PROTAMINE-INDUCED HYPOTENSION AND BRADYCARDIA IN A CARDIAC TRANSPLANTPATIENT

Purpose: The potential for functional reinnervation of the transplante d heart in man is controversial. We report the sudden onset of bradyca rdia in a cardiac transplant patient following a period of hypotension subsequent to the administration of protamine, Possible mechanisms un derlying this response-including reinnervation of the transplanted hea rt, are assessed. Clinical features: Eight weeks after cardiac transpl antation, a patient returned to-hospital for a left femoral- tibial ar tery bypass vein graft. The patient was anaesthetized using general an aesthesia, Upon completion of the procedure, protamine was administere d to reverse the heparin-induced anticoagulation. Although administrat ion of a 5.0 mg ''test-dose'' appeared to be without cardiovascular ef fect, after an additional 20.0 mg, blood pressure decreased from 98/52 to 62/40 mmHg, After blood pressure reached its nadir, heart rate dec reased precipitously from 57 to 29 beats.min(-1). Conclusions: This re port demonstrates that heart rate can change considerably in patients who have undergone cardiac transplantation. It is argued that the chan ge in heart rate observed in the present report cannot be explained by reinnervation of the transplanted heart, as the patient had undergone transplantation only eight weeks previously, Rather, we suggest that the change was mediated by mechanisms intrinsic to the transplanted he art and extrinsic to the CNS.