CHICAGO (October 24, 2007) -- Combat physicians in war-torn areas like Iraq and Afghanistan may be able to accurately predict which casualties require massive blood transfusions (MT), and thereby increase a soldier's chances of survival, according to research published in the October issue of The Journal of the American College of Surgeons. The study found that the presence of a combination of three variables -- assessed immediately upon arrival at the combat support hospital -- is highly predictive of which soldiers will need MT, thus allowing physicians to mobilize the necessary resources to transfuse large amounts of blood. The three variables are hemoglobin 11g/dL, International Normalized Ratio > 1.5, and a penetrating injury mechanism such as those caused by improvised explosive devices (IEDs) or high-powered weapons.
Hemorrhage (blood loss) is the leading cause of death on the battlefield. Severely injured patients require MT to restore adequate delivery of oxygen to the body. "The sooner we know that a solider needs a massive blood transfusion, the better," said Martin A. Schreiber, MD, FACS, chief of trauma at Oregon Health & Science University, Portland. "Since we have limited access to blood products in combat hospitals and we rely heavily on walking blood banks, it is crucial to be able to mobilize these precious resources early after patients are injured."
Identifying donors and then testing their blood for viruses like hepatitis C and HIV can take up to one hour, a critical period of time in a severely injured patient.
This retrospective cohort analysis included 558 combat victims treated at two combat support hospitals in Iraq. Patients who required MT (n=247), defined as delivery of 10 units of a combination of stored red blood cells and fresh whole blood in the first 24 hours after injury, were compared with patients who did not (n=311). Potentially predictive variables studied were age, gender, mechanism of injury, International Normalized Ratio (INR, the ratio of a patient's prothrombin time to a normal, or control, sample that is used to determine the blood's tendency to clot), prothrombin time, partial thromboplastin time, hemoglobin level and platelet count.
Based on a stepwise logistic regression analysis, a hemoglobin level 11 grams/deciliter (g/dL), INR >1.5 and a penetrating injury mechanism (e.g., injuries resulting from improvised explosive devices (IEDs) and high-powered weapons), were found to be independently predictive of the need for MT. The single most predictive variable was a hemoglobin level 11 g/dL, with an odds ratio of 7.7. Researchers determined that a combination of these three variables reliably predicts the need for MT.
Dr. Schreiber added that this work is a unique addition to the literature on predictors of MT because the study population consisted primarily of young male patients with injuries sustained by IEDs and high-powered weapons, which is quite different from a typical civilian population. Despite these facts, mortality in the MT group was identical to the mortality reported by a recently published study from a large civilian center.
Researchers also found that coagulopathy (a defect in the body's blood clotting process) occurs early after injury in severely injured combat victims and is associated with the need for MT and high mortality. Mortality was 39 percent in the MT group and 1 percent in the non-MT group (p<0.001).
The primary finding of this study is that the combination of hemoglobin 11 g/dL, INR > 1.5, and a penetrating mechanism reliably predict the need for MT. Using rapid laboratory technology, these variables are available within a few minutes of the patients' arrival, allowing the treating physicians to organize the resources necessary to deal with an MT patient. Dr. Schreiber is a Lieutenant Colonel in the Unites States Army Reserve.
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