Hi Walter, I'm Dr. Deb.
I recently came online and see that your question hasn't been answered. I'm so sorry that you've had to wait for a response, especially given the nature of your question.
Please accept my sincere condolences on your loss; I know this must have been heartbreaking for you and your family.
The diagnosis of ITP is not necessarily an easy one to make and while I'm not disputing this diagnosis, the causes of a low platelets are varied. If you'll indulge me for a moment, I'll cover the possible causes which then might dictate possible treatment options.
1. Increased destruction as might be seen in Rickettesial or tick diseases. In a case like this or any case where a tick disease might be a factor, I'd start these patients on Doxycycline immediately.
Unfortunately, Vitamin K is not the standard treatment for a tick disease although it would be if a rodenticide was suspected (see below).
Auto-immune diseases such as ITP can also cause increased destruction as you know. High doses of steroids are the initial treatment of choice.
If ITP is suspected and steroids are not effective after 7-14 days, then other immunosuppressive drugs should be considered:
a) Azathioprine (Imuran®). Combination therapy with prednisone and azathioprine has been reported to have longest survival times.
b) Cyclosporine (Neoral®): Neoral® is preferred over Sandimmune® because of more consistent absorption. However it has used on a limited basis because it is costly and requires therapeutic drug monitoring within the first 24-48 hrs then every few weeks
c) Leflunomide: 4mg/kg every 24h. Leflunomide has been reported in a few studies to be effective in treating immune-mediated and inflammatory diseases. Very expensive.
2. Decreased production in the bone marrow. Some sort of underlying cancerous problem would be suspected. It would take a bone marrow biopsy to detect such a problem and obviously the prognosis is poor.
3. Sequestration such as in the spleen. Unfortunately, this is usually associated with a cancerous process, too, such as lymphoma. An ultrasound with a needle aspirate can be helpful in making this diagnosis.
4. Rodenticide poisoning. Even if there's not a high suspicion that this is the problem, treating with Vitamin K can be started since there is no downside to doing so.
5. Cancer elsewhere in the boy.
So, my approach to thrombocytopenia would be to start Doxycycline, start steroids, (usually I give an injection of Vincristine once if ITP is suspected), consider other immunosuppressive drugs if indicated, give transfusion if the platelets are low enough, start Melatonin (since it has been shown to increase platelet production), and give the owners a guarded prognosis.
If a rodenticide is suspected or is even a long-shot possibility, then I'll start Vitamin K at the same time.
Although the vet may not have felt that Vitamin K was indicated if they were certain that no rat poison had been ingested, it wouldn't have been harmful. I have to confess I don't understand the attitude that was shown to you either. It has no place in communication with owners as far as I'm concerned.
I know that you are absolutely devastated by Tacitus' death since everything happened so incredibly quickly. I also have to wonder whether or not he might have gone into DIC (LINK) given his rapid decline. This is a complicated cascade of events but ultimately is fatal.
Even though I know this isn't what you necessarily will want to hear, I would be doing a disservice to both you and him if I were less than truthful and honest. I hope you understand.
I also hope this helps you to understand what treatment options are usually considered in these cases.
Again, my condolences to you and your family. Deb