Do not leave them unsupervised. If a cat fight erupts keep your hands out of it. Do not attempt to handle or pick up either cat. Clap hands and shout, bang a pot with a spoon, throw water, anything to startle them, but don't ever reach into a tangled mass of fighting cats. It always sounds much worse than it is.
Declawed cats have no alternative except to bite.
When things have cooled down considerably, go over each of their bodies carefully checking for damage. Bites and punctures wounds can become infected and abscess. Call your vet if you suspect that an abscess is forming. You must watch for signs of stress. Spraying, indiscriminate urination and defecation, mewing and hiding behaviors are also associated with anxiety and stress.