Residual nitrous oxide in operating room personnel.

The concentrations of nitrous oxide in the blood and end-tidal air of 10 operating-room nurses were assayed by gas chromatography immediately and 1, 2, 5, and 21 h after 3 hours of exposure to an average of 380 ppm of nitrous oxide in operating-room air. In the second trial the nurses' end-tidal air concentrations of nitrous oxide were assayed on Monday, Wednesday, Friday and Sunday morning, and on Sunday afternoon and evening to reveal a possible accumulation of nitrous oxide during a routine week. After cessation of exposure there was a rapid decrease in the blood concentrations of nitrous oxide during the first hour (from 153 +/- 110 microgram/1 to 48 +/- 20 microgram/l at 1 h; means +/- s.d.), followed by a slower decrease. Small amounts (mean +/- s.d.: 18 +/- 6 microgram/l) of nitrous oxide were still measurable on the following morning 21 h after exposure. At 2 or 5 h after exposure there was an increase in blood and end-tidal air concentrations of nitrous oxide in seven and nine nurses, respectively. The end-tidal air concentrations of nitrous oxide were greater on Wednesday (22 +/- 7 microgram/l) than on Monday morning (8.4 +/- 1.5 microgram/l), but on Friday they were similar to those measured on Monday morning. The concentrations measured on Sunday, i.e. 2 days after exposure, were similar (average 15 microgram/l) to those measured during the week. It is concluded that, after cessation of exposure to nitrous oxide, there is a rapid decrease in the concentrations in blood and end-tidal air, but small amounts of nitrous oxide remain in the body for at least 3 days after cessation of exposure.