Acute pulmonary hypertension complicating the arterial switch procedure.

Two neonates undergoing arterial switch procedure developed life-threatening pulmonary hypertension intraoperatively. In one patient, bradycardia, hypotension, and electrocardiographic (ECG) evidence of myocardial ischemia suddenly occurred 20 minutes after uneventful weaning from cardiopulmonary bypass. Lifting a palpably hypertensive main pulmonary artery (MPA) resulted in reproducible hemodynamic improvement. Because the patient was already on full ventilatory support and a nitroglycerin infusion, the MPA was suspended onto the anterior chest wall. In the other patient, after removal of intraoperative drapes, severe generalized swelling and cyanosis were noted. The central venous pressure had risen to 25 mmHg, and the PO2 had dropped to 52 mmHg on 100% FIO2. The systolic arterial pressure and ECG remained normal. Immediate reexploration revealed a palpably hypertensive MPA. The coronary arteries implanted more laterally on the neoaorta were uncompromised. Amrinone loading and infusion produced immediate improvement. We believe that surgeons should be aware that pulmonary hypertension can cause coronary artery compression and right heart failure in neonates undergoing the arterial switch procedure. Lateral placement of the coronary artery and aggressive use of pulmonary vasodilators can minimize the problem.