Correlation of metabolic acidosis with outcome following injury and its value as a scoring tool

This study looked at preresuscitation arterial pH as a predictor of outcome in injury. Seriously injured patients admitted to the Trauma Service over a 5-month period were evaluated prospectively. Data collected included basic patient demographics, initial arterial blood gas determinations (ABGs) including pH, bicarbonate (HCO3), base deficit or excess (BASE), admitting trauma score (TS), discharge injury severity score (ISS), total blood products used for initial resuscitation (TBP), and outcome. There were 191 patients averaging 34.7 years old with average TS 13.6, ISS 19.5, initial pH 7.38 +/- 0.09, HCO3 20.9 +/- 4.0, and BASE -3.3 +/- 4.7. The average TBP was 1309 cc, and overall mortality was 13/191 (6.8%). Comparing survivors to nonsurvivors, the ISS (18.2 vs. 38.3), TS (14.1 vs. 7.8), TBP (976 vs. 5881 cc), HCO3 (21.1 vs. 17.6), and BASE (-3.1 vs. -5.8) data were significantly different; pH (7.38 vs. 7.36) and age (34.4 vs. 38.5) were not. Using multiple regression with TBP as the dependent variable, BASE, age, TS, and to a lesser extent pH and HCO3 correlated (r = 0.536; p < 0.001); using outcome as the dependent variable, only TS and age correlated (r = 0.465; p < 0.0001). Although metabolic acidosis (pH, HCO3, BASE) predicts the TBP used, it does not improve on TS and age for predicting outcome.