ObjectivesWorldwide, an estimated 10 million adults annually experience significant myocardial injury after non-cardiac surgery. Our aim is to assess whether preoperative and postoperative serum B-type natriuretic peptides levels (BNP) could be used as a predictor of postoperative complications in hypertensive and diabetic patients post non-cardiac surgery.DesignProspective observational study.SettingSingle tertiary-care centre in northern India.ParticipantsThis study included 260 adult participants with known hypertension and diabetes who were planned for elective non-cardiac surgery.InterventionsA preoperative BNP level (baseline BNP) was measured within 24 hours of surgery and another postoperative BNP level was measured within 24 hours of surgery.Main outcome measuresThe primary outcome was the change in BNP levels (delta BNP) between the postoperative and the preoperative BNP levels (baseline BNP) with respect to the baseline BNP and the development of postoperative complications within 30 days of surgery.ResultsThe study established a correlation between delta BNP and baseline BNP (Pearson’s correlation coefficient=0.60; p=0.01). Our study found an increased serum BNP both in the preoperative period and the postoperative period in the patient group that developed complications, respectively (152.02 pg/mL±106.56 vs 44.90 pg/mL±44.22; t=4.120; p≤0.001); (313.99 pg/mL±121.29 vs 83.95 pg/mL±70.19; t=7.73; p≤0.001).ConclusionsWe found that an increased serum baseline and postoperative BNP is potentially important predictor for the development of postoperative complications. Serum BNP has the potential to emerge as a cost-effective test for risk-stratification for postoperative complications in patients undergoing non-cardiac surgery. It has promising prognostic advantages including modification of surgical procedures, deferral of surgery and the ability to tailor therapy postoperatively.