Blood lactate monitoring in critically ill patients: a systematic health technology assessment. Crit Care Med. 2009;37:2827-2839. [PMID: 19707124 DOI: 10.1097/ccm.0b013e3181a98899]

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.

Outcome effectiveness of the severe sepsis resuscitation bundle with addition of lactate clearance as a bundle item: a multi-national evaluation

Introduction

Implementation of the Surviving Sepsis Campaign (SSC) guidelines has been associated with improved outcome in patients with severe sepsis. Resolution of lactate elevations or lactate clearance has also been shown to be associated with outcome. The purpose of the present study was to examine the compliance and effectiveness of the SSC resuscitation bundle with the addition of lactate clearance.

Methods

This was a prospective cohort study over 18 months in eight tertiary-care medical centers in Asia, enrolling adult patients meeting criteria for the SSC resuscitation bundle in the emergency department. Compliance and outcome results of a multi-disciplinary program to implement the Primary SSC Bundle with the addition of lactate clearance (Modified SSC Bundle) were examined. The implementation period was divided into quartiles, including baseline, education and four quality improvement phases.

Results

A total of 556 patients were enrolled, with median (25th to 75th percentile) age 63 (50 to 74) years, lactate 4.1 (2.2 to 6.3) mmol/l, central venous pressure 10 (7 to 13) mmHg, mean arterial pressure (MAP) 70 (56 to 86) mmHg, and central venous oxygen saturation 77 (69 to 82)%. Completion of the Primary SSC Bundle over the six quartiles was 13.3, 26.9, 37.5, 45.9, 48.8, and 54.5%, respectively (P <0.01). The Modified SSC Bundle was completed in 10.2, 23.1, 31.7, 40.0, 42.5, and 43.6% patients, respectively (P <0.01). The ratio of the relative risk of death reduction for the Modified SSC Bundle compared with the Primary SSC Bundle was 1.94 (95% confidence interval = 1.45 to 39.1). Logistic regression modeling showed that the bundle items of fluid bolus given, achieve MAP >65 mmHg by 6 hours, and lactate clearance were independently associated with decreased mortality - having odds ratios (95% confidence intervals) 0.47 (0.23 to 0.96), 0.20 (0.07 to 0.55), and 0.32 (0.19 to 0.55), respectively.

Conclusions

The addition of lactate clearance to the SSC resuscitation bundle is associated with improved mortality. In our study patient population with optimized baseline central venous pressure and central venous oxygen saturation, the bundle items of fluid bolus administration, achieving MAP >65 mmHg, and lactate clearance were independent predictors of outcome.

[Objectives of hemodynamic resuscitation]

Cardiovascular failure or shock, of any etiology, is characterized by ineffective perfusion of body tissues, inducing derangements in the balance between oxygen delivery and consumption. Impairment in oxygen availability on the cellular level causes a shift to anaerobic metabolism, with an increase in lactate and hydrogen ion production that leads to lactic acidosis. The degree of hyperlactatemia and metabolic acidosis will be directly correlated to the development of organ failure and poor outcome of the individuals. The amount of oxygen available at the tissues will depend fundamentally on an adequate level of perfusion pressure and oxygen delivery. The optimization of these two physiologic parameters can re-establish the balance between oxygen delivery and consumption on the cellular level, thus, restoring the metabolism to its aerobic paths. Monitoring variables such as lactate and oxygen venous saturations (either central or mixed) during the initial resuscitation of shock will be helpful to determine whether tissue hypoxia is still present or not. Recently, some new technologies have been developed in order to evaluate local perfusion and microcirculation, such as gastric tonometry, near-infrared spectroscopy and videomicroscopy. Although monitoring these regional parameters has demonstrated its prognostic value, there is a lack of evidence regarding to its usefulness during the resuscitation process. In conclusion, hemodynamic resuscitation is still based on the rapid achievement of adequate levels of perfusion pressure, and then on the modification of oxygen delivery variables, in order to restore physiologic values of ScvO(2)/SvO(2) and resolve lactic acidosis and/or hyperlactatemia.

