Self-administration of a nitrous oxide/oxygen mixture may be more effective than oxygen alone as an adjunct analgesic treatment in reducing moderate to severe breakthrough cancer pain, according to results from a double-blind randomized clinical trial published in the European Journal of Pain.
A total of 240 people with cancer who were experiencing breakthrough pain were randomly assigned to receive, in addition to immediate-release morphine sulphate, a nitrous oxide/oxygen mixture (n=180) or oxygen (n=60). Pain was assessed with the 0 to 10 numeric rating scale at baseline, at 5 and 15 minutes after the start of treatment, and 5 minutes after treatment.
Baseline pain scores were comparable in both treatment groups (6.6±1.2 in patients treated with the mixture vs 6.6±1.3 in patients receiving oxygen). Pain reduction was greater in patients receiving the gas mixture vs oxygen alone at 5 minutes after administration (2.8±1.3 vs 5.5±1.2, respectively; P <.01) and at 15 minutes (2.0±1.1 vs 5.6±1.3, respectively; P <.01).
In addition, patient satisfaction was found to be higher in the nitrous oxide/oxygen group compared with the oxygen group (P <.01). Although a greater percentage of patients administered the gas mixture vs oxygen alone experienced nausea (13.9% vs 11.7%, respectively), no significant overall differences between the 2 groups was observed with regard to adverse events.
The nitrous oxide/oxygen mixture “can be used widely in low-resource settings because it exhibits analgesic properties and causes a low incidence of side effects,” noted the investigators.
Liu Q, Gao LL, Dai YL, et al. Nitrous oxide/oxygen mixture for analgesia in adult cancer patients with breakthrough pain: a randomized, double-blind controlled trial [published online December 11, 2017]. Eur J Pain. doi: 10.1002/ejp.1144