THE EFFECT OF DILUTE VASOPRESSIN SOLUTION ON THE FORCE NEEDED FOR CERVICAL DILATATION - A RANDOMIZED CONTROLLED TRIAL

Objective: To assess the force needed to mechanically dilate the cervi x of a nonpregnant woman after intracervically injecting dilute (0.05 U/mL] vasopressin solution. Methods: In a randomized, double-blind stu dy, equal amounts of either a dilute vasopressin solution or placebo ( normal saline) were injected into the intracervical stroma at 4- and 8 -o'clock positions, just beneath the mucosal surface, in 52 women imme diately before cervical dilatation in preparation for operative hyster oscopy When vasopressin solution was used, 20 mL of a dilute solution (4 U of 0.05 U/mL of vasopressin in 80 mt of normal saline) was inject ed. An electronic strain gauge and load cell were used to measure the peak linear force needed to dilate the cervix from 3 mm to 11 mm, usin g half-size metal dilators. Results: The mean (+/- standard error of t he mean) total peak linear force needed to dilate the cervix from 3 to 11 mm in the treated (vasopressin) and control (placebo) groups was 2 0.29 +/- 1.22 lb (range 5.54-40.82) and 37.05 +/- 2.55 lb (range 6.11- 52.2), respectively, a statistically significant difference. The mean total peak linear force needed to dilate the cervix in the treated gro up and in the control group in 0.5-mm increments from 3 to 11 mm was 1 .14 +/- 0.07 lb (range 0.81-1.69) and 2.08 +/- 0.07 lb (range 1.64-2.4 3), respectively, also a statistically significant difference. With in creasing parity, significantly less force was needed to dilate the cer vix from 3 to 11 mm in the treated group than in the control group (P < .001). Conclusions: Administration of dilute vasopressin solution (0 .05 U/mL) to the cervical stroma significantly reduces the force neede d to dilate the cervix. (C) 1997 by The American College of Obstetrici ans and Gynecologists.