Additive depressant effects of amiodarone given with halothane in isolated hearts.

The antidysrhythmic drug amiodarone may be given during general anesthesia. We examined the single and combined direct cardiac effects of amiodarone and halothane in the isolated guinea pig heart. Guinea pig hearts were isolated and perfused retrogradely through the aorta with oxygenated Krebs-Ringer solution at 37 degrees C at constant pressure (55 mm Hg). Variables measured in 61 hearts included spontaneous heart rate (HR), atrioventricular conduction time (AVCT), isovolumetric left ventricular pressure (LVP), and coronary flow (CF). Amiodarone was administered as a single bolus into the retrogradely perfused aortic root and halothane was vaporized into the perfusing solution. Mean control values of pooled data before treatment were as follows: HR, 228 +/- 4 (SEM) beats/min; AVCT (during atrial pacing at 240 beats/min), 82 +/- 2 ms; LVP, 97 +/- 4 mm Hg; and CF, 6.1 +/- 0.2 mL.min-1.g-1. Amiodarone, 100 micrograms and 200 micrograms, decreased HR by 8% +/- 2% and 8% +/- 2%, increased AVCT by 5 +/- 2 and 15 +/- 3 ms, decreased LVP by 22% +/- 3% and 27% +/- 3%, and increased CF by 20% +/- 1% and 40% +/- 2%, respectively; all these changes were sustained for 60 min and, except for HR, were dose dependent. Halothane, 0.5% and 1%, transiently and dose-dependently decreased HR by 6% +/- 2% and 12% +/- 2% increased AVCT by 4 +/- 2 and 8 +/- 2 ms, decreased LVP by 15% +/- 3% and 31% +/- 3%, and increased CF by 2% +/- 1% and 6% +/- 2%.(ABSTRACT TRUNCATED AT 250 WORDS)