Skin microcirculation responses to severe local cooling.

When skin is exposed to cold, cutaneous blood flow is initially restricted due to sympathetic vasoconstriction. Prolonged exposure to cold has a secondary protective vasodilator effect. In the present study, the effects of severe and prolonged local cold on the cutaneous microcirculation were assessed. In 10 young healthy subjects, laser Doppler skin flux and flux motion were measured at the calf during 20 min of local ice cooling and 15 min subsequent recovery. In the 6th minute of cooling, mean skin flux decreased to 58 +/- 6% of the resting value (p < 0.05), then increased and reached 129 +/- 10% of the resting value at the end of the cooling period, followed by a phase of reactive hyperemia with a maximum of 225 +/- 24% (p < 0.05). Mean flux motion frequency, spontaneously present at rest with a frequency of 2.6 +/- 0.2 cycles/ min decreased rapidly during the first minutes of cold exposure, was absent during the 6th to the 10th minute, reappeared and started to increase from the 11th minute and reached 4.4 +/- 0.3 cycles/min during the recovery period (p < 0.05). This study seems to indicate that the phenomenon of protective increase of cutaneous microcirculatory blood flow consists of an initial phase of vasodilation, followed by a phase of active and enhanced microvessel vasomotor activity.