The Inadequate Oxygen Delivery Index and Low Cardiac Output Syndrome Score As Predictors of Adverse Events Associated with Low Cardiac Output Syndrome Early after Cardiac Bypass

Objectives: To evaluate the effectiveness of two scoring systems, the inadequate oxygen delivery index, a risk analytics algorithm (Etiometry, Boston, MA) and the Low Cardiac Output Syndrome Score, in predicting adverse events recognized as indicative of low cardiac output syndrome within 72 hours of surgery. Design: A retrospective observational pair-matched study. Setting: Tertiary pediatric cardiac ICU. Patients: Children undergoing cardiac bypass for congenital heart defects. Cases experienced an adverse event linked to low cardiac output syndrome in the 72 hours following surgery (extracorporeal membrane oxygenation, renal replacement therapy, cardiopulmonary resuscitation, and necrotizing enterocolitis) and were matched with a control patient on criteria of procedure, diagnosis, and age who experienced no such event. Interventions: None. Measurements and Main Results: Of a total 536 bypass operations in the study period, 38 patients experienced one of the defined events. Twenty-eight cases were included in the study after removing patients who suffered an event after 72 hours or who had insufficient data. Clinical and laboratory data were collected to derive scores for the first 12 hours after surgery. The inadequate oxygen delivery index was calculated by Etiometry using vital signs and laboratory data. A modified Low Cardiac Output Syndrome Score was calculated from clinical and therapeutic markers. The mean inadequate oxygen delivery and modified Low Cardiac Output Syndrome Score were compared within each matched pair using the Wilcoxon signed-rank test. Inadequate oxygen delivery correctly differentiated adverse events in 13 of 28 matched pairs, with no evidence of inadequate oxygen delivery being higher in cases (p = 0.71). Modified Low Cardiac Output Syndrome Score correctly differentiated adverse events in 23 of 28 matched pairs, with strong evidence of a raised score in low cardiac output syndrome cases (p < 0.01). Conclusions: Although inadequate oxygen delivery is an Food and Drug Administration approved indicator of risk for low mixed venous oxygen saturation, early postoperative average values were not linked with medium-term adverse events. The indicators included in the modified Low Cardiac Output Syndrome Score had a much stronger association with the specified adverse events.