Best practice & research. Clinical anaesthesiology
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Best Pract Res Clin Anaesthesiol · Sep 2005
ReviewThe concept of anaesthetic-induced cardioprotection: mechanisms of action.
The mechanisms by which ischaemia reperfusion injury can be influenced have been the subject of extensive research in the last decades. Early restoration of arterial blood flow and surgical measures to improve the ischaemic tolerance of the tissue are the main therapeutic options currently in clinical use. In experimental settings ischaemic preconditioning has been described as protecting the heart, but the practical relevance of interventions by ischaemic preconditioning is strongly limited to these experimental situations. ⋯ Hence, the anaesthetist himself can substantially influence the critical situation of ischaemia reperfusion during the operation by choosing the right anaesthetic. A better understanding of the underlying mechanisms of anaesthetic-induced cardioprotection not only reflects an important increase in scientific knowledge but may also offer the new perspective of using different anaesthetics for targeted intraoperative myocardial protection. There are three time windows when a substance may interact with the ischaemia reperfusion injury process: (1) during ischaemia, (2) after ischaemia (i.e. during reperfusion), and (3) before ischaemia (preconditioning).
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Best Pract Res Clin Anaesthesiol · Sep 2005
ReviewNew and alternative delivery concepts and techniques.
The suitability of any method of delivering anaesthetic vapours to the breathing system can be judged only if seen in relation to the fresh gas flow. Due to its advantage in essentially reducing anaesthetic gas and vapour consumption, low-flow anaesthesia has become the acknowledged method of performing inhalational anaesthesia. Conventional plenum vaporizers, connected to the fresh gas supply, meet all technical needs for efficient, safe and simple performance of low-flow and minimal-flow anaesthesia. ⋯ The injection of liquid anaesthetics into the breathing system with the aid of a motor syringe seems most promising; however, such a technique is not approved, and in its simple version contravenes several regulations of the technical norm. Closed-loop feedback control of metering anaesthetic gases and vapours, as realized in the PhysioFlex and ZEUS anaesthetic workstations, allows the realization of 'quantitative closed-system anaesthesia' in clinical practice. If complex anaesthetic gas compositions are used, including for instance nitrous oxide, closed-system anaesthesia can be performed in clinical practice only with such sophisticated machines.
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An 'ideal' anaesthetic can be approached by using a combination of different compounds. A variety of anaesthetic techniques has been described to ensure safe administration and an early recovery with high patient satisfaction. In particular, the inhalational anaesthetics desflurane and sevoflurane, with their rapid pharmacokinetics, re-established the notion of balanced anaesthesia as an equivalent, well-controllable technique. With the choice of anaesthetics and anaesthetic adjuvants clinically available today, especially the combination of a volatile anaesthetic with a short-acting opioid, balanced anaesthesia represents a big step towards an ideal anaesthetic.
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Best Pract Res Clin Anaesthesiol · Sep 2005
ReviewNitrous oxide: a unique drug of continuing importance for anaesthesia.
Early attempts to use nitrous oxide as a sole anaesthetic foundered because of its low potency. It has been used successfully as an adjunct to more potent anaesthetics, however, since 1868. By enabling reduced doses of more potent anaesthetics, nitrous oxide reduces the cost of anaesthesia and limits cardiorespiratory side effects. ⋯ Perhaps the greatest argument for the continued use of nitrous oxide is that it reduces the incidence of recall of intraoperative awareness. Reduced pharmacokinetic variability compared with other anaesthetics, especially intravenous agents, is likely to be a most important reason for this, although evidence is emerging that nitrous oxide also has pharmacodynamic advantages. There are specific situations in which nitrous oxide should not be used, but in the absence of these, its use can be favourably recommended.
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The volatile anaesthetics sevoflurane and desflurane feature new and promising properties. Their low blood and tissue solubility enables rapid onset of and emergence from anaesthesia, thus enhancing patient safety and comfort. ⋯ The first part focuses on pharmacokinetic issues such as substance properties, uptake and elimination. The second part covers the effects of inhaled anaesthetics on organ systems, with emphasis on the central nervous system, the cardiovascular system, the respiratory tract, liver and kidneys.