STUDIES ON GANGRENE FOLLOWING COLD INJURY. V. THE USE OF FLUORESCEIN AS AN INDICATOR OF LOCAL BLOOD FLOW: FLUORESCEIN TESTS IN EXPERIMENTAL FROSTBITE 1

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Abstract
Analyses were made of the distribution of intraven. injected fluorescein in normal ears of rabbits and in ears severely injured by cold. The results showed that both the entrance of the dye into and the exit of dye from the injured regions were slower than the exchanges observed in uninjured tissues. The maximum intensity of fluorescence reached in frostbitten skin was lower than the maximum recorded in normal skin. Repeated tests on the same animal showed that the exchanges of dye became progressively slower with time after injury. When both ears of rabbits were frostbitten and procaine block of the stellate ganglion was produced on one side, the tests with fluorescein showed earlier and higher maximum intensity of fluorescence in the frostbitten ear on the side blocked. The greater intensity of fluorescence on the side having increased blood flow as the result of blockage of the stellate ganglion was attributed to the longer persistence of blood flow through true capillaries and, hence, greater opportunity for exchange of dye between the blood and interstitial fluid. Edema fluid was taken from frostbitten feet of rabbits after the intraven. injn. of fluorescein. The fluorescein conc. was at least twice as great as that in the blood. The mechanisms of impaired dye exchange in frostbitten tissues are discussed, and an hypothesis is presented in which the impairment of dye exchange is attributed to reduction of available surface for diffusion by the development of stasis in the true capillaries following cold injury.