First, her breathing is thankfully only slightly elevated but with pink gums that is fine. Now I would note that her appetite loss will be associated with the same nausea that has caused her to vomit. At her age, we do have a few concerns, this could be a gut infection (bacterial, viral), or secondary to an organ issue (eg liver or kidney disease). Cancer is also possible at her age but we'd hope not likely here since she only has just developed signs.
With this all in mind, we can try some home supportive care just now. First, you can try an OTC pet safe antacid.[ie Pepcid (0.25-0.5 mg per pound every 12-24 hours),Omeprazole (0.25-0.5 mg per pound every 24 hours), Tagamet (3-5 mg per pound every 8-12hrs)]. Whichever you choose, we’d give this 20 minutes before food to allow absorption. Though do double check with your vet if she has a known health issues or is on any medications you haven't mentioned. Of course, if you give this and she cannot keep it down due to nausea that is usually a red flag that we need to bypass her mouth with injectable anti-vomiting medication from a local vet.
Afterwards, let's try giving small meals of a light diet (eg rice with scrambled egg, cottage cheese, boiled chicken, boiled white fish, or meat baby food (as long as its garlic/onion free)). If she cannot be tempted but we can stop the nausea, we can try syringe feeding watered down canned puppy food if need be.
Finally as dehydration is a risk even if she is drinking (especially if we do have organ dysfunction here), we need to keep an eye on her hydration. To check that she isn't dehydrated, there are a few things you can test. Further to checking for gum moisture, do make sure she doesn’t have sunken eyes and that she doesn’t have a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a good video HERE- (https://www.youtube.com/watch?v=KducLdeqGsM)). If you are seeing any signs of dehydration already, then that would be our cue to have her seen before this becomes an additional issue for her (especially as it is often dehydration that makes them feel unwell).
Overall, Kizzy's signs do raise a few concerns here. Therefore, we’d want to start supportive care now. Of course, if she cannot keep that or water down at any point, appears weak or dehydrated, or doesn’t respond to the above within 12-24 hours; then we'd want to get the local vet involved. They can assess hydration, check bloods to make sure her organs are ok and exclude any sinister viruses present. Based on their exam findings, the local vet can treat with injectable anti-vomiting medication, fluids, +/- antibiotics to get her settled.
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