Der Anaesthesist
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General anaesthesia and peripheral neuronal blockade are techniques which were introduced into clinical practice at the same time. Although general anaesthesia was accepted significantly faster due to effective new drugs and apparent ease of handling, neuronal blockade has recently gained great importance. The reasons are in particular newer aids such as industrially produced catheter sets, nerve stimulators and ultrasound guidance which have facilitated that these economical techniques can be used not only for intraoperative anaesthesia but also for perioperative analgesia without any major risks for the patients. ⋯ By using low concentrations of these potent drugs even for a longer period of time, no toxic plasma levels are seen with the exception of artificial intravasal injections. Additives such as opioids and alpha 2-sympathomimetics are also used. While the use of opioids is controversial, alpha 2-sympathomimetics are able to accelerate the onset and to extend the duration of regional anaesthesia and analgesia.
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Inapparent adverse intraoperative wakefulness is still a relevant problem in modern anaesthetic routine. It can be associated with serious negative effects on the postoperative recovery of the patients. Several different procedures have been developed to monitor and therefore avoid intraoperative situations of wakefulness during general anaesthesia. ⋯ There is a hierarchical correlation between certain values of the MLAEP and intraoperative wakefulness defined by purposeful movements, amnesic awareness with only implicit recall and conscious awareness with explicit recall. For some of the most commonly used anaesthetics reasonable threshold values of the MLAEP for the different states of consciousness have already been determined. Future studies in broad patient populations with all of the different routinely used anesthetics and procedures will have to finally identify the importance of the recording of mid-latency auditory evoked potentials as a routine method to assess the depth of anaesthesia.
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The endotracheal tube (ETT) is a considerably flow-dependent and, therefore, variable mechanical load. Conventional modes of respiratory support cannot adequately compensate for the tube resistance in inspiratorion and not at all in expiration. Automatic tube compensation (ATC) compensates for the flow-dependent pressure drop across the tracheal tube by a positive pressure support in inspiration and by a negative pressure support in expiration. ⋯ In addition, successful extubation could be better predicted with this mode in difficult-to-wean patients compared to other modes. There are no special rules in the clinical application of ATC. However, to prevent overassist the support level of the ventilatory mode which is combined with ATC should be reduced.