Plasma lactate: Diagnostic and prognostic value

Effect of alcohol on the lactate/pyruvate ratio of recently injured adults

OBJECTIVE

To compare the ability of plasma (lactate) and the plasma lactate/pyruvate (L/P) ratio to predict shock-related outcome after injury and also to examine the influence of plasma ethanol on any relationships found.

DESIGN

Prospective observational study.

SETTING

Emergency departments in the UK and the Republic of South Africa.

PATIENTS

Blood samples were taken at presentation from 232 adult patients 1-23 hrs (median, 3.5 hrs) after sustaining an injury or injuries deemed sufficiently severe to require inpatient care.

MEASUREMENTS

Plasma concentrations of lactate, pyruvate, and ethanol, anatomical severity of injury, development of multiple organ failure, and 30-day survival were determined.

RESULTS

At 90% specificity for predicting subsequent mortality and/or multiple organ failure, plasma lactate >or=3.85 mmol/L was 23% (5% to 41%) more sensitive than an L/P ratio of >or=42.76. At 90% sensitivity for ruling out morbidity, plasma lactate <1.6 mmol/L is 6% (-1% to 13%) more specific than an L/P ratio of <14.08. High L/P ratios were noted to be associated with a detectable plasma alcohol level. A post hoc regression analysis showed that alcohol-positive/-negative status was a much stronger predictor of the L/P ratio than was anatomical severity of injury, shock, or time after injury.

CONCLUSIONS

Plasma lactate alone is a better predictor than the L/P ratio of shock-related outcome after injury. The interpretation of L/P ratios after injury is confounded in the presence of elevated plasma ethanol.

Hyperlactatemia during acute severe asthma

OBJECTIVE

To evaluate arterial lactate levels during treatment of acute severe asthma (ASA) and the prognostic value of arterial hyperlactatemia in ASA.

DESIGN

Prospective study.

SETTING

A respiratory intensive care unit (ICU) of a university hospital.

PATIENTS

29 consecutive patients admitted to the ICU for ASA not intubated on admission and with a peak expiratory flow (PEF) < 150 l/min or an arterial carbondioxide tension (PaCO2) > 40 mm Hg. All patients received standardized treatment during the first 24 h including i.v. and nebulized salbutamol, i.v. theophylline, and dexamethasone.

MEASUREMENTS AND RESULTS

Arterial lactate levels were serially measured by an enzymatic method during the first 24 h following admission. On admission, the mean arterial lactate level was 3.1 +/- 0.38 mmol/l (range 1.1-10.4); 17 patients (59%) had arterial hyperlactatemia with a lactate level > 2 mmol/l. No difference was found in lactate levels between patients with progressively worsening asthma and those with an acute onset of severe asthma. No correlation was found between arterial lactate levels on admission, on the one hand, and respiratory rate (RR), heart rate, PEF, pH, PaCO2, arterial oxygen tension, potassium, phosphorus, creatine kinase, or transaminase values on admission, on the other hand. All patients developed an important but transient increase in arterial lactate levels during treatment, with a peak at 7.72 +/- 0.46 mmol/l and a mean elevation of 4.62 +/- 0.45 mmol/l (range 0.4-12.1), from the initial admission value contrasting with a significant clinical improvement assessed by RR, PEF, and arterial blood gas parameters.

CONCLUSION

This study suggests that, in ASA, arterial hyperlactatemia is frequently present on admission to the ICU. Delayed hyperlactatemia is a constant finding during treatment of ASA. Initial or delayed hyperlactatemia seems of no prognostic value because none of the patients required mechanical ventilation. The effects of therapy for acute asthma on lactate metabolism still need to be studied.