Military’s Early Use of Blood Transfusions Saved Lives of Wounded Warriors

By Brenda L. Mooney

SAN ANTONIO—Blood transfusion as quickly as possible was a lifesaver for wounded warriors in Afghanistan.

How important was it?

A study published in the Journal of the American Medical Association found that blood product transfusion within minutes of injury or prior to hospitalization was very significantly associated with greater 24-hour and 30-day survival than delayed or no transfusion in medically evacuated U.S. military combat casualties in Afghanistan.1

Background information in the article notes that hemorrhage is a leading cause of preventable death in both military and civilian trauma care.

Study authors led by Fort Sam Houston, TX, researchers pointed out early transfusion for hemorrhagic shock should improve survival, but that published data on prehospital transfusion had not demonstrated a survival advantage in previous studies.

Spc. Diana Fontenelle, medic, 3rd Squadron, 61st Cavalry Regiment, 4th Infantry Brigade Combat Team, 4th Infantry Division, preps blood for an incoming trauma patient in 2014 at the Destroyer Aid Station at Forward Operating Base Pasab, which was one of a few that could give blood transfusions, increasing the ability to stabilize patients. Photo by Sgt. Nelson Robles

For the study, the researchers focused on the association of prehospital transfusion and time to initial transfusion with injury survival. Included in the study were U.S. military combat casualties in Afghanistan between April 2012 and Aug. 7, 2015.

All participants were rescued alive by medical evacuation (MEDEVAC) from point of injury with either a traumatic limb amputation at or above the knee or elbow or shock, which was defined as a systolic blood pressure of less than 90 mm Hg or a heart rate greater than 120 beats per minute.

Complete data was available for 386 patients among the 400 patients within the matched groups. For them, prehospital transfusion was associated with a 74% lower risk of death over 24 hours, and a 61% lower risk of death over 30 days.

Results indicated that time to initial transfusion, whether given prehospital or during hospitalization, was associated with reduced 24-hour mortality only up to 15 minutes after MEDEVAC rescue—with a median of 36 minutes after injury.

“The findings support prehospital transfusion in this setting,” the authors wrote.

Researchers emphasized that results of the study should be interpreted within the context of the military trauma system in which the transfusions were given.

 

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.

“First, during the time frame of this study, the ‘golden hour rule’ was in effect, which had been mandated by the US Secretary of Defense,” they explained. “This policy prescribed that injured service members designated as urgent evacuation casualties arrive at a location equipped with surgical capability within one hour from the time of initial MEDEVAC request. The golden hour rule fueled expansion of the MEDEVAC service and forward-deployed surgical resources, resulting in the median total evacuation time of 47 minutes for patients in this study population.”

In addition, the study authors pointed out that military casualties receive prompt life-saving treatment at the point of injury from trained medical and nonmedical first responders with an initial emphasis on control of massive external hemorrhage, adding, “This is an advantage not currently available to most civilian trauma patients.”

Another advantage is that all deaths in the military population resulted in complete autopsy examinations, including prehospital deaths, they wrote.

“The increase in survival observed in this study is significant, consistent with a UK study of military casualties but distinct from civilian studies,” the article explained. “The conditional 30-day survival analysis among 24-hour survivors revealed how an approach used in some previous studies may be flawed. Excluding prehospital and early deaths within 24 hours of hospital admission, which are primarily due to hemorrhage may introduce survival bias, rendering the true association between injury mortality and early transfusion undetectable.”

Time to initiate transfusion during hospitalization could be shorter than the time to prehospital transfusion, so the researchers cautioned that it is critical to evaluate time to first transfusion without regard to location.

“Transfusion is a critical intervention in the treatment of hemorrhagic shock, however, the exact length of time to hemorrhagic death will vary for each individual patient depending on injury pattern and available hemorrhage-control capabilities,” they pointed out. “It may be challenging for civilian and immature military trauma systems to deliver transfusion resources in time to prevent exsanguination, especially with a tolerance margin as narrow as these results suggest.”

An accompanying editorial from by Eric A. Elster, MD, and Jeffrey Bailey, MD, of the Uniformed Services University of the Health Sciences, in Bethesda, MD, noted that, “Attempts to replicate this approach and determine the transferability of prehospital transfusion for severely injured civilian patients have so far been unsuccessful. This inability to demonstrate a benefit in civilian patients is related more to the variability of treatment in the prehospital system rather than the heterogeneity of civilian vs military patient populations. This suggests the need for a broader strategy that allows for adoption and dissemination of best practices (as was done with prehospital blood transfusion in combat zones) to bring these military advances into the larger civilian trauma care model.”2

The commentators also wrote that the study puts a spotlight on “the ongoing need for accurate data collection in combat zones to support the military’s efforts to continuously improve outcomes by assessing the effectiveness of previous care processes; and the imperative to bring this strategy home by developing a national trauma system that promotes bilateral exchange of information and expertise between military and civilian trauma and injury care systems.”

The editorial emphasizes that systematic data collection through the military Joint Trauma System was essential in in transforming combat casualty care in Iraq and Afghanistan, adding that a similar approach could benefit civilian trauma care.

Elster and Bailey said the report “also highlights the critical need for a national system to exist as a partner with the Joint Trauma System, one that leverages the lessons learned from combat and is able to validate and apply them when appropriate to civilian settings. Only such a systems-based approach will enable the large multicenter studies and interconnected data systems required to rapidly advance trauma care in the United States. With such a system in place, both civilian and military personnel involved in trauma care from the point of injury to postoperative recovery will have the insights, information, and skills to provide optimal care to every patient they encounter.”

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