title: Relation between isoflurane concentration, body temperature and EEG variables during hypothermic cardiopulmonary bypass in juvenile sheep.
abstract: Isolation of lungs from the circulation during cardiopulmonary bypass (CPB) results in the loss of end-tidal anaesthetic measurement as a monitor of anaesthetic depth. The objective of our study was to test whether the isoflurane concentration measured at the oxygenator exhaust (ISO(PO-OX)) could be used as an alternative. Five juvenile ewes were anaesthetised for experimental aortic valve replacement during hypothermic CPB. One sheep recovered from anaesthesia with signs of CNS excitement and was excluded from electroencephalogram (EEG) data analysis. ISO(PO-OX) was similar to the end-tidal anaesthetic concentration measured before start of CPB (ISO(ET(PRE-CPB))) and was positively correlated (P<0.001; R=0.431) to the bypass temperature (T(CPB)). EEG burst suppression ratio was negatively correlated with the oesophageal temperature (T(ESO)) (P=0.002; R=0.433) whilst data analysis revealed only a weak association between EEG variables and ISO(PO-OX). Therefore, EEG monitoring may be the only valuable quantitative measure of adequate anaesthetic depth during hypothermic CPB.
authors.affiliation: Central Laboratory Animal Facility, Hannover Medical School, Hannover, Germany. otto.klaus@mh-hannover.de
authors.forename: Klaus A
authors.initials: KA
authors.lastname: Otto
authors.forename: Hans-Klaus
authors.initials: HK
authors.lastname: Höffler
authors.forename: Serghei
authors.initials: S
authors.lastname: Cebotari
authors.forename: Igor
authors.initials: I
authors.lastname: Tudorache
mesh_terms: D000818:Animals; D001831:Body Temperature; D002315:Cardiopulmonary Bypass / Q000379:methods*; D004569:Electroencephalography; D005260:Female; D007036:Hypothermia, Induced; D007530:Isoflurane / Q000008:administration & dosage; D016343:Monitoring, Intraoperative / Q000379:methods*; D012756:Sheep
chemical_list: D007530:Isoflurane