Dysnatremia and risk of bloodstream infection in dialysis patients

BACKGROUND: Emerging data suggest that sodium disarrays including hyponatremia are potential risk factors for infection ensuing from impairments in host immunity, which may be exacerbated by coexisting conditions (i.e. mucosal membrane and cellular edema leading to breakdown of microbial barrier function). While dysnatremia and infection-related mortality are common in dialysis patients, little is known about the association between serum sodium levels and the risk of bloodstream infection in this population. METHODS: Among 823 dialysis patients from the national Biospecimen Registry Grant Program who underwent serum sodium testing over the period January 2008–December 2014, we examined the relationship between baseline serum sodium levels and subsequent rate of bloodstream infection. Bloodstream infection events were directly ascertained using laboratory blood culture data. Associations between serum sodium level and the incidence of bloodstream infection were estimated using expanded case mix–adjusted Poisson regression models. RESULTS: In the overall cohort, ∼10% of all patients experienced one or more bloodstream infection events during the follow-up period. Patients with both lower sodium levels <134 mEq/l and higher sodium levels ≥140 mEq/l had higher incident rate ratios (IRRs) of bloodstream infection in expanded case mix analyses (reference 136–<138 mEq/l), with adjusted IRRs of 2.30 [95% confidence interval (CI) 1.19–4.44], 0.77 (95% CI 0.32–1.84), 1.39 (95% CI 0.78–2.47), 1.88 (95% CI 1.08–3.28) and 1.96 (95% CI 1.08–3.55) for sodium levels <134, 134–<136, 138–<140, 140–<142 and ≥142 Eq/l, respectively. CONCLUSIONS: Both lower and higher baseline serum sodium levels were associated with a higher rate of subsequent bloodstream infections in dialysis patients. Further studies are needed to determine whether correction of dysnatremia ameliorates infection risk in this population.