Evaluation of waste anesthetic gases, monitoring strategies, and correlations between nitrous oxide levels and health symptoms

Abstract

The release of waste anesthetic gases (WAG) in hospital operating rooms (ORs) was evaluated to determine if staff exposure to nitrous oxide exceeded the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) and investigate possible correlations between symptoms and nitrous oxide exposure. The monitoring strategy consisted of nitrous oxide measurements by personal monitoring of the anesthetists and scrub nurses, and area monitoring at the exhaust grills. In addition, room ventilation rates and carbon dioxide concentrations were measured. Self-administered questionnaires were given to both the operating room personnel and staff on control wards. Nitrous oxide levels exceeded the current TLV of 50 ppm in 4 of 12 ORs. Anesthetists typically received the highest nitrous oxide exposure. There was a strong correlation (r2 = 0.90) for nitrous oxide dosimetry results between anesthetists and scrub nurses, and a fair correlation (r2 = 0.35) between area monitoring results and the anesthetists' personal exposures. Carbon dioxide levels commonly exceeded 1000 ppm on control wards. A correlation between reported symptoms and nitrous oxide exposure was not demonstrated. Reported symptoms more closely correlated with carbon dioxide levels. Nitrous oxide dosimetry of the anesthetists appears to be the only accurate strategy for monitoring human exposure to WAG in an operating room.