Anaesthesia
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Twenty patients, ASA grades 1 and 2, aged 18-65 years were admitted to an open study to investigate the ease of tracheal intubation after induction of anaesthesia with propofol without the use of muscle relaxants after the chance observation that propofol 2.5 mg/kg allowed easy laryngoscopy and tracheal intubation. Satisfactory intubation conditions were achieved in 19 patients.
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The pharmacokinetics of a constant rate infusion of propofol were studied in 11 patients who received total intravenous anaesthesia for ENT surgery. Alfentanil was administered as an exponentially decreasing infusion using a computer-assisted infusion device with a constant target plasma alfentanil concentration of 300 ng/ml. Propofol was infused at a constant rate of 6 mg/kg/hours. ⋯ Only three data sets were significantly underestimated after the infusion was stopped (mean bias 11.9% (SD 25.5]. The elimination half-life of alfentanil was approximately 75 minutes (SD 21). We conclude that alfentanil does not interfere with the pharmacokinetic profile of propofol but that propofol induces higher plasma alfentanil concentrations than expected.
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Ninety patients scheduled to undergo minor gynaecological surgery were divided into three groups. Group 1 received propofol only, for both induction and maintenance of anaesthesia. ⋯ The incidence of nausea in group 1 was 0%, in group 2, 3.4% and in group 3, 9.4%. No patient vomited.
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Propofol and methohexitone were evaluated as hypnotics in a total intravenous anaesthesia technique without nitrous oxide in 50 patients of ASA grade 1 or 2. Analgesia was provided by a constant alfentanil infusion and the depth of anaesthesia was controlled by varying the infusion rate of propofol or methohexitone. Induction and intubation responses were smooth and moderate in the propofol group and side effects were few. ⋯ Postoperatively 96% of the propofol patients were clear-headed within 20 minutes, in contrast to only 48% in the methohexitone group. We conclude that propofol together with alfentanil, both given by a bolus plus infusion technique, provide controllable and satisfactory total intravenous anaesthesia without recourse to nitrous oxide or other inhalational agents. Methohexitone was not as satisfactory as propofol.
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Comparative Study
An additional tactile test. Further developments in tactile tests to confirm laryngeal placement of tracheal tubes.
An additional clinical test to confirm laryngeal placement of tracheal tubes is described. Using the new test, placement was confirmed in all of 50 patients studied in whom difficulty would have been anticipated using previously described tactile tests (male patients with lower molar teeth). Two anaesthetists with small hands averaged 98% confirmations in two series each of 100 consecutive unselected intubations. ⋯ The three tactile tests are reviewed and analysed. In the authors' combined experience of 14 cases of difficult laryngoscopy the tests gave reliable confirmation in 12 patients. Familiarity with these tests is stressed to be important for their reliable implementation.