The effect of pH versus base deficit on organ failure in trauma patients.

ABSTRACT

BACKGROUND: Base deficit (BD) calculations are affected by trauma-related changes in circulating concentrations of anions after injury. In contrast, pH is a direct measurement that corresponds to hypoperfusion. We hypothesized that changes in pH would more closely correspond to organ dysfunction compared with changes in BD. MATERIALS AND METHODS: BD and pH values were collected for the first 48 h after injury from a retrospective cohort of 74 multiply injured adult patients who were admitted to the surgical intensive care unit for a minimum of 1 wk. Mean and extreme (minimum pH and maximum BD) values of pH and BD were determined for day 1 (0-24 h) and for day 2 (24-48 h) after injury. Organ dysfunction was measured by averaging daily sequential organ failure assessment scores over the entire duration of intensive care unit admission. BD and pH values were compared with mean modified sequential organ failure assessment scores by univariate and multivariate linear regression. RESULTS: Organ dysfunction corresponded more closely with changes in pH compared with those in BD. Minimum pH and maximum BD showed better correspondence to organ dysfunction compared with mean values. Minimum pH values at 24-48 h had the highest univariate (r(2) = 0.43) correspondence to organ dysfunction. In contrast, mean BD values at 24-48 h showed no correspondence (r(2) = 0.07) to organ dysfunction. Multivariate analysis demonstrated that 24-48 h of minimum pH had the highest numerical effect on organ dysfunction. CONCLUSIONS: Correspondence between organ dysfunction and BD deteriorated in contrast to increasing correspondence between organ dysfunction and pH measured within 48 h after injury.