Effects of tolazoline and prostacyclin on pulmonary hypertension in infants after cardiac surgery

Abstract

Objective: To evaluate the hemodynamic effects of tolazoline and prostacyclin in infants with pulmonary vasospasm after cardiac surgery.

Design: Prospective cohort study.

Setting: Pediatric ICU.

Patients: The cohort consisted of 42 infants and children with congenital heart disease and pulmonary hypertension who underwent corrective surgery and were monitored postoperatively using pulmonary artery catheters. Fourteen infants (2 to 12 months old) in this group required postoperative treatment with tolazoline or prostacyclin.

Interventions: Tolazoline was administered as a bolus of 0.5 mg/kg for treatment of persistent pulmonary hypertension or acute pulmonary hypertensive crisis. If its effectiveness was proved after 30 mins by hemodynamic measurements, a continuous iv infusion of 0.5 mg/kg/hr was established. Higher doses of tolazoline were avoided. If tolazoline treatment did not fulfill the criteria for pulmonary vasodilation, prostacyclin was given by continuous iv infusion at a starting rate of 5 ng/kg/min, followed by 10 ng/kg/min. In three patients, the infusion rate was increased to 15 ng/kg/min.

Results: Bolus administration of tolazoline resulted in a distinct pulmonary vasodilation in seven infants: mean pulmonary artery pressure and pulmonary vascular resistance decreased by an average of 35% and 45%, respectively. In these patients, tolazoline was infused over the following 12 to 72 hrs. One infant who received tolazoline for 72 hrs developed a clinically important gastrointestinal hemorrhage. In seven nonresponders to tolazoline, prostacyclin (PGI2) at an infusion rate of 5 ng/kg/min led to pulmonary vasodilation in five patients, at an iv infusion rate of 10 ng/kg/min in all seven infants studied. The latter dose of PGI2 reduced the mean pulmonary artery pressure by an average of 37%, and pulmonary vascular resistance by 43%. Transient withdrawal of prostacyclin in five infants demonstrated its short half-life and clinical effectiveness. Apart from a facial flush, no side-effects were encountered using PGI2 as an infusion over durations ranging from 12 to 504 hrs.

Conclusions: These data suggest that, if tolazoline in a relatively low dose proves to be inefficient, prostacyclin can still be used as a safe and effective drug for treatment of pulmonary vasospasm. Prostacyclin offers more than a pharmacologic alternative to increased tolazoline dosages.