Lack of preconditioning against ischaemia-induced VF by isoflurane when used as the sole anaesthetic agent

Dr. Coker, Susan, Prof. Kane, Kathleen. University of Strathclyde SIPBS, 27 Taylor Street, Glasgow, G4 0NR, Great Britain.

The volatile anaesthetic, isoflurane, has been reported to have preconditioning effects. However, in most in vivo studies (e.g. Wang et al., 2006) it has been given in addition to the primary anaesthetic, thus lowering arterial blood pressure (BP) substantially during the preconditioning period. The aim of this work was to compare ischaemia-induced arrhythmias in rats anaesthetized with either isoflurane or sodium pentobarbital. Anaesthesia was induced in male Sprague-Dawley rats (401±24g) with sodium pentobarbital 60 mg/kg i.p. or by inhalation of 5% isoflurane in oxygen, reduced to 1.5 to 2.5% for maintenance (n=10 per group). Limb lead ECGs and carotid arterial BP were recorded. After commencing artificial ventilation, performing a left thoracotomy and placing a ligature around the left coronary artery, heart rate was 430±18 and 354±10* beats/min and mean BP was 125±11 and 102±4* mmHg in the pentobarbital and isoflurane groups respectively (*P<0.05, Mann-Whitney U test). After coronary artery occlusion the incidences of VT, VF and the mortality due to sustained VF were 100, 70 and 30% in the pentobarbital group and 100, 70 and 50% in the isoflurane group. In survivors the total numbers of VPBs (1001±268 (n=7) and 306±118 (n=5)) and duration of VT (69±25.2 and 9.8±6.1s) tended to be lower in the isoflurane group. This study demonstrated that anaesthesia with isoflurane, compared to pentobarbital, did not reduce the incidence of ischaemia-induced VT, VF or mortality but may limit the usefulness of the model for the study of ectopic activity.

Wang et al., (2006) Anesth. Analg. 103: 281-288.