Sodium Abnormalities Are an Independent Predictor of Complications in Total Joint Arthroplasty: A Cautionary Tale

Electrolyte levels are commonly obtained as part of the preoperative workup for total joint arthroplasty, but limited information exists on the interplay between electrolyte abnormalities and outcomes. The National Surgical Quality Improvement Program was queried for primary, elective total hip arthroplasty and total knee arthroplasty (THA, TKA) performed between 2011 and 2017. Three patient groups were compared: normal (control), hypernatremia, and hyponatremia. The primary outcomes were length of stay (LOS) and 30-day adverse events: complications, readmissions, reoperations, and mortality. A total of 244,538 TKAs and 145,134 THAs were analyzed. The prevalence of hyponatremia and hypernatremia was 6.9% and 1.0%, respectively. After controlling for any baseline differences, hypernatremia was an independent predictor of ventilation >48 hours (THA, odds ratio [OR] 3.53), unplanned intubation (THA, OR 3.14), cardiac arrest (THA, OR 2.42), pneumonia (THA, OR 2.16), Clostridium difficile infection (OR 4.66 and 3.25 for THA and TKA, respectively), LOS >2 days (THA, OR 1.16), and mortality (THA, OR 4.69). Similarly, hyponatremia was an independent predictor of LOS >2 days (TKA, OR 1.21), readmission (TKA, OR 1.40), reoperation (OR 1.32 and 1.47 for THA and TKA, respectively), surgical site infections (OR 1.39 and 1.54 for THA and TKA, respectively), and transfusion (OR 1.13 and 1.20 for THA and TKA, respectively). As the focus of total joint arthroplasty continues to shift toward value-based payment models and outpatient surgery, caution should be exercised in patients with abnormal preoperative sodium levels, particularly hypernatremia, because of significantly increased risk of prolonged LOS and 30-day adverse events.