Liver and intestinal lactate metabolism in patients with acute hepatic failure undergoing liver transplantation

Cardiac lipotoxicity and fibrosis underlie impaired contractility in a mouse model of metabolic dysfunction-associated steatotic liver disease

The leading cause of death among patients with metabolic dysfunction-associated steatotic liver disease (MASLD) is cardiovascular disease. A significant percentage of MASLD patients develop heart failure driven by functional and structural alterations in the heart. Previously, we observed cardiac dysfunction in hepatocyte-specific peroxisome proliferator-activated receptor alpha knockout (Ppara HepKO), a mouse model that exhibits hepatic steatosis independent of obesity and insulin resistance. The goal of the present study was to determine mechanisms that underlie hepatic steatosis-induced cardiac dysfunction in Ppara HepKO mice. Experiments were performed in 30-week-old Ppara HepKO and littermate control mice fed regular chow. We observed decreased cardiomyocyte contractility (0.17 ± 0.02 vs. 0.24 ± 0.02 μm, p < 0.05), increased cardiac triglyceride content (0.96 ± 0.13 vs. 0.68 ± 0.06 mM, p < 0.05), collagen type 1 (4.65 ± 0.25 vs. 0.31 ± 0.01 AU, p < 0.001), and collagen type 3 deposition (1.32 ± 0.46 vs. 0.05 ± 0.03 AU, p < 0.05). These changes were associated with increased apoptosis as indicated by terminal deoxynucleotidyl transferase dUTP nick end labeling staining (30.9 ± 4.7 vs. 13.1 ± 0.8%, p < 0.006) and western blots showing increased cleaved caspase-3 (0.27 ± 0.006 vs. 0.08 ± 0.01 AU, p < 0.003) and pro-caspase-3 (5.4 ± 1.5 vs. 0.5 ± 0.3 AU, p < 0.02), B-cell lymphoma protein 2-associated X (0.68 ± 0.07 vs. 0.04 ± 0.04 AU, p < 0.001), and reduced B-cell lymphoma protein 2 (0.29 ± 0.01 vs. 1.47 ± 0.54 AU, p < 0.05). We further observed elevated circulating natriuretic peptides and exercise intolerance in Ppara HepKO mice when compared to controls. Our data demonstrated that lipotoxicity, and fibrosis underlie cardiac dysfunction in MASLD.

Comparing the accuracy of prediction models to detect clinically relevant post-hepatectomy liver failure early after major hepatectomy

BACKGROUND

Arterial lactate measurements were recently suggested as an early predictor of clinically relevant post-hepatectomy liver failure (PHLF). This needed to be evaluated in the subgroup of major hepatectomies only.

METHOD

This observational cohort study included consecutive elective major hepatectomies at Karolinska University Hospital from 2010 to 2018. Clinical risk factors for PHLF, perioperative arterial lactate measurements and routine lab values were included in uni- and multivariable regression analysis. Receiver operating characteristics and risk cut-offs were calculated.

RESULTS

In total, 649 patients constituted the study cohort, of which 92 developed PHLF grade B/C according to the International Study Group of Liver Surgery (ISGLS). Lactate reached significantly higher intra- and postoperative levels in PHLF grades B and C compared to grade A or no liver failure (all P < 0.002). Lactate on postoperative day (POD) 1 was superior to earlier measurement time points in predicting PHLF B/C (AUC 0.75), but was outperformed by both clinical risk factors (AUC 0.81, P = 0.031) and bilirubin POD1 (AUC 0.83, P = 0.013). A multivariable logistic regression model including clinical risk factors and bilirubin POD1 had the highest AUC of 0.87 (P = 0.006), with 56.6% sensitivity and 94.7% specificity for PHLF grade B/C (cut-off ≥0.32). The model identified 46.7% of patients with 90-day mortality and had an equally good discriminatory potential for mortality as the established ISGLS criteria for PHLF grade B/C but could be applied already on POD1.

CONCLUSION

The potential of lactate to predict PHLF following major hepatectomy was inferior to a prediction model consisting of clinical risk factors and bilirubin on first post-operative day.

Surgical Science and the Evolution of Critical Care Medicine

Surgical science has driven innovation and inquiry across adult and pediatric disciplines that provide critical care regardless of location. Surgically originated but broadly applicable knowledge has been globally shared within the pages Critical Care Medicine over the last 50 years.

A Selective Fluorescent l-Lactate Biosensor Based on an l-Lactate-Specific Transcription Regulator and Förster Resonance Energy Transfer

Selective detection of l-lactate levels in foods, clinical, and bacterial fermentation samples has drawn intensive attention. Many fluorescent biosensors based on non-stereoselective recognition elements have been developed for lactate detection. Herein, the allosteric transcription factor STLldR from Salmonella enterica serovar Typhimurium LT2 was identified to be stereo-selectively respond to l-lactate. Then, STLldR was combined with Förster resonance energy transfer (FRET) to construct a fluorescent l-lactate biosensor FILLac. FILLac was further optimized by truncating the N- and C-terminal amino acids of STLldR between cyan and yellow fluorescent proteins. The optimized biosensor FILLac10N0C exhibited a maximum emission ratio change (ΔRmax) of 33.47 ± 1.91%, an apparent dissociation constant (Kd) of 6.33 ± 0.79 μM, and a limit of detection of 0.68 μM. FILLac10N0C was applied in 96-well microplates to detect l-lactate in bacterial fermentation samples and commercial foods such as Jiaosu and yogurt. The quantitation results of FILLac10N0C exhibited good agreement with that of a commercial l-lactate biosensor SBA-40D bioanalyzer. Thus, the biosensor FILLac10N0C compatible with high-throughput detection may be a potential choice for quantitation of l-lactate in different biological samples.

The Effects of sodium bicarbonate Ringer’s solution on acute kidney injury and the clinical outcomes after liver transplantation: A randomized controlled trial

Background: Acute kidney injury is the most common complication after liver transplantation. Sodium bicarbonate Ringer’s solution is a new type of crystalloid solution that has been recently used in the clinical setting. Whether sodium bicarbonate Ringer’s solution reduces the occurrence of postoperative AKI and improves the clinical outcomes of liver transplantation patients is not clear.

Objective: To compare the effects of sodium bicarbonate Ringer’s solution versus normal saline on acute kidney injury and clinical outcomes following classic orthotopic liver transplantation.

Methods: Sixty-four participants were randomly assigned to the sodium bicarbonate Ringers (BRS) group or the normal saline (NS) group. The primary outcomes were the incidence and severity of acute kidney injury after liver transplantation. The secondary outcomes included the rate of renal replacement therapy, length of mechanical ventilation, stay in the ICU, stay in the hospital after surgery and 30-day mortality. Other outcomes included the concentration of sodium, chloride, bicarbonate, anion gap, lactate concentration and changes in chloride preoperatively and postoperatively.

