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11 PROLONGED PENILE ERECTION RELATED TO ORAL SILDENAFIL THERAPY AND NITRIC OXIDE FOR NEONATAL PRIMARY PULMONARY HYPERTENSION
  1. N. L. Miller,
  2. J. A. Roth
  1. University of Virginia, Charlottesville

Abstract

Introduction Prolonged penile erection (PPE) is an extremely rare condition in the newborn. Previous reports in the literature have implicated polycythemia, birth trauma, congenital syphilis and idiopathic factors as proposed etiologies. We report 2 cases of PPE in the newborn during treatment with nitric oxide (NO) and oral sildenafil for primary pulmonary hypertension (PPHN).

Methods Retrospective review of the 2 cases was performed. The first case is of an infant born at 39 weeks gestation by cesarean section due to fetal tachycardia and maternal fever. Postnatally, the newborn developed respiratory failure related to PPHN. Inhaled nitric oxide (iNO) therapy was initiated to lower pulmonary artery pressures. The infant developed a prolonged erection within 30 minutes of initiation of the iNO. The second case is that of an infant born at 37 weeks gestation by spontaneous vaginal delivery. On physical examination, the infant was found to have a heart murmur. Echocardiogram revealed cor triatriatum and PPHN. The infant was started on oral sildenafil to produce pulmonary vascular relaxation. Within one hour of initiating the sildenafil, PPE was observed.

Results Urologic consultation confirmed PPE in both infants. The phallus of the first infant remained tumesced for 3 days, but never exhibited rigidity. Spontaneous detumescence occurred 10 minutes after cessation of the inhaled nitric oxide. The phallus of the second infant exhibited waxing and waning degrees of tumescence for the duration of oral sildenafil therapy.

Conclusions Increased arterial inflow is the primary hemodynamic event in the development of penile erection. NO acts as a messenger molecule stimulating guanylate cyclase, and leading to the formation of cyclic guanosine monophosphate (cGMP). cGMP then acts through calcium-gated potassium channels to cause vascular smooth muscle relaxation. Phosphodiesterases (PDE) are an integral component of cyclic nucleotide signaling. PDE5 is found in high concentration within the smooth muscle of the pulmonary vasculature and corpus cavernosum. Therefore, PDE5 inhibitors such as sildenafil. known to improve erectile dysfunction. have also been used in the treatment of PPHN. We hypothesize that the NO administered in the first case and the oral sildenafil given in the second case resulted in a high flow state leading to prolonged penile erection. By the proposed mechanism, hypoxia and acidosis would not occur. The clinical course of PPE of the newborn differs greatly from that of priapism. In most instances, spontaneous detumescence occurs, and therefore observation rather than surgical therapy is advocated.

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