The art of anaesthesia . etres of mercury (Courtesy of Dr. K. Connell. Johnsons Surgery, Appleton.) is required that a much stronger ether vapor be breathedduring induction than is needed merely to maintain anaes-thesia. (Figs. 48 and 49). To induce anaesthesia rapidly, the vapor must be soabundant as to exert a vapor tension of at least 180millimetres (Figs. 48 and 49). This gradually crowdsthe required amount of ether into the blood and nervoussystem. When the blood approaches the proper satura-tion, as indicated by the signs of anaesthesia, the amount COMPLETE GENERAL ANAESTHESIA 69 of ethe
The art of anaesthesia . etres of mercury (Courtesy of Dr. K. Connell. Johnsons Surgery, Appleton.) is required that a much stronger ether vapor be breathedduring induction than is needed merely to maintain anaes-thesia. (Figs. 48 and 49). To induce anaesthesia rapidly, the vapor must be soabundant as to exert a vapor tension of at least 180millimetres (Figs. 48 and 49). This gradually crowdsthe required amount of ether into the blood and nervoussystem. When the blood approaches the proper satura-tion, as indicated by the signs of anaesthesia, the amount COMPLETE GENERAL ANAESTHESIA 69 of ether present in the air breathed is gradually lowereduntil finally, in ideal anaesthesia, the pressure of ether vaporin the lung balances the tension of ether dissolved in theblood and the patient sleeps in quiet, uniform anaesthesia ofthe desired depth. This is finally achieved at a level of 50millimetres of ether tension; or by volumetric percentageI20H80 ANAESTHETIC EQUILIBRIUM ESTABLISHED AT 50mm ? ? —^^—^?^^*. 8-12 ADULT 4 M- PERIQD < INDUCTION U 20- 40 y< CONTINUANCE Fia. 49.—Plot of ether vapor pressure in pulmonary tidal air and ether tension in body in 6rsthour of ideal anaesthesia. (Courtesy of Dr. K. Connell, Johnsons Surgery, Appleton.) per cent, of the air breathed should be ether vapor(Figs. 48, 49 and 50). At this level, both the small childand robust alcoholic sleep in anaesthesia of proper foregoing facts throw light on the following:The value of warming liquid ether to promote evapora-tion (not the value of warming ether vapor, which is nil).Safety of the open drop mask with its hoar frost evapo-rating surface (much reduced evaporating temperature). 70 ANESTHESIA The efficiency of the closed system of anesthetization(because of the heat from rebreathing). The greater efficiency of using a warmed apparatus(warm metal) for induction. If one sets an ether vapor bottle in water 100° F., theether vapor which is
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