Configuration of the microcirculation in pre-eclampsia: possible role of the venular system

OBJECTIVE: To test the hypothesis that during pre-eclampsia microvascular function and structure are disturbed, which contributes to raised venular resistance. METHODS: The microcirculation of the skin and bulbar conjunctiva was studied in 11 women with preeclampsia and nine parous controls, both in the third trimester and 3 months postpartum. Using intravital videomicroscopy, arteriolar and venular diameters were determined in the conjunctiva. In addition, skin capillary densities and morphology were determined. RESULTS: Conjunctival venular diameters were 30% smaller in pre-eclampsia compared with controls, both during pregnancy (P < 0.01) and postpartum (P = 0.045). Arteriolar diameters also tended to be smaller; however, this difference was not statistically significant. In women with pre-eclampsia we found a higher percentage of tortuous/dilated skin capillaries (5%) compared with controls (0%; P < 0.05). Three months postpartum, this difference had disappeared. Skin capillary densities did not differ between the groups. CONCLUSION: Women with severe pre-eclampsia have narrow venules, both during manifest disease and postpartum. Possibly, these narrow venules raise venular resistance and with it, hydrostatic pressure in the capillary bed. The latter, in turn, may explain the higher number of tortuous/dilated capillaries in women with preeclampsia. These findings support an important role of the venous system in the pathogenesis of pre-eclampsia.