Anaesthesia
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Randomized Controlled Trial Clinical Trial
Airway obstruction with cricoid pressure.
Cricoid pressure may cause airway obstruction. We investigated whether this is related to the force applied and to the technique of application. We recorded expired tidal volumes and inflation pressures during ventilation via a face-mask and oral airway in 52 female patients who were anaesthetised and about to undergo elective surgery. ⋯ An expired tidal volume of < 200 ml was taken to indicate airway obstruction. Airway obstruction did not occur without cricoid pressure, but did occur in one patient (2%) with cricoid pressure at 30 N, in 29 patients (56%) with 30 N applied in an upward and backward direction and in 18 (35%) patients with cricoid pressure at 44 N. Cricoid pressure applied with a force of 44 N can cause airway obstruction but if cricoid pressure is applied with a force of 30 N, airway obstruction occurs less frequently (p = 0.0001) unless the force is applied in an upward and backward direction.
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Cricoid pressure is used to protect the lungs from contamination with gastric contents during tracheal intubation. We studied the effect of cricoid pressure applied with a yoke on 30 anaesthetised patients examined fibreoptically through a laryngeal mask airway. We assessed the effect of 20, 30 and 44 N on the internal appearance of the cricoid and vocal cords. ⋯ Associated difficulty in ventilation was present in 15 patients (50%) and 18/30 (60%) had vocal cord closure with associated difficult ventilation, at forces up to 44 N. Cricoid occlusion was unrelated to age and body mass index but females were at greater risk. Orthodox values of cricoid pressure, applied with a yoke, may produce obstruction at the level of the cricoid cartilage or vocal cords, with implications for tracheal intubation and ventilation by mask.
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Randomized Controlled Trial Comparative Study Clinical Trial
Bispectral index monitoring: comparison of two types of electrode.
Bis-monitoring is a new method of monitoring anaesthetic depth. Bis-monitoring is easy to perform, but the Bis-monitor and the original, disposable electrodes are expensive. The aim of this study was to determine whether the original Zipprep electrodes could be replaced by the much cheaper electrocardiogram electrodes. ⋯ The impedance in the electrocardiogram electrodes was higher than in the Zipprep electrodes, but this did not affect the bispectral index. No other problems with either type of electrode were detected. It is concluded that Zipprep electrodes can be replaced by electrocardiogram electrodes in normal clinical practice.
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Randomized Controlled Trial Clinical Trial
Effect of clonidine premedication on haemodynamic responses to fibreoptic bronchoscopy.
The usual haemodynamic response to fibreoptic bronchoscopy is an increase in heart rate and blood pressure. We therefore compared, in a prospective, randomised, double-blind study, the effect of two doses of oral clonidine premedication (150 microg or 300 microg) with placebo (control group) on the haemodynamic alterations in 62 patients who underwent elective fibreoptic bronchoscopy. Significant increases in blood pressure and heart rate were observed during fibreoptic bronchoscopy only in the control group. ⋯ Compared with the control group, time to awakening was significantly longer only in patients premedicated with 300 microg clonidine. In conclusion, premedication with 150 microg oral clonidine attenuates haemodynamic responses to fibreoptic bronchoscopy, without causing excessive haemodynamic depression and sedation. These data encourage the administration of clonidine as premedication in patients undergoing fibreoptic bronchoscopy, particularly in those with, or at risk for, coronary artery disease.