If you are having an emergency and have to move a heavy dog who cannot get up, roll them on to a bath towel and drag the towel with pup on it. You can even use the towel as a sling and have two people slide or carry the dog.
If you have to move a very heavy dog a long distance, especially up or down stairs, and it is not a timed emergency, call AmbuVet. Their number is easy: (800)AmbuVet. Explain your predicament and they will send a vet tech or two who are not only licensed but are able to hoist, carry and deliver your dog for you.