Circulatory reaction to heat and cold in vibration-induced white finger with and without sympathetic blockade--an experimental study.

Central nervous, sympathetic mechanisms and local factors influencing the vascular response to cold in the finger skin were studied with plethysmographic and laser-Doppler methods in a chamber with controlled temperatures from 45 to about 5 degrees C, with and without sympathetic finger blockade. Blood flow and pressure were assessed after finger occlusion, together with finger heating and cooling, in workers with vibration-induced white finger (VWF) and in healthy persons not exposed to cold or vibration. Finger blood flow at vasodilatation, as measured by finger arterial inflow (FAI) after occlusion was smaller in the VWF group than in the reference subjects both with and without anesthesia, and capillary flux in the anesthetized finger tended to be smaller. At vasoconstriction, with or without anesthesia, the VWF subjects had lower FAI values than the referents. The studied flow and pressure variables differed considerably between the groups. The peripheral resistance of the VWF subjects was higher than that of the referents. This difference was the most pronounced after finger anesthesia. A possible pathogenetic mechanism in VWF is an increase in peripheral resistance due to a local defect in the vessels, with subsequent reduction in flow and intramural pressure.