Self-administered nitrous oxide: an adjunct analgesic.

In a pilot study of 26 patients, a mixture of 50% nitrous oxide and 50% oxygen (N2O-O2) appeared to be an effective and safe analgesic for the incision and drainage of closed-space infections. The analgesic effect of N2O-O2, as measured by a Mean Analgesic Index, is augmented by both amnesic and dissociative effects, ie, patients remembered experiencing significantly less pain than they complained of during the procedure (p less than .01) and reported significantly more pain than they appeared to be having, as recorded by an observer (p less than .01). The patient's recollected pain, however, correlated well (r = .68) with the observer's assessment. Forty-two percent of patients had undergone a similar or identical procedure in the past without the benefit of N2O-O2 and made uniformly favorable comparative statement concerning the analgesic effect of the gas.