Biomarkers for pediatric sepsis and septic shock

Sepsis is a clinical syndrome defined by physiologic changes indicative of systemic inflammation, which are likely attributable to documented or suspected infection. Septic shock is the progression of those physiologic changes to the extent that delivery of oxygen and metabolic substrate to tissues is compromised. Biomarkers have the potential to diagnose, monitor, stratify and predict outcome in these syndromes. C-reactive protein is elevated in inflammatory and infectious conditions and has long been used as a biomarker indicating infection. Procalcitonin has more recently been shown to better distinguish infection from inflammation. Newer candidate biomarkers for infection include IL-18 and CD64. Lactate facilitates the diagnosis of septic shock and the monitoring of its progression. Multiple stratification biomarkers based on genome-wide expression profiling are under active investigation and present exciting future possibilities.

Mild hypothermia therapy reduces blood glucose and lactate and improves neurologic outcomes in patients with severe traumatic brain injury

PURPOSE

The study aimed to investigate the association between blood glucose or lactate and the outcomes of severe traumatic brain injury (TBI), and to evaluate the effect of mild hypothermia therapy on glucose and lactate levels.

METHODS

Eighty-one patients with TBI were randomly divided into normothermia (n = 41) and mild hypothermia (n = 40) group. Body temperature of hypothermia group was maintained at 32.7°C for 72 hours. Arterial blood glucose and lactic acid were determined before and after hypothermia therapy. Glasgow Outcome Scale (GOS) score was assessed 3 months after the treatment.

RESULTS

The mean glucose (7.04 ± 0.51 vs 9.71 ± 1.63 mmol/L, P < .05) in the hypothermia group was lower than in the normothermia group after hypothermia therapy. There were more patients with good neurologic function (GOS 4-5) in the hypothermia group than in the normothermia group (75.0% vs 51.2%, P = .038). Multivariate regression analysis showed that blood glucose greater than 10 mmol/L (adjusted risk ratio, 5.7; 95% confidence interval, 1.4-13.2; P < .05) was an independent predictor for poor neurologic outcomes in these patients, and hypothermia therapy was an independent predictor for favorable outcomes (risk ratio, 4.9; 95% confidence interval, 1.0-15.6; P < .05). No significant association between lactate and GOS scores was identified in the multivariate analysis.

CONCLUSION

Hyperglycemia after TBI was associated with poor clinical outcomes, but the predictive value of blood lactate level requires further investigation. Hypothermia therapy improves neurologic outcomes in patients with severe TBI, and reduction in blood glucose may be partially responsible for the improved outcomes.

Clinical correlates of arterial lactate levels in patients with ST-segment elevation myocardial infarction at admission: a descriptive study

Introduction

Blood lactate measurements can be used as an indicator of hemodynamic impairment and relate to mortality in various forms of shock. Little is known at the moment concerning the clinical correlates of systemic lactate in patients with ST-segment elevation myocardial infarction (STEMI).

Methods

To assess the relation of systemic arterial lactate levels in STEMI patients with clinical correlates at presentation in the catheterization laboratory, we measured arterial lactate levels with a rapid point-of-care technique, immediately following femoral sheath insertion. The study population (n= 1,176) was divided into tertiles with lactate levels ≤1.1 (n = 410), 1.2 to 1.7 (n = 398) and ≥1.8 mmol/l (n = 368). We compared both baseline characteristics and outcome measures of the three lactate groups.

Results

Factors independently associated with higher lactate levels were hypotension, heart rate, thrombolysis in myocardial infarction (TIMI) flow 0 to 1, diabetes and non-smoking. Mortality at 30 days in the three groups was 2.0%, 1.5% and 6.5%. The latter group also showed lower blush grades and greater enzymatic infarct sizes. An intra aortic balloon pump (IABP) was used more frequently in patients with higher lactate levels (4.2%, 7.6% and 14.7%).

