The effect of vascular coiling on venous perfusion during experimental umbilical cord encirclement

OBJECTIVE: The aim of these studies was to compare venous perfusion in umbi lical cords subjected to a standardized tight encirclement force. Compariso ns were made between cords from normal pregnancies and those complicated by gestational diabetes mellitus and intrauterine growth restriction. STUDY DESIGN: The cannulated cord segment was wrapped around a plastic cont ainer, which in turn was attached with nylon string to a hanging graduated measuring cylinder in which known volumes of water could be applied for wei ght. The cord was perfused with Krebs solution to a constant venous perfusi on pressure of 40 mm Hg. Weights of 100-g increments were applied until tot al cessation of venous perfusion was observed. The weight. length, number o f vascular coils, and degree of hydration were recorded for each cord. The coiling index was defined as the number of vascular coils per 10 cm of cord . RESULTS: Regression analysis of 34 cords (normal, n = 16; gestational diabe tes mellitus, n = 12; intrauterine growth restriction, n = 6) identified a significant inverse correlation (P = .0003, Spearman rank correlation) betw een coiling index and the minimum weight required to occlude venous perfusi on. Cords from pregnancies complicated by intrauterine growth restriction d isplayed a higher frequency of vascular coiling and were more easily occlud ed (median weight, 350 g) than were cords from pregnancies complicated by g estational diabetes mellitus, which were less coiled and tended to resist o cclusion (median weight, 1100 g). CONCLUSION: During experimental cord encirclement there was a significant i nverse relationship between vascular coiling and susceptibility to cord ven ous occlusion when traction was applied to the encirclement.