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Am J Gastroenterol. 2001 May;96(5):1553-7.

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

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Service des Maladies du Foie et de l'Appareil Digestif, H pital de Bicêtre, Université Paris-Sud, Le Kremlin-Bicêtre, France.



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.


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.


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.


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.

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