Protamine and left ventricular function: a transesophageal echocardiography study

The effect of protamine sulfate on left ventricular function was evaluated in 23 patients undergoing heart surgery requiring cardiopulmonary bypass (CPB). Ventricular function was assessed by measuring cardiac index with a thermodilution pulmonary artery catheter and fractional shortening with transesophageal echocardiography (TEE). After CPB, a heparin-neutralizing dose of protamine was infused continuously for 5 min. Hemodynamic variables were obtained and fractional shortening was measured before protamine administration (time 0), during protamine infusion (2.5 and 5 min), and after the infusion (10 and 15 min after the start of protamine). Patients with a preoperative ejection fraction > or = 50% had no statistically significant changes in either cardiac index or fractional shortening with protamine administration, when compared to time 0. However, patients with a preoperative ejection fraction < 50% had a significant decrease in fractional shortening which occurred during and immediately after protamine administration when compared to time 0 (P < 0.01), with no associated change in hemodynamics. Our results suggest that protamine may have a negative inotropic effect that is apparent in patients with impaired ventricular function.