Clinical use of lactate monitoring in critically ill patients

Prognostic Role of MELD-Lactate in Cirrhotic Patients' Short- and Long-Term Prognosis, Stratified by Causes of Cirrhosis

OBJECTIVES

Recently, model for end-stage liver disease-lactate (MELD-LA) proved to be a superior predicting factor of inpatient mortality in patients with chronic liver disease. The study's objective was to evaluate the ability of MELD-LA to predict both short- and long-term mortality in critically ill cirrhotic patients stratified by causes of cirrhosis.

MATERIALS AND METHODS

This was a retrospective observational research of 469 cirrhotic patients entering intensive care unit. Clinical parameters and prognostic scores were measured and collected in the first 24 hours after entering intensive care unit. Follow-up duration was at least 5 years. Independent relationship between MELD-LA and mortality was evaluated by multivariate logistic regression analyses. Discrimination of scoring system was evaluated by the area under the receiver operating characteristic curve. Calibration of the score was evaluated by Hosmer-Lemeshow goodness of fit test for significance.

RESULTS

The MELD-LA score (odds ratio: 1.179, 95% confidence interval: 1.112-1.250, P < 0.001) was an independent risk factor for 15-day mortality. The area under the curve of MELD-LA was the highest (0.808, 95% confidence interval: 0.765-0.852) in predicting 15-day mortality and it had superior calibration. We found MELD-LA showed the best discrimination ability in cirrhotic patients caused by both alcohol and hepatitis (0.783, 95% confidence interval: 0.651-0.915) or alcohol alone (0.805, 95% confidence interval: 0.743-0.867).

CONCLUSIONS

MELD-LA performs better for predicting short-term prognosis in critically ill cirrhotic patients, especially caused by both alcohol and hepatitis or alcohol alone.

Neisseria gonorrhoeae physiology and pathogenesis

Neisseria gonorrhoeae is an obligate human pathogen that is the cause of the sexually transmitted disease gonorrhoea. Recently, there has been a surge in gonorrhoea cases that has been exacerbated by the rapid rise in gonococcal multidrug resistance to all useful antimicrobials resulting in this organism becoming a significant public health burden. Therefore, there is a clear and present need to understand the organism's biology through its physiology and pathogenesis to help develop new intervention strategies. The gonococcus initially colonises and adheres to host mucosal surfaces utilising a type IV pilus that helps with microcolony formation. Other adhesion strategies include the porin, PorB, and the phase variable outer membrane protein Opa. The gonococcus is able to subvert complement mediated killing and opsonisation by sialylation of its lipooligosaccharide and deploys a series of anti-phagocytic mechanisms. N. gonorrhoeae is a fastidious organism that is able to grow on a limited number of primary carbon sources such as glucose and lactate. The utilization of lactate by the gonococcus has been implicated in a number of pathogenicity mechanisms. The bacterium lives mainly in microaerobic environments and can grow both aerobically and anaerobically with the aid of nitrite. The gonococcus does not produce siderophores for scavenging iron but can utilize some produced by other bacteria, and it is able to successful chelate iron from host haem, transferrin and lactoferrin. The gonococcus is an incredibly versatile human pathogen; in the following chapter, we detail the intricate mechanisms used by the bacterium to invade and survive within the host.

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.

The Lactate/Albumin Ratio Predicts Mortality in Critically Ill Patients with Acute Kidney Injury: An Observational Multicenter Study on the eICU Database

OBJECTIVE

The serum lactate/albumin ratio (LAR) can be used to independently predict mortality due to sepsis. However, whether the LAR predicts the outcomes of critically ill patients with acute kidney injury (AKI) remains unclear. This study was performed to assess the prognostic value of the LAR in critically ill AKI patients.

METHODS

This retrospective observational study enrolled AKI patients, and all data were collected through the eICU Collaborative Research Database. Outcomes included in-hospital and intensive care unit (ICU) death. Multivariate Cox regression analysis was used to determine independent risk factors. Forest plots and smoothing curves were generated. A series of subgroup analyses were performed to further validate the robustness of the findings.

RESULTS

A total of 4666 eligible patients were enrolled. We divided the participants into four groups according to the LAR: quartile (Q)1 (LAR < 0.46, n = 1167), Q2 (0.46 ≤ LAR < 0.79, n = 1162), Q3 (0.79 ≤ LAR < 1.49, n = 1170), and Q4 (LAR ≥ 1.49, n = 1167). The LAR, when analyzed as a continuous variable, was associated with hospital and ICU mortality (adjusted hazard ratio [HR] 1.22, 95% confidence interval [CI] 1.18-1.26, P < 0.0001 for both). The risk of in-hospital and ICU mortality increased with increasing LAR Q relative to Q1. The smoothing curves revealed a continuous linear association after adjusting for all covariates. By the Kaplan-Meier analysis, patients in the higher LAR group showed significantly shorter survival time. By the receiver operating characteristic analysis, LAR was efficient in predicting in-hospital mortality (area under the curve [AUC]: 0.717) and ICU mortality (AUC: 0.733). A positive and consistent effect of the LAR was seen in all subgroups analyses after adjusting for all covariates.

CONCLUSION

A high LAR is an independent risk factor for in-hospital and ICU mortality in critically ill patients with AKI. Further prospective studies are needed to validate these result.

The Pyruvate Dehydrogenase Complex in Sepsis: Metabolic Regulation and Targeted Therapy

Anaerobic glycolysis is the process by which glucose is broken down into pyruvate and lactate and is the primary metabolic pathway in sepsis. The pyruvate dehydrogenase complex (PDHC) is a multienzyme complex that serves as a critical hub in energy metabolism. Under aerobic conditions, pyruvate translocates to mitochondria, where it is oxidized into acetyl-CoA through the activation of PDHC, thereby accelerating aerobic oxidation. Both phosphorylation and acetylation affect PDHC activity and, consequently, the regulation of energy metabolism. The mechanisms underlying the protective effects of PDHC in sepsis involve the regulation on the balance of lactate, the release of inflammatory mediators, the remodeling of tricarboxylic acid (TCA) cycle, as well as on the improvement of lipid and energy metabolism. Therapeutic drugs that target PDHC activation for sepsis treatment include dichloroacetate, thiamine, amrinone, TNF-binding protein, and ciprofloxacin. In this review, we summarize the recent findings regarding the metabolic regulation of PDHC in sepsis and the therapies targeting PDHC for the treatment of this condition.

Investigating the biochemical effects of heat stress and sample quenching approach on the metabolic profiling of abalone (Haliotis iris)

INTRODUCTION

Ocean temperatures have been consistently increasing due to climate change, and the frequency of heatwave events on shellfish quality is a growing concern worldwide. Typically, shellfish growing areas are in remote or difficult to access locations which makes in-field sampling and sample preservation of shellfish heat stress difficult. As such, there is a need to investigate in-field sampling approaches that facilitate the study of heat stress in shellfish.

OBJECTIVES

This study aims to apply a gas chromatography-mass spectrometry (GC-MS) based metabolomics approach to examine molecular mechanisms of heat stress responses in shellfish using abalone as a model, and compare the effects of different quenching protocols on abalone metabolic profiles.

METHODS

Twenty adult Haliotis iris abalone were exposed to two temperatures (14 °C and 24 °C) for 24 h. Then, haemolymph and muscle tissues of each animal were sampled and quenched with 4 different protocols (liquid nitrogen, dry ice, cold methanol solution and normal ice) which were analyzed via GC-MS for central carbon metabolites.

RESULTS

The effects of different quenching protocols were only observed in muscle tissues in which the cold methanol solution and normal ice caused some changes in the observed metabolic profiles, compared to dry ice and liquid nitrogen. Abalone muscle tissues were less affected by thermal stress than haemolymph. There were 10 and 46 compounds significantly influenced by thermal stress in muscle and haemolymph, respectively. The changes of these metabolite signatures indicate oxidative damage, disturbance of amino acid and fatty acid metabolism, and a shift from aerobic metabolism to anaerobic pathways.

CONCLUSIONS

The study provided insights into the heat response of abalone, which could be useful for understanding the effects of marine heatwaves and summer mortality events on abalone. Dry ice appeared to be a suitable protocol, and safer in-field alternative to liquid nitrogen, for quenching of abalone tissues.

Nomogram Models to Predict Postoperative Hyperlactatemia in Patients Undergoing Elective Cardiac Surgery

Objectives: Postoperative hyperlactatemia (POHL) is common in patients undergoing cardiac surgery and is associated with poor outcomes. The purpose of this study was to develop and validate two predictive models for POHL in patients undergoing elective cardiac surgery (ECS).

Methods: We conducted a multicenter retrospective study enrolling 13,454 adult patients who underwent ECS. All patients involved in the analysis were randomly assigned to a training set and a validation set. Univariate and multivariate analyses were performed to identify risk factors for POHL in the training cohort. Based on these independent predictors, the nomograms were constructed to predict the probability of POHL and were validated in the validation cohort.

