I don't know if your dog would need anesthesia for the ear swab. My experiences with the culture were from a direct draw from the bladder and no anesthesia was used. The other experience was when my girl had her bladder cancer surgery and they did a liver biopsy, saw infection and did a culture on that. This one, of course, was conducted under surgical anesthesia.
Anesthesia carries risks, especially in an elderly, ill dog. I know that my little Tipper went through several rounds of extensive tests to see if she was strong enough for her bladder surgery. I know this case is different from yours.
It may be that your vet isn't giving up, but instead sees this as a case out of her hands that needs specialized care. When my Tipper was sick, my vet referred us to an internal medicine specialist. This is the vet that found the bladder polyp (pre-cancer) and that my dog had a horrible asymptomatic urinary tract infection. These were found on ultrasound. My vet was stunned, since she gave no symptoms. I know she took months of antibiotics to clear the infection.
In my case, I found the specialists to be more cold and impersonal (except for Tippy's cardiologist--she was so kind). The focus was on curing the illness and these are the steps to do this. If you chose to go the specialist route, be prepared. It is very expensive. I found that I could get my medications from my family vet much less expensive than the specialty hospital.
And, sadly, there is a point when you have to detach yourself from the love you have for your dog and really look at the quality of life. In my case, it took the specialty vet telling us that we had done everything we could--we had no more medical options. (One of my dog's medications put her in irreversible kidney failure).
If Mandy is able to eat, drink and eliminate that sounds encouraging. I don't know about the sneezing/runny nose part. I would examine the nasal discharge so you can tell the vet the color and thickness. It could be that the nasal discharge could be swabbed? Maybe this is a sign that the ear infection is draining and clearing. With my sinus infections, I could tell when my ears were opening because I would get a nasty drainage in the back of my throat. I'm not a medical person, so don't get your hopes up from that, but who knows.
Sending prayers and hugs for Mandy.
With Mac is it a wait and see whether this returns again or not. He had a good day yesterday. I pray for a good day today. We will face tomorrow when it arrives.
-Sandra (Scottie Dog)