In vitro comparison of output fluid temperatures for room temperature and prewarmed fluids.
Warming plastic bags containing intravenous solutions in a microwave oven (MWO) raised the temperature from 18 degrees C to an average of 34.1 degrees, 40.2 degrees, and 42.8 degrees C when treated for 120, 150, and 160 seconds, respectively. Fluids at 18 degrees C, when passed through a blood warmer, resulted in temperatures at the distal end (DE) of about 27 degrees C; but if the bags were priorly warmed to 42 degrees C, fluids arrived at the DE at a temperature of about 30 degrees C. Fluids heated by MWO to 42 degrees C through a single short tubing 180 cm long arrived at the DE at a temperature of 33.7 degrees C. Fluids administered at operating room ambient temperature of 18 degrees C arrived to the DE with a temperature of about 19 degrees C, thus most likely contributing to lowering the body temperature of traumatized patients treated with large volumes given at rapid flows. One group of 19 patients undergoing repair of injuries to extremities received infusions warmed by MWO to 42 degrees, while other groups received them at about 20 degrees. After an initial fall, average temperature in the former tended toward normal levels while in the latter, body temperature declined. The simple expedience of MWO warming of the bags to 42 degrees C, and flowing through shorter administration tubing, appears to ameliorate this complication and in some cases prevents it.