Result: Sixty-two patients completed the trial and were analyzed, with 31 patients in each group. There was a significantly lower rate of postoperative acute kidney injury in the BRS group (14/31, 45.2%) than in the NS group (24/31, 77.4%), with a relative risk of 0.58 (95% CI, 0.38–0.90; p = 0.009). The severity of AKI in the BRS group was lower than that in the NS group (Z = -2.932, p = 0.003). There was no significant difference observed in the secondary outcomes. For other outcomes, the concentration of preoperative sodium was lower than postoperative sodium in the NS group (137.2 vs. 140.4, p = 0.009). The concentration of preoperative chloride was lower than that of postoperative chloride in the NS group (102.9 vs. 106.2, p < 0.001). The change in the concentration of chloride in the BRS group was lower than that in the NS group (1.6 vs. 4.7, p = 0.006).

Conclusion: Sodium bicarbonate Ringer’s solution reduced the incidence and severity of acute kidney injury after classic orthotopic liver transplantation.

Slightly different metabolomic profiles are associated with high or low weight duck foie gras

Understanding the evolution of fatty liver metabolism of ducks is a recurrent issue for researchers and industry. Indeed, the increase in weight during the overfeeding period leads to an important change in the liver metabolism. However, liver weight is highly variable at the end of overfeeding within a batch of animals reared, force-fed and slaughtered in the same way. For this study, we performed a proton nuclear magnetic resonance (¹H-NMR) analysis on two classes of fatty liver samples, called low-weight liver (weights between 550 and 599 g) and high-weight liver (weights above 700 g). The aim of this study was to identify the differences in metabolism between two classes of liver weight (low and high). Firstly, the results suggested that increased liver weight is associated with higher glucose uptake leading to greater lipid synthesis. Secondly, this increase is probably also due to a decline in the level of export of triglycerides from the liver by maintaining them at high hepatic concentration levels, but also of hepatic cholesterol. Finally, the increase in liver weight could lead to a significant decrease in the efficiency of aerobic energy metabolism associated with a significant increase in the level of oxidative stress. However, all these hypotheses will have to be confirmed in the future, by studies on plasma levels and specific assays to validate these results.

Acid-base abnormalities and liver dysfunction

In addition to the kidneys and lungs, the liver also plays an important role in the regulation of the Acid-Base Equilibrium (ABE). The involvement of the liver in the regulation of ABE is crucial because of its role in lactic acid metabolism, urea production and in protein homeostasis. The main acid-base imbalance that occurs in patients with liver cirrhosis is Respiratory Alkalosis (RAlk). Due to the fact that in these patients additional pathophysiological mechanisms that affect the ABE are present, other disorders may appear which compensate or enhance the primary disorder. Conventional ABE reading models fail to identify and assess the underlying disorders in patients with liver cirrhosis. This weakness of the classical models led to the creation of new physicochemical mathematical models that take into account all the known parameters that develop and affect the ABE. In addition to the RAlk, in patients with liver cirrhosis, metabolic alkalosis (due to hypoalbuminemia), hyponatremic metabolic acidosis, hyperchloremic metabolic acidosis, lactic acidosis and metabolic alkalosis due to urea metabolism are some of the pathophysiological mechanisms that affect the ABE.

Metabolomic serum abnormalities in dogs with hepatopathies

Hepatopathies can cause major metabolic abnormalities in humans and animals. This study examined differences in serum metabolomic parameters and patterns in left-over serum samples from dogs with either congenital portosystemic shunts (cPSS, n = 24) or high serum liver enzyme activities (HLEA, n = 25) compared to control dogs (n = 64). A validated targeted proton nuclear magnetic resonance spectroscopy platform was used to assess 123 parameters. Principal component analysis of the serum metabolome demonstrated distinct clustering among individuals in each group, with the cluster of HLEA being broader compared to the other groups, presumably due to the wider spectrum of hepatic diseases represented in these samples. While younger and older adult control dogs had very similar metabolomic patterns and clusters, there were changes in many metabolites in the hepatopathy groups. Higher phenylalanine and tyrosine concentrations, lower branched-chained amino acids (BCAAs) concentrations, and altered fatty acid parameters were seen in cPSS dogs compared to controls. In contrast, dogs with HLEA had increased concentrations of BCAAs, phenylalanine, and various lipoproteins. Machine learning based solely on the metabolomics data showed excellent group classification, potentially identifying a novel tool to differentiate hepatopathies. The observed changes in metabolic parameters could provide invaluable insight into the pathophysiology, diagnosis, and prognosis of hepatopathies.

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.

Primary Nonfunction of the Liver Allograft

Severe allograft dysfunction, as opposed to the expected immediate function, following liver transplantation is a major complication, and the clinical manifestations of such that lead to either immediate retransplant or death are the catastrophic end of the spectrum. Primary nonfunction (PNF) has declined in incidence over the years, yet the impact on patient and healthcare teams, and the burden on the organ pool in case of the need for retransplant should not be underestimated. There is no universal test to define the diagnosis of PNF, and current criteria are based on various biochemical parameters surrogate of liver function; moreover, a disparity remains within different healthcare systems on selecting candidates eligible for urgent retransplantation. The impact on PNF from traditionally accepted risk factors has changed somewhat, mainly driven by the rising demand for organs, combined with the concerted approach by clinicians on the in-depth understanding of PNF, optimal graft recipient selection, mitigation of the clinical environment in which a marginal graft is reperfused, and postoperative management. Regardless of the mode, available data suggest machine perfusion strategies help reduce the incidence further but do not completely avert the risk of PNF. The mainstay of management relies on identifying severe allograft dysfunction at a very early stage and aggressive management, while excluding other identifiable causes that mimic severe organ dysfunction. This approach may help salvage some grafts by preventing total graft failure and also maintaining a patient in an optimal physiological state if retransplantation is considered the ultimate patient salvage strategy.

Retrospective evaluation of the prognostic utility of plasma lactate concentration and serial lactate measurements in dogs and cats presented to the emergency room (January 2012 - December 2016): 4863 cases

OBJECTIVE

To determine the prognostic significance of plasma lactate concentration, plasma lactate clearance, and delta lactate in dogs and cats presented to an emergency room (ER).

DESIGN

Retrospective study.

SETTING

University teaching hospital.

