Prediction of mortality after major burn: physiological versus biochemical measures

Objective. To compare the predictive power of serum lactic acid (LA) and physiological score (Tobiasen's Abbreviated Burn Severity Index [ABSI]) after major burn. This prospective, analytical study was conducted at the Liaquat University of Medical and Health Sciences (LUMHS) Burn Unit (Jamshoro, Pakistan) from June 2007 to May 2008.

Eighty adult patients presenting with burn injury of varying etiology with body surface area (BSA) of ≥ 20% were enrolled in the study. The outcome measures included acute phase death (≤ 3 days), and death within first week, second week, and fourth week of admission. The ABSI score and lactate values were stratified into 4 groups to facilitate comparison. The correlation of outcome variables with independent variables was analyzed to measure linear association with Pearson's correlation coefficient. The proportionality of differences in hazard ratios was tested by the Cox proportional hazard method. The receiver-operator characteristics (ROC) curve analysis using the area under the curve (AUC) was determined using ABSI ≥ 12 and LA ≥ 4.0 mmol/L as a cutoff for a "positive test."

The mean age of patients (47 men and 33 women) was 31 years. The mean body surface area affected was 42%. Mean BSA affected for patients who died was 64.9%. A statistically significant negative correlation of death during acute phase death and within the first week of admission was observed for LA compared to ABSI. When the Cox proportional hazard model was constructed, LA was found to be statistically significant (P = 0.001). The difference between areas under receiver-operator characteristics (AUROC) was insignificant. Considering ABSI and LA 4 mmol/L or greater as a "positive test," LA was found to have a sensitivity of 89.7% at 100% specificity, while ABSI has a 79.3% sensitivity at 100% specificity.

This study has once again shown the clinical usefulness of ABSI. Measurement of serum LA has emerged as a new promising approach and a predictive tool for early death after major burn.