RESERPINE, guanethidine sulfate, and some tranquilizers are known to modify the neuroeffector action of levarterenol bitartrate in animals.1, 2 This fact and clinical experience have led anesthesiologists to recommend that elective operations be postponed until 2 or 3 weeks after therapy with these drugs has been discontinued. Recently Crandell3 introduced the "ephedrine response test" to more accurately predict the time when patients receiving resperine would be suitable candidates for elective operation. This report presents our clinical findings concerning this test when used as a screening test to predict the occurrence of hypotension during anesthesia in patients receiving known or unknown antihypertensive or tranquilizing drugs.
—With the patients in the supine position three baseline BP and pulse rate readings were obtained. Using a slightly different dosage schedule from that presented by Crandell, we gave our patients 5 mg of ephedrine sulfate intravenously. During the next