Friday, July 17, 2009
A dear friend lost her 15 month old lab, Sophie, yesterday to a tragic accident. Sophie went swimming and drank too much water while playing resulting in water toxicity also known as hypernatremia.I had no idea a dog could die from this, and it was quite sudden. She went swimming in the morning, to lethargic, to gone before the evening due to her body chemistry being completely out of whack. Because her case was acute and sudden, the vet was not able to reverse the damage done.
Hypernatremia is defined as an elevated sodium concentration in the blood. Although mild hypernatremia is often detected on serum chemistry panels, hypernatremia does not commonly warrant specific treatment. When marked hypernatremia is present, however, clinical signs can be severe and can result in death. The treatment of hypernatremia can be challenging, and success depends on an understanding of sodium and water balance.
The brain is the major organ affected by hypernatremia. When a hyperosmolar state develops, water from brain cells moves down the osmotic gradient into the extracellular space. This results in brain parenchymal cell dehydration and an overall decrease in brain volume. The cerebral veins rupture as a result of pia mater blood vessel tearing, resulting in subarachnoid and intracerebral hemorrhage. At presentation, affected animals have evidence of neurologic disease. They can exhibit lethargy, ataxia, and weakness, which progress to seizures, coma, and death in severe cases. Clinical signs appear as the serum sodium concentration approaches 170 mEq/L. When hypernatremia develops slowly, the brain has time to compensate, and neurologic signs are minimal. However, when hypernatremia occurs acutely, more severe and potentially irreversible neurologic signs develop.
The prognosis for patients with hypernatremia depends on the underlying cause, severity of hypernatremia and clinical signs at presentation, and response to fluid administration. Hypernatremia has a high mortality rate in humans, and mortality has been found to be associated with the initial plasma sodium concentration, severity of neurologic signs at presentation, and response to treatment. A recent study of hypernatremic dogs and cats found a 42% mortality rate; another study in kittens with experimentally induced hypernatremia found a 30% mortality rate in the first 24 hours. One dog with diabetes insipidus and a plasma sodium concentration of 203 mEq/L was treated and survived. By understanding the pathophysiologic basis of this disorder and using this basis to guide appropriate treatment choices, clinicians can successfully manage severe hypernatremia.
I keep thinking of the Spring Fling I photographed and all of those lab babies having the time of their life fetching balls out of the pond and swimming non stop. I felt compelled to share Sophie’s story to maybe prevent this tragic accident from happening again to someone else. Thanks for reading and for sharing.