An evaluation of eight methods of using fluorescein to predict the viability of skin flaps in the pig.

The brightness of the fluorescence of fluorescein can be increased by the use of special (interference) filters that allow visualization of the dye when much smaller doses have been given. Standard random-pattern skin flaps were made in pigs and low (1 mg/kg) and high (500 mg) doses of fluorescein were given intravenously. The dye distribution in the flaps was evaluated visually, photographically, and with a dermofluorometer. All the methods proved reasonably accurate in predicting survival, although in an occasional flap, readings by all the methods were off by as much as 3.5 cm. The traditional Wood's lamp visualization proved to be as accurate as any of the newer methods. The inaccuracies of the fluorescein test are probably inherent in the method, since it only measures vascularity at the time the dye is given--and blood supply can change. The main advantage of low-dose fluorescein is that it allows repeated injections at reasonably close intervals. For serial observations, the dermofluorometer is unquestionably the best method.