Performance comparison of improvised prehospital blood warming techniques and a commercial blood warmer

Prehospital transfusion of packed red blood cells (PRBC) may be life saving for hypovolaemic trauma patients. PRBCs should preferably be warmed prior to administration but practical prehospital devices have only recently become available. The effectiveness of purpose designed prehospital warmers compared with previously used improvised methods of warming has not previously been described.

Expired units of PRBCs were randomly assigned to a warming method in a bench study. Warming methods were exposure to body heat of an investigator, leaving the blood in direct sunlight on a dark material, wrapping the giving set around gel heat pads or a commercial fluid warmer (Belmont Buddy Lite). Methods were compared with control units that were run through the fluid circuit with no active warming strategy.

The mean temperature was similar for all methods on removal from the fridge (4.5°C). The mean temperatures (degrees centigrade) for all methods were higher than the control group at the end of the circuit (all P≤0.001). For each method the mean (95% CI) temperature at the end of the circuit was; body heat 17.2 (16.4-18.0), exposure to sunlight 20.2 (19.4-21.0), gel heat pads 18.8 (18.0-19.6), Buddy Lite 35.2 (34.5-36.0) and control group 14.7 (13.9-15.5).

All of the warming methods significantly warmed the blood but only the Buddy Lite reliably warmed the blood to a near normal physiological level. Improvised warming methods therefore cannot be recommended.