British journal of anaesthesia
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Comparative Study
Relationship between approximate entropy and visual inspection of irregularity in the EEG signal, a comparison with spectral entropy.
Several measures have been developed to quantify the change in EEG from wakefulness to deep anaesthesia. Measures of signal complexity or entropy have been popular and even applied in commercial monitors. These measures quantify different features of the signal, however, and may therefore behave in an incomparable way when calculated for standardized EEG patterns. ⋯ Spectral entropy and approximate entropy of EEG are two totally different measures. They change similarly in deepening anaesthesia due to an increase in slow activity. In some cases, however, they may change in opposite directions when the EEG signal properties change during anaesthesia. Failure to understand the behaviour of these measures can lead to misinterpretation of the monitor readings or study results if no reference to the raw EEG signal is taken.
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Airway management complications causing temporary patient harm are common, but serious injury is rare. Because most airways are easy, most complications occur in easy airways: these complications can and do lead to harm and death. Because these events are rare, most of our learning comes from large litigation and critical incident databases that help identify patterns and areas where care can be improved: but both have limitations. ⋯ All airway management techniques fail and prediction scores are rather poor, so many failures are unanticipated. Avoidance of airway complications requires institutional and individual preparedness, careful assessment, good planning and judgement, good communication and teamwork, knowledge and use of a range of techniques and devices, and a willingness to stop performing techniques when they are failing. Analysis of major airway complications identifies areas where practice is suboptimal; research to improve understanding, prevention, and management of such complications remains an anaesthetic priority.
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Intraoperative hypotension is associated with increased risk of perioperative complications. The N-methyl-d-aspartate (NMDA) receptor (NMDA-R) antagonist xenon (Xe) induces general anaesthesia without impairment of cardiac output and vascular resistance. Mechanisms involved in cardiovascular stability have not been identified. ⋯ In vivo, Xe anaesthesia does not alter sympathetic activity and baroreflex gain, despite increased mean arterial pressure. In vitro, Xe decreases the uptake of NE in neuronal cells by the inhibition of NET. This inhibition might be related to NMDA-R antagonism and explain increased NE concentrations at the synaptic cleft and in plasma, contributing to cardiovascular stability during Xe anaesthesia.
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Letter Multicenter Study
Goal-directed therapy: each therapeutic regimen needs its indication.