Preoperative Hyponatremia Is an Independent Risk Factor for Prolonged Hospital Stay After Anterior Cervical Discectomy and Fusion

Objective: To determine the association of preoperative hyponatremia with short-term postoperative complications and health care utilization (length of stay, readmissions) after anterior cervical fusion and discectomy (ACDF). Methods: Patients who underwent ACDF were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Patients who had revision surgery, trauma, vertebral malignancy, or infection were excluded. Eunatremia was defined as sodium (Na) level between 135 and 145 mEq/L, whereas hyponatremia was defined as Na < 135 mEq/L. Preoperatively, patients with hyponatremia were matched 1:1 with patients with eunatremia using propensity score matching based on age, sex, American Society of Anesthesiologists score, and baseline comorbidities. Minor adverse events included superficial infection, dehiscence, urinary tract infection, pneumonia, and renal insufficiency or failure. Serious adverse events included deep wound infection, reintubation, pulmonary embolism, cerebrovascular accident, cardiac arrest, deep vein thrombosis, sepsis, return to operating room, and death within 30 days. Complications were analyzed using bivariate and logistic analysis with significance set at P < 0.05. Results: Of the 9094 patients undergoing ACDF, 3.64% (n = 331) were preoperatively hyponatremic. Preoperative hyponatremia was an independent risk factor for postoperative pneumonia after ACDF (odds ratio [OR], 4.47; P = 0.020) and extended length of hospital stay >1 SD above the mean (OR, 1.71; P = 0.042). Preoperative hyponatremia was an independent risk factor for having a serious adverse event (OR, 2.40; P = 0.005) and any adverse event (OR, 2.44; P = 0.009). Conclusions: Preoperative hyponatremia is an independent risk factor for pneumonia and prolonged length of stay after ACDF.