The effect of isoflurane and temperature on the actions of muscle relaxants in rat in vitro

Anesthesia and Analgesia
L AzizM Hirakawa


Hypothermia and isoflurane alone increase the potencies of steroidal muscle relaxants (MRs). We studied the combined influence of isoflurane and hypothermia on MR potency. Phrenic nerve-hemidiaphragm preparations of rats were mounted in modified Krebs' solution and aerated with 5% CO2-95% O2 gas mixture at 37 degrees C and 4% CO2 at 27 degrees C to maintain the CO2 content constant. Phrenic nerves were stimulated with 0.1 Hz supramaximal impulses and elicited tension of the diaphragm was recorded. Isoflurane 1% was added after stabilization of twitch tension and MR was added 60 min later. Twitch tension was reduced by 20% +/- 2.5% at 37 degrees C and 3.5% +/- 0.7% at 27 degrees C from control with only isoflurane. The IC50 (inhibitory concentration, 50%) values of the MRs decreased significantly (P < 0.05) with isoflurane at both temperatures. The ratios of the IC50 values without and with isoflurane of the benzylisoquinolinium MRs were significantly more at both temperatures (P < 0.05) indicating the enhancement of potentiation of their action by isoflurane over steroidal MRs. When the soluble concentration of isoflurane at 27 degrees C was kept similar to that of at 37 degrees C, the ratios of all the MRs were reduced signifi...Continue Reading


Oct 1, 1987·Anesthesiology·J E CannonR D Miller
Jan 1, 1981·Anesthesia and Analgesia·L FarrellD R Waud
Jun 1, 1981·Anesthesia and Analgesia·R R Bartkowski, J C Horrow
May 28, 1958·The Journal of Physiology·B BIGLANDE ZAIMIS
Mar 1, 1946·British Journal of Pharmacology and Chemotherapy·E BULBRING


Jun 1, 1999·Canadian Journal of Anaesthesia = Journal Canadien D'anesthésie·A A AhmedY Amaki

Related Concepts

Neuromuscular Nondepolarizing Agents
Respiratory Diaphragm
Drug Augmentation
Muscle Relaxation Phase
Nerve-Muscle Preparation
Rats, Holtzman
Rats, Laboratory
In Vitro [Publication Type]

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