title: Cardiopulmonary bypass reduces the minimum alveolar concentration for isoflurane.
abstract: 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.
authors.affiliation: Department of Anesthesiology (Multidisciplinary Neuroprotection Laboratories), Duke University Medical Center, Durham, NC, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.forename: H Mayumi
authors.initials: HM
authors.lastname: Homi
authors.forename: Betty E
authors.initials: BE
authors.lastname: Smith
authors.forename: Hilary P
authors.initials: HP
authors.lastname: Grocott
mesh_terms: 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
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane