THE ANALGETIC EFFECTS OF LOW CONCENTRATIONS OF NITROUS OXIDE COMPARED IN MAN WITH MORPHINE SULPHATE 1

Abstract

Fifteen healthy J subjects, varying in age from 18 to 34 yrs., were studied for the analgesic effects of low concs. of nitrous oxide as compared with those from the subcut. adm. of morphine sulphate. The principal conclusions were based on the observations of the effect on the pain perception threshold produced from heat radiation of the skin of the forehead by the technique of Chapman and Jones. The influence on pain arising from muscle ischemia, as a result of exercise of the hand under conditions of vascular occlusion, were also noted. As these latter observations were highly subjective, they were only used as supplementary support of the conclusions. Two components of the pain experience were measured the threshold of pain perception and, as far as possible, the pain reaction, as judged by the beginning of wincing. N2O in 20% conc. in O2 was as effective an analgesic agent as morphine, 15 mg./150 lb. of body wt. N2O in this conc. did not impair consciousness and was effective as long as it was not allowed to escape from the closed respiratory system, whereas the morphine effect passed through a maximum and, since it was metabolized, the effect then disappeared. Unlike morphine, N2O in this conc. was not usually associated with undesirable side effects.