Local reflex in microcirculation in human cutaneous tissue.

Blood flow in cutaneous tissue measured by the local 133Xenon washout technique decreased about 35 per cent during venous stasis of 40 mmHg in three normal subjects. The response was unaffected by block of the nerve three cm proximally to the labeled area. When the tissue was infiltrated with lidocaine or with phentolamine, blood flow remained constant, indicating that the decrease in blood flow is due to an arteriolar vasoconstrictor response to increase in venous transmural pressure. Local venous stasis elicited a vasoconstrictor response in an adjoining area not affected by the stasis. The response was blocked by lidocaine applied to the side of stasis. In 2 chronically sympathectomized patients, the vasoconstrictor response was abolished in the denervated limbs but present on the non-operated side (1 patient with unilateral sympathectomy). The results indicate that the vasoconstrictor response to an increase in venous transmural pressure is due to a local nervous mechanism involving sympathetic adrenergic fibres, most likely a sympathetic axon reflex.