Vibration aftereffects on vasoconstrictor response to cold in the normal finger.

The acute effects of unilateral 30 min exposure to hand-arm vibration on the vasoconstrictor response to cold in a finger from both hands were investigated in 12 healthy men (age 18-38 years) who had never worked with vibrating tools. One hand was exposed to accelerations of 4.0 and 16.0 m.s-2 on 2 different days. The vasoconstrictor response to cold (R%) was expressed as the relative decrease in finger systolic blood pressure, measured using cuff and strain gauge techniques, when the finger was cooled from 30 to 10 degrees C. The R% of both third fingers were measured simultaneously before unilateral vibration exposure and 15, 60 and 120 min after the end of each exposure. The R% of both fingers were not affected by the low acceleration vibration (P > 0.10). Exposure to the high acceleration vibration was followed by an unchanged R% of the exposed finger but an increased R% of the non-exposed finger after 15 min (P < 0.05); there was an equal increase of 30%-40% in R% of both fingers after 60 min (P < 0.05). The R% of both fingers had returned to normal after 120 min (P > 0.10). The results would indicate that short-term exposure to vibration induces a transitory hyperreactive central vasoconstrictor drive to the central sympathetic nervous system or circulating agents, which initially was locally counteracted by an induced hyporeactive vasoconstrictor function of local vasomotor mechanisms of the vibration exposed digital arteries. The hyperreactive vasoconstrictor effect demonstrated may contribute to the development of vibration-induced white finger if cumulative exposure time were to be considerably increased.