Anesthesiology
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Major differences in plasma volume expansion between infusion fluids are fairly well known, but there is a lack of methods that express their dynamic properties. Therefore, a closer description enabled by kinetic modeling is presented. ⋯ The relative efficiency of crystalloid infusion fluids differs depending on whether the entire dilution-time profile or only the maximum dilution is compared. Kinetic analysis and simulation is a useful tool for the study of such differences.
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There is an unsettled discussion about whether the distribution of local anesthetic is free or inhibited when performing brachial plexus blocks. This is the first study to use magnetic resonance imaging (MRI) to help answer this question. ⋯ This study demonstrated that MRI is useful in examining local anesthetic distribution in axillary blocks because it can show the correlation between MRI distribution pattern and clinical effect. The cross-sectional spread of fluid around the brachial-axillary artery was often incomplete-inhibited, and the clinical effect often inadequate.
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As propofol is a high-clearance drug, plasma propofol concentrations can be influenced by cardiac output (CO), which can easily change in response to several factors. If propofol is metabolized in the lungs, the difference between pulmonary and arterial propofol concentrations might also be affected by CO. The objective of the current study was to assess how much plasma propofol concentrations are affected by CO and to determine how much the lungs take part in propofol elimination and in concentration changes affected by CO in anesthetized swine. ⋯ An inverse relation was observed between CO and propofol concentrations. The lungs appear to have a minor effect on plasma propofol concentrations during constant infusion in anesthetized swine.
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The antidepressant amitriptyline is commonly used orally for the treatment of chronic pain, particularly neuropathic pain, which is thought to be caused by high-frequency ectopic discharge. Among its many properties, amitriptyline is a potent Na(+) channel blocker in vitro, has local anesthetic properties in vivo, and confers additional blockade at high stimulus-discharge rates (use-dependent blockade). As with other drug modifications, adding a phenylethyl group to obtain a permanently charged quaternary ammonium derivative may improve these advantageous properties. ⋯ N-phenylethyl amitriptyline appears to have a narrow therapeutic range but is much more potent than lidocaine, providing a block duration several times longer than any clinically used local anesthetic. Further work in animal models of neuropathic pain will assess the potential use of this drug.