Depressant effect of anesthetics and calcium antagonists on uterine contractility is thought to be related in interaction with calcium. The effects of halothane (HAL), enflurane (HNF) and isofluranc (ISO) nn mechanical activity of longitudinal myometrium strips (0.3 × 10 mm) from pregnant rats were compared at levels equivalent to 0.5, 1 and 2 MAC (minimum alveolar concentration) for the rat at 2.5 or 5.0 mM Ca2+ concentrations. Tissues were supertused with Krebs solution containing 2.5 or 5.0 mM Ca2+, with or without anesthetics and 10-6 M verapamil. Mechanical responses to electrical stimuli (1 Hz) were recorded isometrically using a force displacement transducer Results (contractile force as a percentage of control) were expressed as mean ± SEM. Raising the external calcium concentration from 0.5 to 5 mmol/I. increased contractile force. All three anesthetics, even at low concentrations, significantly depressed contractility. The extent ot contractile depression was greatest in the presence ot HAL and least with ISO. Depression of contractions was smaller at all levels of anesthetics al 5.0 mM Ca2+ Verapamil caused a dose-dependent depression ni uterine contractility. The interaction of verapamil and volatile anesthetics was found to he additive. With verapamil in the superfusate ENF exerted the most depressant effect. We conclude that clinically used concentrations of volatile anesthetics modify Ca2+ availability and depress uterine contractility, most likely by affecting calcium intlux into the myoplasm. General anesthesia, especially by ENF. in patients being treated with verapamil may represent a higher risk.
|Publication status||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology