Articles: anesthetics.
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Neurotoxicity of local anesthetics: altered perineurial permeability, edema, and nerve fiber injury.
A quantitative, in situ experimental method was developed employing the rat sciatic nerve to study the neurotoxicity of local anesthetic solutions applied directly to an intact peripheral nerve bundle. One-milliliter volumes of 2-chloroprocaine, 3%; tetracaine, 1%; lidocaine, 2%; bupivacaine, 0.75%; or sodium chloride, 0.2%; were injected with a 30-gauge needle beneath the mesoneurium but exterior to the epineurium. The wound was closed and the animals were normally maintained until the nerves were reexposed for quantitative biophysical and morphologic testing 24 h to 4 weeks later. ⋯ Electron microscopy revealed abnormal mast cells and proliferation of endoneurial fibroblasts in addition to Schwann cell injury and axonal dystrophy. This study shows that extrafascicular administration of clinically used concentrations of local anesthetic solutions can alter perineurial permeability, producing changes in the endoneurial environment that are associated with neurotoxic injury. Perineurial and endoneurial fibrotic changes may be a late consequence of peripheral nerve injury with anesthetic solutions producing altered perineurial permeability with endoneurial edema.
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The place of computerization in intravenous anaesthesia delivery: Although total intravenous anaesthesia may have advantages over inhalational anaesthesia in certain circumstances, it has drawbacks from the point of view of feedback control. The ideal agent is not available, although di-isopropylphenol holds promise. There is an undefinable end-point. ⋯ The anaesthetist is still required for, amongst other things, specifying the desired depth of anaesthesia and varying it during the operation, and for responding to unforeseen crises. It may be hoped that, by liberating the anaesthetist from those tasks which can be automated, more time can be devoted to patient monitoring and other aspects of anaesthetic care, thereby improving patient safety. There is an undoubted place for computerized delivery of anaesthesia in teaching (particularly teaching pharmacokinetic principles) and in research (for standardization of anaesthetic depth).