Inhibited response to isoproterenol and altered action potential of beating rat heart cells by human serum in septic shock.

Human serum, obtained within 24 hours after the onset of septic shock, was evaluated for its effects on the chronotropic response of cultured rat myocardial cells to isoproterenol. Transmembrane action potential (AP) was measured in some experiments. Sera obtained after the first four to five hours, when central venous pressure (CVP) was normal or high, inhibited increased cell beats, while this property was not evidenced for samples taken soon after septic shock when CVP was low. Sera were also found to alter AP in much the same way as Sotalol, an adrenergic beta-blocking drug. These two effects were never observed with control sera obtained from healthy male adults at rest. These findings demonstrate that sera from patients in septic shock depress the beta-adrenergic response of rat myocardial cells, after the early phase of septic shock characterized by sympathoadrenergic activity. They strongly suggest the mediation of unidentified humoral factors, which might interfere in the pathogenesis of myocardial dysfunction during the intermediate phase of septic shock.