Results: A total of 1,430 patients (10.6%) developed POHL after ECS. Age, preoperative left ventricular ejection fraction, renal insufficiency, cardiac surgery history, intraoperative red blood cell transfusion, and cardiopulmonary bypass time were independent predictors and were used to construct a full nomogram. The second nomogram was constructed comprising only the preoperative factors. Both models showed good predictive ability, calibration, and clinical utility. According to the predicted probabilities, four risk groups were defined as very low risk (<0.05), low risk (0.05–0.1), medium risk (0.1–0.3), and high risk groups (>0.3), corresponding to scores of ≤ 180 points, 181–202 points, 203–239 points, and >239 points on the full nomogram, respectively.

Conclusions: We developed and validated two nomogram models to predict POHL in patients undergoing ECS. The nomograms may have clinical utility in risk estimation, risk stratification, and targeted interventions.

Murburn precepts for lactic-acidosis, Cori cycle, and Warburg effect: Interactive dynamics of dehydrogenases, protons, and oxygen

It is unresolved why lactate is transported to the liver for further utilization within the physiological purview of Cori cycle, when muscles have more lactate dehydrogenase (LDH) than liver. We point out that the answer lies in thermodynamics/equilibriums. While the utilization of NADH for the reduction of pyruvate to lactate can be mediated via the classical mechanism, the oxidation of lactate (with/without the uphill reduction of NAD⁺ ) necessitates alternative physiological approaches. The latter pathway occurs via interactive equilibriums involving the enzyme, protons and oxygen or diffusible reactive oxygen species (DROS). Since liver has high DROS, the murburn activity at LDH would enable the cellular system to tide over the unfavorable energy barriers of the forward reaction (~476 kJ/mol; earlier miscalculated as ~26 kJ/mole). Further, the new mechanism does not necessitate any "smart decision-making" or sophisticated control by/of proteins. The DROS-based murburn theory explains the invariant active-site structure of LDH isozymes and their multimeric nature. The theoretical insights, in silico evidence and analyses of literature herein also enrich our understanding of the underpinnings of "lactic acidosis" (lowering of physiological pH accompanied by lactate production), Warburg effect (increased lactate production at high pO₂ by cancer cells) and approach for cancer therapy.

Engineered l-Lactate Responding Promoter System Operating in Glucose-Rich and Anoxic Environments

Bacteria equipped with genetically encoded lactate biosensors are promising tools for biopharmaceutical production, diagnostics, and cellular therapies. However, many applications involve glucose-rich and anoxic environments, in which current whole-cell lactate biosensors show low performance. Here we engineer an optimized, synthetic lactate biosensor system by repurposing the natural LldPRD promoter regulated by the LldR transcriptional regulator. We removed glucose catabolite and anoxic repression by designing a hybrid promoter, containing LldR operators and tuned both regulator and reporter gene expressions to optimize biosensor signal-to-noise ratio. The resulting lactate biosensor, termed ALPaGA (A Lactate Promoter Operating in Glucose and Anoxia), can operate in glucose-rich, aerobic and anoxic conditions. We show that ALPaGA works reliably in the probiotic chassisEscherichia coliNissle 1917 and can detect endogenous l-lactate produced by 3D tumor spheroids with an improved dynamic range. In the future, the ALPaGA system could be used to monitor bioproduction processes and improve the specificity of engineered bacterial cancer therapies by restricting their activity to the lactate-rich microenvironment of solid tumors.

Osmotically Enabled Wearable Patch for Sweat Harvesting and Lactate Quantification

Lactate is an essential biomarker for determining the health of the muscles and oxidative stress levels in the human body. However, most of the currently available sweat lactate monitoring devices require external power, cannot measure lactate under low sweat rates (such as in humans at rest), and do not provide adequate information about the relationship between sweat and blood lactate levels. Here, we discuss the on-skin operation of our recently developed wearable sweat sampling patch. The patch combines osmosis (using hydrogel discs) and capillary action (using paper microfluidic channel) for long-term sweat withdrawal and management. When subjects are at rest, the hydrogel disc can withdraw fluid from the skin via osmosis and deliver it to the paper. The lactate amount in the fluid is determined using a colorimetric assay. During active sweating (e.g., exercise), the paper can harvest sweat even in the absence of the hydrogel patch. The captured fluid contains lactate, which we quantify using a colorimetric assay. The measurements show the that the total number of moles of lactate in sweat is correlated to sweat rate. Lactate concentrations in sweat and blood correlate well only during high-intensity exercise. Hence, sweat appears to be a suitable biofluid for lactate quantification. Overall, this wearable patch holds the potential of providing a comprehensive analysis of sweat lactate trends in the human body.

Diagnostic Modalities in Critical Care: Point-of-Care Approach

The concept of intensive care units (ICU) has existed for almost 70 years, with outstanding development progress in the last decades. Multidisciplinary care of critically ill patients has become an integral part of every modern health care system, ensuing improved care and reduced mortality. Early recognition of severe medical and surgical illnesses, advanced prehospital care and organized immediate care in trauma centres led to a rise of ICU patients. Due to the underlying disease and its need for complex mechanical support for monitoring and treatment, it is often necessary to facilitate bed-side diagnostics. Immediate diagnostics are essential for a successful treatment of life threatening conditions, early recognition of complications and good quality of care. Management of ICU patients is incomprehensible without continuous and sophisticated monitoring, bedside ultrasonography, diverse radiologic diagnostics, blood gas analysis, coagulation and blood management, laboratory and other point-of-care (POC) diagnostic modalities. Moreover, in the time of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, particular attention is given to the POC diagnostic techniques due to additional concerns related to the risk of infection transmission, patient and healthcare workers safety and potential adverse events due to patient relocation. This review summarizes the most actual information on possible diagnostic modalities in critical care, with a special focus on the importance of point-of-care approach in the laboratory monitoring and imaging procedures.

A Wearable Patch for Prolonged Sweat Lactate Harvesting and Sensing

Operating at low sweat rates, such as those experienced by humans at rest, is still an unmet need for state-of-the-art wearable sweat harvesting and testing devices for lactate. Here, we report the on-skin performance of a non-invasive wearable sweat sampling patch that can harvest sweat at rest, during exercise, and post-exercise. The patch simultaneously uses osmosis and evaporation for long-term (several hours) sampling of sweat. Osmotic sweat withdrawal is achieved by skin-interfacing a hydrogel containing a concentrated solute. The gel interfaces with a paper strip that transports the fluid via wicking and evaporation. Proof of concept results show that the patch was able to sample sweat during resting and post-exercise conditions, where the lactate concentration was successfully quantified. The patch detected the increase in sweat lactate levels during medium level exercise. Blood lactate remained invariant with exercise as expected. We also developed a continuous sensing version of the patch by including enzymatic electrochemical sensors. Such a battery-free, passive, wearable sweat sampling patch can potentially provide useful information about the human metabolic activity.

The Effects of Live Transport on Metabolism and Stress Responses of Abalone (Haliotis iris)

The New Zealand abalone industry relies mostly on the export of processed products to distant Asian markets, notably China. Over the past five years, live export of high quality abalone from New Zealand has proven successful. However, transport of live animals is associated with multiple stressors that affect survival and meat quality at the end of the transport phase. Better understanding of transport-derived stress is needed to improve transport conditions and recovery at destination to ensure high product quality and safety throughout the supply chain. To this end, we applied an untargeted GC-MS-based metabolomics approach to examine the changes in metabolite profiles of abalone after a 2-day transport event and subsequent water re-immersion for 2 days. The results revealed alterations of many metabolites in the haemolymph and muscle of post-transported abalone. Decreased concentrations of many amino acids suggest high energy demands for metabolism and stress responses of transported abalone, while increases of other amino acids may indicate active osmoregulation and/or protein degradation due to oxidative stress and apoptosis. The accumulation of citric acid cycle intermediates and anaerobic end-products are suggestive of hypoxia stress and a shift from aerobic to anaerobic metabolism (resulting from aerial exposure). Interestingly, some features in the metabolite profile of reimmersed abalone resembled those of pre-transported individuals, suggesting progressive recovery after reimmersion in water. Evidence of recovery was observed in the reduction of some stress biomarkers (e.g., lactic acid, succinic acid) following reimmersion. This study revealed insights into the metabolic responses to transport stress in abalone and highlights the importance of reimmersion practices in the supply chain of live animal exports.

Differentiating Upper Extremity Necrotizing Soft Tissue Infection From Serious Cellulitis and Abscess

Introduction

Necrotizing soft tissue infection (NSTI) of the upper extremity (UE) is a rapidly progressing infection that requires early diagnosis and emergent treatment to decrease risks of loss of limb or life. Clinical presentation, particularly of early NSTI, can appear similar to serious cellulitis or abscess. The purpose of this study was to identify factors that are associated with NSTI rather than serious cellulitis and abscess to differentiate patients with similar clinical presentations.

