Change in canal pressure with cervical cerclage

Abstract

KATHLEEN HUHN, WILLIAM WATSON, Mayo Clinic College of Medicine, Obstetrics and Gynecology, Rochester, Minnesota OBJECTIVE: To determine the pressure and temporal changes associated with cerclage placement. STUDY DESIGN: Models of a cervix were made using smooth and skeletal muscle tissue to a uniform width and central canal diameter. Different types of suture (0-Prolene and 5 mm Mersilene) and cerclage types (McDonald and Shirodkar) were loosely placed in each ‘‘cervix’’ model. A LuMax fiber optic pressure transducer catheter was placed in the canal at the level of the cerclage stitch and tightened with the initial pressure recorded. The catheter was than advanced past the cerclage site and serial measurements were taken at 0.5 cm intervals along the length of the model. Readings were reported at one minute intervals for a total of ten minutes for each cerclage. The percent change in pressure for each sample was recorded. RESULTS: The average initial canal pressures after securing the cerclage stitch was 174.6 cm H20 (SD 23.5). The average canal pressure at the 10 minute mark was significantly reduced (P ! .001) to 69.9 cm H20 (SD 25.4) resulting in a mean decrease in canal pressure of 62.3%. The average total zone of pressure recorded around the level of the cerlage stitch was 1.69 cm (SD 0.59). At the ten minute mark, this 1.56 cm (SD 0.56) zone of pressure had not signicantly decreased (P = .17). Two models were re-evaluated 24-hours after stitch placement and had canal pressures of 35-40 cm H20 and a zone of pressure which decreased from 2.5 cm to 1.0 cm. CONCLUSION: While the pressure within the canal decreased signficantly within the first ten minutes after cerclage placement, the zone of pressure generated by the cerclage placement remained constant. The initial canal and zone of pressure decreased to relatively low levels by the following day. SMFM Abstracts S155