Medical Technology Associates: Halogenated Agent & N2O Exposure Monitoring

Halogenated Agent & Nitrous Oxide Exposure Monitoring

Anesthesia is as common to medical care as is antiseptic care of wounds; however, for too long, exposure to and control of waste anesthetic gases (WAGs) and vapors during special procedures have put healthcare workers in jeopardy. At any given time, more than 250,000 people who work in hospitals, operating rooms, dental offices, and veterinary clinics might be exposed unnecessarily to harmful levels of WAGs.

The waste anesthetic gases and vapors of concern are nitrous oxide and halogenated agents (vapors) such as halothane, enflurane, methoxyflurane, trichlorethylene, and chloroform. The list of workers with potential for exposure to WAGs includes, nurses, physicians, surgeons, obstetricians, gynecologists, operating room technicians, recovery room personnel, dentists, veterinarians and their assistants, and other auxiliaries. Hospital emergency room personnel may also be exposed, but not on a regular basis.

OSHA, therefore, has developed technical instructions designed to give guidance for coping with exposure to WAGs. The instructions cover sampling methods, leak test procedures, medical surveillance, disposal methods, training and exposure to WAGs.

Exposure Concentrations: No worker should be exposed to concentrations of WAGs greater than 2 parts per million (ppm) of any halogenated anesthetic agent, based on the weight of the agent collected for a 45-liter air sample by charcoal absorption over a sampling period not to exceed one hour.

Controlled agents and their respective weights corresponding to 2 ppm are: chloroform, 9.76 mg/cu m; trichloroethylene, 10.75 mg/cu m; halothan, 16.15 mg/cu m; methoxyflurane, 13.5 mg/cu m; enflurane, 151 mg/cu m; fluroxene, 10.31 mg/cu m.

When such agents are used in combination with nitrous oxide, levels of the halogenated agents well below 2 ppm are achievable. In most situations, control of nitrous oxide to a time-weighted average concentration of 25 ppm during the anesthetic administration period will result in levels of about 0.5 ppm of the halogenated agent.

The occupational exposure to nitrous oxide, when used as the sole anesthetic agent, shall be controlled so that no worker is exposed at eight-hour, time-weighted, average (TWA) concentrations greater than 25 ppm during anesthetic administration.

A complete WAGs management program includes at the outset, the application of a well-designed WAGs scavenging system. Such a system will consist of a collecting device (scavenging adapter) to collect WAGs and vapors from breathing systems at the site of overflow; a ventilation system to carry WAGs from the operating room; and, a method or device for limiting both positive and negative pressure variations in the breathing circuit which may be used by scavenging systems. Most anesthesia equipment being manufactured today includes scavenging systems.

The remainder of the WAGs management program should include work practices minimizing gas leakage, the application of a routine equipment maintenance program so that gas leaks are minimized, and periodic exposure monitoring and provision for adequate general ventilation.