ANIMALS

A total of 8,321 animals with a plasma lactate concentration measured with 4,863 presenting to the ER and 1,529 dogs and 444 cats having a measurement within 4 hours of admission.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Plasma lactate concentration of dogs and cats presented to a university teaching hospital was retrospectively evaluated. Of dogs and cats with a plasma lactate concentration measured within 4 hours of admission to the ER, hyperlactatemia was common, and the prevalence of hyperlactatemia for dogs 78% (361/462) and cats 67% (78/116) was highest when evaluated within the first 30 minutes following admission. The distribution of patient's plasma lactate concentration was significantly higher in non-survivors compared to survivors at all time points evaluated (P < 0.001). Both lactate clearance (P = 0.010) and delta lactate (P = 0.013) were significantly different between survivors and nonsurvivors. A delta lactate > 4.5 mmol/L was 100% (95% CI: 95 to 100%) specific for nonsurvival in patients with hyperlactatemia measured within 1 hour of admission to the ER. The most common cause of hyperlactatemia was shock in dogs (24%) and urinary tract diseases in cats (22%). Shock was associated with the highest mortality rate in both dogs (61%) and cats (77%). Hyperlactatemia was significantly associated with increased mortality for dogs with shock (P = 0.001), respiratory diseases (P = 0.022), diabetes mellitus (P = 0.018), and liver dysfunction (P = 0.006).

CONCLUSIONS

Hyperlactatemia was associated with mortality in both dogs and cats when measured at any time point in the 4 hours following admission to the ER. Serial lactate measurement may also be a valuable tool to guide clinical management decisions.

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.

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.

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 and Unsatisfactory Outcomes in Critically Ill Children in the Immediate Post-operative Period of Liver Transplantation

OBJECTIVES

Serum lactate is a useful biomarker of tissue perfusion in critically ill patients. We evaluated the behavior of serum lactate in children in the pediatric intensive care unit (PICU) immediately after liver transplantation and its association with surgical complications, graft dysfunction and 90-day mortality.

MATERIALS AND METHODS

A prospective observational study carried out between November 2009 and December 2019. Multidisciplinary PICU at the University Children's Hospital, Fundación Cardioinfantil-IC, Bogotá, Colombia.

MEASUREMENTS AND MAIN RESULTS

Patients between 1 month and 18 years of age who were in the immediate post-operative period following living-donor or cadaveric liver transplantation were included. A total of 145 patients with a median age of 14 months (IQR 8-60) met the inclusion criteria. Biliary atresia was the main diagnosis in 56.5% of the cases. A serum lactate level > 3.0 mmol/L on admission to the PICU was associated with biliary complications (AUC 0.73 95% CI 0.54-0.93; p = 0.05) and mortality (AUC 0.72 95% CI 0.63-0.8; p = 0.01). A lactate level > 2 mmol/L after 6 h in the PICU was associated with mortality (AUC 0.70 95% CI 0.54-0.83; p = 0.02). Higher lactate levels and lack of clearance were associated with the presence of tardus et parvus waveforms (p = 0.001) on liver Doppler, primary dysfunction (p < 0.001), arterial thrombosis (p < 0.001) and neurological complications (p = 0.04). There was an inverse correlation between admission lactate and the volume of fluids administered during surgery (rho = 0.36; p < 0.001). A total procedure time > 350 min, along with a vasopressor score > 7 and elevated lactate, were associated with worse outcomes (p < 0.001).

CONCLUSIONS

In post-operative pediatric liver transplant patients, the level of serum lactate is associated with post-operative surgical complications and mortality.

Increased ratio of P[v-a]CO2 to C[a-v]O2 without global hypoxia: the case of metformin-induced lactic acidosis

The ratio of venoarterial CO₂ tension to arteriovenous O₂ content difference (P[v-a]CO₂/C[a-v]O₂) increases when lactic acidosis is due to inadequate oxygen supply (hypoxia); we aimed to verify whether it also increases when lactic acidosis develops because of mitochondrial dysfunction (dysoxia) with constant oxygen delivery. Twelve anaesthetised, mechanically ventilated pigs were intoxicated with IV metformin (4.0 to 6.4 g over 2.5 to 4.0 h). Saline and norepinephrine were used to preserve oxygen delivery. Lactate and P[v-a]CO₂/C[a-v]O₂ were measured every one or two hours (arterial and mixed venous blood). During metformin intoxication, lactate increased from 0.8 (0.6-0.9) to 8.5 (5.0-10.9) mmol/l (p < 0.001), even if oxygen delivery remained constant (from 352 ± 78 to 343 ± 97 ml/min, p = 0.098). P[v-a]CO₂/C[a-v]O₂ increased from 1.6 (1.2-1.8) to 2.3 (1.9-3.2) mmHg/ml/dl (p = 0.004). The intraclass correlation coefficient between lactate and P[v-a]CO₂/C[a-v]O₂ was 0.72 (p < 0.001). We conclude that P[v-a]CO₂/C[a-v]O₂ increases when lactic acidosis is due to dysoxia. Therefore, a high P[v-a]CO₂/C[a-v]O₂ may not discriminate hypoxia from dysoxia as the cause of lactic acidosis.

Dengue hepatitis with acute liver failure: Clinical, biochemical, histopathological characteristics and predictors of outcome

BACKGROUND

Hepatitis infection from non-hepatotropic viruses such as dengue virus (DENV) is increasing worldwide. There is increasing recognition of the changing epidemiology and atypical presentations of DENV infection including acute liver failure (ALF). There is paucity of data regarding incidence, disease characteristics, and markers of prognosis in patients who develop DENV-related ALF.

METHODS

We aimed to study the incidence, clinical features, laboratory characteristics, and determinants of outcome in patients of DENV presenting with ALF. We reviewed all patients with DENV infection and focused on DENV-related ALF from 2014 to 2017. Diagnosis of DENV and ALF was confirmed by serological tests and standard criteria, respectively.

RESULTS

Thirty-six patients (20 men, mean age 32.3) developed ALF among 10 108 patients with DENV infection (0.35%). Twenty-one patients died (58.3%). Although bilirubin, aspartate and alanine aminotransferase, and international normalized ratio were markedly elevated in all patients with DENV ALF, there was no statistically significant difference between survivors and non-survivors. Lactate levels, pH at admission, and model for end-stage liver disease (MELD) score were the only predictors of mortality. Lactate levels were significantly higher in non-survivors (11.5 ± 4.2 mmol/L) than survivors (6.3 ± 3.6 mmol/L) (P < 0.001). MELD score in non-survivors (26.7 ± 10.2) was significantly higher than in survivors (20 ± 7.2) (P = 0.039). Receiver operator characteristic curve showed lactate or pH to be a superior prognostic marker than MELD with an area under the curve of 0.80, 0.79, and 0.70, respectively.

CONCLUSION

Dengue hepatitis progressed to ALF in 0.35%. Development of ALF was associated with a high mortality (> 50%). Lactate level, pH, and MELD score at admission were significant determinants of outcome.

