Cardiovascular effects of atropine sulfate preparations in vagotomized dogs under halothane anesthesia

The cardiovascular effects of 3 preparations of atropine sulfate were studied acutely in open-chest, vagotomized dogs under endotracheal halothane anesthesia. Indices of myocardial performance (LVdp/dt/CPIP and maximum ascending aortic blood acceleration) showed insignificant changes when varying doses of IV atropine (0.04 mg/kg and 0.04 mg/kg) were given. However, mean ascending aortic pressure fell by 20 percent following the larger doses of 2 commercial preparations containing antibacterial preservatives, and only 9 percent following a "pure" (USP) atropine preparation. Calculated changes in systemic vascular resistance closely followed actual pressure values. These results indicate that atropine, even in large doses, causes little or no depression of ventricular function independently of its chronotropic action. However, atropine does cause a fall in blood pressure, seemingly due to peripheral vasodilation, particularly in commercial preparations containing preservatives.