Anaesthesia
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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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Randomized Controlled Trial Comparative Study Clinical Trial
The effect of cerebrospinal fluid dilution of isobaric 0.5% bupivacaine used for spinal anaesthesia.
A prospective study was conducted to see the effect on spinal anaesthesia of the dilution of isobaric 0.5% bupivacaine with cerebrospinal fluid. Sixty patients were randomly allocated to three groups. In group 1, patients received 3 ml isobaric 0.5% bupivacaine intrathecally without aspirating cerebrospinal fluid. ⋯ The only statistical difference was the time to reach complete motor block, which was shorter in group 1 as compared to groups 2 and 3 (6.9 SD 1.4 min versus 11.3 SD 3.0 and 13.5 SD 3.9 min respectively). The mean value of maximum decrease in systolic blood pressure was small, being less than 15% of the pre-operative value for each group. In conclusion, the effect of diluting isobaric 0.5% bupivacaine with cerebrospinal fluid, 1 ml and 2 ml, is minimal and it is an unnecessary procedure with limited clinical effect.
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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.