Pre-hospital trauma care: a proposal for more efficient evaluation

Although mortality is an important outcome parameter for pre-hospital trauma care, it is influenced by many factors other than pre-hospital trauma care alone. We therefore studied an alternative method to evaluate pre-hospital trauma care by calculating the change in probability of survival (Ps) according to the TRISS methodology, before and directly after the pre-hospital trauma care. Correlations between patient characteristics and a change in Ps were assessed. Further, required sample sizes were calculated for an 80% power to detect a hypothetical 3% reduction in mortality and the corresponding change in Ps. In 140 of 191 patients with an Injury Severity Score > or =16, the Ps did not change. In 36, the Ps increased and in 15 patients, the Ps decreased. Between these three groups, significant differences were found in Revised Trauma Score and age, but no clear differences in Injury Severity Score or mortality. A 3% difference in mortality would require 6800 patients, in contrast to 3500 when the change in Ps was the primary outcome parameter. A change in Ps is a promising outcome parameter for a more efficient evaluation of pre-hospital trauma care. A good collaboration is, however, required between ambulance services and the trauma center for reliable registration.