A composite outcome for neonatal cardiac surgery research

Abstract

Objective: The objective of this study was to determine whether a composite outcome, derived of objective signs of inadequate cardiac output, would be associated with other important measures of outcomes and therefore be an appropriate end point for clinical trials in neonatal cardiac surgery.

Methods: Neonates (n = 76) undergoing cardiac operations requiring cardiopulmonary bypass were prospectively enrolled. Patients were defined to have met the composite outcome if they had any of the following events before hospital discharge: death, the use of mechanical circulatory support, cardiac arrest requiring chest compressions, hepatic injury (2 times the upper limit of normal for aspartate aminotransferase or alanine aminotransferase), renal injury (creatinine >1.5 mg/dL), or lactic acidosis (an increasing lactate >5 mmol/L in the postoperative period). Associations between the composite outcome and the duration of mechanical ventilation, intensive care unit stay, hospital stay, and total hospital charges were determined.

Results: The median age at the time of surgery was 7 days, and the median weight was 3.2 kg. The composite outcome was met in 39% of patients (30/76). Patients who met the composite outcome compared with those who did not had a longer duration of mechanical ventilation (4.9 vs 2.9 days, P < .01), intensive care unit stay (8.8 vs 5.7 days, P < .01), hospital stay (23 vs 12 days, P < .01), and increased hospital charges ($258,000 vs $170,000, P < .01). In linear regression analysis, controlling for surgical complexity, these differences remained significant (R(2) = 0.29-0.42, P < .01).

Conclusions: The composite outcome is highly associated with important early operative outcomes and may serve as a useful end point for future clinical research in neonates undergoing cardiac operations.

Trial registration: ClinicalTrials.gov NCT00934843.

Keywords: 20; 21; ALT; AST; CI; CPB; CPR; ECMO; ICU; IQR; RACHS-1; Risk Adjustment for Congenital Heart Surgery 1; alanine aminotransferase; aspartate aminotransferase; cardiopulmonary bypass; cardiopulmonary resuscitation; confidence interval; extracorporeal membrane oxygenation; intensive care unit; interquartile range.

Published by Mosby, Inc.

Figures

FIGURE 1

Composite outcome and postoperative outcomes. Box-whisper plot of postoperative outcomes and composite outcome. Box represents IQR. Dark bar represents median. Whiskers extend to range of outcome up to 1.5 × the IQR. Circles represent outliers beyond 1.5 × the IQR. 0 =patients who met no composite outcome, 1 = patients who met only 1 composite outcome criteria,>1 = patients who met ≥2 composite outcome criteria. There is a statistically significant increase in median hospital stay, median ICU stay, median mechanical ventilation, and median hospital charges between each category (P<.01, Table 4). ICU, Intensive care unit; IQR, interquartile range.

FIGURE 2

Clinical or laboratory criteria of composite outcome met and postoperative outcomes. Box-whisper plot of postoperative outcomes and whether clinical criteria, laboratory criteria only, or no composite outcome criteria were met. Box represents IQR. Dark bar represents median. Whiskers extend to range of outcome up to 1.5 × the IQR. Circles represent outliers beyond 1.5 × the IQR. None =patients who met no composite outcome, laboratory only =patients who met only laboratory composite outcome criteria, clinical =patients who met any of the clinical composite outcome criteria (CPR, death, ECMO). There is a statistically significant increase in median hospital stay, ICU stay, duration of mechanical ventilation, and hospital charges between each category (P<.01, Table 5). ICU, Intensive care unit; IQR, interquartile range; CPR, cardiopulmonary resuscitation; ECMO, extracorporeal membrane oxygenation.