Fig. 4. Summary of the effects of three anesthetics on cardiac ionic currents. Percent block of current amplitude for ICa,L, INa, and IKirwere determined at test potentials displayed in figure 3and described in the text. For ICa,Land INa, peak current amplitude was measured. For IKir, current amplitude was measured at the end of a 50-ms test pulse. The concentration of Xe was 80%. As published previously, 21,22the concentrations of sevoflurane were 3.0% on ICa,L, 2.0% on INa, and 2.6% on IKir. The concentrations of halothane on the corresponding ionic currents were 1.2%, 1.0%, and 2.0%, respectively. Each concentration of halothane and sevoflurane, but not Xe, depressed the respective current.