Factors affecting systemic oxygen delivery after Norwood procedure with Sano modification

Abstract

Background: The physiologic goal of management after a Norwood procedure is to optimize systemic oxygen delivery, as indicated by oxygen excess factor (OEF). Factors were examined that might affect systemic oxygen delivery after the Norwood procedure with right ventricle-to-pulmonary artery (RV-PA) conduit as the pulmonary blood supply.

Methods: Hemodynamic data of 9 patients (mean age, 25.0 days; mean weight, 2.9 kg) who underwent a modified Norwood operation for hypoplastic left heart syndrome (HLHS) between April 2003 and April 2008 were retrospectively analyzed. Variables were obtained by manometry and oximetry from indwelling catheters in the systemic artery, pulmonary artery, and superior vena cava at 3- to 6-hour intervals for 72 hours postoperatively. Systemic (Qs) and pulmonary (Qp) blood flow, systemic vascular resistance (SVR), and pulmonary vascular resistance (PVR) were calculated.

Results: A significant increase in SVR and decrease in PVR occurred during the first 6 hours, which might be inductive to sudden cardiovascular collapse. SVR and PVR significantly decreased over time through 24 hours, followed by a lower steady increase. OEF was closely correlated with SVR (p < 0.0001). No correlation of OEF with PVR (p = 0.65) was noted among the assumed variables. Mixed venous oxygen saturation (SVO(2)) and OEF were strongly correlated. Pulmonary arterial pressure and OEF were weakly correlated.

Conclusions: Postoperative management strategies to maintain a low SVR, rather than manipulating PVR, appear to be rational to achieve adequate oxygen delivery after a Norwood procedure with Sano modification. The SVO(2) provides reliable prediction of OEF during postoperative hemodynamic recovery.