Clinicoepidemiological profile of acute postoperative hyponatraemia in patients undergoing joint replacement surgery: A prospective observational study.

Background: Postoperative hyponatraemia is frequently misunderstood or undiagnosed after orthopaedic surgery, such as total knee and hip replacements, which is associated with increased morbidity. Limited and primarily retrospective literature exists on postoperative hyponatraemia in hip and knee arthroplasties. Key risk factors include preoperative hyponatraemia, older age, female sex, lower body weight, fluid imbalance, and surgical stress.

Methods: This prospective observational study aimed to investigate the incidence of postoperative hyponatraemia and associated factors in 225 orthopaedic surgical patients. Pre-existing hypornatremia cases were excluded. The patients' serum sodium, potassium, blood urea nitrogen, creatinine, glucose, and haemoglobin levels were measured before the surgery and on the first postoperative day.

Results: Postoperative hyponatraemia was detected in 30.6% (n = 69) of the 225 participating patients; among them, 91.6% had mild, 7.2% had moderate, and 1.4% had severe hyponatraemia. People with diabetes (odds ratio = 3.4; 95% confidence interval 1.36-13.4) and patients with blood loss > 300 mL (odds ratio = 10.3; 95% confidence interval 2.98-16) were more susceptible. Patients with hyponatraemia experienced an extended hospital stay.

Conclusion: One-third of the normonatraemic orthopaedic surgical patients developed postoperative hyponatraemia. Significant risk factors identified include diabetes and intraoperative blood loss exceeding 300 mL. This study allows for a focused evaluation of how surgical procedures influence sodium levels by excluding patients with preoperative hyponatraemia, unlike previous research studies.