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Canadian Journal of Anesthesia, Vol 14, 69-78, Copyright © 1967 by Canadian Anesthesiologists' Society

The Effect of General Anaesthesia on the Tolerance of Cerebral Ischaemia in Rabbits

J. A. BAIN M.D.1, D. V. CATTON M.D., F.R.C.P.(C)1, J.M. R. COX M.D.1, and W. E. SPOEREL M.D., F.R.C.P.(C)1

1 Department of Anaesthesia and Department of Physiology, University of Western Ontario, London, Ontario

General anaesthesia has been reported to increase the tolerance to cerebral ischaemia. In rabbits the technique of inflating a pneumatic tourniquet around the neck was used to produce cerebral ischaemia for periods of three, six, nine, ten, or twelve minutes. A standard anaesthetic technique with nitrous-oxide-oxygen and succinylcholine was maintained for at least 45 minutes prior to this occlusion; potent anaesthetic agents (halothane, methoxyflurane, cyclopropane, and ether) were added for comparison, and these agents were also used in oxygen alone. Artificial ventilation through an orotracheal tube was maintained throughout the experiment until the recovery of reflexes and adequate spontaneous respiration. Normothermia was maintained, and pH and blood gases were kept in normal range. Blood pressure, E.E.G., and E.C.G. were recorded, and the absence of cortical electrical activity throughout the period of occlusion was considered evidence of cerebral ischaemia. The addition of halothane to the standard nitrous-oxide-oxygen mixture increased the 24-hour survival rate following three minutes of cerebral ischaemia from 36 to 95 per cent and following six minutes of cerebral ischaemia the survival rate was increased from 21 per cent to an average of 72 per cent by halothane, methoxyflurane, and cyclopropane. Only one of six unanaesthetized rabbits survived six minutes of ischaemia. Nitrous-oxide-oxygen supplemented by the same inhalation agents produced a survival rate of 57 per cent following nine minutes of ischaemia, and the survival rose to 67 per cent when these agents were used with oxygen alone. Further prolongation of the ischaemic period to ten and twelve minutes did not reduce this survival rate, but the neurological defects of 24 hours became increasingly severe. Survival was not influenced by the blood pressure level at the time of tourniquet release but was largely dependent on the duration of effective resuscitation measures such as artificial respiration and prolonged intubation in the post-ischaemic period.

Note:

Presented at the Annual Meeting of the Canadian Anaesthetists' Society in Banff, Alberta, June 1966.

Dr. Bain held a fellowship of the Medical Research Council in 1965; Dr. Cox was an M.R.C. Fellow in 1963-64.






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Copyright © 1967 by the Canadian Anesthesiologists' Society.