Articles: nerve-block.
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alpha(2)-Adrenoceptor agonists like clonidine, dexmedetomidine, and ST-91, inhibit nociceptive reflex activity predominantly by a spinal mode of action. They mimic the action of the inhibitory transmitter noradrenaline, which is released from the terminals of bulbospinal monoaminergic pathways. The inhibition by noradrenaline is due partly to hyperpolarization of the postsynaptic neuronal membrane; however, the selective antinociceptive effect of the alpha(2)-adrenoceptor agonists results from reduction of the release of the excitatory transmitters such as glutamate and substance P, blockade of the binding of substance P to spinal neurones, and enhancement of the action of the inhibitory transmitter, 5-hydroxytryptamine. ⋯ Moreover, impulse conduction in C fibres of peripheral nerves is far more reduced by these compounds than that in A fibres. Antinociceptive effects are reported to occur in various models of clinical pain, e.g. the formalin test, adjuvans-induced arthritis, autotomy following deafferentation, and "hyperalgesia" after nerve ligation. Therefore, the mechanisms involved in antinociception may also be responsible for the analgesia produced by alpha(2)-adrenoceptor agonists.
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Paravertebral analgesia is highly effective in blocking unilateral afferent input from the trunk, but its bilateral use does not appear to have been described. Eight patients undergoing major abdominal vascular surgery had pre-operative bilateral paravertebral catheters inserted. A dose of 25 ml of bupivacaine 0.5% divided between the two catheters provided the basis of an effective intra-operative analgesic regimen which was continued postoperatively by infusion of bupivacaine for 4 days. ⋯ Three patients were not admitted to the intensive care unit, where mean stays for the group was 10 h (range 0-24 h) and mean hospital stay was 10 days (range 7-14). There were no additional demands made on the nursing staff and no postoperative pain-related complications occurred. We conclude that bilateral paravertebral analgesia, as part of a balanced analgesic technique, is an alternative method of providing effective afferent blockage for major abdominal surgery.
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Regional anesthesia · Nov 1995
Clinical TrialArea of paresthesia as determinant of sensory block in axillary brachial plexus block.
Paresthesia is widely considered a useful indicator for locating components of the brachial plexus using the axillary approach. While establishing axillary brachial plexus blocks, the authors attempted to correlate the area of paresthesia with the effectiveness of the sensory block. ⋯ Eliciting paresthesia at the nerve supplying the area of a planned surgical incision is a reliable determinant of successful axillary brachial plexus block.