Anaesthesia
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Comparative Study Clinical Trial Controlled Clinical Trial
A comparison of the Invos 3100 and the Critikon 2020 near-infrared spectrophotometers as monitors of cerebral oxygenation.
Assessment of cerebral oxygenation using near-infrared spectroscopy in intensive care is increasing. We compared the ability of the Invos 3100 and the Critikon 2020 monitors to produce stable and consistent readings of regional cerebral oxygen saturation in resting volunteers. Failure to obtain any stable reading with the Critikon occurred in eight out of 18 subjects (44.4%) and with the Invos in three out of 15 subjects (20%). ⋯ The within-monitor variability was significantly higher for the Invos (p = 0.0124). Neither monitor is able to give stable and consistent readings over time, particularly in male subjects. The unacceptably high failure rate of the recently introduced Critikon 2020 will limit or prevent its clinical use.
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Randomized Controlled Trial Clinical Trial
The effect of a heat and moisture exchanger on humidity in a low-flow anaesthesia system.
The heat and humidity in a low-flow breathing system was measured in order to study the inherent humidifying properties of the system at low fresh gas flows (< 1 and 21.min-1) and whether a heat and moisture exchanger could compensate for the loss of heat and humidification occurring at higher fresh gas flows (51.min-1) in these systems. Sixty patients were randomly divided into three groups (< 1, 2 and 51.min-1 fresh gas flows) with a heat and moisture exchanger and three groups without a heat and moisture exchanger in the breathing system. ⋯ Three more measurements were performed at 10, 30 and 60 min after control. At low fresh gas flows the humidifying properties of the low-flow breathing system are adequate (i.e. provide an absolute humidity > 20 mg.l-1) but at a fresh gas flow of 51.min-1 there is a need for a heat and moisture exchanger for adequate humidification of the inspired gas.
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Comment Letter Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of the Macintosh and McCoy laryngoscope blades.
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To determine the contribution of extracranial oxygenation on regional cerebral oxygenation measured by an Invos 3100 near-infrared spectrometer, we measured oxygenation in blood drawn from both the facial vein (draining substantially blood from forehead areas) and the jugular venous bulb. There was no correlation between regional cerebral oxygenation and facial vein oxygenation (p = 0.35) but there was a significant correlation between regional cerebral oxygenation and jugular venous bulb oxygenation (p = 0.027). ⋯ Individual changes in jugular venous bulb oxygenation were poorly reflected. Data obtained by this near-infrared spectroscopy device are an unreliable guide to the adequacy of cerebral oxygenation.
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A method of identifying the epidural space is described in which the traditional loss of resistance to air technique is combined with amplification of the sound made by the epidural needle as it traverses the interspinous ligament and the ligamentum flavum and then enters the epidural space. The method retains all the advantages of the loss of resistance to air technique whilst, in addition, the auditory amplification gives a slightly earlier warning of entry into the epidural space. The apparatus necessary is readily available and the technique is easy to use. In addition to being useful in difficult epidurals, the technique would also be an excellent teaching aid.