Muscle Relaxers: References

- Updated on August 3, 2021

Gencarelli PJ, Swen J, Koot HW, Miller RD, The effects of hypercarbia and hypocarbia on pancuronium and vecuronium neuromuscular blockades in anesthetized humans, Anesthesiology. 1983 Nov;59(5):376-80.
To determine the effects of hypercarbia and hypocarbia on a pancuronium or vecuronium neuromuscular blockade, 54 patients were anesthetized with halothane and 60% nitrous oxide in oxygen. In 30 patients, end-tidal PCO2 was maintained at either 25 mmHg (3.5 kPa, N = 10), 41 mmHg (5.5 kPa, N = 10), or 56 mmHg (7.5 kPa, N = 10). Five patients in each group then were given pancuronium or vecuronium 0.022 mg/kg iv. Neither maximal depressions of twitch tension nor recovery indexes (time for spontaneous recovery of twitch tension from 25 to 75% of control) were altered by hypercarbia or hypocarbia. The remaining 24 patients were divided into three equal groups. Either pancuronium (N = 8) or vecuronium (N = 8) was administered iv as continuous infusion at a rate sufficient to produce a 50% depression of twitch tension. In the remaining eight patients, no muscle relaxant was given. After twitch tension was stable, half of the patients in each group had hypercarbia induced, which depressed twitch tension in all three groups. The patients who received vecuronium had a significantly larger decrease in twitch tension than those who received pancuronium or no muscle relaxant. Conversely, in the remaining patients, hypocarbia produced a significant increase in twitch tension. There was no difference in the magnitude of the increases in twitch tension among the three groups. The authors conclude that pre-muscle relaxant administration-induced hypercarbia or hypocarbia has no effect on a subsequent neuromuscular blockade from pancuronium or vecuronium.

Hoylea G, The action of carbon dioxide gas on an insect spiracular muscle, Journal of Insect Physiology, Volume 4, Issue 1, March 1960, Pages 63-79
Zoology Department, University of Glasgow, Scotland
Carbon dioxide gas in low concentrations causes the relaxation of the closer muscle of the spiracle of Schistocerca gregaria in the face of continued motor nervous excitation. The gas acts directly on events in the neuromuscular transmission sequence. It causes the magnitudes of the junctional potentials and of the twitch tension to fall, the extent of the fall increasing as the carbon dioxide concentration increases. It was not found possible to relate the change in tension exactly to the change in electrical potential.

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