Now I have to say that I am concerned about your lad.
At this age, vomiting and anorexia can quickly take a toll on them.Therefore, we do need to be proactive here, especially if he may have some belly discomfort (a reason to not move, and risk pain in dog logic) and has that elevated breathing rate (which sounds like a discomfort based elevation instead or anemia or oxygen issues). Now based on the signs we are seeing, we do have a few concerns for the nausea causing both his vomiting and refusing to eat. Common causes we need to consider include bacterial or viral gastroenteritis, pancreatitis, parasites/protozoa infections, general dietary indiscretions, and ingestion of harmful items (thankfully less likely here). Though at his age, we'd also have to consider Gi signs secondary to organ issues (ie kidney, liver), metabolic disease, and even cancer. So, we need to tread with care for your lad.
With this all in mind and if he has been off color for a week, we'd be best to have him seen as soon as possible. His vet can pinpoint which of those issues are present and address them to get him back to normal before we see dehydration and collapse from weakness. And I think this is truly best if he has gut discomfort as well.
Otherwise, we can try some home supportive care to try to settle his stomach. To start, you can consider treating with an OTC pet safe antacid [ie Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid), Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac), 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.
Once he is more settled, you can plan to try small meals of a light/easily digestible diet. Examples you can use are cooked white rice with boiled chicken, boiled white fish, or scrambled eggs, or meat baby food (garlic/onion free only) There are also OTC vet diets (ie Hill’s I/D or Royal Canin’s sensitivity) that can be used too. 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. And if he won't eat but isn't actively vomiting, we could try syringe feeding a puree of these or even try Nutrical paste, Clinicare or Dogsure liquid diets, or puppy food. Those last ones will just get more in per bite and help given his body some energy to fight this.
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 your lad. Therefore, if he is sore, we'd be safest to have him seen. Otherwise, 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; then we'd want to get his vet involved. They can assess his hydration, check bloods, ensure there are no sinister lumps or bumps present that shouldn't be, or any sinister viruses present. Depending on their findings, his vet can treat with injectable anti-nausea medication, appetite stimulants, fluids, +/- antibiotics to settle his stomach and get him back feeling like himself.
Please take care,
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