Background and purpose
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.
Methods
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).
Results
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/m2 was significantly associated with higher pain intensity (P = 0.03). No serious adverse events were attributable to 50% N2O−O2 inhalation.
Conclusions
Inhalation of a fixed 50% N2O−O2 mixture is efficient to reduce LP‐induced pain and anxiety.