Postoperative hemodynamics after Norwood palliation for hypoplastic left heart syndrome

Hemodynamics after Norwood palliation for hypoplastic left heart syndrome (HLHS) have been incompletely characterized, although emphasis has been pierced on the role that an excess pylmonary-to-systemic blood flow ratio (Q(p)/Q(s)) may play in causing hemodynamic instability. Studies suggest that maximal oxygen delivery occurs at a Q(p)/Q(s) <1, However, it remains unclear to what extent cardiac output can increase with increasing pulmonary perfusion. One approach is to use the oxygen excess factor <Omega>, an index of systemic oxygen delivery, and compare Omega with measured Q(p)/Q(s). We measured Q(p)/Q(s) and Omega in neonates after Norwood palliation for HLHS, and determined how they were related. In addition, we determined the temporal course of surrogate indexes of systemic perfusion in the early postoperative period. Arteriovenous oxygen saturation difference, blood lactate, and Omega were recorded on admission and every 3 to 12 hours for 2 days in 18 consecutive infants with HLHS or variant after Norwood palliation. Three infants required extracorporeal membrane oxygenation (ECMO) 6 to 9 hours after admission. These infants had higher Q(p)/Q(s), blood lactate, arteriovenous oxygen saturation difference, and lower Omega than non-ECMO patients. In non-ECMO patients between admission and 6 hours, Omega decreased significantly despite no appreciable change in Q(p)/Q(s). We conclude that: (1) Oxygen delivery is significantly decreased at 6 postoperative hours unrelated to Q(p)/Q(s). This modest decline in oxygen delivery is insufficient to compromise tissue oxygenation. (2) Patients requiring ECMO have significant derangements in oxygen delivery. (C) 2001 by Excerpta Medica, Inc.