Abstract 13374: Effect of Increasing Fraction of Inspired Oxygen on Cerebral NIRS and Systemic Cardiac Output in Early Post-operative Single Ventricle Patients
Background: The use of pulse oximetry (SpO2) as an estimate of cardiac output (CO) in shunted single ventricle patients ignores pulmonary venous and mixed systemic venous saturation (MVO2). With a shunt providing fixed resistance to pulmonary blood flow, increasing inspired oxygen (FiO2) may increase SpO2 symmetrically with MVO2, thus maintaining CO, while increasing tissue oxygen delivery.
Methods: Stable early post-operative SV patients following Blalock-Taussig shunt or Sano conduit were prospectively enrolled. The study procedure was performed when patients were on stable inotropic support and ventilator settings. Baseline vital signs, SpO2, cerebral near-infrared spectroscopy (NIRS), and arterial blood gas (ABG) were recorded. Baseline FiO2 was at the primary team’s discretion. Patients were randomized to initial concentration of 21% or 80% oxygen, and repeat vital signs, SpO2, NIRS, and ABG were obtained after 30 minutes at each concentration. Arterial-venous oxygen saturation (AVO2) difference was calculated at baseline, 21%, and 80% FiO2 using SpO2 and NIRS as surrogates for systemic arterial saturation and MVO2.
Results: Twenty patients were consented for the study procedure. One patient was in room air, with the remainder ranging from 25-50% (mean 31.25%). There was no change in vital signs, pH or pCO2 with changes in FiO2. With increasing FiO2, there was an increase in SpO2 and NIRS. There was no change in the AVO2 difference between 21% (14-52) and baseline FiO2 (12-48) (p=0.4502) or baseline and 80% (14-58) (p=0.1258). There was an increase in AVO2 difference from 21% to 80% (p=0.038).
Conclusions: Increasing FiO2 increased SpO2 and NIRS with no change in AVO2 difference from 21% to 25-50% FiO2, consistent with increased oxygen delivery without reduction in CO. At 80% FiO2, however, there was decreased systemic CO compared to 21%. Future studies are required to evaluate the optimal oxygen concentration (25-50%) to provide improved tissue oxygen delivery while maintaining systemic CO.
- © 2013 by American Heart Association, Inc.