Comparison of the Profiles of Postoperative Systemic Hemodynamics and Oxygen Transport in Neonates After the Hybrid or the Norwood Procedure

Abstract

Background-After the Norwood procedure, early postoperative neonatal physiology is characterized by hemodynamic instability and imbalance of oxygen transport that is commonly attributed to surgical myocardial injury and a systemic inflammatory response to cardiopulmonary bypass (CPB). Because the Hybrid procedure (arterial duct stenting and bilateral pulmonary artery banding) avoids CPB, cardioplegic arrest, and circulatory arrest, we hypothesized that the Hybrid procedure is associated with superior postoperative hemodynamics and oxygen transport. Methods and Results-Oxygen consumption (VO 2 ) was continuously measured using respiratory mass spectrometry for 72 hours after Hybrid (nϭ6) and Norwood (nϭ13) procedures. Arterial, superior vena cava, and pulmonary venous blood gases and pressures were measured at 2-to 4-hour intervals to calculate systemic and pulmonary blood flows (Qs, Qp), and systemic vascular resistance (SVR), total pulmonary vascular resistance including pulmonary arterial band or B-T shunt (tPVR), cardiac output (CO), oxygen delivery (DO 2 ), and oxygen extraction ratio (ERO 2 ). Rate-pressure product was calculated as heart rateϫsystolic arterial pressure. When compared with the Norwood procedure, the early postoperative Hybrid patients had lower CO, higher SVR, and higher Qp:Qs ratios. In addition, the DO 2 and VO 2 were both lower in the Hybrids with higher ERO 2 and lactate levels. This early postoperative pattern reversed after 48 hours. Conclusions-Although Hybrid procedure avoids CPB and cardioplegic arrest, the early hemodynamic profile is not superior to the Norwood in terms of cardiac output and control of pulmonary blood flow. These data strongly suggest that a "hands off" approach to postoperative care in Hybrid patients may not be appropriate in patients with preoperative diminished myocardial function; and in such patients a Norwood-derived management strategy (afterload reduction and inotropic support) should be considered.

Use of Mathematical Modeling to Compare and Predict Hemodynamic Effects Between Hybrid and Surgical Norwood Palliations for Hypoplastic Left Heart Syndrome

“…However, pulmonary artery banding can accentuate right ventricular afterload and lead to significant myocardial injury, and reproducible optimal regulation of pulmonary blood flow through bilateral branch banding remains difficult to achieve. 5,21 Notwithstanding these differences, the goal of the hybrid management is not unlike that of the surgical strategies: To effectively palliate HLHS patients through the neonatal period with minimal morbidity and mortality, preserving ventricular function while allowing normal growth and development, especially in the pulmonary vascular bed. However, questions remain as to whether the hybrid approach leads to equivalent palliation as the conventional Norwood operations.…”

“…This finding is in agreement with a recent study of postoperative stage 1 hemodynamics in which the mean Qp/Qs ratio was 1.8 in patients who underwent the hybrid procedure, whereas 28% of the patients had a Qp/Qs ratio of Ͼ2:1 and 11% had a ratio of Ͼ3:1. 21 The difficulty in reproducibly restricting pulmonary blood flow through bilateral banding would likely accentuate the suboptimal systemic and cerebral oxygen deliveries in patients undergoing the hybrid procedure.…”

Right Ventricular Diastolic Performance in Children With Pulmonary Arterial Hypertension Associated With Congenital Heart Disease

“…Pulmonary and systemic blood flows were measured by the Fick method using measured oxygen consumption by mass spectrometry as a gold-standard measurement. 17 The time constant of RV relaxation (τ), peak change in minimum pressure over time (RV dp/dt minimum), and right ventricular end-diastolic pressure (RVEDP) were measured using high-fidelity micromanometer catheters (Millar Instruments, Inc, Houston, TX) as gold-standard measures of RV relaxation and filling pressures. 18 …”

Letter by Phillips Regarding Article, “Comparison of the Profiles of Postoperative Systemic Hemodynamics and Oxygen Transport in Neonates After the Hybrid or the Norwood Procedure: A Pilot Study”

“…I want to compliment Li et al on a very unique study 1 evaluating oxygen consumption and delivery during the first 72 hours postoperatively in patients with hypoplastic left heart syndrome treated by either the Norwood procedure (nϭ13) or the hybrid procedure (nϭ6). The study design was excellent; however, it is my opinion that there are several problems with the study and the conclusions drawn by the authors.…”