Anaesthesia
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Several factors have to be considered in determining the cost of applying a new inhalational anaesthetic such as desflurane into clinical practice. Factors beyond the immediate control of the anaesthetic practitioner include the price set by the manufacturer (although this may be influenced by economic and political pressures), and the physical-pharmacological properties of the anaesthetic (e.g. vaporization, potency, solubility). The anaesthetic practitioner can minimise cost by applying lower inflow rates. ⋯ The use of lower inflow rates presupposes that such rates do not allow the production of toxic compounds in recirculating gases. Modern equipment makes low-flow anaesthesia reliable and easy to control, and as desflurane is not degraded by the standard carbon dioxide absorbents, its use in low-flow systems is effective and economical. These cost considerations do not take into account the savings that may result from a more rapid recovery from anaesthesia, nor do they take into account the increased expense of capital equipment needed to apply a new anaesthetic.
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The relevant physiological and pharmacokinetic differences between adults and infants and children are considered, and the advantages and disadvantages of the available inhalational anaesthetics are discussed. Desflurane shows promise as a new paediatric anaesthetic as it allows rapid changes in the depth of anaesthesia. However, irritant effects on the airways make desflurane unsuitable for induction. Desflurane anaesthesia, following halothane induction, seems to be well tolerated.
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Increased duration of anaesthetic administration has implications for recovery from anaesthesia, has cardiovascular effects, and potential for toxicity through metabolism and breakdown of the anaesthetics. Recovery of function after desflurane or sevoflurane anaesthesia, because of the low blood gas and tissue solubilities of these agents, is more rapid than after halothane, isoflurane or enflurane, with recovery being most rapid after desflurane. Increased duration of anaesthesia amplifies the differences in rate of recovery because of the additional anaesthetic (greater with more soluble agents) dissolved in tissues. ⋯ Sevoflurane undergoes considerable metabolism, producing free fluoride ion, with plasma concentrations proportional to dose and duration of anaesthesia exceeding 50 microM in approximately 7% of patients. In rats, the effects of a toxic breakdown product of sevoflurane, CF2 = C(CF3)OCH2F (compound A), are also dose- and duration-dependent, with lower concentrations producing toxic effects as duration of exposure increases. The clinical importance of the metabolism and in vitro breakdown of sevoflurane has still to be adequately tested.
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Desflurane is a new volatile, inhaled anaesthetic that differs significantly from presently available inhaled agents in being halogenated solely with fluorine. This fluorination produces a lower solubility and increased resistance to biodegradation. ⋯ Limitations include a lesser potency and greater pungency at concentrations exceeding 1 minimum alveolar concentration (MAC). Other pharmacological properties are similar to those of isoflurane.
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In 1994, 66% of all surgery in the USA was performed as ambulatory surgery. Day surgery is also expanding to other countries worldwide. To provide safe anaesthesia and good outcomes for longer and more extensive operations performed in ambulatory facilities, patients must be carefully evaluated before surgery, their home readiness must be assessed, and they must fully understand all relevant information. ⋯ If a patient does not have an escort home, the surgical procedure should be cancelled or the patient admitted to the hospital. As the number of patients and complexity of scheduled surgical procedures increases, the outcome of day surgery will increasingly depend on the anaesthetist's skills. The recently introduced short-acting drugs may further improve the outcome after day surgery by facilitating rapid recovery and an early return to normal daily activities.