Lactate as a fulcrum of metabolism

Mistakenly thought to be the consequence of oxygen lack in contracting skeletal muscle we now know that the L-enantiomer of the lactate anion is formed under fully aerobic conditions and is utilized continuously in diverse cells, tissues, organs and at the whole-body level. By shuttling between producer (driver) and consumer (recipient) cells lactate fulfills at least three purposes: 1] a major energy source for mitochondrial respiration; 2] the major gluconeogenic precursor; and 3] a signaling molecule. Working by mass action, cell redox regulation, allosteric binding, and reprogramming of chromatin by lactylation of lysine residues on histones, lactate has major influences in energy substrate partitioning. The physiological range of tissue [lactate] is 0.5–20 mM and the cellular Lactate/Pyruvate ratio (L/P) can range from 10 to >500; these changes during exercise and other stress-strain responses dwarf other metabolic signals in magnitude and span. Hence, lactate dynamics have rapid and major short- and long-term effects on cell redox and other control systems. By inhibiting lipolysis in adipose via HCAR-1, and muscle mitochondrial fatty acid uptake via malonyl-CoA and CPT1, lactate controls energy substrate partitioning. Repeated lactate exposure from regular exercise results in major effects on the expression of regulatory enzymes of glycolysis and mitochondrial respiration. Lactate is the fulcrum of metabolic regulation in vivo.

Lactate Improves Prediction of Short-Term Mortality in Critically Ill Patients With Cirrhosis: A Multinational Study

Lactate levels and lactate clearance are known predictors of outcome in critically ill patients in the intensive care unit (ICU). The prognostic value of lactate is not well established in liver cirrhosis and acute-on-chronic liver failure (ACLF). The aim of this study was to assess the prognostic value of lactate levels and clearance in critically ill patients with cirrhosis. Patients with cirrhosis admitted to the ICU were studied at the University Medical Center Hamburg-Eppendorf (n = 566, derivation cohort) and the Medical University of Vienna and the University Hospitals Leuven (n = 250, validation cohort). Arterial lactate was measured on admission and during the first 24 hours. Patients were followed for 1 year and outcome was assessed. Admission lactate was directly related to the number of organs failing and to 28-day mortality (area under receiver operating characteristic [AUROC] 0.72; P < 0.001). This also applied to lactate follow-up measurements after 6, 12, and 24 hours (P < 0.001 for all, AUROC > 0.70 for all). Lactate clearance had significant predictive ability for 28-day mortality in patients with elevated serum lactate ≥5 mmol/L. Admission lactate and 12-hour lactate clearance (in patients with admission lactate ≥5 mmol/L), respectively, were identified as significant predictors of 1-year mortality, independent of Chronic Liver Failure Consortium acute-on-chronic liver failure score (CLIF-C ACLFs). A lactate-adjusted CLIF-C ACLFs was developed (CLIF-C ACLFs_Lact ), which performed significantly better than the original CLIF-C ACLFs in prediction of 28-day mortality in the derivation and validation cohort. Conclusion: Lactate levels appropriately reflect severity of disease and organ failure and were independently associated with short-term mortality in critically ill patients with liver cirrhosis. Lactate is a simple but accurate prognostic marker, and its incorporation improved performance of CLIF-C ACLFs significantly.

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.

Lessons learnt from managing a case of dengue hemorrhagic fever complicated with acute liver failure and acute kidney injury: a case report

Background

Dengue is a common arboviral infection with a diverse spectrum of clinical manifestations. Dengue hemorrhagic fever is a more severe form of infection characterized by plasma leak and hemoconcentration. Although hepatic dysfunction is common in dengue illness, massive liver necrosis is rarely reported. Lactic acidosis is a poor prognostic marker in liver failure related to dengue. Management of acute renal injury in dengue hemorrhagic fever due to prolonged shock is challenging as the fluid reabsorption during the recovery phase expands the intravascular volume and precipitates heart failure and pulmonary edema.

Case presentation

We report the case of a 43-year-old Sri Lankan Sinhalese woman with serologically confirmed dengue fever presenting with evidence of plasma leakage developing acute liver failure evidenced by deranged liver functions, coagulopathy, and altered sensorium and acute kidney injury with anuria. She had elevated serum lactate levels. In addition to the “standard care,” she was managed with intravenously administered N-acetyl cysteine and blood transfusions, even in the absence of bleeding or dropping packed cell volume, targeting a higher packed cell volume anticipating a better oxygenation at tissue level. Continuous veno-venous hemodialysis was employed and continued for 138 hours removing the fluids reabsorbed during the recovery phase to prevent her from developing heart failure and pulmonary edema. She made full recovery with no sequelae.

Conclusions

N-acetyl cysteine and packed cell transfusion aiming at a higher packed cell volume to maintain adequate tissue perfusion during shock may be beneficial in acute liver failure due to dengue virus. The use of a continuous form of renal replacement such as continuous veno-venous hemodialysis is of paramount importance in managing fluid states in the recovery phase of dengue hemorrhagic fever in those with renal impairment. Interesting observations made in the fluid dynamics during the reabsorption phase need further studies preferably with an animal model.

The Science and Translation of Lactate Shuttle Theory

Once thought to be a waste product of anaerobic metabolism, lactate is now known to form continuously under aerobic conditions. Shuttling between producer and consumer cells fulfills at least three purposes for lactate: (1) a major energy source, (2) the major gluconeogenic precursor, and (3) a signaling molecule. "Lactate shuttle" (LS) concepts describe the roles of lactate in delivery of oxidative and gluconeogenic substrates as well as in cell signaling. In medicine, it has long been recognized that the elevation of blood lactate correlates with illness or injury severity. However, with lactate shuttle theory in mind, some clinicians are now appreciating lactatemia as a "strain" and not a "stress" biomarker. In fact, clinical studies are utilizing lactate to treat pro-inflammatory conditions and to deliver optimal fuel for working muscles in sports medicine. The above, as well as historic and recent studies of lactate metabolism and shuttling, are discussed in the following review.

Repeat lactate level predicts mortality better than rate of clearance

BACKGROUND

Lactate clearance has been developed into a marker of resuscitation in trauma, but no study has compared the predictive power of the various clearance calculations. Our objective was to determine which method of calculating lactate clearance best predicted 24-hour and in-hospital mortality after injury.

STUDY DESIGN

Retrospective chart review of patients admitted to a Level-1 trauma center directly from the scene of injury from 2010 to 2013 who survived >15min, had an elevated lactate at admission (≥3mmol/L), followed by another measurement within 24h of admission. Lactate clearance was calculated using five models: actual value of the repeat level, absolute clearance, relative clearance, absolute rate, and relative rate. Models were compared using the areas under the respective receiver operating curves (AUCs), with an endpoint of death at 24h and in-hospital mortality.