Methods

This study uses a retrospective cohort design that compares patients ultimately diagnosed with UE NSTI versus those diagnosed with UE serious cellulitis or abscess. Cohorts were matched using the Laboratory Risk Indicators for Necrotizing Fasciitis (LRINEC) score in the setting of UE soft tissue infection. Laboratory values, vital signs, subjective symptoms, and social factors including substance abuse and domiciled status were recorded. Continuous variables were compared using the Mann-Whitney U test, whereas categorical variables were compared using the chi-squared test or the Fisher exact test (for expected values less than 5). A binary logistic regression for continuous and categorical variables was also performed. Significance was set at p<0.05. Univariate and multivariate analyses were performed.

Results

Multivariate statistical analysis and clinical interpretation of data identified four factors more associated with a diagnosis of NSTI than serious cellulitis or abscess: elevated lactate on hospital presentation, a patient-reported history of fever, male gender, and homelessness. 

Conclusions

In patients with upper extremity infections, the clinical presentation of NSTI and serious cellulitis or abscess may appear similar. In this retrospective cohort of patients matched with LRINEC scores, elevated lactate, subjective fever, male gender, and homelessness were significantly associated with NSTI rather than serious cellulitis or abscess. 

Differentiating Lower Extremity Necrotizing Soft Tissue Infection from Severe Cellulitis by Laboratory Parameters and Relevant History Points

Background

Necrotizing soft tissue infection (NSTI) of the lower extremity (LE) is a rapidly progressing infection that requires early diagnosis and prompt treatment to decrease risks of loss of limb or life. Clinical presentation, particularly of early NSTI, can appear similar to severe cellulitis. The purpose of this study is to identify factors that are associated with NSTI rather than severe cellulitis to differentiate patients with similar clinical presentation.

Methods

This retrospective cohort design study compares patients finally diagnosed with LE NSTI versus those diagnosed with severe cellulitis. Cohorts were matched using the modified Laboratory Risk Indicator for Necrotizing Fasciitis (m-LRINEC) score in the setting of LE soft tissue infection. Laboratory values, vital signs, subjective symptoms, and social factors including substance abuse were recorded. Univariate and multivariate analyses were performed.

Results

Multivariate statistical analysis and clinical interpretation of data identified four factors more associated with a diagnosis of NSTI than severe cellulitis: elevated lactate, a patient-reported history of fever, male gender, and intravenous substance user.

Conclusion

In patients with lower extremity infections, the clinical presentation of NSTI and severe cellulitis may appear similar. In this retrospective cohort of patients matched with m-LRINEC scores, elevated lactate, subjective fever, male gender, and intravenous substance abuser were significantly associated with NSTI rather than severe cellulitis. Further studies of these factors in the clinical setting can help tailor the differential diagnosis in the care of patients with severe lower extremity infections. Matched with m-LRINEC scores, elevated lactate, subjective fever, male gender, and intravenous substance abuser were significantly associated with NSTI rather than severe cellulitis. Further studies of these factors in the clinical setting can help tailor the differential diagnosis in the care of patients with severe lower extremity infections.

Effect of Dihydropyridine Calcium Channel Blocker on Mortality of Hypertension Patients With Moderate-Severe Pulmonary Acute Respiratory Distress Syndrome: A Multicenter Retrospective Observational Cohort Study

The aim was to evaluate the effect of dihydropyridine calcium channel blocker on the prognosis for moderate-severe pulmonary acute respiratory distress syndrome in hypertension patients.

DESIGN

A retrospective, observational, multicenter cohort study.

SETTING

A total of 307 patients without propensity score matching and 186 adult inpatients with propensity score matching diagnosed with hypertension and moderate-severe pulmonary acute respiratory distress syndrome in five teaching hospitals in Jiangsu province, China, from December 2015 to December 2020 were enrolled.

PATIENTS

A total of 307 patients without propensity score matching and 186 patients with propensity score matching diagnosed with hypertension and moderate-severe pulmonary acute respiratory distress syndrome were included in the final analysis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic characteristics and clinical characteristics were recorded. The propensity score matching method was used to eliminate the difference between group with dihydropyridine calcium channel blocker and group without dihydropyridine calcium channel blocker. The primary outcome was in-hospital mortality. We used univariate and multivariate regression analyses for both patients with or without propensity score matching to assess the effect of these variables on mortality. In the subset of 186 patients with propensity score matching, in-hospital mortality was 53.2%. Inpatient mortality was significantly higher in patients treated with dihydropyridine calcium channel blocker than in those not treated with dihydropyridine calcium channel blocker of patients without propensity score matching (65.4% vs 40.4%; p < 0.01). Multivariate analysis for patients without propensity score matching showed that dihydropyridine calcium channel blocker (hazard ratio, 1.954; 95% CI, 1.415-2.699), lactate dehydrogenase greater than or equal to 600 U/L (hazard ratio, 3.809; 95% CI, 2.106-4.531), and lactate greater than or equal to 2 mmol/L (hazard ratio, 1.454; 95% CI, 1.041-2.029) were independently associated with in-hospital mortality. Based on univariate analysis for patients with propensity score matching, dihydropyridine calcium channel blocker (hazard ratio, 2.021; 95% CI, 1.333-3.064), lactate dehydrogenase greater than or equal to 600 U/L (hazard ratio, 4.379; 95% CI, 2.642-7.257), and lactate greater than or equal to 2 mmol/L (hazard ratio, 2.461; 95% CI, 1.534-3.951) were independently associated with in-hospital mortality. In contrast, patients not treated with dihydropyridine calcium channel blocker had a significant survival advantage over those treated with dihydropyridine calcium channel blocker in both patients without or with propensity score matching (p < 0.001; p = 0.001 by Kaplan-Meier analysis).

CONCLUSIONS

Dihydropyridine calcium channel blocker, lactate dehydrogenase greater than or equal to 600 U/L, and lactate greater than or equal to 2 mmol/L at admission were independent risk factors for patients with hypertension and moderate-severe pulmonary acute respiratory distress syndrome.

Addition of admission lactate levels to Baux score improves mortality prediction in severe burns

Risk adjustment and mortality prediction models are central in optimising care and for benchmarking purposes. In the burn setting, the Baux score and its derivatives have been the mainstay for predictions of mortality from burns. Other well-known measures to predict mortality stem from the ICU setting, where, for example, the Simplified Acute Physiology Score (SAPS 3) models have been found to be instrumental. Other attempts to further improve the prediction of outcome have been based on the following variables at admission: Sequential Organ Failure Assessment (_aSOFA) score, determinations of _aLactate or Neutrophil to Lymphocyte Ratio (_aNLR). The aim of the present study was to examine if estimated mortality rate (EMR, SAPS 3), _aSOFA, _aLactate, and _aNLR can, either alone or in conjunction with the others, improve the mortality prediction beyond that of the effects of age and percentage total body surface area (TBSA%) burned among patients with severe burns who need critical care. This is a retrospective, explorative, single centre, registry study based on prospectively gathered data. The study included 222 patients with median (25th–75th centiles) age of 55.0 (38.0 to 69.0) years, TBSA% burned was 24.5 (13.0 to 37.2) and crude mortality was 17%. As anticipated highest predicting power was obtained with age and TBSA% with an AUC at 0.906 (95% CI 0.857 to 0.955) as compared with EMR, _aSOFA, _aLactate and _aNLR. The largest effect was seen thereafter by adding _aLactate to the model, increasing AUC to 0.938 (0.898 to 0.979) (p < 0.001). Whereafter, adding EMR, _aSOFA, and _aNLR, separately or in combinations, only marginally improved the prediction power. This study shows that the prediction model with age and TBSA% may be improved by adding _aLactate, despite the fact that _aLactate levels were only moderately increased. Thereafter, adding EMR, _aSOFA or _aNLR only marginally affected the mortality prediction.

Enhancing the tropism of bacteria via genetically programmed biosensors

Engineered bacteria for therapeutic applications would benefit from control mechanisms that confine the growth of the bacteria within specific tissues or regions in the body. Here we show that the tropism of engineered bacteria can be enhanced by coupling bacterial growth with genetic circuits that sense oxygen, pH or lactate through the control of the expression of essential genes. Bacteria that were engineered with pH or oxygen sensors showed preferential growth in physiologically relevant acidic or oxygen conditions, and reduced growth outside the permissive environments when orally delivered to mice. In syngeneic mice bearing subcutaneous tumours, bacteria engineered with both hypoxia and lactate biosensors coupled through an AND gate showed increased tumour specificity. The multiplexing of genetic circuits may be more broadly applicable for enhancing the localization of bacteria to specified niches.

