Cardiopulmonary bypass reduces the minimum alveolar concentration for isoflurane.
OBJECTIVE
The purpose of this investigation was to determine the influence of cardiopulmonary bypass (CPB) on the minimum alveolar concentration (MAC) of isoflurane in a rat model of CPB.


METHODS
Prospective.


METHODS
University research laboratory.


METHODS
Sprague-Dawley rats.


METHODS
Using tail-clamp methodology, the pre- and post-CPB MAC for isoflurane was studied.


RESULTS
Rats were anesthetized with isoflurane, intubated, ventilated, and surgically prepared for CPB, after which they were randomized to either Sham-operated or CPB groups. The CPB group (n = 10) underwent 90 minutes of normothermic nonpulsatile CPB. The Sham group (n = 13) were cannulated but did not undergo CPB. Pre- and post-CPB MAC determinations were compared within groups using a paired Student t test. The CPB group had a pre-CPB baseline isoflurane MAC of 1.09% +/- 0.11% versus 1.09% +/- 0.08% in the Sham group (p = 0.90). Twenty minutes after CPB, the CPB group exhibited a decrease in MAC to 0.98% +/- 0.14% (p = 0.0026, compared with baseline). The MAC in the Sham group was unchanged (p = 0.5852, compared with baseline). Two hours after CPB, the MAC in the CPB group remained lower compared with baseline at 0.99% +/- 0.14% (p = 0.0032).


CONCLUSIONS
CPB resulted in a small (10%) but significant reduction in the MAC for isoflurane. The mechanism behind this reduction in MAC is not clear but may be related to CPB-induced cerebral injury.
Yang
Hong
H
Department of Anesthesiology (Multidisciplinary Neuroprotection Laboratories), Duke University Medical Center, Durham, NC, USA.
Homi
H Mayumi
HM
Smith
Betty E
BE
Grocott
Hilary P
HP
D018685:Anesthetics, Inhalation / Q000493:pharmacokinetics*; D000818:Animals; D001831:Body Temperature / Q000502:physiology; D002315:Cardiopulmonary Bypass / Q000379:methods*; D006439:Hemodynamics / Q000502:physiology; D007442:Intubation, Intratracheal / Q000379:methods; D007530:Isoflurane / Q000493:pharmacokinetics*; D008297:Male; D023421:Models, Animal; D011650:Pulmonary Alveoli / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D018685:Anesthetics, Inhalation; D007530:Isoflurane