Tissue heat content and distribution during and after cardiopulmonary bypass at 17 degrees C.
We measured afterdrop and peripheral tissue temperature distribution in eight patients cooled to approximately 17 degrees C during cardiopulmonary bypass and subsequently rewarmed to 36.5 degrees C. A nasopharyngeal probe evaluated trunk and head temperature and heat content. Peripheral tissue temperature (arm and leg temperature) and heat content were estimated using fourth-order regressions and integration over volume from 30 tissue and skin temperatures. Peripheral tissue temperature decreased to 19.7+/-0.9 degrees C during bypass and subsequently increased to 34.3+/-0.7 degrees C during 104+/-18 min of rewarming. The core-to-peripheral tissue temperature gradient was -5.9+/-0.9 degrees C at the end of cooling and 4.7+/-1.5 degrees C at the end of rewarming. The core-temperature afterdrop was 2.2+/-0.4 degrees C and lasted 89+/-15 min. It was associated with 1.1+/-0.7 degrees C peripheral warming. At the end of cooling, temperatures at the center of the upper and lower thigh were (respectively) 8.0+/-5.2 degrees C and 7.3+/-4.2 degrees C cooler than skin temperature. On completion of rewarming, tissue at the center of the upper and lower thigh were (respectively) 7.0+/-2.2 degrees C and 6.4+/-2.3 degrees C warmer than the skin. When estimated systemic heat loss was included in the calculation, redistribution accounted for 73% of the afterdrop, which is similar to the contribution observed previously in nonsurgical volunteers.


CONCLUSIONS
Temperature afterdrop after bypass at 17 degrees C was 2.2+/-0.4 degrees C, with approximately 73% of the decrease in core temperature resulting from core-to-peripheral redistribution of body heat. Cooling and rewarming were associated with large radial tissue temperature gradients in the thigh.
Rajek
A
A
Department of Cardiothoracic and Vascular Anesthesia, University of Vienna, Austria.
Lenhardt
R
R
Sessler
D I
DI
Grabenwöger
M
M
Kastner
J
J
Mares
P
P
Jantsch
U
U
Gruber
E
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000758:Anesthesia; D001132:Arm; D001831:Body Temperature; D002315:Cardiopulmonary Bypass; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007036:Hypothermia, Induced; D007432:Intraoperative Period; D007866:Leg; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal; D011184:Postoperative Period; D017694:Rewarming; D012881:Skin Temperature; D013816:Thermodynamics; D013997:Time Factors