Prediction of Mortality After Major Burn: Physiological Versus Biochemical Measures
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Abstract: Objective. To compare the predictive power of serum lactic acid (LA) and physiological score (Tobiasen’s Abbreviated Burn Severity Index [ABSI]) after a 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. Methods. Eighty adult patients presenting with burn injuries 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.” Results. 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. Conclusion. 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.
Address correspondence to:
Dr. SM Tahir, FCPS
Department of Plastic & Burn Surgery
Liaquat University of Medical & Health Sciences
Jamshoro
35 Gulshan-e-Yasin, Unit No. 09
Latifabad, Hyderabad, Sindh
Pakistan
Phone: 0300-3018532
E-mail: Syedsahib1@yahoo.com
Although the chances of survival after burn injury have steadily increased over the last 3 decades, the prediction of mortality from burn injury is still a subject of interest for burn surgeons. This is due to the fact that an accurate method that quantitatively summarizes severity of burn injuries has various practical applications. It provides clinicians not only a base for clinical decisions, but also assists in understanding the relative contributions of different prognostic criteria. These estimates would also be useful to patients’ families and medical professionals making medical and financial decisions regarding their care.1 The simplest formula for the prediction of mortality from burns should be based on a minimal set of easily obtainable variables. A classic example that calculates the percent likelihood of mortality is the patient’s age in years plus the percentage of the body-surface area (BSA) that was burned.2 This formula, while easy to remember, is only useful for early outcomes assessment and has various limitations regarding long-term survival or mortality prediction. The Abbreviated Burn Severity Risk Index (ABSI)3 has been a more reliable and more frequently used formula in clinical practice for more than 15 years.
Mortality prediction in individual patients by any scoring system is limited and in general, no better than good clinical judgment. Therefore, decisions for individual patients should never be based solely on a statistically derived injury severity score.
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