23 Mar 10
By A Nichol, M Egi, V Pettila, R Bellomo, C French, G Hart et al
Higher lactate concentrations within the normal reference range (“relative hyperlactatemia”) are not considered clinically significant. We tested the hypothesis that relative hyperlactatemia is independently associated with an increased risk of hospital death.
Retrospective observational study of prospectively obtained intensive care database of 7155 consecutive critically ill patients admitted to the Intensive Care Units (ICUs) of four Australian university hospitals. We assessed the relationship between ICU admission (LacADM), maximal (LacMAX) and time-weighted (LacTW) lactate levels and hospital outcome in all patients and in those patients whose LacADM (n=3964), LacMAX (n=2511) and LacTW (n=4584) lactate was under 2 mmol.L-1 (relative hyperlactatemia).
We obtained 172,723 lactate measurements. Higher LacADM and LacTW concentration within the reference range was independently associated with increased hospital mortality (LacADM: odds ratio (OR) 2.1, 95% confidence interval (CI) 1.3-3.5, P=0.01; LacTW OR 3.7, 95% CI 1.9-7.00, P<0.0001). This significant association was first detectable at lactate concentrations > 0.75 mmol.L-1. Furthermore, in patients whose lactate never exceeded 2 mmol.L-1, higher LacTW remained strongly associated with higher hospital mortality (LacTW OR 4.8, 95% CI 1.8-12.4, P<0.001).
In critically ill patients, relative hyperlactataemia is independently associated with increased hospital mortality. Blood lactate concentrations >0.75 mmol.L-1 can be used by clinicians to identify patients at higher risk of death. The current reference range for lactate in the critically ill may need to be re-assessed.