Mechanisms for edema formation in normal pregnancy and preeclampsia evaluated by skin capillary dynamics.

Disturbances of vasomotor activity and veno-arteriolar reflex mechanism probably promote cutaneous edema formation. Videophotometric capillaroscopy was used to measure nailfold skin capillary blood cell velocity (CBV) and its response to increased transmural pressure induced by venous occlusion in healthy subjects, normal pregnancies and patients with preeclampsia. Vasomotion, assessed by rhythmic variation of CBV, was also recorded. Both frequency (3-10 cycles/minute) and amplitude (0.01-0.23 mm/s) of CBV fluctuations were similar in all groups investigated. In healthy controls basal CBV was positively correlated with the amplitude of individual velocity fluctuations (r = 0.89). CBV response to venous occlusion was significantly reduced (p less than 0.05) in preeclampsia compared to normal pregnancies and non-pregnant controls. This finding indicates impaired veno-arteriolar reflex which may contribute to the edema formation seen in preeclampsia. It is suggested that vasomotor activity may serve as a physiological modulator of vascular resistance and hence CBV.