Skin fluorescence, a method to predict amputation site healing

Abstract

Although skin blood flow is an important determinant of amputation site healing, most techniques to evaluate it are cumbersome and indirect. We have prospectively compared a new, simple and direct technique, skin fluorescence (SF), with a more established indirect method, segmental limb blood pressures (BP), to determine the value of each in predicting amputation healing of an ischemic extremity. Twenty-six consecutive patients with ischemic tissue loss were studied prior to amputation. Thigh, calf, and ankle BP were measured; then SF was determined by injecting 10–15 mg/kg of fluorescein intravenously and examining the limb with uv light. BP of > 50 mm Hg was considered adequate for amputation wound healing; yellow SF indicated adequate skin blood flow. In each case, the most distal site predicted to heal by either method was selected for amputation. Thirty amputations were performed (6 digital, 3 transmetatarsal, 11 below knee, and 10 above knee) with an 80% healing rate. When SF and BP disagreed on the level of amputation, fluorescein always predicted a more distal site. SF accurately predicted amputation healing in 80% of cases. In the remaining 20%, amputation failures were due to infection in two and deep tissue necrosis in four. BP was accurate and useful in 47% of cases. In 14 patients BP indicated the need for a higher level of amputation than was successfully performed. In two patients BP measurement was indeterminate due to “stiff arteries.” Furthermore, in two patients amputations failed despite BP > 50 mm Hg. We conclude that SF helps the surgeon select a more distal level of amputation than segmental limb pressures, and one that has a high likelihood of healing.