Fingertip temperature during cardiopulmonary bypass.

Temperature changes in the nasopharynx, fingertip, forearm and extracorporeal circuit were continuously monitored, starting 10 min before and up to 16 min into the rewarming period of hypothermic (32 degrees C) cardiopulmonary bypass in 14 patients operated on for coronary artery revascularization. Arterial blood temperature was the first to increase after starting rewarming, followed by the nasopharynx and the fingertip temperatures. Fingertip temperature started to increase abruptly 6.2 (2.02 SD) min after rewarming started. At this point, nasopharyngeal temperature was 34.2 degrees C (1.42 SD) and took a further 8.3 min to reach 37 degrees C. Assuming that increasing fingertip temperature indicates a central thermoregulatory response to warming, we suggest that nasopharyngeal temperature is a poor monitor of brain temperature. We also suggest that fingertip temperature may be used to monitor the point at which cerebral temperature reaches 'normothermia'. Further body warming, using arterial temperatures > or = 39 degrees C, should be avoided because of the danger of brain hyperthermia.