Predicting the outcome of hip fracture patients by using N-terminal fragment of pro-B-type natriuretic peptide

Objective: To examine the prognostic value of perioperative N-terminal fragment of pro-brain natriuretic peptide (NT-proBNP) in hip fracture patients. Design: Blinded prospective cohort study. Setting: Single centre trial at Turku University Hospital in Finland. Participants: Inclusion criterion was admittance to the study hospital due to hip fracture during the trial period of October 2009-May 2010. Exclusion criteria were the patient's refusal and inadequate laboratory tests. The final study population consisted of 182 patients. Primary and secondary outcome measures: NT-proBNP was assessed once during the perioperative period and later if clinically indicated, and troponin T (TnT) and ECG recordings were evaluated repeatedly. The short-term (30-day) and long-term (1000 days) mortalities were studied. Results: Median (IQR) follow-up time was 3.1 (0.3) years. The median (IQR) NT-proBNP level was 1260 (2298) ng/L in preoperative and 1600 (3971) ng/L in postoperative samples (p=0.001). TnT was elevated in 66 (36%) patients, and was significantly more common in patients with higher NT-proBNP. Patients with high (>2370 ng/L) and intermediate (806-2370 ng/L) NT-proBNP level had significantly higher short-term mortality compared with patients having a low (<806 ng/L) NT-proBNP level (15 vs 11 vs 2%, p=0.04), and the long-term mortality remained higher in these patients (69% vs 49% vs 27%, p<0.001). Intermediate or high NT-proBNP level (HR 7.8, 95% CI 1.03 to 59.14, p<0.05) was the only independent predictor of short-term mortality, while intermediate or high NT-proBNP level (HR 2.27, 95% CI 1.30 to 3.96, p=0.004), the presence of dementia (HR 1.74, 95% CI 1.13 to 2.66, p=0.01) and higher preoperative American Society of Anesthesiologists' (ASA) classification (HR 1.59, 95% CI 1.06 to 2.38, p=0.02) were independent predictors of long-term mortality. Conclusion: An elevated perioperative NT-proBNP level is common in hip fracture patients, and it is an independent predictor of short-term and long-term mortality superior to the commonly used clinical risk scores.