Impaired Postural Vasoconstriction: A Contributory Cause of Oedema in Patients with Chronic Venous Insufficiency

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Abstract
Dependent oedema is a common feature in patients suffering from venous insufficiency. Postural vasoconstriction which prevents oedema has been shown to be impaired in several conditions complicated by dependent oedema. We therefore investigated the postural vasoconstrictor response, foot swelling rate and capillary density in eight patients with venous insufficiency and seven normal controls. Foot skin blood flow was measured on the pulp of the big toe using laser–Doppler flowmetry with the foot at heart level (H) and placed approximately 1 metre below the heart (D). Postural fall in flow was calculated as (H – D) × 100/H. Foot swelling rate was measured simultaneously using a strain gauge Plethysmograph. Postural vasoconstriction was impaired in venous insufficiency at 62 ± 12% compared to 88 ± 4% in controls ( P < 0.02). Capillary density in the forefoot was assessed using television microscopy and was significantly reduced in the venous insufficiency group at 26.83 ± 2.74 per mm2 compared to 36.96 ± 1.09 per mm2 ( P < 0.01). These findings suggest impaired postural vasoconstriction may contribute to the formation of oedema characteristic of venous insufficiency. The apparent reduction in capillary density may be implicated in the pathogenesis of venous ulceration to which such patients are prone.