British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Model-based automatic feedback control versus human control of end-tidal isoflurane concentration using low-flow anaesthesia.
We studied the clinical use of an automatic feedback control system to adjust the end-tidal anaesthetic concentration with a low-flow method. The end-tidal controller uses two input signals (the end-tidal and inspiratory concentrations) to control the isoflurane concentration in the fresh gas flow, using a model-based algorithm. We studied 22 ASA I-III patients during elective surgery lasting more than 2 h. ⋯ The automatic control system was more accurate and stable than the human controller for step increases and step decreases, with less overshoot/undershoot and greater stability [e.g. maximal overshoot 14.7 (SD 3.7)% and 18 (8.1)% respectively for +0.6 vol% step changes, and 19.8 (3.7)% and 30.7 (13.2)% respectively for +0.3 vol% step changes]. However, the automatic control system showed a faster response time than the manual method only with large increasing steps (e.g. 149 (32) s and 205 (57) s respectively for +0.6 vol% step changes) and was not different from manual control for decreasing steps. Automatic control of the end-tidal isoflurane concentration can be better than human control in a clinical setting, and this task could be done automatically.
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Thirty volunteers underwent intradermal skin testing with increasing concentrations of rocuronium and cisatracurium to evaluate weal and flare responses, and whether either agent would cause mast cell degranulation and sensitization upon re-exposure. We found that intradermal injection of rocuronium and cisatracurium at concentrations > 10(-4) M resulted in positive weal (>8 mm) responses, and positive flare responses at > 10(-4) and > 10(-5) M respectively. ⋯ Skin testing with rocuronium and cisatracurium should be performed at concentrations < 10(-4) and < 10(-5) M respectively to avoid false-positive responses. The ability of these agents to produce positive weal and flare responses at relatively low concentrations may explain the high incidence of potential reactions reported.
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Kartagener's syndrome is a hereditary syndrome involving a combination of dextrocardia (situs inversus), bronchiectasis and sinusitis, transmitted as an autosomal recessive trait. We describe a patient who had three anaesthetics over a period of a few months. Discussion relates to anaesthetic considerations in the syndrome and to recent findings relating to the molecular mechanisms of left-right development.
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Though he had no formal training in engineering, John Blease of Merseyside invented numerous devices that greatly benefited the practice of anaesthesia. Starting with the turning of component parts for simple anaesthetic machines in the 1930s, he was introduced to clinical anaesthesia and became skilled in the art of dental anaesthesia. ⋯ After World War II he improved this into the Blease 'Pulmoflator', which was the first British positive-pressure ventilator in commercial production. From then until the early 1960s he patented many other inventions, duly utilized in the manufacture of anaesthetic equipment, in which industry the Blease name survives in the company he founded.