Predictive accuracy of the TRISS survival statistic is improved by a modification that includes admission pH

To determine if pH measured at the time of hospital admission and corrected for PCO2 was an independent predictor of trauma survival.

Phase 1 was a retrospective case-control analysis of 1708 patients, followed by multivariate multiple logistic regression analysis of a subset of 919 patients for whom the Revised Trauma Score (RTS), Injury Severity Score (ISS), and pH were available. Phase 2 was a prospective comparison of a mathematical model of survival derived in phase 1 (pH-TRISS) with the TRISS method in 508 of 1325 subsequently admitted trauma patients.

Urban level 1 trauma center.

All patients admitted with blunt or penetrating trauma during the study period.

Survival vs mortality.

In phase 1, factors significantly associated with mortality by t test and chi 2 analysis included the RTS, ISS< Glasgow Coma Scale, corrected pH (CpH), and sum of the head, chest, and abdominal components of the Abbreviated Injury Scale-85 (AIS85) (HCAISS) (for all, P < .0001). The TRISS statistic was also a significant predictor of survival (P < .004). Age, sex, and the extremity and soft tissue components of the AIS85 were not associated with mortality. In a multivariate analysis of the RTS, HCAISS, and CpH, all were significant predictors of mortality. Even when controlling for RTS and HCAISS, CpH remained a significant predictor of mortality (P < .008). In phase 2, when pH-TRISS was tested prospectively against TRISS in a new group of patients, the new statistic appeared to provide a more accurate prediction of survival.

The arterial pH measurement obtained on hospital arrival and corrected for PCO2 is a significant independent predictor of survival and adds to the predictive accuracy of the TRISS survival statistic. Age, sex, and the extremity and soft tissue components of the AIS85 did not contribute to the accuracy of the TRISS statistic in this patient population.