigm has been that SAHL is a marker of tissue hypoxia. Accordingly, SAHL has been interpreted to indicate the presence of an ‘oxygen debt’ or ‘hypoperfusion’, which leads to increased lactate generation via anaerobic glycolysis. In light of such interpretation of the meaning of SAHL, maneuvers to increase oxygen delivery have been proposed as its treatment. Moreover, lactate levels have been proposed as a method to evaluate the adequacy of resuscitation and the nature of the response to the initial treatment for sepsis. However, a large body of evidence has accumulated that strongly challenges such notions. Much evidence now supports the view that SAHL is not due only to tissue hypoxia or anaerobic glycolysis. Experimental and human studies all consistently support the view that SAHL is more logically explained by increased aerobic glycolysis secondary to activation of the stress response (adrenergic stimulation). More importantly, new evidence suggests that SAHL may actually serve to facilitate bioenergetic efficiency through an increase in lactate oxidation. In this sense, the characteristics of lactate production best fit the notion of an adaptive survival response that grows in intensity as disease severity increases. Clinicians need to be aware of these developments in our understanding of SAHL in order to approach patient management according to biological principles and to interpret lactate concentrations during sepsis resuscitation according to current best knowledge.

Lactate clearance is a useful biomarker for the prediction of all-cause mortality in critically ill patients: a systematic review and meta-analysis*

OBJECTIVES

Lactate clearance has been widely investigated for its prognostic value in critically ill patients. However, the results are conflicting. The present study aimed to explore the diagnostic accuracy of lactate clearance in predicting mortality in critically or acutely ill patients.

DATA SOURCES

Databases of Medline, Embase, Scopus, and Web of Knowledge were searched from inception to June 2013.

STUDY SELECTION

Studies investigating the prognostic value of lactate clearance were defined as eligible. The searched item consisted of terms related to critically ill patients and terms related to lactate clearance.

DATA EXTRACTION

The following data were extracted: the name of the first author, publication year, subjects and setting, mean age of study population, sample size, male percentage, mortality of study cohort, definition of clearance, and the initial lactate level. Relative risk was reported to estimate the predictive value of lactate clearance on mortality rate, with relative risk less than 1 indicating that lactate clearance was a protective factor. Meta-analysis of diagnostic accuracy of lactate clearance in predicting mortality was performed by using hierarchical summary receiver operating characteristic model.

DATA SYNTHESIS

A total of 15 original articles were included in the study. Because of the significant heterogeneity across studies (I = 61.4%), random-effects model was used to pool relative risks. The pooled relative risk for mortality was 0.38 (95% CI, 0.29-0.50). The overall sensitivity and specificity for lactate clearance to predict mortality were 0.75 (95% CI, 0.58-0.87) and 0.72 (95% CI, 0.61-0.80), respectively. The diagnostic performance improved slightly when meta-analysis was restricted to ICU patients, with sensitivity and specificity of 0.83 (95% CI, 0.67-0.92) and 0.67 (95% CI, 0.59-0.75), respectively.

CONCLUSION

Our study demonstrates that lactate clearance is predictive of lower mortality rate in critically ill patients, and its diagnostic performance is optimal for clinical utility.

The storage stability and concentration of acetoacetate differs between blood fractions

BACKGROUND

Plasma concentrations of 3-hydroxybutyrate (3HB) are measured more often than acetoacetate (AcAc) which may be due to the reported storage instability of AcAc. The aims of the study were to compare the storage stability of AcAc in different blood fractions over time (90days) when stored at -80°C and to determine the postprandial concentration of AcAc in whole blood, plasma and red blood cells.

METHODS

Blood was collected from fasting subjects (n=5): whole blood, plasma and red blood cells were isolated and deproteinised in perchloric acid, and supernatants were stored at -80°C until analysis. Postprandial concentrations of AcAc in whole blood, plasma and red blood cells were determined at regular intervals over 420min, after subjects (n=23) had consumed a mixed test meal.

RESULTS

Storing deproteinised plasma at -80°C resulted in no significant change in AcAc concentration over 60days. In contrast, whole blood AcAc concentrations significantly decreased by 51% (p=0.018) within 30days. The concentration of AcAc in fasting and postprandial plasma was notably higher than that of whole blood and red blood cells.

