Retrospective evaluation of the association between hyponatremia and neurological dysfunction in hospitalized foals (2012-2016): 109 cases.

Objective Hyponatremia and rapid correction of hyponatremia can lead to neurological abnormalities. The objective of the study was to determine whether plasma sodium concentrations (Na+) and speed of correction of hyponatremia are significantly associated with neurological abnormalities in foals. Design Retrospective cohort study 2012 to 2016. Setting Equine hospital. Animals One hundred and nine foals <6 months old with hyponatremia (Na+ concentration <= 125 mmol/L). Interventions Case records were reviewed for any foal with hyponatremia. Clinicopathological findings, presence or absence of neurological signs on the day of the lowest Na+ concentration measured and the following 5 days, diagnosis and outcome were recorded, and changes in Na+ concentration per hour were calculated for up to 5 subsequent days. Logistic regression was used to assess the association between presence or absence of neurological signs, Na+ concentration, other known risk factors for neurological dysfunction in foals, and possible confounders. Measurements and Main Results In the final multivariable model, only Na+ (odds ratio [OR]: 0.86; 95% CI 0.79-0.95; P = 0.002) and BUN concentrations (OR: 1.04; 95% CI: 1.02-1.06; P = 0.001) were significantly associated with neurological signs. Changes in Na+ concentrations per hour were not associated with neurological signs on any day after the lowest Na+ concentration had been measured (P = 0.18-0.82), and development of new neurological signs following correction of hyponatremia was not reported in any foal. Conclusions Na+ concentrations were associated with the development of neurological signs in hyponatremic foals. Increased BUN concentrations might contribute to neurological dysfunction, but further studies are necessary to confirm or refute these findings.