I.m. temperature probes were used in humans during and after hypotherm
ic cardiopulmonary bypass (CPB). After rewarming to apparent normother
mia of the body core, we found that the temperature of the vastus late
ralis muscle remained well below the nasopharyngeal temperature at the
time of weaning from bypass. This reduced muscle temperature represen
ts a considerable deficit in total body heat which may account for a l
arge proportion of the afterdrop in temperature which occurs in the po
stoperative period. There was no morbidity associated with the use of
the i.m. probes which could be incorporated into standard clinical pra
ctice.