RESULTS

3910 patients had an elevated admission lactate concentration on admission (mean=5.6±3.0mmol/L) followed by a second measurement (2.7±1.8mmol/L). Repeat absolute measurement best predicted 24-hour (AUC=0.85, 95% CI: 0.84-0.86) and in-hospital death (AUC=0.77; 95% CI, 0.76-0.78). Relative clearance was the best model of lactate clearance (AUC=0.77, 95% CI: 0.75-0.78 and AUC=0.705, 95% CI: 0.69-72, respectively) (p<0.0001 for each). A sensitivity analysis using a range of initial lactate measures yielded similar results.

CONCLUSIONS

The absolute value of the repeat lactate measurement had the greatest ability to predict mortality in injured patients undergoing resuscitation.

Acid-base disorders in liver disease

Alongside the kidneys and lungs, the liver has been recognised as an important regulator of acid-base homeostasis. While respiratory alkalosis is the most common acid-base disorder in chronic liver disease, various complex metabolic acid-base disorders may occur with liver dysfunction. While the standard variables of acid-base equilibrium, such as pH and overall base excess, often fail to unmask the underlying cause of acid-base disorders, the physical-chemical acid-base model provides a more in-depth pathophysiological assessment for clinical judgement of acid-base disorders, in patients with liver diseases. Patients with stable chronic liver disease have several offsetting acidifying and alkalinising metabolic acid-base disorders. Hypoalbuminaemic alkalosis is counteracted by hyperchloraemic and dilutional acidosis, resulting in a normal overall base excess. When patients with liver cirrhosis become critically ill (e.g., because of sepsis or bleeding), this fragile equilibrium often tilts towards metabolic acidosis, which is attributed to lactic acidosis and acidosis due to a rise in unmeasured anions. Interestingly, even though patients with acute liver failure show significantly elevated lactate levels, often, no overt acid-base disorder can be found because of the offsetting hypoalbuminaemic alkalosis. In conclusion, patients with liver diseases may have multiple co-existing metabolic acid-base abnormalities. Thus, knowledge of the pathophysiological and diagnostic concepts of acid-base disturbances in patients with liver disease is critical for therapeutic decision making.

Modified model for end-stage liver disease improves short-term prognosis of hepatitis B virus-related acute-on-chronic liver failure

AIM

To investigate whether the short-term prognosis of hepatitis B virus (HBV)-related acute-on-chronic liver failure (ACLF) could be improved by using a modified model for end-stage liver disease (MELD) including serum lactate.

METHODS

This clinical study was conducted at the First Affiliated Hospital, Fujian Medicine University, China. From 2009 to 2015, 236 patients diagnosed with HBV-related ACLF at our center were recruited for this 3-month follow-up study. Demographic data and serum lactate levels were collected from the patients. The MELD scores with or without serum lactate levels from survival and non-survival groups were recorded and compared.

RESULTS

Two hundred and thirty-six patients with HBV-ACLF were divided into two groups: survival group (S) and non-survival group (NS). Compared with the NS group, the patients in survival the S group had a significantly lower level of serum lactate (3.11 ± 1.98 vs 4.67 ± 2.43, t = 5.43, P < 0.001) and MELD score (23.33 ± 5.42 vs 30.37 ± 6.58, t = 9.01, P = 0.023). Furthermore, serum lactate level was positively correlated with MELD score (r = 0.315, P < 0.001). Therefore, a modified MELD including serum lactate was developed by logistic regression analysis (0.314 × lactate + 0.172 × MELD - 5.923). In predicting 3-month mortality using the MELD-LAC model, the patients from the S group had significantly lower baseline scores (-0.930 ± 1.34) when compared with those from the NS group (0.771 ± 1.32, t = 9.735, P < 0.001). The area under the receiver operating characteristic curve (AUROC) was 0.859 calculated by using the MELD-LAC model, which was significantly higher than that calculated by using the lactate level (0.790) or MELD alone (0.818). When the cutoff value was set at -0.4741, the sensitivity, specificity, positive predictive value and negative predictive value for predicting short-term mortality were 91.5%, 80.10%, 94.34% and 74.62%, respectively. When the MELD-LAC scores at baseline level were set at -0.5561 and 0.6879, the corresponding mortality rates within three months were 75% and 90%, respectively.

CONCLUSION

The short-term prognosis of HBV-related ACLF was improved by using a modified MELD including serum lactate from the present 6-year clinical study.

Perioperative Management of Lactic Acidosis in End-Stage Liver Disease Patient

Lactic acidosis (LA) in end-stage liver disease (ESLD) patients has been recognized as one of the most complicated clinical problems and is associated with increased morbidity and mortality. Multiple-organ failure, associated with advanced stages of cirrhosis, exacerbates dysfunction of numerous parts of lactate metabolism cycle, which manifests as increased lactate production and impaired clearance, leading to severe LA-induced acidemia. These problems become especially prominent in ESLD patients, that undergo partial hepatectomy and, particularly, liver transplantation. Perioperative management of LA and associated severe acidemia is an inseparable part of anesthesia, post-operative and critical care for this category of patients, presenting a wide variety of challenges. In this review, lactic acidosis applied pathophysiology, clinical implications for ESLD patients, diagnosis, role of intraoperative factors, such as anesthesia and surgery-related, vasoactive agents impact, and also current treatment options and modalities have been discussed.

EASL Clinical Practical Guidelines on the management of acute (fulminant) liver failure

The term acute liver failure (ALF) is frequently applied as a generic expression to describe patients presenting with or developing an acute episode of liver dysfunction. In the context of hepatological practice, however, ALF refers to a highly specific and rare syndrome, characterised by an acute abnormality of liver blood tests in an individual without underlying chronic liver disease. The disease process is associated with development of a coagulopathy of liver aetiology, and clinically apparent altered level of consciousness due to hepatic encephalopathy. Several important measures are immediately necessary when the patient presents for medical attention. These, as well as additional clinical procedures will be the subject of these clinical practice guidelines.

Alcohol consumption decreases lactate clearance in acutely injured patients

INTRODUCTION

Alcohol, a common risk factor for injury, has direct toxic effects on the liver. The use of lactate clearance has been well described as an indicator of the adequacy of resuscitation in injured patients. We investigated whether acutely injured patients with positive blood alcohol content (+BAC) had less lactate clearance than sober patients.

METHODS

We conducted a retrospective cohort study of acutely injured patients treated at an urban Level 1 trauma centre between January 2010 and December 2012. Blood alcohol and venous lactate levels were measured on all patients at the time of arrival. Study subjects were patients transported directly from the scene of injury, who had an elevated lactate concentration on arrival (≥3.0mmol/L) and at least one subsequent lactate measurement within 24h after admission. Lactate clearance ([Lactate1-Lactate2]/Lactate1) was calculated for all patients. Chi-squared tests were used to compare values from sober and intoxicated subjects. Lactate clearance was plotted against alcohol levels and stratified by age and Injury Severity Score (ISS).

