Figure 3. Mortality of Prehospital Transfusion Recipients vs Matched Nonrecipients.

Adjusted mortality curves were estimated by Cox proportional hazards modeling at the median value of each covariate. The median values for the matching factors were set as follows: (1) 0, explosives for mechanism of injury; (2) 1, yes for documented prehospital shock; (3) 2, two or more traumatic limb amputations below the knee or elbow, or 1 above the knee or elbow; (4) 1, Abbreviated Injury Scale score for head injury of 2; and (5) 1, yes for hemorrhagic torso injuries. The median values for the additional covariates were set as follows: age of 26 years, injury year of 2012, US Army DUSTOFF transport team, yes for prehospital tourniquet, and 29 minutes from injury occurrence to medical evacuation rescue. There were no patients lost to follow-up and the median survival times were 1440 minutes (24 hours) for the 24-hour survival analysis and 30 days for the 30-day survival analysis. HR indicates hazard ratio.