Postural hypotension induced by atropine sulfate.

Previous tests on the use of large doses of atropine for the treatment of anticholinesterase poisoning have revealed postural hypotension following the administration of 2 mg. of this drug. In this study on 78 normal adult males, the cardiovascular responses to positional change after 2 mg. atropine have been measured and the mechanisms elucidated. Blood pressure response to tilting was normal during control and placebo phases, but showed a profound alteration after atropine. T HE recommended therapy for anti-cholinesterase intoxication is atropine sulfate and artificial respiration.' The use of anticholinesterases as insecticides and their potential use as chemical warfare nerve gas agents has rekindled an interest in this well-known parasympatholytic drug and the manual methods of resuscitation. Atropine sulfate has found a wide range of clinical applications. In most instances it is prescribed in small doses (0.3 mg. to 0.6 mg.). However, it has been established that human tolerance to this drug in the presence of anti-cholinesterase agents is enormous.2 Its immediate injection in case of exposure is imperative , and the recommended initial dose is 2 mg. In civil defense emergencies and possible insecticide exposures, it may become necessary to administer this large dose of atropine to normal, but potentially poisoned, individuals. This possibility has made it desirable to determine the physiologic effects resulting in normal individuals from the intramuscular injection of 2 mg. of atropine sulfate. Previous reports have detailed the muscular, visual and psychologic effects of doses of atropine up to 3 mg.3 In a study conducted by this group on 200 normal college men,4 no serious signs or symptoms were noted following the administration of the recommended initial intramuscular dose. However, hypotension and vertigo were observed in some individuals 413 while they were standing. Accordingly, it seemed appropriate to investigate specific cardiovascular responses of normal adults to the intramuscular injection of 2 mg. of atropine sulfate. In the current study the phenomenon of atropine-induced postural hypotension has been carefully assayed along with an attempt to determine the mechanism of this action. METHODS The experimental procedure consisted of three phases carried out on a series of 73 normal male military subjects,* who were in a random height and weight range and whose average age was under 25 years. In the first (control) phase, blood pressure, pulse rate, and temperature were recorded before any injection was given. During the second (placebo) phase these same measurements were made from …