[The differential effects of isoproterenol on +dp/dt max and -dp/dt max under volatile anesthetics in rat]

The purpose of this study is to examine the effects of isoproterenol on +dp/dt max and -dp/dt max under volatile anesthetics in rat.

Firstly, under different halothane or isoflurane (0, 0.5 MAC, 1.0 MAC, 2.0 MAC) concentrations, hemodynamic parameters were recorded simultaneously. Secondly, under different halothane or isoflurane concentrations (0, 0.5 MAC, 1.0 MAC, 2.0 MAC), the inotropic response to isoproterenol was also studied with cumulative (0, 5, 50, 100, 500, 1000 pg) concentrations and hemodynamic parameters were simultaneously recorded.

There were significant decreases in +dp/dt max and -dp/dt max in halothane and isoflurane treated rats. The decreases in +dp/dt max and -dp/dt max were greater in halothane treated rats than those in isoflurane treated rats (P < 0.05) under 2 MAC halothane. The responses of +dp/dt max and -dp/dt max to 500 and 1000 pg isoproterenol were significantly reduced by 2 MAC halothane compared with the control (P < 0.05). There were no significant changes in +dp/dt max and -dp/dt max by administration of isoproterenol under isoflurane anesthesia.

Isoflurane has less effects on +dp/dt max and -dp/dt max, compared with halothane. It is possible that halothane, but not isoflurane, has some effects on the responsiveness to isoproterenol.