Managing pain and anxiety during transabdominal chorionic villus sampling. A noninferiority randomized trial of nitrous oxide vs local anesthesia

Abstract

Introduction: Transabdominal chorionic villus sampling (CVS) is an invasive procedure for prenatal diagnosis reported to be associated with anxiety and pain. In this context, the need for analgesia during CVS has been considered useful. Even though several authors have been interested in pain management during amniocentesis, no study has been published on pain reduction during CVS. Our objective was to evaluate pain and anxiety management during transabdominal CVS using nitrous oxide (N₂ O) and local anesthesia.

Material and methods: In a randomized controlled noninferiority trial, self-administered nitrous oxide (N₂ O) inhalation (equimolar premix of oxygen and nitrous oxide) was compared with local anesthesia (1% lidocaine) before CVS. Primary outcome was pain and secondary outcome was anxiety, both measured on a visual analog scale 30-60 minutes before, immediately after (5-10 minutes) and 30-60 minutes after CVS. With a statistical power of 90%, type I error of 5% and two-sided test and potential exclusions, a sample size of 96 patients per group was enrolled and randomized. No patient was enrolled before the trial registration date.

Results: From 13 March 2013 through 10 February 2015, 192 patients (96 per group) were screened and randomized. Most characteristics were similar across groups. Pain in the N₂ O group was 2.65 ± 0.22 vs 3.32 ± 0.26 in local anesthesia group [mean ± standard error of mean (SEM)]. Mean anxiety in the N₂ O group was 3.17 ± 0.27 vs 5.19 ± 0.30 in the local anesthesia group.

Conclusion: N₂ O was as efficient and even superior to local anesthesia for both pain and anxiety reduction during CVS, as the 95% confidence intervals were both below the prespecified noninferiority margin of 0.8 and below zero.

Keywords: anxiety; chorionic villus sampling; local anesthesia; nitrous oxide; pain.