Hypotension following cimetidine administration during cardiopulmonary bypass.

Intravenous administration of cimetidine may occasionally cause profound hypotension. Cimetidine 200 mg was administered as a bolus injection to patients whilst on cardiopulmonary bypass and subsequent changes in systemic arterial pressure were recorded. A statistically significant fall in arterial pressure was observed (p less than 0.001), which was attributable to a fall in systemic vascular resistance.