Changes in brain natriuretic peptide concentrations after cardiac surgery: kinetics and prognostic value

B-type natriuretic peptide (BNP) is a cardiac neurohormone specifically secreted from the ventricles in response to volume expansion and pressure overload. Plasma levels of BNP have been shown to be elevated in patients with left ventricular dysfunction and correlate with prognosis. The purpose of the present study was to determine the variations of BNP levels in cardiac surgery patients and to look for a possible association between BNP levels and perioperative cardiac complications.

Methods

After ethics committee approval and patient informed consent, we studied 94 consecutive patients undergoing elective coronary artery (36) or valve surgery (58). BNP was measured using a fluorescence immunoassay Test (Triage, Biosite Inc) before surgery (day 0), and at days 1 and 5 after surgery. Anesthesia and cardiopulmonary bypass management was standardized for all patients. Postoperative cardiac complication (CC) was defined as hemodynamic instability requiring inotropic support > 4 hours, congestive heart failure in ward and cardiac death.

Results

At day 0, the levels of BNP were significantly associated with the NYHA class (P = 0.003) and LVEF (P = 0.002), but neither with the type of cardiac disease nor with preoperative pulmonary artery catheter measurements. BNP concentrations increased in all patients at day 1 and remained elevated in plateau at day 5. At day 1, BNP concentrations were associated with the occurrence of cardiac complications (Fig. 1) and length of stay in intensive care unit. Using ROC curve analysis, the best predictive value (for cardiac complications) of BNP at day 1 was 450 pg/ml.

Figure 1

Conclusion

Plasma BNP levels increased in all patients after cardiac surgery and remained elevated until day 5. High BNP levels at day 1 were significantly associated with postoperative cardiac complications.