Patient-administered nitrous oxide/oxygen inhalation provides safe and effective analgesia for percutaneous liver biopsy: a randomized placebo-controlled trial

Am J Gastroenterol. 2001 May;96(5):1553-7. doi: 10.1111/j.1572-0241.2001.03776.x.


Objective: Although percutaneous liver biopsy (PLB) can be a painful procedure, common practice has not included intravenous sedation or analgesia. Patient-administered nitrous oxide/oxygen (N2O/O2) inhalation has demonstrated analgesic efficacy in various procedures associated with mild to moderate pain. The aim of this study was to investigate the safety and efficacy of analgesia with N2O/O2 inhalation for PLB.

Methods: One hundred consecutive patients undergoing a first PLB (for chronic hepatitis C: 56, for alcoholic liver disease: 23, for miscellaneous reasons: 21). Patients were randomly assigned to self-administrate from a facial mask with a demand valve, for 5 min before and during biopsy, either a breathing mixture of 50% N2O/O2 (N2O group, n = 51), or a breathing oxygen placebo (P group, n = 49). Liver biopsy was performed at bedside after adequate local anesthesia with xylocaine. At the end of the procedure, patients were asked to self-evaluate pain experienced using a visual analogue scale (VAS) with scoring from 0 to 100 mm.

Results: N2O/O2 administration resulted in the absence of pain in a significantly higher number of patients treated than in patients of the P group: 19 versus 2, respectively (p = 0.0001). Patients receiving N2O/O2 had significantly lower pain scores than those of the P group: 12+/-12 versus 28+/-19 mm (p < 0.0001). No serious complication was observed. Side effects of N2O/O2 were minor and reversible. The average cost per biopsy was 4 US dollars.

Conclusions: Patient-administered N2O/O2 inhalation provides safe and effective analgesia, at a reasonable cost, for PLB. Its routine use could be useful for the management of patients with chronic liver disease undergoing PLB as it may enhance patients compliance with future biopsies.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Administration, Inhalation
  • Adult
  • Analgesia, Patient-Controlled* / adverse effects
  • Analgesia, Patient-Controlled* / economics
  • Analgesia, Patient-Controlled* / standards
  • Biopsy / methods*
  • Drug Combinations
  • Female
  • Health Care Costs
  • Humans
  • Liver / pathology*
  • Male
  • Middle Aged
  • Nitrous Oxide / adverse effects
  • Nitrous Oxide / therapeutic use*
  • Oxygen / adverse effects
  • Oxygen / therapeutic use*
  • Safety


  • Drug Combinations
  • Nitrous Oxide
  • Oxygen