Effects of volatile anesthetics on elastic stiffness in isometrically contracting ferret ventricular myocardium

of halothane, isoflurane, and sevoflurane on elastic stiffness, which reflects the degree of cross-bridge attachment, were studied in intact cardiac muscle. Electrically stimulated (0.25 Hz, 25°C), isometrically twitching right ventricular ferret papillary muscles (n 15) at optimal length (Lmax) were subjected to sinusoidal length oscillations (40 Hz, 0.25– 0.50 % of Lmax peak to peak). The amplitude and phase relationship with the resulting force oscillations was decom-posed into elastic and viscous components of total stiffness in real time. Increasing extracellular Ca2 concentration in the presence of anesthetics to produce peak force equal to control increased elastic stiffness during relaxation, which suggests a direct effect of halothane and sevoflurane on cross bridges. sinusoidal length oscillations; cross bridges; calcium THERE IS EVIDENCE THAT the volatile anesthetics halo