Preoperative hyponatremia is associated with increased postoperative complications and s hort-to long-term mortality in geriatric hip fracture patients: a retrospective cohort study

Background Preoperative hyponatremia is a common electrolyte disorder in geriatric patients, but the adverse effects of hyponatremia on postoperative prognosis have not been fully recognized. The objective of the present study was to investigate the associations of preoperative hyponatremia with postoperative complications, short-term (before the 30th day) and long-term (before the 365th day) overall mortality for geriatric patients with hip fractures. Methods The clinical data of patients aged 60 years or older who underwent surgical treatment for hip fracture from January 2015 to December 2021 at the Seventh Medical Center, Chinese PLA General Hospital, were retrospectively analyzed, and the patients were divided into hyponatremic and normonatremic groups according to their sodium level at admission. Multivariate logistic regression and Cox proportional hazards models were used to calculate the odds ratios (ORs) for postoperative complications and the hazard ratios (HRs) for mortality. Subgroup analyses based on specific populations were performed to explore the relationship between hyponatremia and postoperative mortality. Results A total of 1901 patients were included in this study, with an incidence of preoperative hyponatremia of 12.8% (243/1440). A total of 16.5% (314/1901) of the patients experienced postoperative complications during hospitalization, 4.3% (82/1901) died within 30 days, and 14.7% (279/1901) died within 1 year. Compared with normonatremic patients, hyponatremic patients had higher odds of postoperative complications (OR = 2.34, 95% CI 1.53–3.58), and higher 30-day (HR = 2.23, 95% CI = 1.16–4.30) and 1-year (HR = 1.78, 95% CI = 1.23–2.59) mortality. Subgroup analyses revealed that the associations between hyponatremia and long-term mortality were significantly stronger in older patients and those with higher American Society of Anesthesiologists (ASA) grades (both P  < 0.001). Conclusion Preoperative hyponatremia is associated with increased postoperative complications and short- to long-term mortality after hip fracture surgery in geriatric patients. Preoperative hyponatremia might be a valuable risk factor for improving the prognosis of hip fracture surgery.