Bolus injection of cimetidine and hypotension in patients in the intensive care unit. Incidence and mechanisms

Abstract

Incidence and mechanisms of cimetidine-induced hypotension were investigated during the first intravenous injection of cimetidine (200 mg over three minutes) in 68 consecutive patients in the intensive care unit. Systolic pressure decreased more than 5 mm Hg (average, 14 mm Hg) in 50 patients, exceeding 30 mm Hg in nine (13%), while heart rate and pulmonary artery pressure (seven patients) did not change. Blood pressure decreased significantly more in patients requiring vasoconstrictor drug support. The arterial vasodilator properties of cimetidine were demonstrated in 12 normal volunteers in whom brachial artery cimetidine infusions caused a significant decrease of forearm vascular resistance. This effect was more pronounced when forearm vessels were preconstricted with dopamine hydrochloride (n = 6) or norepinephrine (n = 6), pointing toward an interference of cimetidine with sympathetically mediated vasoconstriction. Thus, intravenous injection of cimetidine in critically ill patients, presumably through arterial vasodilatation, is frequently associated with decreases of blood pressure, particularly in patients requiring vasoconstrictor drug support.