FoR ~ANY YEARS anaesthetists have felt the need for a non-explosive anaesthetic agent possessing none of the. disadvantages assocmted with chloroform, trichlorethylene and mtrous o~ide, rhat is, the agent should be non-hepatotoxm, stable in the presence of soda lime and heat, an~ have a high therapeu :ie ratio. Since most heavily fluorinated hydrocarbons are not m2qamma)le, and many possess anaesthetic properties,, they present interesting pos,,ibilities. Robbins (1) found that some hydrocarbons had greater therapeutic rati.os than chloroform or ether, but that when they were used, severe hypotension, cardiac arrhythmias and slamulation of skeletal mtlscle occurred. In 1956, Rav ent6s and Suckhng synthesized and investigated a series of fluorinated hydrocarbons, and one in particular-CF8 CHC [Br (Fluothane)-was found to have potent anaesthetic properties (2). The first clinical trial has been reported by Johnstone (8)_who studied the human cardiovascular response to Fluqthane| PH-YSmAL I~OPFmTmS Fluothane| is a clear colourless liquid wath a rather pleasant odour. It has a specific gravity of 1 86 at 20 ~ C. and a bolhng point of 50.2. ~ C. Vapour pressur~ at 20 ~ C. is 248 rnm. Hg. Off/water solubility is 880 compared to 100 for chlo{oform and 8~2 for ether. When exposed to hght, Fluothane decomposes slowly, forming volatile acids. This can be prevented by storing it in amber-coloured bottles or by adding thymol 0.01 per cent W/W. Fluothane is non-infammable, non-explosive and stable in the presence of soda hme. Fluothane should not be confused with Fluomar| (trittuoro-ethyl-vinyl ether), an inflammable fuorinated ether with somewhat different properties, described by Orth (4) and Gamza, et d. (5). PHARMACOLOGY Ravent6s (2) investigated the pharmacological actaons o]: Fluothane in-animals and reported that full surgical anaesthesia was achieved after using a 2-4 per cent concentration of Fluotaane in air or oxygen for two tc five minutes. Anaesthesia was maintained with a concentration of 3.,t-0.8 per cent in premedicated dogs, and 1-1.2 per c.ent in unpremedicated ones. On the basis of aFluothane@ was supphed by Ayerst,
IN PRovmlNC ANAESTHESIA for routine cases for surgery, practising anaesthetists assume that the patient is in satisfactory clinical condition during anaesthesia as long as the respiration appears adequate, the cardiovascular system is stable, and the general colour is good. This study was originally initiated to confirm the belief that these clinical impressions were correct. METHODPatients were chosen at random for general anaesthesia. There were no prior decisions as to the choice of anaesthetic agents, technique, or types of patients (age or physical condition). There were 17 thoracotomies out of the 75 cases studied. Arterial blood samples were taken from the brachial or radial artery prior to the induction of anaesthesia; subsequently samples were taken at 30-minute intervals either as single arterial punctures or from an indwelling needle in the radial artery. Blood samples were analysed for Pao_o, Paco2, pH, and HCO8 by the Astrup method (Radiometer and Instrumentation Laboratories). Minute volumes and tidal volumes were measured with a Wright respirometer. RESULTSPreoperative Pao..,
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