RESULTS

Serial lactate concentration measurements were obtained in 3910 patients; 1674 of them had +BAC. Patients with +BAC were younger (mean age: 36.6 [SD 14.7] vs 41.0 [SD 19.9] years [p=0.0001]), were more often male (83.4% vs 75.9% [p=0.0001]), had more minor injuries (ISS<9) (33.8% vs 27.1% [p=0.0001]), had a lower in-hospital mortality rate (1.4% vs 3.9% [p=0.0001]), but also had lower average lactate clearance (37.8% vs 47.6% [p=0.0001]). The lactate clearance of the sober patients (47.6 [SD 33.5]) was twice that of those with +BAC >400 (23.5 [SD 6.5]). Lactate clearance decreased with increasing BAC irrespective of age and ISS.

CONCLUSIONS

In a large group of acutely injured patients, a dose-dependent decrease in lactate clearance was seen in those with elevated BAC. This relationship will cause a falsely elevated lactate reading or prolong lactate clearance and should be taken into account when evaluating patients with +BAC.

Arterial Lactate Concentration at the End of an Elective Hepatectomy Is an Early Predictor of the Postoperative Course and a Potential Surrogate of Intraoperative Events

OBJECTIVES

To test the prognostic impact of arterial lactate concentration at the end-of-surgery (LCT-EOS) on postoperative outcome after elective liver-resections and to identify the predictors of an increase in LCT-EOS.

BACKGROUND DATA

A recent systematic-review of risk-prediction-models for liver resections has evidenced their poor accuracy and a deficit in the evaluation of intraoperative events. LCT-EOS is a marker of impaired tissue oxygenation.

METHODS

This prospectively-designed study was based on a training-cohort of 519 patients and a validation-cohort of 466 patients. For each of the endpoints (high comprehensive complication index (CCI) scores, 90-day-mortality and severe-morbidity), prognostic-models were built by logistic-regression using the training-cohort. These models were thereafter tested in the validation-cohort and their performance (discrimination, accuracy, calibration) assessed. Independent predictors of LCT-EOS were also identified.

RESULTS

In the training-cohort, LCT-EOS cutoff best discriminating high-CCI, 90-day-mortality and severe-morbidity were 3, 3 and 2.8 mmol/L (and the corresponding AUROC 0.86, 0.87 and 0.76). LCT-EOS was an independent predictor of endpoints and adding LCT-EOS to the other predictors increased by 16.4%, 34.5% and 17.7% the accuracy of the models for high-CCI, 90-day-mortality and severe-morbidity, respectively. The models had high calibration and accuracy. Diabetes, repeat-hepatectomy, major-hepatectomy, synchronous-major-procedure, inflow-occlusion and blood-transfusion were independent predictors of LCT-EOS >3 mmol/L.

CONCLUSIONS

LCT-EOS >3 mmol/L is an early predictor of postoperative-outcome and should be used as a tool to determine patients requiring critical-care and as an endpoint in studies measuring the impact of perioperative interventions.

Management in acute liver failure

Acute liver failure (ALF) is a rare, potentially fatal complication of severe hepatic illness resulting from various causes. In a clinical setting, severe hepatic injury is usually recognised by the appearance of jaundice, encephalopathy and coagulopathy. The central and most important clinical event in ALF is occurrence of hepatic encephalopathy (HE) and cerebral edema which is responsible for most of the fatalities in this serious clinical syndrome. The pathogenesis of encephalopathy and cerebral edema in ALF is unique and multifactorial. Ammonia plays a central role in the pathogenesis. The role of newer ammonia lowering agents is still evolving. Liver transplant is the only effective therapy that has been identified to be of promise in those with poor prognostic factors, whereas in the others, aggressive intensive medical management has been documented to salvage a substantial proportion of patients. A small fraction of patients undergo liver transplant and the remaining are usually treated with medical therapy. Therefore, identification of the complications and causes of death in such patients, and use of appropriate prognostic models to identify those who need liver transplant and those who can be managed with medical treatment is a vital component of therapeutic strategy. In this review, we discuss the various pathogenetic mechanisms and treatment options available.

Analysis of predictors for lactate elimination after reperfusion in recipients of living-donor liver transplantation

BACKGROUND

Graft-recipient weight ratio (GRWR) is the only documented predictor that influences the lactate elimination after reperfusion in living-donor liver transplantation (LDLT). This study was performed to investigate the predictors of lactate elimination after reperfusion in recipients of adult LDLT.

METHODS

The medical records of 159 patients who underwent LDLT were analyzed. Lactate level (mmol/L) was measured from just before the initiation of surgery (P0) and 5, 60, and 120 minutes after reperfusion of graft (R0, R1, and R2, respectively). The change of lactate level after reperfusion was defined as difference between lactate level measured at R0 and R2. Patients were divided into accumulation and elimination groups. Donor and recipient factors were compared between the 2 groups.

RESULTS

Lactate accumulation occurred in 80 of 159 recipients (50.3%), and elimination occurred in 79 (49.7%). GRWR and Model for End-Stage Liver Disease (MELD) score were higher in the elimination group. Lactate at R0 was lower in the elimination group.

CONCLUSIONS

Higher GRWR and MELD score and lower lactate level immediate after reperfusion of graft were predictors of lactate elimination after reperfusion during adult LDLT.

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.

Etiology and therapeutic approach to elevated lactate levels

Lactate levels are commonly evaluated in acutely ill patients. Although most often used in the context of evaluating shock, lactate levels can be elevated for many reasons. While tissue hypoperfusion may be the most common cause of elevation, many other etiologies or contributing factors exist. Clinicians need to be aware of the many potential causes of lactate level elevation as the clinical and prognostic importance of an elevated lactate level varies widely by disease state. Moreover, specific therapy may need to be tailored to the underlying cause of elevation. The present review is based on a comprehensive PubMed search between the dates of January 1, 1960, to April 30, 2013, using the search term lactate or lactic acidosis combined with known associations, such as shock, sepsis, cardiac arrest, trauma, seizure, ischemia, diabetic ketoacidosis, thiamine, malignancy, liver, toxins, overdose, and medication. We provide an overview of the pathogenesis of lactate level elevation followed by an in-depth look at the varied etiologies, including medication-related causes. The strengths and weaknesses of lactate as a diagnostic/prognostic tool and its potential use as a clinical end point of resuscitation are discussed. The review ends with some general recommendations on the management of patients with elevated lactate levels.

Lactate metabolism in chronic liver disease

BACKGROUND

In the healthy liver there is a splanchnic net-uptake of lactate caused by gluconeogenesis. It has previously been shown that patients with acute liver failure in contrast have a splanchnic release of lactate caused by a combination of accelerated glycolysis in the splanchnic region and a reduction in hepatic gluconeogenesis.

