Effects of Halothane on Isometric Contractions of Isolated Heart Muscle

Abstract

In isometric contractions of an isolated heart muscle preparation exposed to halothane (0.10, 0.40, 0.85, 1.05 and 2.35 volumes per cent), peak developed tension and maximum rate of tension development were reduced as much as 53 per cent and 57 per cent, respectively, in direct proportion to the concentration of the anesthetic. Time to peak tension and total twitch duration were not decreased more than 6.3 per cent by any concentration of halothane. Resting tension was affected only by the highest concentration, 2.35 volumes per cent, which lowered it 6.8 per cent Relaxation time and muscle length were not altered. Recovery from the effect of halothane was essentially complete in each instance. The results are consistent with the concept that halothane exerts its cardiac effects primarily by a direct reduction in active state intensity of heart muscle.