Nitrous oxide for pain management during in-office transcervical sterilization
Awarded 2014
Complex Family Planning Fellowship Research
Emily Schneider, MD
University of New Mexico Health Sciences Center

Background: Hysteroscopic sterilization with Essure is increasingly performed in the outpatient setting. No studied interventions including paracervical block, intravenous or oral sedation, or intrauterine lidocaine, have successfully reduced pain during in-office procedures. Inhaled nitrous oxide with oxygen (NOS) has proven effective for short painful procedures in the outpatient and Emergency Room setting. NOS has analgesic, anxiolytic, and amnestic properties, as well as a vasodilatory effect on smooth muscle. An advantage of NOS is that is has rapid onset and reversal with minimal side effects and few contraindications. The use of NOS during in-office sterilization may reduce patient pain and anxiety, increase patient satisfaction, and ease provider placement of the coils.
Objectives: To evaluate whether NOS is superior to oral sedation for pain management during in-office hysteroscopic sterilization.
Methods: This double blinded randomized controlled trial enrolled women undergoing in-office hysteroscopic sterilization. The intervention group received NOS titrated to a maximum 70%:30% NO:O2 mixture and placebo pills pre procedure. The control group received inhaled O2 during the procedure and 5/325mg hydrocodone/acetaminophen and 1mg lorazepam pre procedure. The primary outcome was maximum procedural pain on a 100 mm Visual Analogue Scale (VAS) 3 – 5 minutes post procedure. A sample size of 30 women per treatment arm was required to detect a clinically significant pain difference of 20 mm on the VAS.
Results: 72 women, 36 per study arm, were randomized to account for unsuccessful bilateral coil placement and drop out after randomization. Two women in the study group and 6 in the control group were excluded due to unsuccessful bilateral coil placement. Mean age of participants was 34.1 ± 5.7 years and mean BMI was 30.1 ± 6.6 kg/m2. Mean maximum procedural pain scores were 22.8 ± 27.6 mm and 54.5 ± 32.7 mm for study and control groups, respectively (p < 0.001). Most study participants (97%) stated NOS should be offered for gynecologic office procedures and 86% would pay for NOS if it were not a covered benefit. Conclusions: NOS decreased pain with in-office hysteroscopic sterilization compared to oral sedation. Given its safety and favorable side effect profile, NOS should be considered for routine availability for in-office hysteroscopic sterilization.