The effect of phenoxybenzamine on the pulmonary vascular bed in surgically corrected ventricular septal defect associated with pulmonary hypertension.

From 1971 to 1977, a total of 43 cases with ventricular septal defect associated with pulmonary hypertension (VSD + PH), ranging from 3 months to 6 years of age, underwent VSD closure using cardiopulmonary bypass with a prophylactic dose of phenoxybenzamine (POB) 1 mg/Kg. Twenty of these cases are included in the present study of the effect of POB on pulmonary hypertension. The ratios of pulmonary to systemic arterial pressures (Pp/Ps) and vascular resistances (Rp/Rs) were measured before, immediately after and 1 month after VSD closure. In all cases, the Pp/Ps before VSD closure was larger than 0.75. Both Pp/Ps and Rp/Rs markedly decreased immediately after VSD closure but rose again 1 month thereafter. These results suggest the possibility of pulmonary vasodilating effect of POB, which could be potentially useful in relieving the right ventricular load in the early postoperative period. The over all mortality was 3 out of 43 cases including 2 late deaths.