Sodium is a mineral in your dog’s blood that is controlled by aldosterone (a hormone) produced by the adrenal glands. This hormone lets the kidneys know when to save sodium from the urine and when to let it go (through urination). Sodium is essential in regulating your dog’s bodily fluids to keep them going where they belong and controls nerve and muscle cells as well. Luckily, chronic (true) hypernatremia is not common in dogs, but acute dehydration hypernatremia is common for some dogs when they do not get enough water, too much exercise, fever, or overheating. That is why it is important that you always provide your dog with plenty of fresh water and, if they are outside, adequate shade so they do not get too hot.

Excess sodium in the blood (hypernatremia) is a dangerous electrolyte imbalance that causes too much sodium (more than 154 mEq/L) and not enough water. Mild hypernatremia is common in dogs from being dehydrated or overheated, but it can be life threatening if the sodium reaches an amount high enough (over 170 mEq/L) to cause symptoms. Hypernatremia can cause the fluid to move from the intracellular spaces to the extracellular spaces, possibly causing a decrease in the volume of cells in the cerebrum (cerebral edema), brain hemorrhage, neurological damage, coma, or death.

The symptoms for hypernatremia are the same whether it is acute or chronic, but they are easier to notice in the acute type of this disorder. The reason for this is because the signs come on suddenly and they are more severe. The chronic type of hypernatremia symptoms happen much slower so you may not notice it as much and the signs are usually less severe because your dog’s body has been able to get used to them. The body will compensate for the imbalance of sodium by using the amino acids and carbohydrates in the brain to keep water in the intracellular space where it needs to be. The symptoms of acute and chronic hypernatremia are:

Types 

Acute hypernatremia is a sudden (and more severe) increase in sodium in your dog’s bloodstream. Chronic hypernatremia is a gradual (and less noticeable) increase of sodium in your dog’s bloodstream.

Hypernatremia (both acute and chronic) can be caused by many things depending on the underlying illness, but it basically all leads to your dog having too much sodium in the bloodstream. This can be from a lack of water, the decrease of water in your dog’s bloodstream, or an increase of sodium in your dog’s body. The most common causes of each are:

The first thing the veterinarian will do is make sure your dog is stable and comfortable. You will need to let the veterinarian know about all of your dog’s symptoms, recent illnesses and injuries, any changes in behavior or eating habits, and if you have made any changes in your dog’s diet recently. Your veterinarian will perform a thorough physical examination of your dog, which will include body temperature, blood pressure, and heart rate. Once he has examined your dog, the veterinarian will need to run some tests to determine what the cause of your dog’s symptoms are. The preliminary tests will be a complete blood count (CBC), electrolyte panel, urinalysis, urine specific gravity, blood chemistry panel, and glucose test.

 Depending on the outcome of these tests, the veterinarian may need to run more tests, such as ACTH stimulation (thyroid test) if hormone imbalance is suspected; endocrine testing, renal exam, liver enzymes, and digital radiographs (x-rays) if your dog has had access to plenty of water and the veterinarian suspects thyroid, kidney, or liver problems. Sometimes it is difficult to determine the cause of the hypernatremia and the veterinarian may want to admit your dog to the hospital for further testing and fluid therapy. Your dog will need to be hospitalized for any type of fluid therapy if chronic hypernatremia is the possible diagnosis because it has to be done gradually due to a risk of cerebral edema.

In any case of acute hypernatremia your veterinarian will want to start fluid therapy as soon as possible to increase water levels and decrease sodium levels. This usually includes IV fluids if your dog is moderately or severely dehydrated, which is usually the case if you noticed symptoms in the first place. With chronic hypernatremia, your dog will need to be in the hospital during the treatment because it has to be done much slower and under observation to reduce the risk of cerebral edema.

Once the veterinarian gets your dog’s sodium and fluid levels back to normal, the underlying cause will have to be treated. If it was a case of vomiting, fever, heatstroke, diarrhea, or inadequate access to water you will be able to take your dog home right away with instructions to watch for any further symptoms. Any other illnesses will have to be treated before you can take your dog home. The veterinarian may possibly want you to stay for a few hours to make sure your dog’s fluid and sodium levels stay normal.

When you take your dog home, you will want to be sure to be alert for any symptoms or problems that may recur. Follow your veterinarian’s instructions exactly and be certain to give your dog any medication as prescribed if necessary. Make sure you return for your dog’s follow-up visit as scheduled. Your dog may be weak or tired for about 24 hours, but after that, everything should be back to normal if the underlying cause was taken care of. If the cause was heat exhaustion or lack of water, be sure to provide extra water and plenty of shade for your dog when they are outside, and bring them indoors when it is too hot.