Hello & welcome, I am Dr. B, a licensed veterinarian. I do apologize that your question was not answered before now, but different experts do come online at different times. Anyway, I have just come online, read about your situation and wanted to help.
First, I must say that I am worried about Oscar.
Vomiting and anorexia for days in young cats is a serious situation. They are high risk for dehydration, weakness due to nutrient loss, and even secondary liver issues. So, we need to be proactive with your lad and get this nausea under control quick! Now in regards ***** ***** questions, our differentials for these nausea signs would include bacterial or viral gastroenteritis, pancreatitis, parasites/protozoa infections, general dietary indiscretions, and ingestion of harmful items (ie toxins, plants, non-edible items).
With this all in mind, we again need to tread with care. If it has been 2 days, we'd be best to have him seen urgently for treatment. Any delay to this and we can at least try some home supportive care to try to settle his stomach. To start, if he hasn’t just vomited (since otherwise we’d need to rest the stomach for a few hours first), you can consider treating with an OTC pet safe antacid like Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid), or Tagamet (More Info/Dose Here @ http://www.petplace.com/article/drug-library/library/over-the-counter/cimetidine-hcl-tagamet). Whichever you choose, we’d give this 20 minutes before offering food to allow absorption. Of course, do double check with your vet if he has a known health issues or is on any medications you haven't mentioned. Also if you give this and he cannot keep it down due to nausea that is usually a red flag that we need to bypass his mouth with injectable anti-vomiting medication from his vet.
While letting that kick in, if he is weak, you can try to boost his blood sugar by rubbing a sugary syrup on his gums. Examples of this include karo syrup, glucose syrup, or even pancake syrup. Once he is more settled, you can plan to try small meals of a light/easily digestible diet. Examples you can use are boiled chicken, boiled white fish, or scrambled eggs, or meat baby food (garlic/onion free only) The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset. As long as improvement is being seen, I usually advise continuing this until the signs are settled, and then weaning slowly back to what you normally feed.
Since dehydration is a risk here, we need to keep an eye on his hydration. To check this and make sure dehydration isn’t an issue, there are a few parameters you can test. Further to checking for gum moisture, you will want to make sure his eyes are not looking sunken and that he doesn’t have a "skin tent" when you lift the skin. To see how to check these, you can find a good video HERE (http://www.ehow.com/video_12232503_dog-dehydrated.html). If you do see any of these signs already, then that would be our cue to have him seen before this becomes an additional issue (especially since its often dehydration that makes them feel unwell).
Overall, a wide range of agents could trigger the signs we are seeing with poor Oscar. Therefore, we’d want to start supportive care to try to settle his stomach. Though if he cannot keep that or water down, appears dehydrated already, or doesn’t respond to the above within 12-24 hours (as this time frame is getting risky); then we'd want to get his vet involved. They can assess his hydration, rule out fever, ensure nothing in his stomach that shouldn't be, or any sinister viruses present. Depending on their findings, his vet can treat with injectable anti-vomiting medication, fluids, appetite stimulants, +/- antibiotics to settle his stomach and get him back feeling like himself.
Please take care,
If you have any other questions, please ask me – I’ll be happy to respond. **Afterwards, I would be grateful if you would rate my service by clicking on the "Rate my Expert' button at the top of the page as this is the only way I am credited for helping you. Thank you for your feedback!: )