Why We Do What We Do: Warming Blood During Transfusion in Trauma

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The other night we had a trauma resuscitation that went very well. In the course of the resuscitation, blood was hung as the patient’s blood pressure dropped after being tachycardic. We were not attentive to warm the blood during its administration. The question arose, why do we need to rewarm blood? I wanted to get an EBM answer and didn’t have it at the tip of my tongue…so I hit the journals. This is what I found:

Massive Transfusion of Blood in the Surgical Patient – Surgical Clin of N Amer 2012

The point of giving blood is to restore an effective volume to achieve end-organ perfusion. Transfusion is to be done in such a way to avoid a lethal triad: acidosis, hypothermia and coagulopathy. I want to focus on hypothermia here in this review. As per the article, hypothermia in all cases less than 32 degrees C causes an increase in mortality by 21%. In trauma, one article suggests the mortality rate rises to 100% independent of all other factors. Due to the decreased enzymatic function at lower temperatures (remember biochemistry with denaturation?) the coagulation cascade is altered. Studies have shown at 35 degrees Celsius our PT and PTT are increased. Other clotting factors including Factor VIIa (which may also have some benefit as an adjunct administered with other blood products in trauma) have decreased function. Von Willebrand Factor as well has decreased efficacy and results in poor platelet adhesion and activation. As per the article, and I quote, “For every 1oC drop in core temperature of the patient there is a 10% reduction in coagulation factor activity.

In other words…if we are resuscitating patient, especially in a massive transfusion protocol where a patient will be receiving more than 10 units of blood, the blood needs to be rewarmed or else they are going to DIE! Please let me know what you think and check out this article because it addresses a lot of great information regarding transfusion including ratios of blood products, effects of academia, TRALI and the military history behind transfusion.

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