Effects of 1,1,1-trichloroethan onhalation on ventricular contractility and heat rate in dogs

Anesthetized dogs were exposed to 1,1,1-trichloroethane (1,1,1-TCE) and the first derivative of left ventricular pressure, left ventricular dp/dt (LV dp/dt) and heart rate were determined to investigate the acute effects of the solvent on left ventricular contractility. The results obtained were as follows. 1. A decrease in peak dp/dt was observed following exposure to 1,1,1-TCE. The threshold concentration to produce the decrease in peak dp/dt was approximately 0.2%. A dose-response relationship between the decrease in dp/dt and the 1,1,1-TCE concentration was observed. 2. Heart rate increased following exposure to 1,1,1-TCE when the concenrtation was relatively low, and decreased when the concentration was high. 3. Effects of controlling heart rate by right atrial pacing on peak dp/dt were investigated. The peak dp/dt rose with the increase in the heart rate and fell with the decrease. 4. A decrease in the peak dp/dt following exposure to 1,1,1-TCE of relatively low cincentration was significantly larger in the group in which the heart rate was hold cinstant by pacing than that in the control group. It is suggested that the increase in the heart rate may be a factor regulating dp/dt when exposed to 1,1,1-TCE of low concentration. 5. A decrease in the peak dp/dt following exposure to 1,1,1-TCE of high concentration was smaller in the group in which the heart rate was hold constant by pacing than that in the control group, while no significant difference was seen. It is supposed that the decrease in the heart rate may be concerned in the decrease in the peak dp/dt when exposed to 1,1,1-TCE of high concentration.