Children with congenital heart disease are at increased risk of developing pulmonary hypertension and pulmonary hypertensive crises which is reflected by increasing the risk of right sided heart failure. Managing pulmonary hypertension is challenging ranging from simple non-selective vasodilators to drugs targeting specifically the pulmonary vessels. Sildenafil is a phosphodiestrase type 5 inhibitor that is safe and efficient in controlling pulmonary hypertension perioperatively.