Veterinary III CFE Practice Exam

The key idea is that correcting hyponatremia must be gradual to prevent brain injury called osmotic demyelination syndrome. When the brain has adapted to low sodium by losing osmolytes, its cells become less able to handle a rapid rise in extracellular osmolality. If sodium is raised too quickly, water shifts out of brain cells, leading to demyelination of white matter, most famously in the pons, which can cause severe, irreversible neurologic damage. Because of this risk, clinicians limit how fast sodium is corrected—typically aiming for only small increases per 24 hours (with tighter limits for chronic cases)—and monitor closely to avoid overcorrection. In practice, this slow, controlled approach prevents the osmotic stress that drives demyelination. Delirium or seizures can be concerns in hyponatremia, but the reason slow correction is emphasized is specifically to avoid osmotic demyelination syndrome. Hastening normalization would raise the risk of that injury, which is why the correct answer focuses on preventing osmotic demyelination.