Abstract 2677: The influence of Systemic Hemodynamics and Oxygen Transport on Cerebral Oxygen Saturation in Neonates after the Norwood Procedure
Objective: Ischemic brain injury is an important morbidity in neonates following the Norwood procedure. Its relationship to hemodynamic instability and an imbalance of oxygen transport is poorly understood.
Methods: Twelve neonates undergoing the Norwood procedure with regional cerebral perfusion were studied. Continuous cerebral oxygen saturation (ScO2) was measured by near-infrared spectroscopy before, during, and after the operative procedure. Continuous oxygen consumption (VO2) was measured by respiratory mass spectrometry. Pulmonary and systemic blood flow (Qp, Qs), systemic vascular resistance (SVR), oxygen delivery (DO2) and oxygen extraction ratio (ERO2) were derived with measurements of arterial (SaO2), superior vena cava and pulmonary venous gases and pressures at 2 - 4 hour intervals during the first 72 hours in the ICU.
Results: Mean ScO2 was 68±13% before operation, 92±6% during regional cerebral perfusion, and reduced to 64±11% after bypass. It further reduced to 54±7% on arrival in the ICU and remained low during the first 24 hours. ScO2 increased to 52±11% at 72 hours, still significantly lower than the preoperative level (p<0.05). Postoperatively, ScO2 was positively closely correlated with SaO2, PaO2 (slope. 0.37 and 0.81, respectively, p<0.0001), mean arterial pressure (slope 0.46, p<0.0001), and moderately correlated with Hb (slope 0.40, p=0.03), Qs and DO2 (slope 2.8 and 0.025, respectively, p<0.0001 for both). It was negatively correlated with SVR (slope -0.15, p=0.006), VO2 (slope -0.07, p=0.04) and ERO2 (slope -33.2, p<0.0001).
Conclusions. ScO2 decreased significantly in neonates during the early postoperative period following the Norwood procedure, and was correlated with SaO2, MAP, Hb (positive) and SVR, VO2, ERO2 (negative). These findings suggest that there are opportunities for hemodynamic interventions to modify systemic oxygen transport whereby the risk of cerebral ischemia may be reduced.