Anaesthesia
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Comparative Study Clinical Trial Controlled Clinical Trial
A comparison of the forces exerted during laryngoscopy. The Macintosh versus the McCoy blade.
The forces exerted at laryngoscopy with the McCoy and Macintosh blades have been compared in 40 patients. The variables measured were the duration of laryngoscopy, the three maximally-applied forces and the mean force. ⋯ It is concluded that the use of the McCoy blade results in significantly less force being applied during laryngoscopy. This may be the reason for the reduction in the stress response reported previously with the use of the McCoy blade.
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Randomized Controlled Trial Comparative Study Clinical Trial
A comparison between the Macintosh and the McCoy laryngoscope blades.
The view of the larynx using the Macintosh laryngoscope and the McCoy levering laryngoscope was assessed in 177 adult patients. The view with the McCoy blade in the neutral position and in the position (neutral or elevated) that gave the 'best' view were recorded. The McCoy blade in the neutral position was associated with a lower incidence of grade 1 views and a higher incidence of grade 2 views than the Macintosh blade. ⋯ In 25 patients, the vocal cords could not be seen with the Macintosh blade; in these patients the view was better with the McCoy blade (the cords were visible) on 14 occasions and worse in one (p = 0.001). We conclude that the McCoy blade in its neutral position does not behave identically to the Macintosh blade. The McCoy blade is a useful aid to difficult intubation but should not replace the Macintosh blade as the first choice laryngoscope.
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Randomized Controlled Trial Clinical Trial
Effect of transcutaneous electrical nerve stimulation on onset of axillary plexus block.
We examined the effect of high frequency transcutaneous electrical nerve stimulation on the onset of brachial plexus block. Three groups of patients scheduled for surgery of the hand had a local anaesthetic block performed with 40 ml mepivacaine 1.5% using the axillary approach. ⋯ There were no differences in the onset of block between the groups. Thus, the frequency-dependent action of local anaesthetics could not be demonstrated.
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Comparative Study Clinical Trial Controlled Clinical Trial
The effect of introducing fibreoptic bronchoscopes on gas flow in laryngeal masks and tracheal tubes.
The laryngeal mask airway, reinforced laryngeal mask airway and tracheal tube were studied to determine (1) flow resistance during simulated inspiration and (2) the maximum size of fibreoptic scope which can be passed down the lumen at clinically useful ventilatory settings. In addition, the flow resistance imposed by the mask aperature bars was quantified. ⋯ Removal of the mask aperture bars resulted in a mean decrease in flow resistance of 3.6%. Our data have shown that the laryngeal mask airway can accommodate a larger fibrescope than either the reinforced laryngeal mask airway or tracheal tube at clinically useful ventilatory settings and that the current recommendations for maximum size of fibrescope should be revised.
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We pointed out in the first of these two articles that the commonest cause of an anaesthetic disaster in young healthy patients is a loss of airway patency then a failure to intubate occurring unexpectedly in the absence of head or neck pathology. Upper airway obstruction is a very common complication of general anaesthesia and all anaesthetists must be trained in the management of this problem. Less obvious are the changes that can occur in the lower airways which can impair gas exchange by increasing ventilation-perfusion mismatch. This article is concerned with these pathophysiological changes that occur during general anaesthesia.