Study of Postmortem Sodium Concentrations in the Brain, Aqueous Humor and Cerebrospinal Fluid of Horses Received at Oklahoma Animal Disease Diagnostic Laboratory

Abstract

Water deprivation/sodium ion toxicosis is well documented in certain species. A normal sodium range as well as a toxic range has been previously established for cattle, poultry and swine. Diagnostic laboratories often receive requests for brain sodium levels to use in conjunction with histological findings for diagnosis of water deprivation/sodium ion toxicosis. No reference values for equine brain sodium concentrations have been found in the literature. Aqueous humor, cerebrospinal fluid, cerebellum, and frontal lobe specimens were harvested from horses with a history that did not suggest a neurologic problem and that were submitted to Oklahoma Animal Disease Diagnostic Laboratory for necropsy. Testing was done at Oklahoma Animal Disease Diagnostic Laboratory in the toxicology laboratory using atomic absorption spectrometry to determine sodium levels in the frontal lobe, cerebrospinal fluid, aqueous humor, and cerebellum of the horse. Samples were tested and statistically show that the probable range for sodium in the horse is 984 ppm to 1724 ppm in the frontal lobe, 827 ppm to 1963 ppm in the cerebellum, 75-199 mEq/L (1711 ppm to 4583 ppm) in the aqueous humor, and 22-250 mEq/L (1992 ppm to 9697 ppm) in the CSF. The brain values will be very useful to veterinarians and diagnosticians across the country. With the increased public awareness of cruelty/neglect cases, these values will allow for more accurate diagnosis of water deprivation/sodium ion toxicosis in horses.