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Ketamine enhances Phase I and Phase II neuromuscular block of succinylcholine


The effect of intravenous injection of ketamine 2, 5 and 10 mg·kg-1 on the neuromuscular blocking action of succinylcholine was studied on the indirectly stimulated adductor pollicis muscle twitch of monkeys anaesthetized with 0.5-1.0 per cent halothane in oxygen. Neuromuscular block was quantified by single twitches evoked at 0.l Hz. The changing nature of neuromuscular block from Phase I to Phase II was monitored periodically by train-of-four fade. In the absence of succinylcholine, ketamine had no consistent neuromuscular effect of its own. In the presence of succinylcholine, ketamine in a dosedependent manner potentiated both the Phase I and the Phase II neuromuscular blocking effect of succinylcholine. In Phase I, 2 mg·kg-1 of ketamine reduced the ED50 of succinylcholine from 0.46 ± 0.07mg·kg-1 to 0.33 ± 0.06mg·kg-1 (P <0.01), and increased its 25-75 per cent recovery index from 4.0 ± 0.4 min to 5.3 ±0.1 min (P < 0.01). In Phase II, ketamine in the same dose deepened a steady neuromuscular block maintained by succinylcholine infusion from 48 ± 3 per cent block to 71 ± 2 per cent block (P < 0.01). We concluded that ketamine potentiates the Phase I and the Phase II neuromuscular blocks of succinylcholine.


Ľeffet de ľinjection intraveineuse de kétamine 2, 5 et 10 mg·kg-1 sur ľaction de la succinylcholine a été étudié chez des singes anesthésiés avec 0.5-1.0 pour cent ďhalothane. Le changement du bloc neuromusculaire a été quantifié par des twitch simples évoqués à 0.1 Hz. Ľaltération du bloc neuromusculaire de la Phase I à la Phase II a été surveillé périodiquement par ľobservation du fade lors ďune ondée-de-quatre. En ľabsence de succinylcholine, la kétamine ne présentait aucun effet neuromusculaire. En présence de succinylcholine la kétamine selon la dose, a potentialisé ľeffet neuromusculaire de la succinylcholine tant sur la Phase 1 que sur la Phase II. Dans la Phase 1, 2 mg·kg-1 de kétamine a réduit la ED50 de la succinylcholine de 0.46 ± 0.07 mg·kg-1 à 0.33 ± 0.06 mg·kg-1 (P < 0.01), et augmenta le 25-75 pour cent ďindex de récupération de 4.0 ± 0.4 min. à 5.3 ± 0.1 min. (P < 0.01). Dans la Phase II, la kétamine à une dose identique a approfondi le bloc neuromusculaire maintenu par la perfusion de succinylcholine de 48 ± 3 pour cent à 71 ± 2 pour cent (P < 0.01). On onclut que la kétamine potentialisé la Phase I et la Phase II du bloc neuromusculaire produit par la succinylcholine.


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Correspondence to Shen Kou Tsai or Chingmuh Lee or Barry Tran.

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Tsai, S.K., Lee, C. & Tran, B. Ketamine enhances Phase I and Phase II neuromuscular block of succinylcholine. Can J Anaesth 36, 120–123 (1989).

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Key words

  • interactions (drug): succinylcholine-ketamine
  • neuromuscular relaxants: succinylcholine
  • depolarizing block
  • Phase II block