Rodenticides

We could all hear my next patient in the waiting room.  His cough sounded deep, wet, and painful.  I guessed before I even saw him that something was very wrong.  This was not the dry hacking cough we have become accustomed to hearing in dogs with infectious tracheobronchitis (kennel cough).  There was a sinister pitch to this that told me he had fluid in his lungs and a hard time breathing without going into a coughing fit.

When my assistant and I walked into the room, you could see a little bit of smeared blood on his white feet.  The owner told us that "Bubba" vomited a little bit of blood the evening before.  He had just started coughing 24 hours ago.

I have extolled the virtues of a complete physical exam in previous posts.  This story has a different moral... Accurate and pertinent history.  Early in my veterinary education, I saw a young puppy that presented for lethargy and limping.  I asked questions about the limp, the food, coughing, sneezing, vomiting, diarrhea, etc.  I whisked the puppy away to visit an orthopedic surgeon to see if she could help me localize the limp.  When I came back and spoke with the owner, I saw tears welling up in her eyes and she produced a bag of rat bait from her purse.  She then told me that he had eaten half of the bait.



A "Rodent Of Unusual Size" from The Princess Bride



This moment of combined shock, frustration (at myself for not asking the right questions and at the owner for not just telling me what the problem was), and revelation has stuck with me ever since.  Anti-coagulant rodenticide can present with a myriad of signs, the best way to diagnose it is by asking the owner the right questions.  

When I asked Bubba's owner if there was any chance that he had eaten any rodent poison, she laughed and said, "no, that was my other dog... and that was about a week ago.  We watched him very closely afterwards and nothing really happened".  This brings me conveniently to the main point of this post:

Most rodent baits do not cause any signs for three to five days... sometimes even longer.  If your dog ingests rodenticide and seems fine the next day, he/she could still be in grave danger of lethal poisoning.

Given the possible exposure to the poison and his clinical signs, I told the owner we should check his coagulation times to see if his blood was clotting appropriately.  Anticoagulant rodenticides essentially rob the body of it's ability to form blood clots.  As a result, animals will bleed inappropriately.  Prolonged blood clotting times and a history of possible exposure to anticoagulant rodenticide is highly suggestive if not diagnostic of poisoning.

This coughing dog was essentially bleeding into his lungs.  This creates a bad situation for two different reasons.  First is the obvious loss of blood, second is the loss of usable lung volume (due to blood filling). Toxicologists will tell you that bleeding into the airway or into the central nervous system creates a poor prognosis.  Our treatment for anticoagulants sometimes does not work quickly enough to stop bleeding into areas that cannot sustain prolonged bleeding.

I administered a vitamin K injection and wrote a prescription for all of her other dogs.  We had a long discussion about plasma transfusions and advanced care.  The story is not quite finished for this dog.  The last time I spoke with Bubba's owner, she said he seems to be doing much better.  He is not out of the woods yet.  The newer generations of these poisons have very long half-lives and can stick around at lethal blood levels for weeks.  However, so far so good for Bubba.