An Elevated Low Cardiac Output Syndrome Score Is Associated With Morbidity in Infants After Congenital Heart Surgery

To evaluate an empirically derived Low Cardiac Output Syndrome Score as a clinical assessment tool for the presence and severity of Low Cardiac Output Syndrome and to examine its association with clinical outcomes in infants who underwent surgical repair or palliation of congenital heart defects.

Prospective observational cohort study.

Cardiac ICU at Seattle Children's Hospital.

Infants undergoing surgical repair or palliation of congenital heart defects.

None.

Clinical and laboratory data were recorded hourly for the first 24 hours after surgery. A Low Cardiac Output Syndrome Score was calculated by assigning one point for each of the following: tachycardia, oliguria, toe temperature less than 30°C, need for volume administration in excess of 30 mL/kg/d, decreased near infrared spectrometry measurements, hyperlactatemia, and need for vasoactive/inotropes in excess of milrinone at 0.5 μg/kg/min. A cumulative Low Cardiac Output Syndrome Score was determined by summation of Low Cardiac Output Syndrome Score on arrival to cardiac ICU, and 8, 12, and 24 hours postoperatively. Scores were analyzed for association with composite morbidity (prolonged mechanical ventilation, new infection, cardiopulmonary arrest, neurologic event, renal dysfunction, necrotizing enterocolitis, and extracorporeal life support) and resource utilization. Fifty-four patients were included. Overall composite morbidity was 33.3%. Median peak Low Cardiac Output Syndrome Score and cumulative Low Cardiac Output Syndrome Score were higher in patients with composite morbidity (3 [2-5] vs 2 [1-3]; p = 0.003 and 8 [5-10] vs 2.5 [1-5]; p < 0.001)]. Area under the receiver operating characteristic curve for cumulative Low Cardiac Output Syndrome Score versus composite morbidity was 0.83, optimal cutoff of greater than 6. Patients with cumulative Low Cardiac Output Syndrome Score greater than or equal to 7 had higher morbidity, longer duration of mechanical ventilation, cardiac ICU, and hospital length of stay (all p ≤ 0.001). After adjusting for other relevant variables, peak Low Cardiac Output Syndrome Score and cumulative Low Cardiac Output Syndrome Score were independently associated with composite morbidity (odds ratio, 2.57; 95% CI, 1.12-5.9 and odds ratio, 1.35; 95% CI, 1.09-1.67, respectively).

Higher peak Low Cardiac Output Syndrome Score and cumulative Low Cardiac Output Syndrome Score were associated with increased morbidity and resource utilization among infants following surgery for congenital heart defects and might be a useful tools in future cardiac intensive care research. Independent validation is required.