Fixed 50:50 mixture of nitrous oxide and oxygen to reduce lumbar-puncture-induced pain: a randomized controlled trial.
Lumbar puncture (LP) has been frequently performed for more than a century. This procedure is still stressful and often painful. The aim of the study was to evaluate the efficacy of a fixed 50% nitrous oxide-oxygen mixture compared to placebo to reduce immediate procedural pain and anxiety during LP.



A randomized controlled trial was conducted involving adults who needed a cerebrospinal fluid analysis. Patients were randomly assigned to inhale either a fixed 50% nitrous oxide-oxygen mixture (50% N2O-O2) or medical air (22% O2-78% N2). Cutaneous application of a eutectic mixture of local anaesthetics was systematically done and all LPs were performed with pencil point 25G needles (20G introducer needle). The primary end-point was the maximal pain level felt by the patient during the procedure, the maximal anxiety level being a secondary outcome, both measured using a numerical rating scale (0-10).



A total of 66 consecutive patients were randomized. The analysis was intention to treat. The maximal pain was 4.9 ± 2.7 for the 33 patients receiving air and 2.7 ± 2.7 for the 33 receiving 50% N2O-O2(P = 0.002). Similarly, the maximal LP-induced anxiety was 4.5 ± 3.1 vs. 2.6 ± 2.6 (P = 0.009), respectively. The number needed to treat to avoid one patient undergoing significant pain (pain score ≥ 4/10) was 2.75. Body mass index >25 kg/m2was significantly associated with higher pain intensity (P = 0.03). No serious adverse events were attributable to 50% N2O-O2inhalation.



Inhalation of a fixed 50% N2O-O2mixture is efficient to reduce LP-induced pain and anxiety.
Service de Neurologie, CHU Clermont-Ferrand, Clermont-Ferrand, France.|Clermont-Ferrand and Inserm U1107, Clermont Université, Université d'Auvergne, Neuro-Dol, Clermont-Ferrand, France.
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Moisset
Service de Neurologie, CHU Clermont-Ferrand, Clermont-Ferrand, France.
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Sia
Biostatistics Unit, Délégation Recherche Clinique et Innovation, CHU Clermont-Ferrand, Clermont-Ferrand, France.
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Pereira
Service de Neurologie, CHU Clermont-Ferrand, Clermont-Ferrand, France.
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Taithe
Service de Neurologie, CHU Clermont-Ferrand, Clermont-Ferrand, France.
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Dumont
Pôle pharmacie, CHU Clermont-Ferrand, Clermont-Ferrand, France.
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Bernard
Service de Neurologie, CHU Clermont-Ferrand, Clermont-Ferrand, France.|Clermont-Ferrand and Inserm U1107, Clermont Université, Université d'Auvergne, Neuro-Dol, Clermont-Ferrand, France.
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Clavelou
D000328:Adult; D000769:Anesthesia, Inhalation; D001007:Anxiety / Q000517:prevention & control / Q000523:psychology; D015992:Body Mass Index; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009339:Needles; D009609:Nitrous Oxide / Q000008:administration & dosage; D010100:Oxygen; D010146:Pain / Q000209:etiology / Q000517:prevention & control*; D010147:Pain Measurement; D013129:Spinal Puncture / Q000009:adverse effects* / Q000523:psychology; D016896:Treatment Outcome
D009609:Nitrous Oxide; D010100:Oxygen
anxiety; lumbar puncture; nitrous oxide; pain; procedural pain