Comparison of serum lactate and base excess in predicting the survival outcome in polytrauma patients

To determine the earlier and better prognostic marker between ‘blood lactate levels’ and base excess’ in polytrauma patients.

Additionally we sought to determine the effect of lactate normalisation time on outcome.

This is a prospective, non-interventional study conducted at our trauma centre after approval from our institutional ethical committee involving 60 polytrauma cases. Revised Trauma Score (RTS) and Injury Severity Score (ISS) on admission were calculated. Arterial blood samples for serum lactate and base excess levels at admission, every 12hours within first 48h after admission and one sample on third day were collected.

All continuous variables were expressed as mean ± standard deviation. They were compared using Student's t-test and Analysis of Covariance. Ability of individual variables in predicting mortality at different time points were compared using Receiver operating characteristic curves (ROC curves). Time to lactate clearance was analysed with outcome using chi-square for trend.

Serum lactate levels on admission were significantly different in non survivors compared to survivors (p=0.006). Base excess at 24 hours was significantly different in non survivors compared to survivors (p =0.012). Serum lactate at 24 h predicted mortality better [Area under the curve(AUC) 0.95 (Confidence interval(CI)-0.86 to 0.99)], than base excess at 24 h [AUC 0.72 (CI-0.59 to 0.83)], p<0.001. Time taken for lactate to normalise ²24 h, 25–48 h and >48 h were associated with mortality of 0%, 30% and 96% respectively.

Serum lactate is an early predictor of outcome compared to base excess. Patients with lactate normalisation time within 48 h had better outcome.