British journal of anaesthesia
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We have examined interactions between midazolam, propofol and alfentanil using two end-points of light sedation (hypnosis) and anaesthesia. Quantal dose-response curves were determined in 400 female patients for the drugs individually and in combination. At the hypnotic end-point, interactions were analysed by fitting the data to a mathematical model where the response depended on the doses of the three drugs with additional terms included to describe non-additive interactions of the various combinations of the three drugs. ⋯ For anaesthesia, dose-related effects could not be demonstrated for midazolam or alfentanil when used alone. The decrease in ED50 of propofol in the presence of the other compounds was propofol-midazolam = 52%, propofol-alfentanil = 73%, propofol-midazolam-alfentanil = 82%. When comparing the different combinations, the responses varied markedly at each end-point assessed and could not be predicted from the responses of the individual agents.
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We have investigated the relationship between the auditory evoked response (AER) and simple tests of conscious awareness at four end-expiratory concentrations (0.0, 0.1, 0.2 and 0.4 MAC) of isoflurane in oxygen in each of eight anaesthetist volunteers, in random order, at least 1 week apart. The early cortical AER was recorded from electrodes at the vertex and inion. Amplitudes of the waves Pa, Nb and Pc and latencies of the waves Na, Pa, Nb, Pb and Nc were measured. ⋯ Amplitudes were greatest and the latencies shortest when there was full response to command. (Nb latency increased from 47.5 to 54.5 ms between partial and no response.) The close correlation between the effects of concentration and level of response, and between concentration and the AER implied that it was difficult to demonstrate those changes in the AER which specifically relate to changes in response. At 0.2 MAC, however, which was the concentration at which all subjects showed some deficit, the response to a shock word was distinguished clearly by Nb latency. In eight of 24 possible comparisons (eight AER variables and three types of psychological test) the AER fitted the response more closely than concentration.
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Twenty-nine departments of anaesthesia in the North of England were questioned about the availability and teaching of fibreoptic tracheal intubation techniques. While 27 departments had both suitable equipment and trained consultant staff, only one offered formal teaching to all its junior anaesthetists.
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The thrombelastograph (TEG) and bleeding time were performed before and 6 h after a single oral dose of aspirin 600 mg in a group of eight healthy volunteers and 12 pregnant patients. Measured TEG variables (r, k, r+k times and maximum amplitude) were unaltered after aspirin although there was a significant prolongation of the bleeding time in both groups. Although the TEG appeared not to detect aspirin-induced changes in platelet function, the TEG measures all phases of coagulation and the unaltered TEG after aspirin suggested a functioning coagulation system.