Objectives: Our aim was to determine NT-proBNP levels in patients undergoing cardiac surgery and if those levels are related to any of the baseline clinical characteristics of patients before surgery or any of the outcomes or events after surgery.
Methods: Prospective, analytic study including 83 consecutive patients undergoing cardiac surgery. Preoperatory and postoperatory data were collected. NT-proBNP levels were measured before surgery, the day of surgery, twice the following day and every 24 h until a total of nine determinations. Venous blood was obtained by direct venipuncture and collected into serum separator tubes. Samples were centrifuged within 20 min from sampling and stored for a maximum of 12 h at 2-8 degrees C before the separation of serum. Serum was stored frozen at -40 degrees C and thawed only once at the time of analysis.
Results: Mean age was 65+/-11.8 years. An Euroscore 6 was found in 30% of patients. NYHA classification was as follows: I:27.7%; II:47%; III:25.3%. Preoperative atrial fibrilation occurred in 20.5% of patients. After surgery 18.1% of patients required inotropes. Only one death was recorded. A great variability was found in preoperative NT-proBNP levels; 759.9 (S.D.:1371.1); CI 95%: 464.9 to 1054.9 pg/ml, with a wide range (6.39-8854). Median was 366.5 pg/ml. Preoperative NT-proBNP levels were unrelated to the type of surgery (CABG vs. others), sex, age and any of the cardiovascular risk factors. NT-proBNP levels were higher in high risk patients (Euroscore 6); (P=0.021), worse NYHA class (P=0.020) and patients with preoperative atrial fibrilation (m 1767 (2205) vs m 621 (1017); P=0.001). After surgery NT-proBNP levels started increasing the following day until the fourth day (P=0.03), decreasing afterwards (P=0.019). These levels were significantly higher in patients requiring inotropes after surgery (P<0.001). We did not find any relationship between NT-proBNP levels and complications rate (P=0.59).
Conclusions: Preoperative NT-proBNP levels depend on preoperative patient status (Euroscore, NYHA class and cardiac rhythm) and they increase significantly after cardiac surgery. This increase is higher when postoperative inotropes are needed. We found no relation between NT-proBNP levels and complications rate. An association have been shown between NT-proBNP levels and the use of inotropes after cardiac surgery.