Impaired transient vasodilation and increased vasoconstriction to digital local cooling in primary Raynaud's phenomenon

Raynaud's phenomenon (RP) is defined as episodic ischemia of the extremities in response to cold. Although the structure of skin capillaries is normal in primary RP, some data suggest impairment of microvascular function. We aimed at testing whether digital skin blood flow was lower in RP than in controls while cooling locally. We further evaluated the contribution of sensory nerves in the response. We recruited 21 patients with primary RP and 20 healthy volunteers matched on age and gender. After a 10-min baseline at 33°C, skin temperature was cooled at 15 or 24°C during 30 min on the forearm and the finger while monitoring perfusion with a custom-design laser Doppler flowmetry probe. Perfusion was also assessed after topical anesthesia. Blood flow was expressed as cutaneous vascular conductance (CVC). Data were subsequently expressed as area above the curve (AAC(0-30)) of the percentage decrease from baseline CVC (%BL). CVC on the dorsum of the finger was lower in RP patients compared with controls at 15°C (AAC(0-30) were 106,237.2 and 69,544.3%BL·s, respectively; P = 0.02) and at 24°C (AAC(0-30) were 86,915 and 57,598%BL·s, respectively; P = 0.04) whereas we observed no significant difference on the finger pad and the forearm. Topical anesthesia increased CVC in patients with RP (P = 0.05), whereas it did not affect reactivity in controls (P = 0.86). Our study shows exaggerated skin microvascular vasoconstriction to local cooling on the dorsum of the finger in primary RP compared with controls. Part of this abnormal response in primary RP depends on sensitive nerves.