Effects of sevoflurane on the contractility of ferret ventricular myocardium

Isotonic and isometric variables of contractility and relaxation of isolated ferret right ventricular papillary muscles were measured before and during exposure to incremental concentrations of sevoflurane (0-4.9% vol/vol) (30 degreesC) (n = 9). In a second group of muscles (n = 8), effects of sevoflurane were compared with those of low [Ca2+](o) (0.45-2.25 mM in steps of 0.45 mM). Sevoflurane caused a reversible concentration-dependent decrease in contractility (ED50 of developed force 4.6 +/- 0.9% vol/vol). When compared with twitches of equal amplitude in low extracellular Ca2+ concentration, sevoflurane accelerated both isometric and isotonic relaxation. The myocardial depressant effect of sevoflurane is less than that of isoflurane and results mainly from a decrease of intracellular Ca2+ availability. The abbreviated isometric relaxation likely reflects a decrease in Ca2+ sensitivity and the faster isotonic relaxation may reflect a mild stimulation of Ca2+ uptake by the sarcoplasmic reticulum.