DISCUSSION

Our data demonstrates that plasma for AcAc analysis can be stored for longer than previously suggested provided that plasma is deproteinised and stored at -80°C.

Stress hyperlactataemia: present understanding and controversy

An increased blood lactate concentration is common during physiological (exercise) and pathophysiological stress (stress hyperlactataemia). In disease states, there is overwhelming evidence that stress hyperlactataemia is a strong independent predictor of mortality. However, the source, biochemistry, and physiology of exercise-induced and disease-associated stress hyperlactataemia are controversial. The dominant paradigm suggests that an increased lactate concentration is secondary to anaerobic glycolysis induced by tissue hypoperfusion, hypoxia, or both. However, in the past two decades, much evidence has shown that stress hyperlactataemia is actually due to increased aerobic lactate production, with or without decreased lactate clearance. Moreover, this lactate production is associated with and is probably secondary to adrenergic stimulation. Increased lactate production seems to be an evolutionarily preserved protective mechanism, which facilitates bioenergetic efficiency in muscle and other organs and provides necessary substrate for gluconeogenesis. Finally, lactate appears to act like a hormone that modifies the expression of various proteins, which themselves increase the efficiency of energy utilisation and metabolism. Clinicians need to be aware of these advances in our understanding of stress hyperlactataemia to approach patient management according to logical principles. We discuss the new insights and controversies about stress hyperlactataemia.

Septic ketoacidosis

Various unmeasured anions other than lactate appear in the blood of septic patients, including ketones. However, the occurrence of sepsis-induced ketoacidosis without diabetes mellitus has not been reported to date. We herein describe severe ketoacidosis in a patient with septic shock despite the absence of diabetes, alcohol and starvation. A 76-year-old woman presented with septic shock due to acute obstructive cholangitis. She exhibited ketoacidosis and a remarkably strong ion gap, except for ketones. Sepsis alone may lead to ketoacidosis in patients without diabetes under specific conditions. The accumulation of ketones and other strong anions can occur in cases involving a decreased metabolic function. There may be a pathological condition called septic ketoacidosis.

Changes in myocardial lactate, pyruvate and lactate-pyruvate ratio during cardiopulmonary bypass for elective adult cardiac surgery: Early indicator of morbidity

BACKGROUND

Myocardial lactate assays have been established as a standard method to compare various myocardial protection strategies. This study was designed to test whether coronary sinus (CS) lactates, pyruvate and lactate-pyruvate (LP) ratio correlates with myocardial dysfunction and predict postoperative outcomes.

MATERIALS AND METHODS

This prospective observational study was conducted on 40 adult patients undergoing elective cardiac surgery with the aid of cardiopulmonary bypass (CPB). CS blood sampling was done for estimation of myocardial lactate (ML), pyruvate (MP) and lactate-pyruvate ratio (MLPR) namely: pre-CPB (T(1)), after removal of aortic cross clamp (T(2)) and 30 minutes post-CPB (T(3)).

RESULTS

Baseline myocardial LPR strongly correlated with Troponin-I at T1 (σ: 0.6). Patients were sub grouped according to the median value of myocardial lactate (2.9) at baseline T1 into low myocardial lactate (LML) group, mean (2.39±0.4 mmol/l), n=19 and a high myocardial lactate (HML) group, mean (3.65±0.9 mmol/l), n = 21. A significant increase in PL, ML, MLPR and TropI occurred in both groups as compared to baseline. Patients in HML group had significant longer period of ICU stay. Patients with higher inotrope score had significantly higher ML (T2, T3). ML with a baseline value of 2.9 mmol/l had 70.83% sensitivity and 62.5% specificity (ROC area: 0.7109 Std error: 0.09) while myocardial pyruvate with a baseline value of 0.07 mmol/l has 79.17% sensitivity and 68.75% specificity (ROC area: 0.7852, Std error: 0.0765) for predicting inotrope requirement after CPB.

CONCLUSION

CS lactate, pyruvate and LP ratio correlate with myocardial function and can predict postoperative outcome.

