Hello I am Dr. Joey. Thanks for trusting me to help you and your pet today. I am a licensed veterinarian with over 16 years of experience. I look forward to working with you.
I am so sorry your dog is going through this and that it sounds to be very stressful to have him seen which makes it very difficult to do testing and rechecks.
The tricky part is knowing if the cough is due to pneumonia (sounds unlikely), an upper respiratory infection (also unlikely) or the congestive heart failure (most likely). Dogs with congestive heart failure can cough for two different reasons. First is if there is fluid accumulation in the lungs, which would be treated with the furosemide (Lasix); some dogs require multiple diuretics like this to get it under control. Second would be if his heart is enlarged and pushing on his airway. This latter would be my top suspicion for the cause of the cough. Did a board certified radiologist read his x-rays (if not then I highly advise this to know if he is truly severely in failure or only mildly and get an opinion on the size of his heart and if this could be pushing on his airway)?
Usually we treat airway irritation with a different medication (codeine) to suppress the cough.
As well, was his blood pressure taken? We need to know if this was high and if so then it would need to be rechecked next week to ensure the enacard is the right dose. As a final very important diagnostic test would be for him to have an echocardiogram (can your vet arrange for this to be done in-house? I know it requires he be sedated again but very important to know what type of heart failure we are contending with). If you prefer not to have him seen right away again, then I recommend you pursue having the films read by a radiologist, if not already done.
As to this culture, I am afraid swabs of the throat really are not useful. There is so much contaminant bacteria (from the mouth) back there that it really doesn't give us much information. Now if he had a tracheal wash or bronchoscopy to get a sample directly from his airways then this is different. Either way, I am skeptical if he truly has congestive heart failure that the cough is related to an antibiotic infection; so I would not expect much benefit from this medication.
Also, as a side note, pimobendan is a fantastic drug but we have to be sure this is needed (this is where the echocardiogram is very useful) and one of its top side effects is to worsen coughing. I have had this occur in a few patients. So, you need to try to gauge if the coughing worsened after you started, and if so then discontinuing for 24-48 hours should see improvement in the cough.
I am at a point I need to know what questions you have.I hope that the information I provided has been helpful.
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