B-Type natriuretic peptide assessment in coronary arterial bypass graft surgery

Background

Although data have shown that B-type natriuretic peptide (BNP) levels correlate with the severity and prognosis of heart failure, there are few studies regarding its levels in cardiac surgery patients.

Objectives

We sought to correlate the clinical and hemodynamic features in postoperative (PO) stay and the levels of BNP.

Methods

A prospective and observational study. We assessed the level of BNP (imunofluorescence – Triage^®) at 1 and 24 hours PO. A BNP level above a cutoff point of 100 pg/ml was found to be highly sensitive and specific for the diagnosis of cardiac heart failure. The population consisted of two groups: group A had levels below 100 pg/ml and group B was above this level. Evaluated at 1 hour of PO stay were: time of cardiopulmonary bypass (CBP), hidric balance (HB), mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), pO₂ and FiO₂ ratio (P/F), mechanical ventilation time (MV) and O₂ central venous saturation (VO₂SAT). The left ventricular function was assessed by two-dimensional echocardiography in the preoperative period (Simpson method) and values under 40% were considered ventricular dysfunction. The Student t-test was used for comparison between the found means.

Results

We investigated 17 patients (three women, median age 58.4 years old; standard deviation = 9.7). Group A was composed of 11 patients and group B of six patients. No statistical difference was found regarding CPB, HB, MAP, HR, CVP, P/F and VO2SAT, whereas the MV time in group A was 211.3 ± 229 min, with regard to group B being 520.8 ± 332.9 min (P = 0.038). At 24 hours PO, the BNP mean level (327.8 ± 206.9 pg/ml) was found in 13 patients (76.4%).

Left ventricular dysfunction was observed in two patients of group B.

Conclusions

Although there was a reduced number of patients, these findings suggest that the BNP levels were related to the mechanical ventilatory time.