Thursday, April 1, 2010

(Almost) Tricked

A few weeks ago, I was presented with a 9 year old dog with acute onset of seizuring and stumbling. He was a well-cared for dog, outdoor only in a fenced in yard, with several other dogs. He was up to date on his vaccines, heartworm preventative, and Vectra flea control. The owners kept no toxins around the yard, no antifreeze, and nothing else that he could have gotten into. The owners mentioned offhandedly that 12 hours before the stumbling and seizuring began, the dog had also been vomiting all over the house. Warning bells started going off.

On presentation, the dog was depressed but aware of his surroundings. He was very dehydrated (about 9%). Physical exam was pretty much unremarkable otherwise.

Bloodwork showed significant azotemia (elevated kidney enzymes), a high white blood cell count (35,000), and significant dehydration. Otherwise, it was unremarkable. About half an hour after arrival, he suffered an incredibly violent seizure.

I couldn't get a urinalysis from the dog, because he was extremely dehydrated and had no urine.

In any other case, antifreeze would have been my first differential. After all, seizures and renal failure together usually only have a handful of differentials - especially when proceeded by prolonged, copious vomiting. I longed for a urine sample. Why?

In dogs that have ingested antifreeze, there are often very specific crystals in the urine (calcium monohydrate). These aren't always present and depend on several factors including time since ingestion, but IF present - they are pretty damn incriminating. Combined with clinical signs and other bloodwork changes, you pretty much have a diagnosis.

Antifreeze wasn't my first differential because exposure seemed impossible in this dog. He was well cared for, kept in a fenced yard with 3 other dogs, none of whom were showing any signs. The owners had NO antifreeze on the premises. The dog never left the fenced in yard and was not unsupervised. Also, his WBC count was very elevated (35,000 is a respectable white blood cell count), and this is not the norm in antifreeze.

I had no urine to look at, and that left me with two diagnostics: blood gases and the commercially available antifreeze test.

Blood gases measure several things: blood pH (which is severely low in antifreeze patients, called acidosis), blood saturation with oxygen and carbon dioxide, and some other parameters. Unfortunately, I blanked on the blood gas for some reason (it'd been a while since I'd had an antifreeze).

So, why not run the antifreeze test, you're probably wondering? After all, if it's positive, then you have your answer, right? Wrong. Recently, the old school antifreeze test went off the market and was replaced by a new, more "user-friendly" test that was good for both dogs AND cats (the previous test didn't always pick up exposure in cats, because they need to ingest only a fraction of what a dog does to die, and the test didn't test for levels that low).

The new test, however, has been rife with problems. Some of my colleagues at other clinics have tested normal, healthy pets and had positive results - even when following all instructions to the letter. This has been seen again and again. I was afraid to run the test in this dog and get a positive, because what would that tell me? It would be a death sentence for this dog, since he'd been sick for > 12 hours (antifreeze needs to be treated within 6-8hrs of ingestion, or it is uniformly fatal).

So, I started aggressive fluid therapy, anti-seizure medications, anti-emetics for nausea, and waited. Two hours later, he had a bladder. We got our urinalysis.

Guess what we found? Calcium monohydrate crystals. I called the owners who elected to euthanize instead of attempting treatment with the VERY expensive antidote (an excellent decision, as he was already severely affected).

In the end, we still have no idea where or how the exposure occurred. None of the other dogs have ever shown signs of toxicity. It's a mystery that will never be solved. I've since decided that the elevated WBC count was due to renal failure and renal inflammation...but that's just another guess in a series of guesses.

3 comments:

Nicki said...

I had a case like that in school. No amount of repeated history taking could help us figure out where the antifreeze came from. That dog also died.

Mara said...

I so don't miss antifreeze toxicity!

http://thecriticalvet.wordpress.com/

Amanda said...

When I was growing up, my parents had three mostly-outdoor dogs. Apparently, they barked sometimes while we were all away, but we only found that out when one died mysteriously of what was diagnosed too late as warfarin poisoning. We had a houseful of pets, and never kept the stuff around, so we were perplexed until we got an anonymous note from someone who claimed our neighbor was at a local bar bragging about throwing a rat poison-laced cheeseburger over our fence to "get rid of the neighborhood noise problem." In hindsight, my father remembered picking up some McDonald's trash from our yard around the same time.

Since then, I've heard a couple other cases of neighbors poisoning outdoor dogs, once with antifreeze. I hope that isn't what happened in your case, because the other dogs could be in danger.