Clinic-on-a-Needle Array toward Future Minimally Invasive Wearable Artificial Pancreas Applications

In order to reduce medical facility overload due to the rise of the elderly population, modern lifestyle diseases, or pandemics, the medical industry is currently developing point-of-care and home medical device systems. Diabetes is an incurable and lifetime disease, accountable for a significant mortality and socio-economic public health burden. Thus, tight glucose control in diabetic patients, which can prevent the onset of its late complications, is of enormous importance. Despite recent advances, the current best achievable management of glucose control is still inadequate, due to several key limitations in the system components, mainly related to the reliability of sensing components, both temporally and chemically, and the integration of sensing and delivery components in a single wearable platform, which is yet to be achieved. Thus, advanced closed-loop artificial pancreas systems able to modulate insulin delivery according to the measured sensor glucose levels, independently of patient supervision, represent a key requirement of development efforts. Here, we demonstrate a minimally invasive, transdermal, multiplex, and versatile continuous metabolites monitoring system in the subcutaneous interstitial fluid space based on a chemically modified SiNW-FET nanosensor array on microneedle elements. Using this technology, ISF-borne metabolites require no extraction and are measured directly and continuously by the nanosensors. Due to their chemical sensing mechanism, the nanosensor response is only influenced by the specific metabolite of interest, and no response is observed in the presence of potential exogenous and endogenous interferents known to seriously affect the response of current electrochemical glucose detection approaches. The 2D architecture of this platform, using a single SOI substrate as a top-down multipurpose material, resulted in a standard fabricated chip with 3D functionality. After proving the ability of the system to act as a selective multimetabolites sensor, we have implemented our platform to reach our main goal for in vivo continuous glucose monitoring of healthy human subjects. Furthermore, minor adjustments to the fabrication technique allow the on-chip integration of microinjection needle elements, which can ideally be used as a drug delivery system. Preliminary experiments on a mice animal model successfully demonstrated the single-chip capability to both monitor glucose levels as well as deliver insulin. By that, we hope to provide in the future a cost-effective and reliable wearable personalized clinical tool for patients and a strong tool for research, which will be able to perform direct monitoring of clinical biomarkers in the ISF as well as synchronized transdermal drug delivery by this single-chip multifunctional platform.

An empirical investigation of deviations from the Beer-Lambert law in optical estimation of lactate

The linear relationship between optical absorbance and the concentration of analytes-as postulated by the Beer-Lambert law-is one of the fundamental assumptions that much of the optical spectroscopy literature is explicitly or implicitly based upon. The common use of linear regression models such as principal component regression and partial least squares exemplifies how the linearity assumption is upheld in practical applications. However, the literature also establishes that deviations from the Beer-Lambert law can be expected when (a) the light source is far from monochromatic, (b) the concentrations of analytes are very high and (c) the medium is highly scattering. The lack of a quantitative understanding of when such nonlinearities can become predominant, along with the mainstream use of nonlinear machine learning models in different fields, have given rise to the use of methods such as random forests, support vector regression, and neural networks in spectroscopic applications. This raises the question that, given the small number of samples and the high number of variables in many spectroscopic datasets, are nonlinear effects significant enough to justify the additional model complexity? In the present study, we empirically investigate this question in relation to lactate, an important biomarker. Particularly, to analyze the effects of scattering matrices, three datasets were generated by varying the concentration of lactate in phosphate buffer solution, human serum, and sheep blood. Additionally, the fourth dataset pertained to invivo, transcutaneous spectra obtained from healthy volunteers in an exercise study. Linear and nonlinear models were fitted to each dataset and measures of model performance were compared to attest the assumption of linearity. To isolate the effects of high concentrations, the phosphate buffer solution dataset was augmented with six samples with very high concentrations of lactate between (100-600 mmol/L). Subsequently, three partly overlapping datasets were extracted with lactate concentrations varying between 0-11, 0-20 and 0-600 mmol/L. Similarly, the performance of linear and nonlinear models were compared in each dataset. This analysis did not provide any evidence of substantial nonlinearities due high concentrations. However, the results suggest that nonlinearities may be present in scattering media, justifying the use of complex, nonlinear models.

The Association of Serum Lactate Level with the Occurrence of Contrast-Induced Acute Kidney Injury and Long-Term Prognosis in Patients Undergoing Emergency Percutaneous Coronary Intervention

Objective

The association of lactate and contrast-induced acute kidney injury (CI-AKI) has not been well established. This prospective study was planned to identify the effects of lactate level on the occurrence of CI-AKI and long-term prognosis with acute myocardial infarction (AMI) patients undergoing emergency percutaneous coronary intervention (PCI).

Methods

A total of 280 patients with AMI who underwent emergency PCI were selected from March 2018 to March 2019. A receiver operating characteristic (ROC) curve was used to analyze the optimal cut-off value of lactate on predicting CI-AKI after PCI. A multivariable logistic regression model was used to explore the significant predictors that might affect the occurrence of CI-AKI after univariate analysis. The primary endpoints were clinical outcomes including events: a combined endpoint of major adverse cardiovascular events, re-hospitalization due to heart failure, and worsening renal function. The Cox regression model was further used to analyze the predictors of the long-term prognosis after PCI.

Results

Among the 280 patients, 64 patients (22.9%) developed CI-AKI after emergency PCI procedure. Multivariable logistic regression analysis revealed that baseline lactate level was the independent risk factor for the development of CI-AKI (OR, 3.657; 95% CI, 2.237–5.978; p<0.001). The area under the ROC curve for predicting CI-AKI of lactate was 0.786, and the optimum cut-off point of lactate was 3.02 mmol/L, with sensitivity of 65.6% and specificity of 85.2%. The incidence of primary endpoints in the high lactate group (lactate ≥3.02mmol/L) was significantly increased compared with the control group [26.3% (42/160) vs 15.8% (19/120), χ²=4.430, p=0.035]. Cox regression analysis also confirmed high lactate was an independent predictor for primary endpoint outcomes at 1-year follow-up (HR, 1.916; 95% CI, 1.118–3.285; p=0.018).

Conclusion

Our study demonstrates that baseline high lactate levels may be associated with an increased risk of CI-AKI and are the important predictors of long-term poor cardiorenal outcomes in AMI patients undergoing emergency PCI.

Lactic Acidosis and the Role of Sodium Bicarbonate: A Narrative Opinion

Lactic acidosis occurs commonly and can be a marker of significant physiologic derangements. However what an elevated lactate level and acidemia connotes and what should be done about it is subject to inconsistent interpretations. This review examines the varied etiologies of lactic acidosis, the physiologic consequences, and the known effects of its treatment with sodium bicarbonate. Lactic acidosis is often assumed to be a marker of hypoperfusion, but it can also result from medications, organ dysfunction, and sepsis even in the absence of malperfusion. Acidemia causes deleterious effects in almost every organ system, but it can also have positive effects, increasing localized blood flow and oxygen delivery, as well as providing protection against hypoxic cellular injury. The use of sodium bicarbonate to correct severe acidemia may be tempting to clinicians, but previous studies have failed to show improved patient outcomes following bicarbonate administration. Bicarbonate use is known to decrease vasomotor tone, decrease myocardial contractility, and induce intracellular acidosis. This suggests that mild to moderate acidemia does not require correction. Most recently, a randomized control trial found a survival benefit in a subgroup of critically ill patients with serum pH levels <7.2 with concomitant acute kidney injury. There is no known benefit of correcting serum pH levels ≥ 7.2, and sparse evidence supports bicarbonate use <7.2. If administered, bicarbonate is best given as a slow IV infusion in the setting of adequate ventilation and calcium replacement to mitigate its untoward effects.

Predicting the need for blood transfusion requirement in postpartum hemorrhage

OBJECTIVE

We aimed to assess the role of lactate and hemoglobin levels as predictors for the need for blood transfusion in post-partum hemorrhage (PPH).

METHODS

A retrospective cohort study of women with PPH in a single university-affiliated tertiary medical center between August 2018 and June 2020. PPH was defined as an estimated excessive blood loss (of more than 500 ml following vaginal delivery and 1000 ml following a cesarean delivery) requiring at least one uterotonic drug and fluid resuscitation. Women were stratified by the need of requiring blood transfusion due to hemorrhage. The criteria for blood transfusion were: (1) clinically severe uncontrollable ongoing hemorrhage; (2) symptomatic anemia (maternal tachycardia >110 beats per minute, dizziness, syncope or presyncope) in the presence of Hb 7-8 g/dL^; or (3) postpartum Hb level < 7 g/dL regardless of maternal symptoms or signs of anemia. Demographic, labor characteristics as well as laboratory data were collected. For all women the Shock Index (SI: heart rate divided by systolic blood pressure) was calculated. Women without available data on immediate (more than 15 min from the bleeding initiation) hemoglobin (Hb) level and lactate concentrations were excluded.

RESULTS

Overall, out of 22,241 deliveries during the study, 94 women were included, of them 26 (23.4%) required blood transfusion. The antepartum Hb level was lower in the transfused group (11.7 ± vs 12.4 ± 1.0 re/dL, p = .01). No significant differences were found in demographic and labor characteristics. In multivariate logistic regression analysis, a lower immediate postpartum Hb and a higher SI higher were associated with blood transfusion requirement (adjusted odds ratio (aOR) 3.45 [CI] 1.82-7.69, p < .001] and aOR 1.25 [CI 1.03-1.55, p = .03], respectively). The combination of SI, immediate postpartum Hb and lactate concentration provided the best integration, with an area under the curve of 0.86, sensitivity 92.65%, specificity 61.54%, positive and negative predictive values of 86.3% and 76.2%, respectively.