Conclusions

In STEMI patients, impaired hemodynamics, worse TIMI flow and non-smoking were related to increased arterial lactate levels. Higher lactate levels were independently related with 30-day mortality and an overall worse response to percutaneous coronary intervention (PCI). In particular, acute mortality was related to admission lactates ≥1.8 mmol/L. Point-of-care measurement of arterial lactate at admission in patients with STEMI has the potential to improve acute risk stratification.

Association of blood lactate with type 2 diabetes: the Atherosclerosis Risk in Communities Carotid MRI Study

BACKGROUND

Accumulating evidence implicates insufficient oxidative capacity in the development of type 2 diabetes. This notion has not been well tested in large, population-based studies.

METHODS

To test this hypothesis, we assessed the cross-sectional association of plasma lactate, an indicator of the gap between oxidative capacity and energy expenditure, with type 2 diabetes in 1709 older adults not taking metformin, who were participants in the Atherosclerosis Risk in Communities (ARIC) Carotid MRI Study.

RESULTS

The prevalence of type 2 diabetes rose across lactate quartiles (11, 14, 20 and 30%; P for trend <0.0001). Following adjustment for demographic factors, physical activity, body mass index and waist circumference, the relative odds of type 2 diabetes across lactate quartiles were 0.98 [95% confidence interval (CI) 0.59-1.64], 1.64 (95% CI 1.03-2.64) and 2.23 (95% CI 1.38-3.59), respectively. Furthermore, lactate was associated with higher fasting glucose among non-diabetic adults.

CONCLUSIONS

Plasma lactate was strongly associated with type 2 diabetes in older adults. Plasma lactate deserves greater attention in studies of oxidative capacity and diabetes risk.

Techniques to assess tissue oxygenation in the clinical setting

The microcirculation plays an essential role in health and disease. Microvascular perfusion can be assessed directly using laser Doppler flowmetry and various imaging techniques or indirectly using regional capnometry and measurement of indicators of mismatch between oxygen delivery and oxygen consumption or indices of disturbed cellular oxygen utilization. Assessment of microvascular oxygen availability implies measurement of oxygen pressure or measurement of hemoglobin oxygen saturation. Microvascular function is assessed using other methods, including venous plethysmography. In this paper, I review current knowledge concerning assessment of the microcirculation with special emphasis on methods that could be used at the bedside.

Early lactate-guided therapy in intensive care unit patients: a multicenter, open-label, randomized controlled trial

RATIONALE

It is unknown whether lactate monitoring aimed to decrease levels during initial treatment in critically ill patients improves outcome.

OBJECTIVES

To assess the effect of lactate monitoring and resuscitation directed at decreasing lactate levels in intensive care unit (ICU) patients admitted with a lactate level of greater than or equal to 3.0 mEq/L.

METHODS

Patients were randomly allocated to two groups. In the lactate group, treatment was guided by lactate levels with the objective to decrease lactate by 20% or more per 2 hours for the initial 8 hours of ICU stay. In the control group, the treatment team had no knowledge of lactate levels (except for the admission value) during this period. The primary outcome measure was hospital mortality.

MEASUREMENTS AND MAIN RESULTS

The lactate group received more fluids and vasodilators. However, there were no significant differences in lactate levels between the groups. In the intention-to-treat population (348 patients), hospital mortality in the control group was 43.5% (77/177) compared with 33.9% (58/171) in the lactate group (P = 0.067). When adjusted for predefined risk factors, hospital mortality was lower in the lactate group (hazard ratio, 0.61; 95% confidence interval, 0.43-0.87; P = 0.006). In the lactate group, Sequential Organ Failure Assessment scores were lower between 9 and 72 hours, inotropes could be stopped earlier, and patients could be weaned from mechanical ventilation and discharged from the ICU earlier.

CONCLUSIONS

In patients with hyperlactatemia on ICU admission, lactate-guided therapy significantly reduced hospital mortality when adjusting for predefined risk factors. As this was consistent with important secondary endpoints, this study suggests that initial lactate monitoring has clinical benefit. Clinical trial registered with www.clinicaltrials.gov (NCT00270673).