The transcapillary exchange of sodium fluorescein in ischaemic limbs measured by fluorescein flowmetry.
The transcapillary exchange of sodium fluorescein in the skin of 36 extremities (19 patients) with arterial occlusive disease was measured using two different ways of analysing the tissue fluorescence, fluorescein flowmetry (FF) and dynamic fluorescein angiography (FA). 7 mg sodium fluorescein/kg body weight was given intravenously. With FF, the transcapillary exchange of sodium fluorescein is expressed in arbitrary units as a fluorescence index. With FA, the time interval from the bolus injection to the first appearance of the fluorescence in the tissue is measured. There was an inverse correlation between pain and fluorescence index. All eight extremities with a fluorescence index of 0.001 density units/s or lower needed amputation, whereas all extremities with higher indices were viable. All extremities requiring amputation had an appearance time of 150 s or more, which contrasted with those remaining viable, having an appearance time of 120 s or less. The results indicate that FF as well as FA are appropriate methods to measure a 'nutritive' transport of solutes in the skin. Theoretically, however, if quantitative values for blood flow are required, we recommend FF, this method being more adequate, since it is influenced both by the fraction of cardiac output distributed to the tissue and by cardiac output itself. If, however, only a prognosis of a limb's viability is needed, FA is sufficient, being easier to perform, only requiring the measurement of the appearance time.