INTRODUCTION: Blood lactate concentration predicts mortality in neonates, 
infants, children and adults, with evidence that it has better predictive power 
than other markers of acid-base status such as absolute base excess or pH.
OBJECTIVE: To investigate whether blood lactate concentration on admission 
predicts mortality in paediatric intensive care and if its addition can improve 
the performance of the Paediatric Index of Mortality 2 (PIM2) mortality 
prediction score.
DESIGN AND SETTING: Retrospective cohort study in one 20-bed UK paediatric 
intensive care unit (PICU) using data from the PICU clinical and blood gas 
analyser databases between 2006 and 2010. Only cases with a blood lactate 
concentration measured at the same time as the PIM2 variables were included. 
Logistic regression was used to assess if blood lactate concentration predicted 
mortality independently of PIM2, adjusting for potential confounders, and if it 
could replace absolute base excess in the PIM2 model.
RESULTS: There were 155 deaths amongst 2,380 admissions (6.5 %). Admission 
lactate in non-survivors was higher than in survivors (mean [standard deviation, 
SD]) 6.6 [5.6] versus 3.0 [2.5] mmol/l, had a positive association with 
mortality [adjusted odds ratio (OR) for death per unit (mmol/l)] increase 1.11 
[95 % confidence interval (CI) 1.06-1.16; p < 0.001] and significantly improved 
the model fit of PIM2 when it replaced absolute base excess (p < 0.001).
CONCLUSIONS: PICU admission blood lactate concentration predicts mortality 
independently of PIM2. Given the limitations of this study, a prospective 
multi-centre evaluation is required to establish whether it should be added to 
the PIM2 model with or without replacement of base excess.