CONCLUSION

The combination of SI, immediate postpartum Hb and lactate levels is a good predictor for the need of blood requirement in PPH.

Lactated Ringer's solution versus normal saline in pediatric living-donor liver transplantation: A matched retrospective cohort study

BACKGROUND

In pediatric living-donor liver transplantation, lactated Ringer's solution and normal saline are commonly used for intraoperative fluid management, but the comparative clinical outcomes remain uncertain.

AIMS

To compare the effect between lactated Ringer's solution and normal saline for intraoperative volume replacement on clinical outcomes among pediatric living-donor liver transplantation patients.

METHODS

This single-center, retrospective trial study enrolled children who received either lactated Ringer's solution or normal saline during living-donor liver transplantation between January 2010 and August 2016. The groups with comparable clinical characteristics were balanced by propensity score matching. The primary outcome was 90-day all-cause mortality, and the secondary outcomes included early allograft dysfunction, primary nonfunction, acute renal injury, and hospital-free days (days alive postdischarge within 30 days of liver transplantation).

RESULTS

We included 333 pediatric patients who met the entry criteria for analysis. Propensity score matching identified 61 patients in each group. After matching, the lactated Ringer's solution group had a higher 90-day mortality rate than the normal saline group (11.5% vs. 0.0%). Early allograft dysfunction and primary nonfunction incidences were also more frequent in the lactated Ringer's solution group (19.7% and 11.5%, respectively) than in the normal saline group (3.3% and 0.0%, respectively). In the lactated Ringer's solution group, four (6.6%) recipients developed acute renal injury within 7 days postoperatively compared with three (4.9%) recipients in the normal saline group. Hospital-free days did not differ between groups (9 days [1-13] vs. 9 days [0-12]).

CONCLUSIONS

For intraoperative fluid management in pediatric living-donor liver transplantation patients, lactated Ringer's solution administration was associated with a higher 90-day mortality rate than normal saline. This finding has important implications for selecting crystalloid in pediatric living-donor liver transplantation. Further randomized clinical trials in larger cohort are necessary to confirm this finding.

Predictive Relevance of Baseline Lactate and Glucose Levels in Patients with Spontaneous Deep-Seated Intracerebral Hemorrhage

(1) Background: As elements of the standard admission blood panel, lactate and glucose represent potential biomarkers for outcome prediction. In patients with intracranial hemorrhage (ICH), data on the predictive value of these blood values is exceedingly sparse. (2) Methods: Between 2014 and August 2020, all patients with deep-seated ICH referred to the neurovascular center at the authors' institution were included in the subsequent study. Serum levels of lactate and glucose at the time of admission were compared with mortality at 90 days. In addition, a multivariate analysis was performed in order to identify independent admission predictors for 90-day mortality. (3) Results: Among the 102 patients with deep-seated ICH, elevated lactate and glucose levels on admission were significantly associated with increased mortality at 90 days. Multivariate logistic regression analysis identified "ICH score ≥3" (p = 0.004) along with "admission hyperlactatemia" (p = 0.025) and "admission hyperglycemia" (p = 0.029) as independent and significant predictors of 90-day mortality in patients with deep-seated ICH. (4) Conclusions: Initially elevated lactate and glucose levels after spontaneous intracerebral hemorrhage are associated with poor outcome, suggesting a potential application for future prognostic models when considered in conjunction with other parameters.

Lessons of the month 1: Salbutamol induced lactic acidosis: clinically recognised but often forgotten

We present the case of an 83-year-old woman, with known asthma, admitted with increasing dyspnoea, wheeze and a productive cough. In addition to maintenance inhaled therapy, the patient was also on long-term mirtazapine and furosemide. Following acute treatment with nebulised salbutamol she became increasingly dyspnoeic and developed a metabolic acidosis with a significantly raised blood lactate level. After cessation of ß₂-adrenergic medication, the patient's clinical condition improved with resolution of her lactic acidosis; salbutamol induced lactic acidosis was diagnosed. This clinical scenario is common but not well described. Here we discuss the mechanisms, investigation and management of raised serum lactate and lactic acidosis in the context of acute asthma and the possible interactions of polypharmacy and comorbidities in the acute medical setting.

Early lactate and glucose kinetics following return to spontaneous circulation after out-of-hospital cardiac arrest

Objective

Lactate has been shown to be preferentially metabolized in comparison to glucose after physiological stress, such as strenuous exercise. Derangements of lactate and glucose are common after out-of-hospital cardiac arrest (OHCA). Therefore, we hypothesized that lactate decreases faster than glucose after return-to-spontaneous-circulation (ROSC) after OHCA.

Results

We included 155 OHCA patients in our analysis. Within the first 8 h of presentation to the emergency department, 843 lactates and 1019 glucoses were available, respectively. Lactate decreased to 50% of its initial value within 1.5 h (95% CI [0.2–3.6 h]), while glucose halved within 5.6 h (95% CI [5.4–5.7 h]). Also, in the first 8 h after presentation lactate decreases more than glucose in relation to their initial values (lactate 72.6% vs glucose 52.1%). In patients with marked hyperlactatemia after OHCA, lactate decreased expediently while glucose recovered more slowly, whereas arterial pH recovered at a similar rapid rate as lactate. Hospital non-survivors (N = 82) had a slower recovery of lactate (P = 0.002) than survivors (N = 82). The preferential clearance of lactate underscores its role as a prime energy substrate, when available, during recovery from extreme stress.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05604-w.

Thinking fast and slow: Lactate and MELD-XI (Model for End-Stage Liver Disease Excluding INR) are useful for estimating mortality after cardiopulmonary resuscitation

BACKGROUND

Intensivists keep getting challenged with prognostication after cardiopulmonary resuscitation (CPR). The model for end-stage liver disease, excluding INR (MELD-XI) score has proven valuable for assessing illness severity. Serum lactate is a readily available and established indicator of general stress and tissue hypoxia. We aimed to evaluate the prognostic value of MELD-XI combined with serum lactate in patients after CPR.

METHODS

A retrospective analysis on 106 patients after CPR was performed. Multivariable Cox regression was performed to evaluate associations with 30-day mortality and neurological outcome by means of Cerebral Performance Category (CPC). An optimal cut-off was calculated by means of the Youden index. Patients were then divided into subgroups based on the optimal cut-offs for MELD-XI and serum lactate.

RESULTS

MELD-XI and lactate were independently associated with mortality. The respective cut-offs were MELD-XI >12 and lactate ≥2.5 mmol/L. Patients were split into three groups: lactate <2.5 mmol/L and MELD-XI ≤12 (low-risk; n=32), lactate ≥2.5 mmol/L or MELD-XI >12 (medium-risk; n=39), and lactate ≥ 2.5mmol/L and MELD-XI >12 (high-risk; n=33). The mortality rates were 6%, 26% and 61% in the low, medium and high-risk group. This combined model yielded in the highest predictive abilities (AUC 0.78 95%CI 0.68-0.85; p=0.03 vs. AUC 0.66 for SOFA score). Worse neurological outcome (CPC 3 or 4) was more common in the medium and high-risk group (6.25%, 10.3% and 9.1%).

CONCLUSIONS

The combination of MELD-XI and lactate concentration at ICU admission was superior to the more complex SOFA score for prediction of mortality after CPR.

False-Positive Enzymatic Alcohol Results in Perimortem Specimens

Herein, we present 2 cases referred to the North Carolina Office of the Chief Medical Examiner (NC OCME) in which ethanol results reported by different hospital laboratories, using alcohol dehydrogenase (ADH)-based assays, were positive, whereas results of headspace gas chromatography testing performed in the NC OCME laboratory were negative. Literature reports suggest that false-positive ethanol measurements from ADH-based assays can occur when a combination of elevated lactate and lactate dehydrogenase (LD) are present in the specimen. The results were reported in perimortem specimens collected from 2 children with unrelated medical conditions. The cases and associated clinical parameters are considered based on the lactate/LD explanation for the false-positive results, to facilitate the recognition of circumstances that can produce erroneous serum ethanol results.

Assessment of the Clinical Interpreter of Death in Life-Threatening Infective Cases Admitted in the Intensive Care Unit of a North-Eastern State of India

Objectives

The clinical factors affecting a patient's condition monitored over time could be useful not only to decide on an intervention that may increase the patients' possibilities of survival but also to predict the treatment outcome. Therefore, this study evaluates the clinical factors as predictors of mortality among severe sepsis patients admitted in the intensive care unit (ICU) of a tertiary care center.

Method

We did a prospective study on over 50 life-threatening infective cases with different causes admitted in the ICU. Clinical and biochemical parameters like temperature, heart rate, blood pressure, bicarbonate levels, blood lactate levels, and pH were monitored at admission, after 24 hours, and after 72 hours. The statistical analysis was done using Microsoft Excel (Microsoft Corporation, Redmond, WA) and the Statistical Package for the Social Studies (SPSS) version 22 (IBM Corp., Armonk, NY). We have obtained ethical clearance from the ethics committee (human) of Assam Medical College and Hospital, Dibrugarh. Before the collection of the data, we also took informed consent from the participants.

