Association of serum sodium with morbidity and mortality in hospitalized patients undergoing major orthopedic surgery.

BACKGROUND: Dysnatremia may predispose to falls and fractures, and serum sodium may influence bone health. Little is known of the association of perioperative dysnatremia and clinical outcomes in those undergoing major orthopedic surgery.

OBJECTIVE: We examined the association of serum sodium (corrected for glucose) with morbidity and mortality in a sample of hospitalized patients undergoing major orthopedic procedures at 2 large academic medical centers.

DESIGN: Retrospective observational study.

SETTING AND PARTICIPANTS: Adult patients admitted to major academic teaching hospitals for a major orthopedic procedure from January 2006 to January 2011.

METHODS: The association of serum sodium with log-transformed hospital length of stay was assessed by fitting linear regression models. The association with 30-day mortality was assessed by fitting Cox proportional hazards models.

RESULTS: There were 16,206 unique admissions, of which 44.8% were male, with a mean age of 62.5 years. Mean corrected serum sodium was 138.5 ± 2.9 mmol/L; 1.2% had moderate/severe hyponatremia, 6.4% had mild hyponatremia, and 2.5% were hypernatremic. In adjusted models, compared with normonatremia, moderate/severe hyponatremia, mild hyponatremia, and hypernatremia were associated with a 1.6-, 1.4-, and 1.4-day-longer hospital stay, respectively, and greater risk of 30-day mortality (hazard ratio [HR]: 2.47, 95% confidence interval [CI]: 1.33-4.59 for moderate/severe hyponatremia; HR: 1.80, 95% CI: 1.21-2.66 for mild hyponatremia; and HR: 2.99, 95% CI: 1.79-4.98 for hypernatremia).

CONCLUSION AND RELEVANCE: Dysnatremia is relatively common in the hospitalized orthopedic population and associated with greater length of stay and 30-day mortality. Future studies should address potential mechanisms underlying these associations and whether correction of perioperative dysnatremia may improve patient outcomes.