Clinical use of lactate monitoring in critically ill patients

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

Metabolic signatures of human adipose tissue hypoxia in obesity

Adipose tissue (AT) hypoxia has been proposed as the cause of obesity-related AT dysfunction, moving the tissue toward a proinflammatory phenotype. In humans, AT oxygenation has been assessed by expression of hypoxia-sensitive genes or direct assessment of O₂ tension; the obvious read out of hypoxia, effects on intermediary metabolism, has not been investigated. We used tissue-specific venous catheterization of subcutaneous abdominal AT in humans to investigate oxygen-related metabolic processes, searching for metabolic signatures relating to hypoxia in obesity. O₂ delivery to AT was reduced in obesity (P < 0.05). However, O₂ consumption was low (<30% of resting forearm skeletal muscle [SM], P < 0.001); this was not related to obesity. AT primarily oxidized glucose, as demonstrated by a respiratory quotient close to 1.0 (higher than SM, P < 0.05). AT was a net producer of lactate, but there was an inverse relationship in venous outflow between lactate-to-pyruvate ratio (a marker of cytosolic redox state) and BMI, suggesting that AT is glycolytic but obese AT is not hypoxic. Although delivery of O₂ to the obese AT is reduced, O₂ consumption is low, and metabolic signatures of human AT do not support the notion of a hypoxic state in obesity.

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.

Lactate/pyruvate ratio as a marker of tissue hypoxia in circulatory and septic shock

In this prospective, observational study, we measured arterial lactate and pyruvate concentrations within the first four hours of shock and at four hour intervals during the first 24 hours in 26 patients with septic and 13 with cardiogenic shock. We also studied 10 intensive care unit patients with normal lactate levels as controls. Seven patients (18%) died during the first 24 hours of shock, 12 (31%) patients died later in the intensive care unit and 21 (54%) were discharged alive from the intensive care unit. Blood lactate values were higher at shock onset in the non-survivors than in the survivors (P=0.02) and remained significantly elevated throughout the study. The lactate/pyruvate ratio at shock onset was significantly higher in the non-survivors (24 [17 to 34] vs 15 [10 to 19], P=0.01) than in the survivors. All patients with cardiogenic shock had hyperlactataemia at the onset of shock, and 69% had a high lactate/pyruvate ratio. Only 65% of patients with septic shock had hyperlactataemia at the onset of shock and 76% of these also had a high lactate/pyruvate ratio. In conclusion, the lactate/pyruvate ratio confirms that hyperlactataemia is frequently, but not solely, due to hypoxia, especially at the onset of shock.

Mechanism of lactic acidosis in children with acute severe asthma

OBJECTIVE

Hyperlactatemia and lactic acidosis are common in adults with acute severe asthma however only a few cases have been reported in children. Type A lactic acidosis is associated with impaired oxygen delivery; type B occurs in the presence of normal oxygen delivery and has been described to occur with excessive adrenergic stimulation. Type A and B lactic acidosis can be distinguished by the blood lactate/pyruvate ratio. Our objectives are to 1) investigate the incidence of hyperlactatemia and lactic acidosis in children with acute severe asthma, and 2) determine whether lactate elevation is type A or B.

DESIGN

Prospective observational study.

SETTING

University-affiliated tertiary care children's hospital.

PATIENTS

All children (n = 105) with acute severe asthma admitted to the pediatric intensive care unit between May 1, 2008 and November 30, 2009 were included.

INTERVENTIONS

Blood lactate concentration was measured on a blood gas analyzer for all blood gas assessments obtained for clinical care. Hyperlactatemia was defined as lactate >2.2 mmol/L and lactic acidosis as lactate >5 mmol/L and pH <7.35. If lactate concentration was >5 mmol/L, consent was requested for measuring blood lactate and pyruvate using enzymatic laboratory methods. Lactate/pyruvate ratio >25:1 indicated type A lactic acidosis.

MEASUREMENTS AND MAIN RESULTS

Eighty-seven (83%) children had lactate >2.2 mmol/L and 47 (45%) had lactate >5 mmol/L. Of those with lactate >5 mmol/L, 33 (70%) had corresponding blood pH <7.35. Lactate/pyruvate ratios were obtained for 16 patients. Of these, lactate/pyruvate ratio was <10 in three patients; 10-25 in 11; >25 in one; and indeterminate in one.

CONCLUSIONS

Lactic acidosis is common in children with acute severe asthma and is primarily type B occurring in the presence of normal oxygen delivery.