Thank you all for the positive karma sent Mathilda's way. The vet took off the patch and gave her a subcutaneous electrolyte injection to hydrate her. The immediate effect was that she looked like a doggy version of Quasimodo until a little later when her body absord the liquid.
The result was pretty amazing. Immediately upon getting home she ran around the yard and woofed down tons of dogfood and water. I think it's fair to say she's pretty much out of the woods.