ENHANCED CHOLINERGIC CUTANEOUS VASODILATION IN RAYNAUDS-PHENOMENON

Background Vasodilator function was determined in patients with Raynau d's phenomenon during intra-arterial infusions of the endothelium-depe ndent and -independent vasodilators, methacholine and sodium nitroprus side, respectively. Reactive hyperemia, induced by 5 minutes of arteri al occlusion with exercise, was also measured. Methods and Results Tot al blood flow was measured in the fingertip and forearm by venous occl usion plethysmography, and blood flow in the forearm skin was determin ed with laser Doppler flowmetry. Basal fingertip blood flow was not si gnificantly different between control subjects and patients with Rayna ud's phenomenon. Infusions of methacholine had no significant effect o n fingertip blood flow in control subjects, whereas patients with Rayn aud's phenomenon showed a significant increase in fingertip blood flow . Basal total forearm blood flow was significantly lower in patients w ith Raynaud's phenomenon than in control subjects. Infusions of methac holine and sodium nitroprusside produced dose-related increases in tot al forearm blood flow that were of similar magnitudes in the two group s, as were the reactive hyperemic responses. Laser Doppler measurement s of forearm skin blood flow, however, showed a significantly greater vasodilator re response to methacholine in patients with Raynaud's phe nomenon than in control subjects. Infusions of sodium nitroprusside pr oduced a relatively small vasodilator response in the skin of the fore arm that was smaller than that to methacholine and not significantly d ifferent between the two groups. Conclusions In Raynaud's phenomenon, a greater vasodilator response to infusions of methacholine in the fin gertip, where changes in blood flow mainly reflect those of skin, and in the skin of the forearm may reflect increased responsiveness of cut aneous blood vessels to stimulation of the endothelium. The mechanism involved is unclear but may result from a general abnormality of blood vessels in the skin, which is related to the pathophysiology of cutan eous vasospasm.