Effects of halothane on the conduction system of the heart in humans

The effects of 2.0 MAC halothane on atrioventricular conduction times in humans were studied. A real-time recording system for the detection of surface His-Purkinje potentials based on signal averaging techniques was used. Recordings were made in 23 patients before and after the administration of halothane. In 18 patients we were able to measure atrial (P-H) and His-Purkinje (H-V) conduction times (78%). A small but statistically significant decrease in P-H conduction times from 115.3 +/- 3.9 (SEM) to 110.8 +/- 4.2 ms was found (P less than or equal to 0.01). H-V conduction times did not change significantly. Heart rates decreased significantly from 87.6 +/- 2.6 to 74.8 +/- 2.5 beats/min (P less than or equal to 0.01). Systolic blood pressures decreased from 118.9 +/- 3.7 to 103.6 +/- 4.2 mm Hg. It is concluded that the decrease in heart rate and the decrease in atrial conduction time caused by halothane can be explained by interactions of several different mechanisms. The specific combination of slowing heart rate and a decrease of atrial conduction time provides a possible explanation for atrial arrhythmias during the administration of halothane.