Anaesthetic gases

It is important to realize that this is a theoretical concept and no such gas actually exists. Hydrogen comes the closest to being a perfect gas as it has the lowest molecular weight. In practice, most commonly used anaesthetic gases obey the gas laws reasonably well. 

Sardas S, Aygun N, Gamli M, et al Use of alkaline comet assay (single cell gel electrophoresis technique) to detect DNA damage in lymphocytes of operating room personnel occupationally exposed to anaesthetic gases. Mutat Res 418(2-3) 93-100, 1998... 

The testing of pure optical isomers can give much insight into the nature of a receptor. An example concerns the anaesthetic gases. It is widely believed that anaesthetic gases exert their action by a structurally nonspecific perturbation of the fluid character of nerve membranes. This view... 

G. Axelsson and R. Rylander. Exposure to anaesthetic gases and spontaneous abortion response bias in a postal questionnaire study. Int. J. Epidemiol., 11 (1982) 250-256. 

Smith, T. C. Carbon monoxide, neon and acetylene analysis in the presence of anaesthetic gases. J. Appl. Physiol. 21, 745 (1966). — Anal. Abstr. 14, 4988 (1967). 

Hospitals and dental surgeries (anaesthetic gases), indusirial sites, laboratories, mines. Victims found in bathrooms, boats, caravans, cars, fires, kitchens Presence offire extinguishers, gas fiies,geyseis, portable heaters... 

The oil solubility of an anaesthetic is of interest, not only because it governs the passage of the anaesthetic into and out of the fat depots of the body, but also because there is a well-established correlation between anaesthetic potency and oil solubility. Figure 2.10 shows a linear inverse relationship between log narcotic concentration and log solubility in oleyl alcohol for a series of common anaesthetic gases. The ordinate of the graph represents the minimum alveolar concentration (MAC), which is that concentration of anaesthetic at which 50% of the patients cease to move in response to a stimulus. The abscissa shows the solubility expressed in terms of the oil/gas partition coefficient. Partition coefficients are widely used to express solubility and are the ratios of the concentration of the gas in the two phases in equilibrium at a given temperature. When, as in this case, one of the phases is the gas itself, the partition coefficient expressed as the liquid/gas (note the order of the phases) concentration ratio is equal to the... 

Anaesthetic gases such as ether which have a high blood solubility (Ostwald solubility coefficient in blood is 12) are transported away from the lungs more rapidly than those such as halothane (Ostwald coefficient = 2.3) and nitrous oxide (Ostwald coefficient = 0.47). As... 

Figure 2.12 Graph of alveolar concentration of anaesthetic gases against time during anaesthetic uptake.

Temperature also influences anaesthetic solubility temperature increase leads to a decrease in solubility as expected from section 2.4.1. Table 2.4 shows the temperamre coefficients of the both water/gas, 2water/gas d oil/gas, Aoii/gas partition coefficients for a range of anaesthetic gases. 

Application of temperature and pressure relationships in the prediction of the solubility of anaesthetic gases in vivo is complicated by the interaction of these gases with the lipids and proteins in the blood and in tissue fluids. 

Barbiturates such as thiopental were once seen as potential intravenous anaesthetics which could replace the anaesthetic gases. Unfortunately, they too are fat soluble and as a result it is extremely difficult to estimate a sustained safe dosage. The initial dose can be estimated safely enough to allow for barbiturate taken up by fat cells (and thus removed from the system). However, further doses eventually lead to saturation of the fat depot, and result in a sudden and perhaps fatal increase of barbiturate levels in the blood supply. 

Hemminki K, Kyyronen P, Lindbohm M-L. 1985. Spontaneous abortions and malformations in the offspring of nurses exposed to anaesthetic gases, cytostatic drugs, and other potential hazards in hospitals, based on registered information of outcome. J Epidemiol Commun Health 39 141-147. 

The kinetics of gas absorption across the lung is simplified by dividing gases into those which react with tissue components in the lung and those which do not. The latter include volatile organic compounds, such as the anaesthetic gases, while the former include common air pollutants, such as ozone and gases of interest in chemical warfare... 

Certain drugs are excreted via expiration the rate of excretion depends on plasma concentration, alveolar air concentration and blood-gas partition. Anaesthetic gases are... 

Figure 10. (left) The structure of fluoranthene, used in the mediated reduction of anaesthetic gases by Compton and coworkers. ... 

Clearance of almost all drugs is by renal, metabolic, and/or biliary mechanisms. There are rare exceptions, such as anaesthetic gases that are exhaled unchanged. However, here we shall concentrate on the typical situation. 

Regardless of structure, anaesthetics and hypnotics have a lipophilicity that approximates to log P = 2.0, the property being lost when this figure is raised or lowered (Hansch, 1971, p. 300). Table 15.1 presents a cross-section of relevant data. In addition, many anaesthetic gases have had partition coefficients determined by gas chromatography (Hansch et al., 1975, Leo et aL, 1975) agreement was excellent. For general information on partition coefficients, see Sections 3.3 and 17.1.. 

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