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 ≥3.85 mmol/L was 23% (5% to 41%) more sensitive than an L/P ratio of ≥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.