Effect of Paracervical Block Volume on Pain Control for Dilation and Aspiration: A Randomized Controlled Trial.

OBJECTIVE: To compare pain scores during office dilation and aspiration between low-volume and high-volume paracervical block of the same dose.

METHODS: We conducted a multi-site, randomized, single-blind, placebo-controlled trial from October 2018 to December 2020. We randomized participants presenting for office dilation and aspiration under minimal sedation stratified by procedural indication (induced abortion vs early pregnancy loss) to a 20-mL buffered 1% lidocaine paracervical block or a 40-mL buffered 0.5% lidocaine paracervical block, both with two units of vasopressin in a standardized technique. To detect a 15-mm or greater difference in pain at the time of cervical dilation with 80% power and a two-sided alpha of 0.05, a total of 104 participants was required. The study was also powered to detect a 20-mm or greater difference in pain at the time of cervical dilation within each stratum (induced abortion and early pregnancy loss). The primary outcome was pain with cervical dilation on a 100-mm visual analog scale in the overall cohort. Secondary outcomes included pain with cervical dilation within each stratum. We used a Wilcoxon rank-sum test to compare median pain scores between groups.

RESULTS: We enrolled 114 participants. There was no difference in median pain scores between low-volume and high-volume groups during dilation (62 mm vs 59 mm, P=.94), aspiration (69.5 mm vs 70 mm, P=.47), postprocedure (25 mm vs 25 mm, P=.76), or overall (60 mm vs 60 mm, P=.23). Stratified by indication, there were no significant differences in scores at any time point between the low-volume and high-volume paracervical block groups. There was decreased overall pain in patients with induced abortion who received the higher volume paracervical block, though this did not reach statistical significance (67.5 mm vs 60.5 mm, P=.08). Pain during paracervical block administration was similar between groups (55 mm vs 45 mm, P=.24) and there was no difference in occurrence of side effects (P=.63).

CONCLUSION: We found no difference in pain with cervical dilation among participants who received the low-volume compared with high-volume paracervical block when studied alone.

CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, NCT03636451.