OCCUPATIONAL EXPOSURE TO ANESTHETIC-GASES DURING PEDIATRIC-SURGERY

Methods. To assess the occupational exposure of the anaesthetist to an aesthetic gases, a total of 1 German and 25 Swiss hospitals were inves tigated. A Bruel & Kjaer Type 1302 multi-gas monitor was used to measu re concentrations of nitrous oxide and halogenated anaesthetic agents in the anaesthetist's breathing zone. Measurements were performed duri ng 114 general anaesthetic, 55 of which were in patients under II year s of age. In these 55 patients, the influence of various factors on th e exposure (time-weighted average concentrations) was estimated by com paring different data groups. The efficiency of the applied scavenging equipment was examined by surveying the exhalation valve with a leak detector (type TIF 5600, TIF Instruments, Miami). Results. Sessions wi th patients under ii years of age revealed much higher anaesthetic gas exposures compared to older patients. The concentrations of nitrous o xide were on average threefold (Fig. 1), those of the halogenated anae sthetics fivefold higher (Fig. 2) for the younger patients. In 11- to 16-year-old patients the exposure level was the same as in adult patie nts. The measurements showed a reduction of 85% in exposure if an effi cient scavenging system (i.e., no waste gas discharge to room air thro ugh the exhalation valve) or lower fresh gas flow were used (Fig. 4); 42% of the inspected scavengers were inefficient, and reduced the expo sure on average by only 30%. In operating theatres with a ventilation rate of at least ten air changes per h, the measured concentrations of anaesthetic gases in the inhalation zone of the anaesthetists were re duced more than 50% compared to poorly ventilated rooms (Figs. 4 and 5 ). The use of tracheal intubation or laryngeal mask airway (LMA) anaes thesia resulted in a reduction of 80% in exposure compared to standard face masks if efficient scavenging was used. The exposures during ses sions with inefficiently scavenged Bain coaxial systems or unscavenged semi-open delivery systems of the Jackson-Rees type were tenfold high er than with scavenged rebreathing circuit systems (Fig. 6). During an aesthesia with IV or double-mask induction, the average levels of inha lation anaesthetics were reduced by about 80% compared to inhalational induction with standard masks (Fig. 7). The anaesthetist's working te chnique is a very important factor that strongly influences the concen trations. Poor work practices, like lifting off the face mask with ana esthetic gas flow turned on, increased the exposure of the anaesthetis t and other operating room personnel drastically, even if the other co nditions (scavenger and room ventilation) were good. Discussion. The e xposure levels of anaesthetic gases are generally higher during anaest hesia in children up to 10 years of age than in older patients. Nevert heless, the measurements showed that exposure during paediatric anaest hesia can be kept below the recommended limit (8-h TWA in Switzerland) of 100 ppm nitrous oxide and 5 ppm halothane or 10 ppm enflurane or i soflurane. Causes of high exposures were particularly high fresh gas f lows often applied without scavenging or together with inefficient sca venging devices and the high part of mask anaesthesia and inhalation i nduction with a loosely held mask. To achieve an effective reduction o f occupational exposure, well-adjusted and maintained scavenging syste ms and low-leakage work practices are of primary importance. As leakag e can never be completely avoided, a ventilation late of at least ten air changes per h should be maintained in operating rooms and rooms wh ere anaesthesia is induced to keep down concentrations of waste anaest hetic gases. High exposure during mask anaesthesia and inhalation indu ction can be prevented by further measures. Using a LMA instead of a s tandard mask reduces the exposure to the same level as endotracheal in tubation. The exposure during induction can be reduced remarkably by t he use of the double-mask system or IV induction. Applying low fresh g as flows reduces not only the exposure concentrations in the theatres, but also the contribution to the environmental burden('greenhouse eff ect' and ozone layer destruction).