A systematic review of the safety of analgesia with 50% nitrous oxide: can lay responders use analgesic gases in the prehospital setting?

A safe and effective form of pain relief would be an advantage in the prehospital treatment of patients experiencing extreme pain. Although used by many emergency medical services, 50% nitrous oxide (an inhaled analgesic known to have good pain relief properties) is not widely used by volunteer and semiprofessional organisations. This review aimed to determine whether 50% nitrous oxide is safe for use by first responders who are not trained as emergency medical technicians. A thorough search of the literature identified 12 randomised controlled trials investigating the use of 50% nitrous oxide (as compared with placebo or conventional analgesic regimens) in a range of conditions. The outcomes analysed for this review were: adverse events, recovery time, and need for additional medication. None of the studies compared the treatments in the prehospital setting; children were well represented. Adverse effects were rare and significant adverse outcomes such as hypotension and oxygen desaturation could not be attributed to nitrous oxide. Compared with patients receiving conventional analgesia, those receiving 50% nitrous oxide did not require additional medication any more frequently and had a faster recovery from sedative effects. The low incidence of significant adverse events from 50% nitrous oxide suggests that this agent could be used safely by lay responders.