Strong relationship between NT-proXNP levels and cardiac output following cardiac surgery in neonates and infants

Background: NT-proXNP, a new natriuretic peptide analyte, incorporates information about the concentrations of both N-terminal pro-atrial and pro-brain natriuretic peptides (NT-proANP, NT-proBNP). We aimed to investigate whether NT-proXNP is a reliable indicator of the cardiac index (CI) and the hemodynamic state in neonates and infants undergoing an open heart surgery. Methods: We enrolled 26 children under the age of 1 year into this prospective study. All patients underwent an elective cardiac operation with cardiopulmonary bypass (CPB) to achieve complete biventricular repair. Peri-operative hemodynamic parameters were assessed by transpulmonary thermodilution and natriuretic peptide levels were recorded. Results: The NT-proXNP level correlated significantly with the simultaneously measured NT-proANP level (r = 0.60, P < 0.001), but more strongly with the NT-proBNP level (r = 0.89, P < 0.001) and the arithmetic sum of both (r = 0.88, P < 0.001). NT-proXNP had a strong correlation with CI (r = ― 0.85, P < 0.001), the stroke volume index (r = ― 0.80, P < 0.001) and the global ejection fraction (r = ― 0.67, P < 0.009) throughout the post-operative period. Conventionally measured parameters such as heart rate, mean arterial pressure and pulse-pressure product exhibited weaker correlations with CI than NT-proXNP. Among laboratory values, creatinine levels correlated significantly with CI (r = ― 0.77, P<0.001) and NT-proXNP (r = 0.76, P < 0.001) during the post-operative period. A post-operative NT-proXNP level of 3079 pool/l was diagnostic for CI <31/min/m 2 with 89% sensitivity and 90% specificity (area under the curve: 0.91 ± 0.05). Conclusion: NT-proXNP is a good marker of cardiac output following pediatric cardiac surgery and might be a useful tool in the recognition of a low output state.