Thank you Kay,
First, while the weather is a wee bit warm tonight, it is not to a level where we’d assume it is related to her signs. Still if she does have a heart or lung condition that you have not noted before (which seems unlikely since you mentioned she is a healthy wee lass), then you can consider putting a fan near her, opening a window, or keeping her in a cooler part of the house.
Otherwise, I am more suspicious that her discomfort is due to the trigger for her profuse vomiting and the associated nausea that will still be unsettling her. Now if Ellie is vomiting profusely just now, we do need to be very concerned and keep a close eye on her. Just to make note of the other signs you are seeing, I do want to say that it is quite common to see cats be withdrawn and lethargic when suffering with GI upset. Furthermore, if she has been vomiting profusely then this will be quite stressful and likely what is inducing her to pant (stress panting is the likely reason for her open mouth appearance). So, these signs are not surprising in a cat that has no history or heart or lung disease but has such an unsettled stomach. Therefore, the main thing is to make sure that we settle this for her as quickly as possible since we don't want her to continue to vomit and potentially cause herself to become dehydrated (since that often makes them feel even more poorly).
Now when kitties start vomiting there can be a number of culprits. This includes bacterial infection, viruses, parasites, dietary indiscretion, cancer, pancreatitis, foreign bodies, and toxins. I am glad to see that you haven't noted that she gotten into anything toxic, since that would obviously be an emergency situation.
And if we can put toxins and foreign material lower on our lists of concerns, then we can try to settle her stomach at home. First thing, because she is actively vomiting, even if she is keen to eat for you, I would rest her tummy for a wee while (8-12 hours) and give it a chance to settle. Let her have access to water, but not huge volumes since overdoing it with the water can cause vomiting as well.
If the vomiting does subside by that point, then tempt her with a small volume (a tablespoon worth to start) of a light/easily digestible diet. Examples of this would be boiled chicken, boiled white fish, scrambled eggs (made with water and not milk), meat baby food (do avoid the ones with garlic powder in the ingredients) or there are also veterinary prescription diets that can be used in cases of gastroenteritis (ie Hill’s I/D or Royal Canin’s sensitivity). Now if she can keep the small amount, she can have a bit more after 30 minutes. And as she keeps it down, she can have a bit more and so on. The aim of these light diets are that they are easy on the compromised GI and tend to be better tolerated.
As well, do keep an eye on her water intake as profuse vomiting can quickly dehydrate a cat (and dehydration will make them feel worse and complicate their situation).If you are concerned that she is becoming dehydrated, then do check her hydration status now. To check this, there are a few things we can test at home. One is whether the eyes appear sunken, if the gums are tacky instead of wet/moist, and whether she has a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a wee video on this HERE. (They use a big dog but it makes it easier to see and the principles are exactly the same) If you are seeing any signs of dehydration already, then that would be a red flag to have her seen urgently by the vet before this gets any further out of control.
Otherwise, if she is not dehydrated, you can try an encourage her to drink but offering fresh water or even low-sodium chicken broth. But since she is vomiting, syringe feeding of fluids is contraindicated since we don't want to cause further vomiting.
Even if we can settle the vomiting, we do have to be concerned about associated nausea, as that can make getting them to eat difficult. There are a number of antacids that are available over the counter and pet friendly. I would advise only treating with one, but the two I tend to recommend are Pepcid (More Info/Dose) or Zantac (More Info/Dose).We tend to give these 30 minutes before offering food to give it time to be absorbed. And of course, we’d want to check with her vet first if she does have any pre-existing health issues or is on any medications you haven’t mentioned.
Overall, there are a range of agents that could be triggering Ellie's vomiting. At the moment, you can try resting her stomach and try the above. If you initiate these treatments and do not see improvement over the next 12-24 hours (we don't want to let it go too long for her) or she has any further violent vomiting episodes or her breathing doesn't settle alongside the vomiting then I would be best to take her to the vet so that they can make sure there is nothing worrisome afoot. The vets will be able to have a feel of her to make sure she has no sinister lumps or bumps or anything that shouldn't be there. As well, the vet will be able to cover her with antibiotics against bacterial gastroenteritis and anti-vomiting medications by injection to help settle her stomach and get her back on track as quick as possible.
Finally, just in case you don't see her settling in the next wee while, I do want to mention that most veterinary practices here do have contingency plans for emergency care for their patients even when they are not open. Therefore, it is worth ringing the practice. Even if they are not open, they will likely have a message to direct you on how to contact their out of hours service. And if you don't have a vet you can find one local to you, you can check the RCVS Register (HERE) to find your local vets or Vets Now (LINK) who are open all nights/weekends. In any case, if you wanted to get her checked out sooner or if the panting especially doesn't settle in the next hour or so then there are options to have her seen tonight too.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,
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