Canadian journal of anaesthesia = Journal canadien d'anesthésie
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Randomized Controlled Trial Clinical Trial
Effects of benzodiazepines on mid-latency auditory evoked potentials.
Midlatency auditory evoked potentials (MLAEP) reflect primary cortical processing of auditory stimuli. The effects of benzodiazepines on MLAEP have not yet been studied. We examined the effects of intravenous induction of general anaesthesia using the benzodiazepines midazolam, diazepam and flunitrazepam on MLAEP in 30 patients scheduled for minor gynaecological procedures. ⋯ The MLAEPs do not change markedly in amplitude or latency during induction of general anaesthesia with benzodiazepines. Primary cortical processing of auditory stimuli seems to be preserved under benzodiazepines. This may be seen in connection with cases of intraoperative awareness and especially the perception of auditory stimuli during anaesthetic regimens where benzodiazepines are used to suppress consciousness.
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Shortly after elicitation of a muscle response by supramaximal stimulation of its motor nerve, there exists a period of refractoriness of neuromuscular transmission when a second stimulation elicits only a submaximal response or no response at all. Many anaesthetics and neuromuscular blocking and facilitatory drugs change the refractoriness of neuromuscular transmission. ⋯ Based on an existing technique of digitization and time expansion of the neurally evoked compound electromyogram (ncEMG), we developed a computer programme of waveform subtraction, and determined in nine normal awake volunteers the various interstimulus intervals when neuromuscular transmission was refractory (RP0), 3/4 refractory (RP.25), half refractory (RP.5), 1/4 refractory (RP.75) or non-refractory (RP1). We confirmed our hypotheses that computer-based waveform subtraction of the digitized ncEMG is a feasible and necessary technique for the accurate determination of the RPs of neuromuscular transmission, and report that the normal values in humans are: RP0 = 1.0 +/- 0.1, RP.25 = 1.3 +/- 0.3, RP.5 = 1.9 +/- 0.3, RP.75 = 2.9 +/- 0.5, and RP1 = 6.6 +/- 1.9 ms (mean +/- SD), respectively, in the ulnar nerve-first dorsal interosseous muscle model.
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Letter Case Reports
The Combitube oesophageal-tracheal double lumen airway for difficult intubation.