Nikki had the same problem after her dental 2 years ago. A week later, we noticed what looked to be an abrasion. It quickly became large and deep. The vet said that some of the medicine during the anesthesia leaked into the surrounding tissue when the iv catheter was being removed. This caused the surrounding tissue to die and slough off. We had to take her to the vet for daily to twice weekly dressing changes with a special high-sugar dressing. When the dead tissue was gone, she needed the leg sutured back together. Dr Sheff said that this was only the second time in 20 years he has seen this happen. He also said that I would not be paying a penny for the treatment. It was his fault the medicine leaked and therefore his responsibility to treat it.