Fluorometric quantification of low-dose fluorescein delivery to predict amputation site healing

This retrospective study evaluated quantification of skin fluorescein delivery by fiberoptic fluorometry as a means of predicting the healing potential of an amputation site. Fluorometry uses a dual-channel fiberoptic light guide--one channel transmits blue light to excite the fluorescein in the skin under study, and the other transmits emitted fluorescence from the skin to a photomultiplier tube where it is measured. Ten minutes after intravenous administration of sodium fluorescein (4 to 8 mg/kg), fluorometric readings were obtained at more than 100 reading sites. In the 86 cases without preoperative cellulitis at the site of amputation, preoperative fluorometry clearly distinguished between healing and nonhealing sites. Healing sites averaged 79% of the fluorescence of a healthy reference area (dye fluorescence index [DFI] = 79), while failing sites averaged only 27% (p less than 0.01 by ANOVA). In all but one case where the DFI was greater than 42, the amputation healed. In all cases where the DFI was less than 38, the amputation failed. In general, uncertainty was limited to sites with values between these limits. The technique maintained its high accuracy in patients with diabetes and for distal amputations. However, it was not accurate at sites of active cellulitis (12 cases). There were no significant adverse effects from the slow injection of the low dose of fluorescein used for this technique. We conclude that fluorometry is an effective means of predicting healing in patients undergoing amputation.