Laser Doppler evaluation of skin vasomotor reflexes during sympathetic stimulation in normals and in patients with primary Raynaud's phenomenon.

Laser Doppler flux measurements were used to determine skin blood flow in 12 patients with primary Raynaud's phenomenon and in 12 healthy age and sex matched control subjects. The vasoconstrictor response to standing, the Valsalva maneuver and a deep breath were used to diagnose local abnormalities of peripheral nerve sympathetic function and were found normal together with a normal catecholamine response to standing upright. However, baseline laser Doppler measured skin blood flow was lower in patients with primary Raynaud's phenomenon (p less than 0.01 in all 3 tests) while resting norepinephrine levels were higher (2.25 +/- 0.33 nmol/l) than in normals (1.31 +/- 0.11 nmol/l; p less than 0.01). These results are consistent with the existence of an elevated sympathetic nervous system activity at rest and a decreased baseline skin blood flow without signs of an excessive sympathetic and skin vascular responsiveness to sympathetic nervous system stimulation.