Abstract
Hyponatremia is a risk factor for adverse surgical outcomes, but limited information
is available on the prognosis of hyponatremic patients who undergo total knee arthroplasty
(TKA). The purpose of this investigation was to compare the incidence of major morbidity
(MM), 30-day readmission, 30-day reoperation, and length of hospital stay (LOS) between
normonatremic and hypontremic TKA patients.The American College of Surgeons National
Surgical Quality Improvement Program database was used to identify all primary TKA
procedures. Hyponatremia was defined as <135 mEq/L and normonatremia as 135 to 145
mEq/L; hypernatremic patients (>145 mEq/L) were excluded. Multivariable logistic regression
was used to determine the association between hyponatremia and outcomes after adjusting
for demographics and comorbidities. An α level of 0.002 was used and calculated using
the Bonferroni correction. Our final analysis included 88,103 patients of which 3,763
were hyponatremic and 84,340 were normonatremic preoperatively. In our multivariable
models, hyponatremic patients did not have significantly higher odds of experiencing
an MM (odds ratio [OR]: 1.05; 99% confidence interval [CI] 0.93–1.19) or readmission
(OR: 1.12; 99% CI: 1–1.24). However, patients with hyponatremia did experience significantly
greater odds for reoperation (OR: 1.24; 99% CI: 1.05–1.46) and longer hospital stay
(OR: 1.15; 99% CI: 1.09–1.21). We found that hyponatremic patients undergoing TKA
had increased odds of reoperation and prolonged hospital stay. Preoperative hyponatremia
may be a modifiable risk factor for adverse outcomes in patients undergoing TKA, and
additional prospective studies are warranted to determine whether preoperative correction
of hyponatremia can prevent complications.
Keywords
hyponatremia - total knee arthroplasty - morbidity - length of hospital stay - reoperation
