Postoperative Abdominal NIRS Values Predict Low Cardiac Output Syndrome in Neonates

Abstract

Background: The development of low cardiac output syndrome (LCOS) after cardiopulmonary bypass (CPB) occurs in up to 25% of neonates and is associated with increased morbidity. Invasive cardiac output monitors such as pulmonary artery catheters have limited availability and are costly. Near-infrared spectroscopy (NIRS) is a noninvasive tool for monitoring regional oxygenation in neonates in the cardiac intensive care unit (CICU). We hypothesize that anterior abdominal NIRS may aid in the early identification of LCOS after cardiac surgery. Methods: Prospective observational study from October 2013 to October 2014 of all neonates with congenital heart disease admitted to the CICU following CPB. Abdominal NIRS values were continuously recorded upon CICU admission and for the subsequent 24-hour period. The primary outcome was the development of LCOS. Low cardiac output syndrome was defined as the presence of metabolic lactic acidosis (pH < 7.3 and lactate > 4) or addition of a new vasoactive agent or a vasoactive inotropic score > 15. Autoregressive time series models were constructed for each patient based on the continuously recorded NIRS values, and patients were stratified by development of LCOS. Results: Twenty-seven neonates met inclusion criteria, of whom 11 developed LCOS. Neonates who developed LCOS had lower constant NIRS values (49% vs 66%, P < .001). Constant NIRS values less than 58% best predicted development of LCOS with a sensitivity of 100% and specificity of 69%. Conclusion: Lower constant anterior abdominal NIRS values in the early postoperative period may allow early identification of neonates at risk for LCOS.