Peripheral temperature monitoring during cardiopulmonary bypass operation

Almost one-third of 24 adult patients undergoing hypothermic cardiopulmonary bypass (CPB) for elective cardiac operation were found to have upper extremity skin and muscle temperatures of 30.0 degrees C or less at termination of CPB despite the return of nasopharyngeal temperature to normal values. Within 45 minutes, the mean nasopharyngeal temperature of these patients fell spontaneously from 37.1 degrees +/- 0.3 degrees C (+/- standard deviation) to 35.1 degrees +/- 0.4 degrees C, a significantly greater fall (p less than 0.005) than was observed for patients with extremity temperatures greater than 30.0 degrees C. Persistent hypothermia of the upper extremities correlated statistically with large body mass; it appears that these patients incur disproportionately large caloric debts during hypothermic CPB. Inadvertent hypothermia after CPB can be minimized if both core and extremity temperatures are utilized to provide an assessment of the adequacy of warming prior to return to spontaneous circulation.