Purpose: An increase of NT-proBNP has been proved to be a predictor for ventilator weaning failure in several medical conditions. However, relation between NT-proBNP and ventilator-weaning outcomes after cardiac surgery has not yet been elucidated. This study was to investigate relationship between blood NT-proBNP and ventilatorweaning outcomes.Methods: A prospective analytical study was at Cardiovascular-thoracic intensive care unit. Cardiac-surgery patients (age 18-80 Y, consented and without exclusion criteria) were included. Blood NT-proBNP was sampling at pre-operation time and at weaning. Early-weaning outcomes were categorized into simple, difficult, and prolong weaning. Late-weaning outcomes were reintubation and suspicious cardiopulmonary compensations. Blood NT-proBNPs were compared among/between early and late-weaning outcomes. Area under the curve and sensitivity/specificity at various cut-off values for poor weaning outcomes were analyzed.Results: A final of 134 patients were analyzed. The mean NT-proBNPs (pre-operation and weaning) were 1,417.8 and 4,532.5 pg/ml, respectively. wide variations of NT-proBNPs were observed. NT-proBNPs were not significantly related to difficult, prolong, and reintubation; but significantly related to suspicious cardiopulmonary compensations. AUC range were 0.43-0.65. Conclusions:NT-proBNP increased 4-5-fold after cardiac surgery. A significant increase was related to sympathetic activation, not weaning-induced LV load. Due to low sensitivity, NT-proBNPs were not good predictors for difficult or prolong weaning and reintubation in post cardiac surgery.