AIMS

The aims of the present study were to investigate lactate metabolism and kinetics in patients with chronic liver disease compared with a control group with normal liver function.

METHODS

A total of 142 patients with chronic liver disease and 14 healthy controls underwent a liver vein catheterization. Blood samples from the femoral artery and the hepatic and renal veins were simultaneously collected before and after stimulation with galactose.

RESULTS

The fasting lactate levels, both in the hepatic vein and in the femoral artery, were higher in the patients than in the controls (P < 0.001) and there were a hepatic net-uptake of lactate in both groups. Fasting lactate concentrations correlated directly with the portal pressure, mean arterial blood pressure, and SaO2 and negatively with ICG clearance.

CONCLUSIONS

Lactate levels are elevated in cirrhotic patients compared to controls relating to portal pressure and aspects of liver dysfunction and the lactate levels seem to increase with the severity of cirrhosis. This may not be caused by decreased gluconeogenesis but merely be due to accelerated glycolysis in the splanchnic region. Future studies should focus on the impact of chronic liver disease on lactate kinetics.

Early lactate clearance as a reliable predictor of initial poor graft function after orthotopic liver transplantation

BACKGROUND

Initial poor graft function (IPGF) following orthotopic liver transplantation is a major determinant of postoperative survival and morbidity. Lactate clearance is a good marker of liver function. In this study, we investigated the clinical utility of early lactate clearance as an early and accurate predictor for IPGF following liver transplantation.

METHODS

This was a prospective observational study of 222 patients referred to the surgical intensive care unit (SICU) after orthotopic liver transplantation. The IPGF group consisted of patients with alanine aminotransferase (ALT) and/or aspartate aminotransferase (AST) >1500 IU/L within 72 hours after orthotopic liver transplantation. Early lactate clearance was defined as lactate at SICU presentation (hour 0) minus lactate at hour 6, divided by lactate at SICU presentation. The model for end-stage liver disease (MELD) score, Child-Pugh score and laboratory data including AST, ALT, total bilirubin (TB) and prothrombin time (PT) were recorded at SICU presentation and compared between the non-IPGF and IPGF groups. Receiver operating characteristic (ROC) curves were plotted to measure the performance of early lactate clearance, MELD score, Child-Pugh score, TB and PT.

RESULTS

IPGF occurred in 45 of the 222 patients (20.3%). The early lactate clearance in the non-IPGF group was markedly higher than that in the IPGF group (43.2+/-13.8% vs 13.4+/-13.7% P<0.001). The optimum cut-off value for early lactate clearance predicting IPGF was 24.8% (sensitivity 95.5%, specificity 88.9%). The area under the curve of the ROC was 0.961, which was significantly superior to MELD score, Child-Pugh score, TB and PT. Patients with early lactate clearance ≤24.8% had a higher IPGF rate (OR=169) and a higher risk of in-hospital mortality (OR=3.625).

CONCLUSIONS

Early lactate clearance can serve as a prompt and accurate bedside predictor of IPGF. Patients with early lactate clearance less than 24.8% are associated with a higher incidence of IPGF.

Management of hepatic encephalopathy

Hepatic encephalopathy (HE), the neuropsychiatric presentation of liver disease, is associated with high morbidity and mortality. Reduction of plasma ammonia remains the central therapeutic strategy, but there is a need for newer novel therapies. We discuss current evidence supporting the use of interventions for both the general management of chronic HE and that necessary for more acute and advanced disease.

The use of terlipressin during living donor liver transplantation: Effects on systemic and splanchnic hemodynamics and renal function

OBJECTIVES

To assess the effect of the intraoperative use of terlipressin on splanchnic hemodynamics and postoperative renal function in patients undergoing liver transplantation.

DESIGN

Open-label, prospective, randomized study.

SETTING

Single-center study.

PATIENTS

Thirty patients who underwent elective, living-donor liver transplantation with portal pressure >20 mm Hg.

INTERVENTIONS

Patients were assigned randomly to one of two equal groups. The control group received saline, whereas the treatment group (TP group) received an initial bolus dose of terlipressin (1 mg over 30 mins) followed immediately by a continuous infusion of 2 μg·kg(-1)·h(-1) for 48 hrs.

MEASUREMENTS AND MAIN RESULTS

Portal pressure and gas exchange (radial artery, portal vein, and hepatic vein, blood gas analyses, and lactate concentration) were assessed at baseline (after ligation of the hepatic artery) and 2 hrs after drug administration. Systemic hemodynamic data and calculated tissue oxygenation parameters were compared throughout the procedure. Renal function was assessed by measurement of serum cystatin C after induction of anesthesia and on the first 2 days postoperatively. After the infusion of terlipressin, portal venous pressure decreased significantly from 26.3 ± 3.3 to 21.3 ± 3.6 mm Hg (p < .001). The mean arterial pressure and systemic vascular resistance were significantly higher in the TP group than in the control group, whereas heart rate and cardiac index were comparable between the groups. Portal and hepatic base excess, and the level of serum lactate, did not differ between the two groups. The serum levels of both cystatin C and creatinine were significantly higher in the control group than in the TP group on postoperative day 2.

CONCLUSION

Perioperative use of terlipressin abrogates the early postoperative decline in renal function of patients who have chronic liver disease and undergo liver transplantation without any detrimental effect on hepatosplanchnic gas exchange and lactate metabolism.

Do bicarbonate-based solutions for continuous renal replacement therapy offer better control of metabolic acidosis than lactate-containing fluids?

INTRODUCTION

Evidence that bicarbonate haemofiltration and dialysate fluids are superior to lactate in patients with acute kidney injury treated by continuous renal replacement therapy (CRRT) remains controversial.

METHODS

We prospectively audited acid-base during the first 48 h of CRRT in 62 patients, using bicarbonate and lactate fluids.

RESULTS

Baseline lactate was greater in the bicarbonate group (4.76 ± 0.77 vs. 2.92 ± 0.5 mmol/l, p < 0.01), but pH, bicarbonate, chloride and base excess were similar. Lactate fell significantly in the bicarbonate group to 2.88 ± 0.3 mmol/l at 24 h and 2.39 ± 0.2 mmol/l at 48 h, but not in the lactate group. Base excess improved more with bicarbonate, median increase in the first 24 h was 51.6% (29.1-96.9) versus 18.5% (-5 to 55) with lactate and 74.2% (38.5-123) versus 36.1% (-3.6 to 68), p < 0.05 at 48 h. However, there were no significant differences in bicarbonate, chloride, pH, blood pressure and vasopressor requirements. 13.3% of patients were switched from lactate to bicarbonate fluids due to failure to correct acidosis. Subgroup analysis of 19 patients with liver failure showed similar results.