Results

The mean age of non-survivors was 44.35±11.64 years and that of survivors was 36.60±9.28 years, and the difference was statistically significant (p-value <0.003). An analysis of values of the various vital signs indicated substantial differences in the mean at different time intervals among survivors and non-survivors (p-value <0.05). Among non-survivors, mean temperature, pulse, and rate of respiration were observed to increase over time while blood pressure and oxygen saturation levels were significantly decreasing. Compared to survivors, the mean lactate levels of non-survivors at different time intervals were statistically significant (p-value <0.05). It is also observed that the pH of non-survivors was lower than survivors, and the mean pH value significantly different at different time intervals among the two groups (p-value <0.05).

Conclusion

The temperature, pulse, rate of respiration, blood pressure, and oxygen saturation levels are essential determinants of patient mortality in those suffering from a severe infection, besides serial lactate levels, bi-carbonate levels, and pH levels.

Rational design of direct electron transfer type l-lactate dehydrogenase for the development of multiplexed biosensor

The development of wearable multiplexed biosensors has been focused on systems to measure sweat l-lactate and other metabolites, where the employment of the direct electron transfer (DET) principle is expected. In this paper, a fusion enzyme between an engineered l-lactate oxidase derived from Aerococcus viridans, AvLOx A96L/N212K mutant, which is minimized its oxidase activity and b-type cytochrome protein was constructed to realize multiplexed DET-type lactate and glucose sensors. The sensor with a fusion enzyme showed DET to a gold electrode, with a limited operational range less than 0.5 mM. A mutation was introduced into the fusion enzyme to increase K_m value and eliminate its substrate inhibition to construct "b2LOxS". Together with the employment of an outer membrane, the detection range of the sensor with b2LOxS was expanded up to 10 mM. A simultaneous lactate and glucose monitoring system was constructed using a flexible thin-film multiplexed electrodes with b2LOxS and a DET-type glucose dehydrogenase, and evaluated their performance in the artificial sweat. The sensors achieved simultaneous detection of lactate and glucose without cross-talking error, with the detected linear ranges of 0.5-20 mM for lactate and 0.1-5 mM for glucose, sensitivities of 4.1 nA/mM∙mm² for lactate and 56 nA/mM∙mm² for glucose, and limit of detections of 0.41 mM for lactate and 0.057 mM for glucose. The impact of the presence of electrochemical interferants (ascorbic acid, acetaminophen and uric acid), was revealed to be negligible. This is the first report of the DET-type enzyme based lactate and glucose dual sensing systems.

Prospective evaluation of plasma lactate parameters for prognosticating dogs with shock

OBJECTIVE

To determine whether admission venous plasma lactate concentration, serially calculated lactate variables, or the Acute Patient Physiologic and Laboratory Evaluation (APPLE_fast ) score could discriminate hospital survivors from non-survivors in dogs presenting to the emergency department with clinical signs of shock.

DESIGN

Prospective case series performed over a 24-month period.

SETTING

Large urban private teaching hospital.

ANIMALS

Seventy-one dogs admitted to the ICU with initial peripheral venous plasma lactate concentration > 2.5 mmol/L and clinical and hemodynamic parameters consistent with shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Heart rate, systolic blood pressure, temperature, initial venous plasma lactate, and APPLE_fast score were recorded at admission. Lactate concentrations were serially recorded at predefined time points and used to calculate lactate variables, including lactime (time lactate > 2.5 mmol/L), lactate clearance ([lactate_initial - lactate_delayed ]/ lactate_initial × 100), and LAC_AREA (area under the lactate concentration versus time curve). Primary outcome was survival to discharge. Overall survival rate was 61%. Admission plasma lactate did not differ between groups (P = 0.28). Lactime was shorter in survivors vs non-survivors (P = 0.03). Lactate clearance at hours (h) 1, 4, 10, and 16 was greater in survivors vs non-survivors (P < 0.05). Final plasma lactate clearance differed between groups (P < 0.05). LAC_AREA at time intervals 1 to 4 hours, 4 to 10 hours, 10 to 16 hours, and 16 to 24 hours was larger in non-survivors vs survivors (P < 0.05). Total LAC_AREA did not differ between groups (P = 0.51). Admission APPLE_fast was not different between survivors and non-survivors (P = 0.16).

CONCLUSIONS

While neither single APPLE_fast nor admission plasma lactate concentration could discriminate between hospital survivors and non-survivors, measures of lactate clearance can prognosticate survival in dogs with shock.

Wearable Osmotic-Capillary Patch for Prolonged Sweat Harvesting and Sensing

Biomarkers in sweat are a largely untapped source of health information. Most of the currently available sweat harvesting and testing devices are incapable of operating under low-sweat rates such as those experienced by humans at rest. Here we analyze the in vitro and in vivo sampling of sweat through osmosis via the use of a hydrogel interfaced with the skin, without need for active perspiration. The hydrogel also interfaces with paper-based microfluidics to transport the fluid via capillary forces toward a testing zone and then evaporation pad. We show that the hydrogel solute content and area of the evaporation pad regulate the long-term extraction of sweat and its associated biomarkers. The results indicate that the platform can sample biomarkers from a model skin system continuously for approximately 12 h. On-skin testing of the platform on both resting and exercising human subjects confirms that it can sample sweat lactate directly from the surface of skin. The results highlight that lactate in sweat increases with exercise and as a direct result of muscle activity. Implementation of such new principles for sweat fluid harvesting and management via wearable patch devices can contribute toward the advancement of next generation wearables.

Lactate and Bilirubin Index: A New Indicator to Predict Critically Ill Cirrhotic Patients’ Prognosis

Objectives. We aimed to perform external validation of the prognostic value of the lactate and bilirubin (LB) index, a new indicator, and compare the ability of the LB index and other scoring systems to predict both short- and long-term mortality in critically ill cirrhotic patients. Materials and Methods. A number of 479 cirrhotic patients admitted into ICU were included in our research. We measured prognostic scores in the first 24 hours including LB index, Child–Pugh, SOFA, CLIF-SOFA, and MELD scores. The LB index was calculated as follows: ln [1000 × lactate (mmol/L) × bilirubin (µmol/L)]/2. The primary outcomes were 28-day and 3-year all-cause mortality. Multivariate logistic regression analyses were used to investigate the independent association between the LB index and the mortality in critically ill cirrhotic patients. The area under the receiver operating characteristic curve was used to assess the prediction accuracy of short- and long-term mortality of the clinical score. Calibration of the score was evaluated by Hosmer–Lemeshow goodness-of-fit test for significance. Results. Multivariate logistic regression analysis identified that the LB index (odds ratio: 5.487, 95% confidence interval: 3.542–8.501, $P<0.001$ ) was the strongest predictor for 28-day mortality. The LB index gave the highest area under the curve (0.791, 95% confidence interval: 0.747–0.836) in predicting 28-day mortality. For predicting 3-year mortality, the model for end-stage liver disease (MELD) score showed better discrimination ability with an area under the curve of 0.726 (95% confidence interval: 0.680–0.771). The risk of mortality significantly increased when the clinical scores were ≥ the optimal cutoff values. Conclusions. The LB index, a simple prognostic indicator, performs well in predicting critically ill cirrhotic patients’ short-term prognosis, while, for long-term prognosis, the MELD score is more appropriate.

Association between serum lactate level during cardiopulmonary resuscitation and survival in adult out-of-hospital cardiac arrest: a multicenter cohort study

We aimed to investigate the association between serum lactate levels during cardiopulmonary resuscitation (CPR) and survival in patients with out-of-hospital cardiac arrest (OHCA). From the database of a multicenter registry on OHCA patients, we included adult nontraumatic OHCA patients transported to the hospital with ongoing CPR. Based on the serum lactate levels during CPR, the patients were divided into four quartiles: Q1 (≤ 10.6 mEq/L), Q2 (10.6-14.1 mEq/L), Q3 (14.1-18.0 mEq/L), and Q4 (> 18.0 mEq/L). The primary outcome was 1-month survival. Among 5226 eligible patients, the Q1 group had the highest 1-month survival (5.6% [74/1311]), followed by Q2 (3.6% [47/1316]), Q3 (1.7% [22/1292]), and Q4 (1.0% [13/1307]) groups. In the multivariable logistic regression analysis, the adjusted odds ratio of Q4 compared with Q1 for 1-month survival was 0.24 (95% CI 0.13-0.46). 1-month survival decreased in a stepwise manner as the quartiles increased (p for trend < 0.001). In subgroup analysis, there was an interaction between initial rhythm and survival (p for interaction < 0.001); 1-month survival of patients with a non-shockable rhythm decreased when the lactate levels increased (p for trend < 0.001), but not in patients with a shockable rhythm (p for trend = 0.72). In conclusion, high serum lactate level during CPR was associated with poor 1-month survival in OHCA patients, especially in patients with non-shockable rhythm.

