Blood concentrations of nitrous oxide in theatre personnel

Blood concentrations of nitrous oxide were measured in anaesthetists, surgeons and theatre nurses. Comparison of anaesthetists and surgeons working in the same theatre showed that in ENT surgeons concentrations were greater (P < 0.01), while in general surgeons they were smaller (P < 0.003). Blood concentrations of nitrous oxide in the "circulating" nurses were low; with scavenging they were unmeasurable. Atmospheric concentrations in the breathing zones were usually greater than the corresponding blood concentrations, but this was not always true. However, a positive correlation between blood and atmospheric concentrations was obtained (r = 0.82). Meticulous use of scavenging devices produced a mean reduction in blood nitrous oxide concentrations of 86% for all groups. The mean blood concentration of nitrous oxide in anaesthetists when scavenging was used was 45 p.p.m. (1.9 micromol/litre). This figure should be taken into account in establishing maximum permitted exposure to nitrous oxide.