Canadian Journal of Anesthesia, Vol 9, 408-413, Copyright © 1962 by Canadian Anesthesiologists' Society

Succinylcholine-Induced Bradycardia with Reference to Methoxyflurane Anaesthesia

¹ Department of Anaesthesia, University of Alberta Hospital Edmonton, Alberta

Healthy adolescent or adult patients were premedicated with morphine or meperidine, and atropine or hyoscine, and anaesthetized with a sequence thiopentone, nitrous oxide, oxygen, methoxynurane. They were arbitrarily divided into three groups and intravenous injections of 2 c.c. 2 per cent succinylcholine given according to three different sequences: (1) immediately following the thiopentone and four minutes later; (2) four and eight minutes after the thiopentone, (3) eight and twelve minutes after the thiopentone. A fourth group was added, for which a sequence similar to sequence 2 was useifl except that, prior to the second injection of succinylcholine, a second injection of thiopentone, one-third of the amount used for induction, was given.

The existing reports of succinylcholine-induced bradycardia and arrhythmias are discussed with reference to the results. The conclusions reached are that the administration of succinylcholine 2 per cent when thiopentone is omitted for induction, or used in minimal dosage not immediately preceding the injection of the relaxant, should be done with caution. The hazard is very small except in those patients suffering from cardiac dysfunction or electrolyte disturbances. A further dose of succinylcholine markedly increases the danger unless prophylactic measures are taken, and a larger dose initially may have a similar effect.

The anaesthesia sequence producing the most marked bradycardia and arrhythmia is unusual in clinical practice and when it is used additional thiopentone is often given. These facts probablv account for the low incidence of serious complications of this nature.