Hyperlactatemia: An Update on Postoperative Lactate

While hyperlactatemia in postoperative cardiac surgery patients was once believed to solely reflect hypoperfusion, either from the accumulated "oxygen debt" during bypass or ongoing inadequate perfusion, our understanding of lactate generation, clearance, and management has evolved. A contemporary understanding of lactate balance is critical to the management of the postoperative patient with hyperlactatemia. In this review, we summarize the current understanding of lactate metabolism in pediatric patients following cardiac surgery and highlight two types of hyperlactatemia: type A, which is secondary to inadequate oxygen delivery and tissue hypoxia, and type B, which in postoperative pediatric cardiac surgery patients largely reflects increased glycolysis driven by the stress response. Both types may coexist; thus, it is imperative that providers first assess the patient for evidence of hypoperfusion. In patients with evidence of adequate perfusion, a type B component is often associated with a concomitant balanced (normal anion gap) metabolic acidosis and hyperglycemia. These patients will benefit from a more nuanced approach to their type B hyperlactatemia, as many will have a benign course and may be managed expectantly.

Continuous Lactate Measurement Devices and Implications for Critical Care: A Literature Review

The aim of this article is to review the literature on lactate measurements in critical care and the current devices used to measure noninvasively and invasively. Lactate measurements are currently being used as a way to measure the severity of sepsis. Intravascular and subcutaneous devices are some of the ways that these measurements can be continuously gathered as well as point-of-care blood tests. New devices that are being currently used with athletes can measure lactate noninvasively. As the advance of technology continues to move at a fast speed, an evaluation of literature is needed to assess the continued support of lactate and the ability to move to noninvasive devices in critical care. A literature search was conducted in February 2020, using PubMed, CINAHL, MEDLINE, and Cochrane databases. There remains support for the use of lactate and continuous lactate monitoring; however, currently, noninvasive devices are not available for the critical care environment. There are invasive techniques that are being used to measure lactate continuously in critical care and are beneficial for the cardiac surgery population. The review of the literature on continuous lactate measurements produced evidence that supports prediction of morbidity and mortality. There are no current noninvasive lactate measurement devices that can be used in critical care, but they are being currently used in the athletic community. Invasive continuous lactate measurement devices are currently being used and beneficial.

Hypernatremia and moderate-to-severe hyponatremia are independent predictors of mortality in septic patients at emergency department presentation: A sub-group analysis of the need-speed trial

STUDY OBJECTIVE

Early risk stratification of septic patients presenting to the emergency department (ED) is challenging. The aim of the study was to evaluate the prognostic role of plasmatic sodium level (_PNa⁺) derangements at ED presentation in septic patients.

METHODS

According to _PNa⁺ at ED presentation patients were divided in eunatremic (136-145 mEq/L), hypernatremic (>145 mEq/L) and hyponatremic (<136 mEq/L). Hyponatremic patients were subsequently divided in mild (130-135 mEq/L), moderate (125-129 mEq/L) and severe (<125 mEq/L). 7 and 30-day mortality was evaluated according to _PNa⁺ derangements and the degree of hyponatremia. The same analysis was then performed only in respiratory tract infection-related (RTI-r) sepsis patients.

RESULTS

879 septic patients were included in this analysis, 40.3% had hyponatremia, 5.7% hypernatremia. Hypernatremia showed higher mortality rates at both endpoints compared to eunatremia and hyponatremia (p<0.0001 for both). Eunatremia and mild hyponatremia were compared vs. moderate-to-severe hyponatremia showing a significant difference in terms of 7 and 30-day survival (p = 0.004 and p = 0.007, respectively). The Cox proportional model identified as independent predictors of 7 and 30-day mortality moderate-to-severe hyponatremia (HR 4.89[2.38-10.03] and 1.79[1.07-3.01], respectively) and hypernatremia (HR 3.52[1.58-7.82] and 2.14[1.17-3.92], respectively). The same analysis was performed in patients with respiratory tract infection-related sepsis (n = 549), with similar results.

CONCLUSION

Both hypernatremia and moderate-to-severe hyponatremia at ED presentation independently predict mortality in septic patients, allowing early risk stratification and suggesting more aggressive therapeutic strategies.

Effects of intraoperative adrenergic administration on postoperative hyperlactatemia in open colon surgery: an observational study

Background

Postoperative Hyperlactatemia (PO-HL) is a frequent condition associated with poor prognosis. In recent years, there has been growing evidence that adrenergic stimulation may contribute to increased lactate levels. The use of adrenergic agonists for the control of intraoperative hypotension is frequent, and its impact on the development of PO-HL is unknown.

Objective

To evaluate whether the use of intraoperative adrenergic agents is associated with the occurrence of PO-HL.

Methods

This was a prospective observational study. The inclusion criteria were undergoing elective open colon surgery, being ≥60 years old and signing informed consent. The exclusion criteria were cognitive impairment, unplanned surgery, and anticipated need for postoperative mechanical ventilation. Baseline and intraoperative variables were collected, and arterial lactate data were collected at baseline and every 6 hours postoperatively for 24 hours. Hyperlactatemia was defined as lactate >2.1 mEq.L^-1.

Results

We studied 28 patients, 61% of whom developed hyperlactatemia. The variables associated with PO-HL in the univariate analysis were anesthetic time, the total dose of intraoperative ephedrine, and lower intraoperative central venous oxygen saturation (ScvO₂). Multivariate analysis confirmed the association between the use of ephedrine (p = 0.004), intraoperative hypotension (p = 0.026), and use of phenylephrine (p = 0.001) with PO-HL.

Conclusions

The use of intraoperative ephedrine, phenylephrine and intraoperative hypotension were independently associated with the development of PO-HL. This finding should lead to new studies in this field, as well as a judicious interpretation of the finding of a postoperative increase in lactate levels.

A deep learning backcasting approach to the electrolyte, metabolite, and acid-base parameters that predict risk in ICU patients

BACKGROUND

A powerful risk model allows clinicians, at the bedside, to ensure the early identification of and decision-making for patients showing signs of developing physiological instability during treatment. The aim of this study was to enhance the identification of patients at risk for deterioration through an accurate model using electrolyte, metabolite, and acid-base parameters near the end of patients' intensive care unit (ICU) stays.

METHODS

This retrospective study included 5157 adult patients during the last 72 hours of their ICU stays. The patients from the MIMIC-III database who had serum lactate, pH, bicarbonate, potassium, calcium, glucose, chloride, and sodium values available, along with the times at which those data were recorded, were selected. Survivor data from the last 24 hours before discharge and four sets of nonsurvivor data from 48-72, 24-48, 8-24, and 0-8 hours before death were analyzed. Deep learning (DL), random forest (RF) and generalized linear model (GLM) analyses were applied for model construction and compared in terms of performance according to the area under the receiver operating characteristic curve (AUC). A DL backcasting approach was used to assess predictors of death vs. discharge up to 72 hours in advance.

RESULTS

The DL, RF and GLM models achieved the highest performance for nonsurvivors 0-8 hours before death versus survivors compared with nonsurvivors 8-24, 24-48 and 48-72 hours before death versus survivors. The DL assessment outperformed the RF and GLM assessments and achieved discrimination, with an AUC of 0.982, specificity of 0.947, and sensitivity of 0.935. The DL backcasting approach achieved discrimination with an AUC of 0.898 compared with the DL native model of nonsurvivors from 8-24 hours before death versus survivors with an AUC of 0.894. The DL backcasting approach achieved discrimination with an AUC of 0.871 compared with the DL native model of nonsurvivors from 48-72 hours before death versus survivors with an AUC of 0.846.

CONCLUSIONS

The DL backcasting approach could be used to simultaneously monitor changes in the electrolyte, metabolite, and acid-base parameters of patients who develop physiological instability during ICU treatment and predict the risk of death over a period of hours to days.

The Prognostic Role of Lactate Concentrations after Aneurysmal Subarachnoid Hemorrhage

Blood lactate concentrations are often used to assess global tissue perfusion in critically ill patients; however, there are scarce data on lactate concentrations after subarachnoid hemorrhage (SAH). We aimed to assess the prognostic role of serial blood lactate measurements on hospital mortality and neurological outcomes at 3 months after SAH. We reviewed all SAH patients admitted to the intensive care unit from 2007 to 2019 and recorded the highest daily arterial lactate concentration for the first 6 days. Patients with no lactate concentration were excluded. Hyperlactatemia was defined as a blood lactate concentration >2.0 mmol/L. A total of 456 patients were included: 158 (35%) patients died in hospital and 209 (46%) had an unfavorable outcome (UO) at 3 months. The median highest lactate concentration was 2.7 (1.8–3.9) mmol/L. Non-survivors and patients with UO had significantly higher lactate concentrations compared to other patients. Hyperlactatemia increased the chance of dying (OR 4.19 (95% CI 2.38–7.39)) and of having UO in 3 months (OR 4.16 (95% CI 2.52–6.88)) after adjusting for confounding factors. Therefore, initial blood lactate concentrations have prognostic implications in patients with SAH; their role in conjunction with other prognostic indicators should be evaluated in prospective studies.

