BACKGROUND AND PURPOSE:

• Solano et al. (BOJG, 2021) compared inhaled nitrous oxide vs 1% lidocaine paracervical infiltration vs no analgesic for pain control during in-office hysteroscopy

METHODS:

• Single-blind stratified randomized clinical trial
• Participants
  • Women undergoing hysteroscopy
  • Performed with 4.3 mm inner sheath, with working channel for semirigid 5 Fr. operating instruments
• Interventions
  • Nitrous oxide | Mask or a buconasal pipette with on-demand intermittent flow, self-controlled by patient
  • 1% lidocaine | 12 ml used for pericervical and paracervical blocks
  • No analgesic | Needle touching cervico-vaginal fold but no puncture
• Study design
  • Participants were stratified into 3 groups depending on indication (biopsy, polypectomy or tubal sterilization)
  • Pain was assessed by a gynecologist blinded to procedures and treatments
  • Intention-to-treat approach
• Primary outcome
  • Pain control: Visual analog scale (VAS) from 0 to 100 mm

RESULTS:

• Participants per group
  • Nitrous oxide group: 105 women
  • 1% lidocaine group: 104 women
  • No analgesic: 105 women
• Baseline characteristics were comparable between groups
• Mean VAS scores after the procedure
  • Nitrous oxide: 34.7 mm
  • 1% lidocaine: 36.1 mm
  • No analgesic: 47.3 mm
• Mean VAS scores were significantly lower in the nitrous oxide (p=0.001) and 1% lidocaine groups vs no analgesic (p=0.010)
• There was no significant difference in VAS scores between nitrous oxide and 1% lidocaine groups (p = 1.0)
• At least 1 adverse event reported
  • Nitrous oxide: 13.4% of patients
  • 1% lidocaine: 25.0% (most commonly bleeding and pain at the puncture site)
  • No analgesic: 20.0%
• Rescue analgesia or atropine were required  
  • Nitrous oxide: 3.8%
  • 1% lidocaine: 7.7%
  • No-analgesic: 14.3% (p=0.010 vs nitrous oxide and p=0.13 vs 1% lidocaine)

CONCLUSION:

• Nitrous oxide and 1% lidocaine were both similarly effective at controlling pain during in-office hysteroscopy
• Nitrous oxide was associated with fewer adverse events
• The authors concluded that nitrous oxide has a better safety profile, is easier to administer and has

…an equivalent analgesic efficacy as the one shown by paracervical block with

lidocaine-1%, widely recognised as the standard treatment, for all in-office hysteroscopic procedures assessed

Learn More – Primary Sources:

Nitrous Oxide vs Lidocaine vs No‐analgesic for In‐office Hysteroscopy: A Randomised Clinical Trial

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