• A Laszlo, N Buljubasic, B Zsolnai, J P Kampine, and Z J Bosnjak.
• Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226.
• Am. J. Obstet. Gynecol. 1992 Sep 1; 167 (3): 804-10.

ObjectiveBoth volatile anesthetics and Ca2+ antagonists decrease uterine contractility. The interactive effects of anesthetics, verapamil, and ryanodine on myometrial muscular activity and on intracellular Ca2+ availability were examined.Study DesignThe effects of minimum alveolar concentrations of 0.5, 1.0, and 2.0 of halothane, enflurane, and isoflurane on electrically stimulated isometric mechanical activity of isolated longitudinal myometrium strips from 45 pregnant rats (15 to 21 days), superfused with Krebs' solution with or without 5.0 mmol/L Ca2+, 10(-7) and 10(-6) mol/L verapamil, and 10(-6) mol/L ryanodine, were compared. Analysis was performed by analysis of variance and Duncan test.ResultsAll three anesthetics and verapamil produced dose-dependent depression of contractility. Increasing the Ca2+ concentration from 2.5 to 5.0 mmol/L in the superfusate partly reversed the depression. An additive effect of verapamil and anesthetics, especially enflurane, on contractile force was observed. Ryanodine had no effect on contractility, but it could partly counteract the depressant effect of anesthetics.ConclusionClinically used concentrations of volatile anesthetics modify Ca2+ availability and depress uterine contractility. General anesthesia, especially by enflurane, in patients being treated with calcium antagonists may represent a higher risk.

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