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 pier ced 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 ma ximal oxygen delivery occurs at a Q(p)/Q(s) <1, However, it remains unclear to what extent cardiac output can increase with increasing pulmonary perfu sion. 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 mea sured Q(p)/Q(s) and Omega in neonates after Norwood palliation for HLHS, an d determined how they were related. In addition, we determined the temporal course of surrogate indexes of systemic perfusion in the early postoperati ve period. Arteriovenous oxygen saturation difference, blood lactate, and O mega were recorded on admission and every 3 to 12 hours for 2 days in 18 co nsecutive infants with HLHS or variant after Norwood palliation. Three infa nts 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 n on-ECMO patients between admission and 6 hours, Omega decreased significant ly 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 compro mise tissue oxygenation. (2) Patients requiring ECMO have significant deran gements in oxygen delivery. (C) 2001 by Excerpta Medica, Inc.