CONCLUSION

Bicarbonate fluids led to a more rapid fall in lactate and greater improvement in base excess during CRRT, but not overall control of acidosis.

Lactate kinetics in human tissues at rest and during exercise

Lactate production in skeletal muscle has now been studied for nearly two centuries and still its production and functional role at rest and during exercise is much debated. In the early days skeletal muscle was mainly seen as the site of lactate production during contraction and lactate production associated with a lack of muscle oxygenation and fatigue. Later it was recognized that skeletal muscle not only played an important role in lactate production but also in lactate clearance and this led to a renewed interest, not the least from the Copenhagen School in the 1930s, in the metabolic role of lactate in skeletal muscle. With the introduction of lactate isotopes muscle lactate kinetics and oxidation could be studied and a simultaneous lactate uptake and release was observed, not only in muscle but also in other tissues. Therefore, this review will discuss in vivo human: (1) skeletal muscle lactate metabolism at rest and during exercise and suggestions are put forward to explain the simultaneous lactate uptake and release; and (2) lactate metabolism in the heart, liver, kidneys, brain, adipose tissue and lungs will be discussed and its potential importance in these tissues.

Increase brain lactate in hepatic encephalopathy: cause or consequence?

Hepatic encephalopathy (HE) is a complex neuropsychiatric syndrome which develops as a result of liver failure or disease. Increased concentrations of brain lactate (microdialysate, cerebrospinal fluid, tissue) are commonly measured in patients with HE induced by either acute or chronic liver failure. Whether an increase in brain lactate is a cause or a consequence of HE remains undetermined. A rise in cerebral lactate may occur due to (1) blood-borne lactate (hyperlactataemia) crossing the blood-brain barrier, (2) increased glycolysis due to energy failure or impairment and (3) increased lactate production/release or decreased lactate utilization/uptake. This review explores the different reasons for lactate accumulation in the brain during liver failure and describes the possible roles of lactate in the pathogenesis of HE.

Current approach to intraoperative monitoring in liver transplantation

PURPOSE OF REVIEW

Although liver transplantation has become a standardized treatment and the only established definite therapy for end-stage liver disease it remains a unique clinical procedure. Increased understanding of the specific pathophysiological changes in end-stage liver disease and the transplantation procedure have led to the adaptation of concepts including overall monitoring of the patient and assessment of specific organ function.

RECENT FINDINGS

Major emphasis is placed on adequate monitoring during perioperative care of liver transplantation patients in order to ensure optimal hemodynamic and respiratory performance. The immediate assessment of metabolism and graft function will also serve to guide therapy according to the individual patient's needs.

SUMMARY

The evolution of monitoring during standardized liver transplantation, as well as currently recommended novel devices and concepts, are described and discussed.

Intensive care management of acute liver failure

PURPOSE OF REVIEW

The mortality of acute liver failure remains unacceptably high and liver transplantation is the only effective treatment available to date. This review focuses on new research developments in the field and aims to provide a pragmatic organ-based treatment approach for liver failure patients requiring intensive care support.

RECENT FINDINGS

The pathophysiological basis for cerebral edema formation in acute liver failure continued to be the focus of various investigations. In-vivo observations confirmed the link between ammonia, cerebral glutamine content and intracranial hypertension. The role of arterial ammonia as an important prognostic indicator formed the basis of prospective, observational studies. Reduced monocytic HLA-DR expression linked acute liver failure with poor prognosis, and the cerebral effects and side effects of vasoactive therapy with terlipressin were investigated with two studies showing contradictory results.

SUMMARY

Despite increased knowledge of the pathophysiological events leading to organ dysfunction in acute liver failure, supportive treatment options remain limited in their efficacy and largely noncurative.

Critical role of hypoxia and A2A adenosine receptors in liver tissue-protecting physiological anti-inflammatory pathway

Whole body exposure of wild type control littermates and A2A adenosine receptor (A2AR) gene deleted mice to low oxygen containing inspired gas mixture allowed the investigation of the mechanism that controls inflammatory liver damage and protects the liver using a mouse model of T cell-mediated viral and autoimmune hepatitis. We tested the hypothesis that the inflammatory tissue damage-associated hypoxia and extracellular adenosine --> A2AR signaling plays an important role in the physiological anti-inflammatory mechanism that limits liver damage during fulminant hepatitis. After induction of T cell-mediated hepatitis, mice were kept in modular chambers either under normoxic (21% oxygen) or hypoxic (10% oxygen) conditions for 8 h. It was shown that the whole body exposure to hypoxic atmosphere caused tissue hypoxia in healthy animals as evidenced by a decrease in the arterial blood oxygen tension and increase of the plasma adenosine concentration (P < 0.05). This "hypoxic" treatment resulted in significantly reduced hepatocellular damage and attenuated levels of serum cytokines in mice with acute liver inflammation. The anti-inflammatory effects of hypoxia were not observed in the absence of A2AR in studies of A2AR gene-deficient mice or when A2AR have been pharmacologically antagonized with synthetic antagonist. The presented data demonstrate that total body hypoxia-triggered pathway provides protection in acute hepatitis and that hypoxia (upstream) and A2AR (downstream) function in the same immunosuppressive and liver tissue-protecting pathway.

Prognostic implications of lactate, bilirubin, and etiology in German patients with acute liver failure

BACKGROUND & AIMS

Among the potentially helpful indicators of poor prognosis in acute liver failure (ALF) are etiology, encephalopathy grade, blood lactate, and King's College Criteria (KCC). The accuracy of these parameters in predicting transplantation or death shows significant variation in different countries.

METHODS

We retrospectively analyzed 102 patients with ALF treated at our institution between 1996 and 2005. Baseline parameters, simplified acute physiology score III (SAPS-III), KCC, Model for End-Stage Liver Disease (MELD) score, and a novel score of bilirubin, lactate, and etiology (BiLE score) were compared between transplant-free survivors and patients who required liver transplantation or died, by using multivariate linear regression analysis and receiver operating characteristics (ROC).

RESULTS

The most common causes of ALF were indeterminate liver failure (21%), acute hepatitis B (18%), acetaminophen ingestion (16%), and Budd-Chiari syndrome (9%). Transplantation-free survival was 38%, 44% of patients underwent liver transplantation, and 18% died without transplantation. Eight-week survival was 77%. The BiLE score was the best predictor of death or need of transplantation, with 79% sensitivity and 84% specificity. ROC analysis revealed a better performance of BiLE score when compared with bilirubin, lactate, MELD score, and SAPS-III (area under the curve: 0.87 +/- 0.04, 0.73 +/- 0.51, 0.73 +/- 0.52, 0.71 +/- 0.05, and 0.68 +/- 0.59, respectively).

CONCLUSIONS

The simple, combined BiLE score emerged as the best predictor of poor outcome in our patient cohort and should be prospectively evaluated in other populations.