Veno-arterial CO2 difference and respiratory quotient after cardiac arrest: An observational cohort study

PURPOSE

To characterize venous-arterial CO₂ difference (ΔpCO₂) and the respiratory quotient (RQ) in post cardiac arrest patients and evaluate the association between these parameters and patient outcome.

MATERIALS AND METHODS

Data were obtained retrospectively from post cardiac arrest patients admitted between 2007 and 2016 to a medical intensive care unit. Comatose, adult patients in whom arterial and venous blood gas analyses were concomitantly performed in the first 24 h were included. Patients were grouped according to the time-point of sampling; 0-6, 6-12 and 12-24 h after admission.

RESULTS

308 patients were included; 174 (56%) died before ICU discharge and 212 (69%) had an unfavorable neurologic outcome. RQ was associated with ICU mortality (OR:1.09 (95%CI: 1.04-1.14; p < 0.01)), although not with neurological outcome. ΔpCO₂ was negatively associated with both ICU mortality (OR: 0.92 (95%CI: 0.86-0.99; p = 0.02)) and poor neurologic outcome (adjusted OR: 0.93 (95%CI: 0.87-0.99; p = 0.02)). ΔpCO₂ predicted an elevated RQ; a ΔpCO₂ above 8.5 mmHg identified a high RQ with reasonable sensitivity and specificity.

CONCLUSIONS

RQ was associated with ICU mortality and ΔpCO₂ identified elevated RQ in the early phase after cardiac arrest. However, ΔpCO₂ were negatively associated with both ICU mortality and neurologic outcome.

Predictors of Operative Intervention in Patients With Lactic Acidosis

BACKGROUND

Lactate levels in clinical practice are often used as a quantitative indicator for the severity of hypoperfusion and the responsiveness to therapeutic interventions. In the hospital acute care setting, lactic acidosis combined with the appropriate clinical exam signs warrants surgical evaluation. The purpose of our study was to evaluate all surgical consults for lactic acidosis in a single community hospital to identify what cofactors were most often predictive of the need for surgical management and operative intervention.

MATERIALS AND METHODS

A retrospective chart review within a 5-year period was conducted on all consultations to general surgery in which patients additionally had lactic acidosis defined as >2mEq. Within this population, various subjective and objective parameters were evaluated. Final analysis compared these parameters between patients with lactic acidosis who underwent surgical intervention and those who did not require operative intervention.

RESULTS

Within the 5-year period, 432 patients met our criteria of a surgical consult placed for lactic acidosis. Final results from the highest quality statistical model showed significant variables as diffuse tenderness on physical exam (P-value = .0010, Odds Ratio (OR) = 2.77) and focal tenderness on physical exam (P-value = .0440, OR = 1.76). The presence of peritoneal signs (P-value = .0521, OR = 2.02) resulted in operative intervention twice as often in patients with lactic acidosis.

DISCUSSION

To better appropriate health care costs, measures need to be taken to ensure resources are being utilized properly. In patients with lactic acidosis, one should go "back to the basics" with the physical examination to determine which patients truly need a surgical consultation.

White adipose tissue browning in critical illness: A review of the evidence, mechanisms and future perspectives

Observational studies suggest better clinical outcomes following critical illness in patients with overweight and obesity (obesity paradox). An understanding of the morphologic, physiologic and metabolic changes in adipose tissue in critical illness may provide an explanation. Recent studies have demonstrated the transformation of white to brown-like adipocytes due to the "browning process," which has been of interest as a potential novel therapy in obesity during the last decade. The characteristics of the browning of white adipose tissue (WAT) include the appearance of smaller, multilocular adipocytes, increased UCP1 mRNA expression, mitochondrial density and respiratory capacity. These changes have been identified in some critical illnesses, which specifically refers to burns, sepsis and cancer cachexia in this study. The pathophysiological nature of WAT browning, underlying mechanisms, main regulators and potential benefits and harms of this process are interesting new areas that warrants further investigations. In this review, we discuss emerging scientific discipline of adipose tissue physiology in metabolic stress, available data, gaps of knowledge and future perspectives. Future investigations in this field may provide insights into the underlying mechanisms and clinical aspects of browning that may further our understanding of the proposed obesity paradox following critical illness, which may in turn open up opportunities for novel therapies to save lives and improve recovery.

Predictive value of perfusion index for mortality in mechanically ventilated patients

AIM

This study aimed to examine the prognostic significance of the perfusion index (PI) in mechanically ventilated patients.

METHODS

Study included sixty patients who had the risk factors for the development of acute respiratory distress syndrome and received mechanical ventilator (MV) support in intensive care unit (ICU) unit between January 2017/January 2018. The demographic characteristics, vital signs, blood gas parameters, lactate levels, prognostic scores, and use of inotropic drugs were recorded. Arterial blood gas and PI measurements at the frontal region were performed at the time of and 12th and 24th hours of admission to the ICU. The patients were followed up for 60 days, and the outcome was recorded.

RESULTS

Twelve patients (20%) died during the first 7 days, and 27 patients (45%) died within 60 days of the admission. Multivariate analyses to determine potential predictors of 7 and 30-day mortality showed that only 24th-hour lactate level was independent predictor of 60-day mortality, and the PI at 24th was the sole independent predictor of 7-day mortality.

CONCLUSION

The PI did not predict 60-day mortality in MV patients who had risk factors for the development of Acute Respiratory Distress Syndrome (ARDS). However, the PI at 24th may be a significant predictor of 7-day mortality.

Transthyretin at Admission and Over Time as a Marker for Clinical Outcomes in Critically Ill Trauma Patients: A Prospective Single-Center Study

Background

Transthyretin (TTR) has been described as a predictor for outcomes in medical and surgical patients. However, the association of TTR on admission and over time on outcomes has not yet been prospectively assessed in trauma patients.

Methods

This is a prospective observational study including trauma patients admitted to the intensive care unit (ICU) of a large Level I trauma center 05/2014–05/2015. TTR levels at ICU admission and all subsequent values over time were recorded. Patients were observed for 28 days or until hospital discharge. The association of outcomes and TTR levels at admission and over time was assessed using multivariable regression and generalized estimating equation (GEE) analysis, respectively.

Results

A total of 237 patients with TTR obtained at admission were included, 69 of whom had repeated TTR measurements. Median age was 40.0 years and median ISS 16.0; 83.1% were male. Below-normal TTR levels at admission (41.8%) were independently associated with higher in-hospital mortality (p = 0.042), more infectious complications (p = 0.032), longer total hospital length of stay (LOS) (p = 0.013), and ICU LOS (p = 0.041). Higher TTR levels over time were independently associated with lower in-hospital mortality (p = 0.015), fewer infections complications (p = 0.028), shorter total hospital and ICU LOS (both p < 0.001), and fewer ventilator days (0.004).

Conclusions

In critically ill trauma patients, below-normal TTR levels at admission were independently associated with worse outcomes and higher TTR levels over time with better outcomes, including lower in-hospital mortality, less infectious complications, shorter total hospital and ICU LOS, and fewer ventilator days. Based on these results, TTR may be considered as a prognostic marker in this patient population.

Eculizumab as an emergency treatment for adult patients with severe COVID-19 in the intensive care unit: A proof-of-concept study

BACKGROUND

Complement pathway inhibition may provide benefit for severe acute respiratory illnesses caused by viral infections such as COVID-19. We present results from a nonrandomized proof-of-concept study of complement C5 inhibitor eculizumab for treatment of severe COVID-19.

METHODS

All patients (N = 80) with confirmed SARS-CoV-2 infection and severe COVID-19 admitted to our intensive care unit between March 10 and May 5, 2020 were included. Forty-five patients were treated with standard care and 35 with standard care plus eculizumab through expanded-access emergency treatment. The prespecified primary outcome was day-15 survival. Clinical laboratory values and biomarkers, complement levels, and treatment-emergent serious adverse events (TESAEs) were also assessed.

FINDINGS

At day 15, estimated survival was 82.9% (95% CI: 70.4%‒95.3%) with eculizumab and 62.2% (48.1%‒76.4%) without eculizumab (log-rank test, P = 0.04). Patients treated with eculizumab experienced a significantly more rapid decrease in lactate, blood urea nitrogen, total and conjugated bilirubin levels and a significantly more rapid increase in platelet count, prothrombin time, and in the ratio of arterial oxygen tension over fraction of inspired oxygen versus patients treated without eculizumab. Eculizumab-associated changes in complement levels, laboratory values, and biomarkers were consistent with terminal complement inhibition, reduced hypoxia, and decreased inflammation. TESAEs of special interest occurring in >5% of patients treated with/without eculizumab were ventilator-associated pneumonia (51%/24%), bacteremia (11%/2%), gastroduodenal hemorrhage (14%/16%), and hemolysis (3%/18%).

INTERPRETATION

Findings from this proof-of-concept study suggest eculizumab may improve survival and reduce hypoxia in patients with severe COVID-19. Randomized studies evaluating the efficacy and safety of this treatment approach are needed.

FUNDING

Programme d'Investissements d'Avenir: ANR-18-RHUS60004.