Warming Characteristics of a Dual Reservoir Cooler/Heater Unit

A study of the Hematherm model 400 dual reservoir cooler/heater was undertaken to determine whether warming times are affected by running both the oxygenator heat exchanger and the warming blanket from a single warming source. Forty patients were divided into two groups of twenty each. Group A patients were warmed to 37°C using only the heat exchanger of the oxygenator. Group B patients were warmed using the oxygenator's heat exchanger and blanket simultaneously at the initiation of warming. There was no statistical difference between the two groups with regards to the patient's body weights, B.S.A.'s and bypass times. Group A showed a significantly faster rise in both arterial and venous blood temperatures. There was no statistical difference demonstrated for the rise in esophageal, bladder or the Hematherm model 400 unit temperatures. The heating blanket did not contribute to the warming of the patient. Using the data obtained from this study, a formula based on the rise in temperature corrected for B.S.A. was developed to predict the total time needed to warm any patient