title: Nitrous oxide for early analgesia in the emergency setting: a randomized, double-blind multicenter prehospital trial.
abstract: OBJECTIVE
  Although 50% nitrous oxide (N(2) O) and oxygen is a widely used treatment, its efficacy had never been evaluated in the prehospital setting. The objective of this study was to demonstrate the efficacy of premixed N(2) O and oxygen in patients with out-of-hospital moderate traumatic acute pain.
  
  
  METHODS
  This prospective, randomized, multicenter, double-blind trial enrolled patients with acute moderate pain (numeric rating scale [NRS] score between 4 and 6 out of 10) caused by trauma. Patients were assigned to receive either 50/50 N(2) O and oxygen 9 L/min (N(2) O group) or medical air (MA) 9 L/min (MA group), in ambulances from two nurse-staffed fire department centers. After the first 15 minutes, every patient received N(2) O and oxygen. The primary endpoint was pain relief at 15 minutes (T15), defined as a NRS ≤ 3 of 10. The NRS was measured every 5 minutes. Secondary endpoints were treatment safety and adverse events, time to analgesia, and patient and investigator satisfaction with analgesia.
  
  
  RESULTS
  Sixty patients were included with no differences between groups in age (median = 34 years, interquartile range [IQR] = 23 to 53 years), sex (37 males, 66%), and initial median NRS of 6 (IQR = 5 to 6). At T15, 67% of the patients in the N(2) O group had an NRS score of 3 or lower versus 27% of those in the MA group (delta = 40%, 95% confidence interval [CI] = 17% to 63%; p < 0.001). The median pain scores were lower in the N(2) O group at T15, 2 (IQR = 1 to 4) versus 5 (IQR = 3 to 6). There was a difference at 5 minutes that persisted at all subsequent time points. Four patients (one in the N(2) O group) experienced adverse events (nausea) during the protocol.
  
  
  CONCLUSIONS
  This study demonstrates the efficacy of N(2) O for the treatment of pain from acute trauma in adults in the prehospital setting.
authors: Service d'Aide Médicale Urgente de la Haute Garonne (SAMU 31), Hôpital Universitaire de Purpan, Toulouse, France.
authors: Jean-Louis
authors: JL
authors: Ducassé
authors: Georges
authors: G
authors: Siksik
authors: Manon
authors: M
authors: Durand-Béchu
authors: Sébastien
authors: S
authors: Couarraze
authors: Baptiste
authors: B
authors: Vallé
authors: Nathalie
authors: N
authors: Lecoules
authors: Patrice
authors: P
authors: Marco
authors: Thierry
authors: T
authors: Lacombe
authors: Vincent
authors: V
authors: Bounes
mesh_terms: D059787:Acute Pain / Q000628:therapy*; D000328:Adult; D000368:Aged; D000698:Analgesia / Q000009:adverse effects / Q000379:methods*; D004311:Double-Blind Method; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide / Q000009:adverse effects / Q000627:therapeutic use*; D010100:Oxygen / Q000009:adverse effects / Q000627:therapeutic use*; D059408:Pain Management / Q000379:methods*; D010147:Pain Measurement; D017060:Patient Satisfaction; D011446:Prospective Studies; D016896:Treatment Outcome
chemical_list: D009609:Nitrous Oxide; D010100:Oxygen