In the PAMPer study of airlifted patients, mortality at 30 days was 23.2 percent among the people who received two units of thawed plasma versus 33.0 percent with standard care (P=0.03).

The research team estimated that when other factors such as prehospital red-cell transfusion are taken into account, the administration of prehospital plasma cut the risk of death by 39 percent compared with standard care (P=0.02).

The improvement in survival became clear three hours after plasma administration began. Mortality at 24 hours and in-hospital mortality were also lower, they said.

In addition, the plasma group also had a lower median prothrombin time upon arrival at the trauma center and less need for a blood transfusion.

The PAMPer researchers found no evidence that prehospital plasma administration reduced the odds of multiorgan failure, transfusion-related reactions, respiratory distress syndrome, or nosocomial infections.

“Prespecified subgroup analyses showed a consistent survival benefit in the plasma group across various injury types, which suggests broad generalizability of the results,” the team concluded.

The 501 cases, most the result of a shooting, were taken from a pool of 7,275 patients transported from 27 air medical bases to nine trauma centers in five states.

Five patients who received plasma had a transfusion-related reaction or allergic reaction versus one patient who received standard care.

The process of giving plasma did not delay transport time to the hospital, which was a median of 42 minutes with plasma and 40 minutes with standard care.

In contrast, in the COMBAT study, 28-day mortality was 15 percent with plasma and 10 percent with control (P=0.37).

In all, 65 patients received plasma and 60 got saline, with 56 percent ultimately requiring a blood transfusion within six hours of injury.

All had a systolic blood pressure below 71 mmHg. Median transport time to the Denver Health Medical Center in Colorado was 19 minutes with plasma and 16 minutes with saline.

“Due to the consistent lack of differences in the analyses, the study was stopped for futility after 144 of 150 planned enrollments,” the researchers said.

“Blood products might be beneficial in settings with longer transport times, but the financial burden would not be justified in an urban environment with short distances to mature trauma centers,” they said.

COMBAT is the first randomized controlled test of prehospital plasma administration in an urban setting where a trauma center is nearby.

Twenty-one percent of the patients in the plasma group and 19 percent in the control group developed infections. The rate of thrombotic events did not differ between the two groups.