Acute methemoglobinemia during cardiopulmonary bypass caused by intravenous nitroglycerin infusion

The case of a patient is presented who was undergoing coronary bypass grafting and who, during cardiopulmonary bypass, became severely cyanotic because of methemoglobinemia after intravenous infusion of nitroglycerin. His condition responded promptly and favorably to the withdrawal of the offending agent and to administration of methylene blue.