Figure 1. The effects of 1 minimum alveolar concentration halothane or desflurane on the inotropic effect of dobutamine. Data are absolute mean values of isometric active force (AF) normalized per cross-sectional area +/- SD (n = 10 in each group). B1 corresponds to baseline values at a calcium concentration of 0.5 mM. B2 corresponds to baseline values after exposure to halogenated anesthetics in the halothane and desflurane groups. Because the baseline values of isometric active force differ markedly among papillary muscles, it is difficult to show a pharmacologic effect when absolute values are used.