British journal of anaesthesia
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Ten patients with cerebral tumours were anaesthetized with thiopentone, 70% nitrous oxide in oxygen and fentanyl. Ventilation was controlled to give mean PaCO2 4.8 (range 3.6-6.7) kPa. Enflurane 2% was administered and ICP and MAP were recorded continuously for 10-15 min. ⋯ There were significant decreases in MAP (P less than 0.001) and CPP (P less than 0.001) during the administration of enflurane. In four patients the administration of enflurane had to be terminated prematurely because of a low CPP. Thus, enflurane has very little effect on ICP in patients with cerebral tumours and low concentrations of enflurane can safely be used during anaesthesia for intracranial operations, provided that the arterial pressure is monitored carefully.
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A method of closed-circuit anaesthesia has been developed in which the end-tidal concentration of the volatile anaesthetic agent used is controlled automatically using a closed-loop servo system. End-tidal anaesthetic concentrations, measured by the Engstrom EMMA, were maintained in the closed circuit by direct liquid injection. The system was tested in the laboratory and in clinical use (12 subjects). ⋯ The major sources of error in the method were the result of zero offset in the Engstrom EMMA which in turn was caused by humidity and the intrinsic characteristic of the simple proportional controller used. These errors were easily correctable, and end-tidal halothane concentration could be controlled to within 0.1%. Mean halothane vapour uptake at a constant end-tidal concentration of 0.8% was 114 ml min-1 at 1 min, 36 ml min-1 at 5 min, 29 ml min-1 at 10 min and between 22 and 18 ml min-1 at 20-35 min.
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Pulmonary gas exchange was studied in association with high frequency ventilation and its relation to the duration of insufflation and end-expiratory pressure investigated. Alveolar deadspace, alveolar ventilation and the alveolar-arterial oxygen difference were obtained in cats receiving a constant minute ventilation. ⋯ A positive end-expiratory pressure (PEEP) decreased the alveolar deadspace in high frequency ventilation. Thus, with the low compressible volume ventilator, more efficient high frequency ventilation can be achieved with a short period of insufflation plus low PEEP.
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Randomized Controlled Trial Comparative Study Clinical Trial
Pattern of change of bronchomotor tone following reversal of neuromuscular blockade. Comparison between atropine and glycopyrrolate.
Specific airways conductance (s. Gaw) was measured using the forced airflow oscillation method, to study the effect of two regimens, commonly used for the reversal of neuromuscular blockade, on bronchomotor tone. Patients who had received neuromuscular blockers and had undergone elective surgery were randomly allocated to receive neostigmine 50 microgram kg-1 given concurrently with either atropine 20 microgram kg-1 (10 patients) or glycopyrrolate 10 microgram kg-1 (10 patients). ⋯ Gaw between the two groups, higher values being found in the atropine group. At 10 min, no significant difference was seen between the groups, although both showed a significant decrease in s. Gaw compared with baseline values (P less than 0.05).
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Comparative Study
Manual jet ventilation v. high frequency jet ventilation during laser resection of tracheo-bronchial stenosis.
Manual jet ventilation (20 b.p.m.) and high frequency jet ventilation (300 b.p.m.) were compared during laser resection of tracheo-bronchial stenosis under general anaesthesia. Both methods provided similar blood-gas tensions at the 10th min of surgery in patients with tracheal stenosis. In patients with bronchial stenosis high frequency jet ventilation resulted in modest hypercarbia and manual jet ventilation appeared to be the preferred method in these particular patients.