Hi Maryjo,
Last year when my Rudder was having breathing trouble before he died, the vet said he would never give Prednisone to a cat with diabetes, let alone a cat that had cardiomyopathy, which is what my Rudder had. He never suggested Lasix either.
I think that somewhere you should try to find a vet that knows more about asthma in cats, because it sounds like Smokie could be having breathing trouble due to asthma, as well as possibly heart trouble, but like Jess said, coughing is usually not a sign of heart failure, unless it is very rare.
You say that Smokie has CRI? Is that Chronic Renal Insufficiency? If so, then Jess also is right that Lasix is very hard on the kidneys and that could make matters worse.
I can't understand a vet giving instructions to give a cat he has not looked at, Lasix or Prednisone, without doing a thorough examination. If you are willing to take her in, and if she is as hard to handle as you have mentioned in the past, I imagine the vet does not want to sedate her, as that would only mask symptoms, or could cause her to get worse. So, I understand you are in a 'catch 22' situation with poor Smokie.
Is she eating okay? Does she have trouble swallowing her food? Why does the vet want her on Clavamox? It just doesn't seem right to throw drugs at a cat that he has not seen recently and really is only guessing at what might be wrong with her.
Do you have an ER vet place that you might take her to? I know that would cost more, but maybe they could handle her more easily, unless it is the drive in the car that gets her so upset. Have you looked to see if you have any vets that would be willing to come to your house to examine her?
I hope you can find some way to have her examined. Has she had any vomiting lately?
Sorry for all the questions, just trying to figure out what could be wrong that she is coughing like she is. Without seeing a vet, it is just a 'guessing game'.
Best wishes and sending prayers that you can find someone that can help.
Hugs,
Jean and Charcoal (GA)