Now I suspect her appetite loss and vomiting are interlinked as nausea can cause both. Common causes for this are gastroenteritis (bacterial, viral), pancreatitis, parasites/protozoa infections, general dietary indiscretions, and ingestion of harmful items or secondary to systemic disease (eg liver or kidney disease, IBD, cancer, etc). Now its good nonedible things are not likely an issue but we need to be careful if her gums are paler then usual as that can be a sign we see in gut blockage but also with internal bleeding (not really fitting with the rest of Katy's signs though). So, we need to keep a close eye here.
As for her GI signs, we can try to counter nausea with 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-nausea medication from a local vet.
Afterwards, let's try tempting her to eat. The hope is she will feel more up to it with the antacid on board. We can try 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)). This is usually better tolerated/absorbed by the compromised gut which means more nutrients in and less GI upset. Else if we don't have active vomiting, we can also gently syringe feed watered down canned puppy food.
Finally as dehydration is a risk, 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, her signs do raise a few concerns here. If she is very pale, I'd lean to having Katy seen now to be safe. Else if its only slight we can try 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, rule out fever, make sure there is nothing in her stomach that shouldn't be there or any sinister viruses present. Based on their exam findings, the local vet can treat with injectable anti-nausea medication, appetite stimulants, +/- antibiotics to get her settled.
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