We propose a single-center, randomized, double-blind, phase II clinical trial in children undergoing Fontan surgery. We plan to compare the effects of perioperative nesiritide, milrinone and placebo infusions on the early postoperative clinical course and neurohumoral profile. The primary aim of the study is to determine whether nesiritide, milrinone or placebo infusion is associated with fewer days alive and out of the hospital within 30 days of surgery. We hypothesize that, when compared to the milrinone and placebo groups, the nesiritide group will have more days alive and out of the hospital within the first 30 days after surgery. Secondary aims are to determine the effects of these infusions on postoperative resource consumption, hemodynamics, arrhythmias, renal function, neurohumoral activation and adverse events. Thirty-nine patients per group (117 total patients) will be enrolled over three years.