Anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Changes in intra-ocular pressure during general anaesthesia. A comparison of spontaneous breathing through a laryngeal mask with positive pressure ventilation through a tracheal tube.
Changes in-intra-ocular pressure during spontaneous ventilation with a laryngeal mask were compared with controlled ventilation using a tracheal tube in 40 patients undergoing intra-ocular surgery under general anaesthesia. Intra-ocular pressure was measured before induction, after establishing the airway, at the end of the operation and after removal of the airway device. Anaesthesia was induced with propofol and maintained with enflurane and nitrous oxide in oxygen. ⋯ At the end of surgery, intra-ocular pressure (mmHg) was 11.2 and 8.6 during spontaneous or controlled ventilation respectively. One min after removal of the device, mean intra-ocular pressure (mmHg) in the tracheal tube group (16.0) was slightly higher than baseline (15.3) and was significantly higher than the laryngeal mask group (10.9) (p < 0.01). Spontaneous ventilation with a laryngeal mask is an acceptable alternative to controlled ventilation with tracheal intubation in elective intra-ocular surgery.
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In characterising the forces exerted during laryngoscopy it is accepted that the significant force component is that which is parallel to the axis of the laryngoscope handle. This paper describes a new method of evaluating the forces exerted at laryngoscopy. A laryngoscope handle has been redesigned, incorporating a force-displacement transducer on the handle at the end opposite to where the blade is attached. ⋯ Thus, the force transmitted to the transducer is essentially constant regardless of where the load is applied along the blade. The output from the system is directly downloaded to a laptop computer and the data analysed almost instantaneously to determine the duration of laryngoscopy, the peak forces applied, the mean force with its standard deviation and graphic display of the data. Provision has been made for data entry checks, recording patient details and study data, and creating a data base for the storage and retrieval of the study details.
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Randomized Controlled Trial Comparative Study Clinical Trial
Haemodynamic and plasma catecholamine responses during total intravenous anaesthesia for laryngomicroscopy. Thiopentone compared with propofol.
We compared the haemodynamic responses to endolaryngeal procedures during anaesthesia with propofol or thiopentone. Two minutes after administration of glycopyrronium 4 micrograms.kg-1 and alfentanil 17.5 micrograms.kg-1 anaesthesia was induced with either propofol 2.0 mg.kg-1 (n = 8) or thiopentone 5.0 mg.kg-1.min-1, respectively. Muscle relaxation was induced and maintained with suxamethonium. ⋯ With propofol, plasma adrenaline concentrations decreased significantly after induction and remained below baseline values throughout the procedure. After insertion of the operating laryngoscope the haemodynamic response was more pronounced with thiopentone than with propofol. Propofol blocks the catecholamine and haemodynamic responses to endolaryngeal procedures more effectively than thiopentone.