[Laughing gas as the principle substance in assessing occupational exposure to inhalation anesthetics]. / Lachgas als Leitsubstanz zur Beurteilung der Arbeitsplatz-belastung mit Narkosegasen.

PURPOSE: In the Federal Republic of Germany limits for the chronic exposure to nitrous oxide and volatile anaesthetics have been prescribed by legislation. According to the technical rules for the handling of hazardous substances TRGS 402 it is legal to measure a single substance in a mixture of hazards, unless the behaviour of all substances is known. Studies about corresponding concentrations of nitrous oxide and volatile anaesthetics in anaesthetic working areas have not yet been carried out. METHODS: During one working week each the concentrations of nitrous oxide, enflurane and desflurane were measured by infrared spectrometry in a working area equipped with air condition and in a non-ventilated operating theatre. Corresponding concentrations of nitrous oxide were measured from the same gas samples. RESULTS: Statistical calculations showed linear correlations of the enflurane and nitrous oxide concentrations in all anaesthetic areas. No linear regression was found between the desflurane and nitrous oxide concentrations. In the working area where desflurane anaesthesias were carried out, significantly higher concentrations of nitrous oxide were observed. Nevertheless the Chi2-test showed no significant differences in the distribution of categorised measurement values. DISCUSSION: Although it is not possible to calculate desflurane concentrations from the nitrous oxide concentrations, measurement of nitrous oxide as leading substance is a valid procedure to assess the exposure of the anaesthesiology workplace to nitrous oxide and volatile anaesthetics. Significant higher nitrous oxide concentrations during desflurane anaesthesia result from early extubation of patients expiring higher concentrations of nitrous oxide.

A novel apparatus for the exposure of cultured cells to volatile agents.

This article presents a novel exposure apparatus that allows the exposure of cultured cells to volatile chemicals, e.g., inhalation anesthetics. The apparatus consists of an exposure chamber and a tightly linked vaporizer unit with pumps and valves allowing adjustable fluxes of mixtures of test chemicals and carrier gas under open and closed-circuit conditions. The exposure chamber uses commercially available cell culture flasks and accommodates up to 12 flasks simultaneously. Both modules fit into a standard culture incubator. The exposure chamber may be mounted onto an oscillating axis to tilt the cultures periodically forth and back, thus allowing direct contact of the cells with test atmosphere. The vaporizer unit is connected to a personal computer which lets the experimenter set the "open" and "close" intervals of individual valves thereby controlling the composition and flow rate of the test gas mixture. The vapor concentration of test chemicals can be monitored at the inlet and outlet using infrared photodetectors or mass spectrometers. Computer-aided processing of exposure protocols allows unattended runs. Exposure protocols can be scripted and stored on disk, thus ensuring interexperimental reproducibility of complex exposure profiles. As an application example, the effect of three volatile anesthetics, halothane, enflurane, and isoflurane, on the viability of three commercially available cell lines (A549--human lung carcinoma, HTC-rat hepatoma, MDCK--Madin-Darby canine kidney) was investigated. After exposure to haloalkyl vapors (3%) for 6 and 24 h, respectively, significantly increased LDH levels versus controls, indicating cellular membrane damage, were detected in A549 and hepatoma cells after exposure for 24 h. Hepatoma cells showed a significant LDH release also after 6 h exposure to isoflurane. On the other hand, LDH release from MDCK cells was not significantly different from controls even after 24 h of continuous exposure to any of the tested anesthetics.

[Effectiveness of anesthetic gas scavengers fulfilling EN 740 requirements with reference to equipment leakage and fresh gas flow]. / Effektivität der Narkosegasabsaugung nach EN 740 unter Berücksichtigung der Geräteleckage und des Frischgasflows.

PURPOSE: During inhalation anaesthesia, contaminations of the working environment be anaesthetic volatiles and nitrous oxide occur. The amount of leaking gases is influenced by leakages of the anaesthetic ventilator, by fresh-gas flows and by the effectivity of the scavenging system. Since 1st January 1996 new ventilators have to be equipped with scavenging devices according to the European standard EN 740. We measured the effectivity of this system with anaesthetic ventilators of a type that is now superseded (mean leakage rate 100 ml/min) and recent devices (mean leakage rate 5 ml/min) using high and low fresh-gas flows. MATERIAL AND METHODS: The anaesthetic ventilators were placed in a non-air-conditioned area. A test lung was ventilated with gas flows of 1 l/min, 3 l/min and 6 l/min (concentrations of nitrous oxide 70%, Enflurane 1%). The ventilation time in each case was 1 h. The minute volume was set to 8 l/min. At 2-minute intervals the concentrations of nitrous oxide and enflurane were measured by a multigas monitor Brüel & Kjaer 1302. The experiments were carried out with an old scavenging device according to DIN 13260 and a new device according to EN 740. RESULTS: Using the scavenging device according to DIN 13260, the concentrations of the pollutant gases were significantly dependent on the fresh-gas flows. No differences were found when using old or new anaesthetic ventilators. Medians of nitrous oxide (n2o) and Enflurane (e): 6 l/min: (n2o) 204 ppm (e) 4.3 ppm 3 l/min: (n2o) 115 ppm (e) 2.1 ppm 1 l/min: (n2o) 61 ppm (e) 0.97 ppm. Scavenging devices according to EN 740 significantly reduced the amount of emitted pollutants. No dependency on fresh-gas flows could be detected. 6 l/min: (n2o) 11.25 ppm (e) 0.05 ppm 3 l/min: (n2o) 10.12 ppm (e) 0.0 ppm 1 l/min: (n2o) 9.5 ppm (e) 0.0 ppm. CONCLUSIONS: The formerly reported dependence of the room air concentrations of anaesthetic volatiles and nitrous oxide from the fresh gas flow are caused by the spillage of pollutants through scavenging devices according to DIN 13260. The use of systems according to EN 740 is not only useful in new devices but must also be recommended for superseded models of anaesthetic ventilators.