Why the study?
Do volatile anesthetics affect dynamic stiffness and shortening in intact mammalian ventricular muscle?
Do volatile anesthetics affect dynamic stiffness and shortening in intact mammalian ventricular muscle?
Volatile anesthetics decrease dynamic stiffness and shortening in cardiac muscle, likely through direct effects on cross bridges.
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Should not change anesthetic selection in patients; extends animal data on myocardial mechanics but leaves open human translation.
To assess the effects of halothane, isoflurane, and sevoflurane on cross bridges in intact cardiac muscle, electrically stimulated (0.25 Hz, 25 degrees C) right ventricular ferret papillary muscles (n = 14) were subjected to sinusoidal load oscillations (37-182 Hz, 0.2-0.5 mN peak to peak) at the instantaneous self-resonant frequency of the muscle-lever system. At resonance, stiffness is proportional to m * omega(2) (where m is equivalent moving mass and omega is angular frequency). Dynamic stiffness was derived by relating total stiffness to values of passive stiffness at each length during shortening and lengthening. Shortening amplitude and dynamic stiffness were decreased by halothane > isoflurane > or = sevoflurane. At equal peak shortening, dynamic stiffness was higher in halothane or isoflurane in high extracellular Ca(2+) concentration than in control. Halothane and isoflurane increased passive stiffness. The decrease in dynamic stiffness and shortening results in part from direct effects of volatile anesthetics at the level of cross bridges. The increase in passive stiffness caused by halothane and isoflurane may reflect an effect on weakly bound cross bridges and/or an effect on passive elastic elements.
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Bartunek et al. (2001) studied this question.
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