Articles: nerve-block.
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Prolonged nerve blockade is potentially useful in the management of many acute and chronic pain problems. Aside from infusions via an indwelling catheter, most currently available nondestructive techniques for prolonging local anesthetic action cannot provide more than 1-2 days of blockade. Bioerodible polymer matrixes have been used to deliver a variety of drugs in patients and animals for periods lasting weeks to years. Previously, dibucaine and bupivacaine were incorporated into copolymers of 1,3 bis(p-carboxyphenoxy) propane-sebacic acid anhydride (1:4), and demonstrated sustained release in vitro following incubation of the drug-polymer matrixes in phosphate-buffered solution (pH 7.4, 37 degrees C). ⋯ This biodegradable polymer system provides a promising new alternative for the delivery of local anesthetics to peripheral nerves to produce prolonged blockade for the management of acute and chronic pain.
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The anatomy of the lumbar plexus and the various approaches used to perform lumbar plexus blockade are reviewed. A single needle technique for a posterior approach to the plexus at the L2-3 interspace is described. This technique was used bilaterally in six intact cadavers, and the extent of spread of an injected dye was documented photographically during a subsequent detailed dissection of the region. ⋯ No dye was seen anterior to the psoas, around the sympathetic chain, on the sacral plexus or in the extradural or subarachnoid spaces. Further studies in patients with needle position and drug disposition being confirmed using computerised tomography and X ray scanning were in agreement with the results observed in the cadavers. This technique represents a simple approach to the lumbar plexus which does not require needle localisation by X ray screening.
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Regional anesthesia · Jul 1993
Randomized Controlled Trial Clinical TrialPulmonary function changes during interscalene brachial plexus block: effects of decreasing local anesthetic injection volume.
During interscalene block, ipsilateral hemidiaphragmatic paresis occurred in all patients who received > 34 ml of local anesthetic in the authors' previous studies. This study was done to determine whether diaphragmatic function could be spared by a smaller local anesthetic volume. ⋯ Reducing the volume of local anesthetic to 20 ml did not prevent the 100% incidence of diaphragmatic paresis or significantly lessen the compromise in pulmonary function that had been reported to occur during interscalene brachial plexus anesthesia.
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Randomized Controlled Trial Comparative Study Clinical Trial
How many interscalenic blocks are there? A comparison between the lateral and posterior approach.
This study compares the areas of analgesia obtained with the lateral and posterior approaches to the interscalene space after injection of equal volumes of anaesthetic solution (40 ml of a mixture of 0.5% bupivacaine with adrenaline 1:200,000 and 2% lignocaine in equal parts). There was a significant difference in the distribution of the areas of analgesia between the two approaches. With the posterior approach, the region supplied by the radial, medial and ulnar nerves and the post-axial border of the upper limb were more frequently involved, whilst with the lateral approach the area of analgesia was usually confined to the regions supplied by the most caudal roots of the cervical plexus and the upper trunk of the brachial plexus (pre-axial border of the upper limb). On these grounds it appears that two different types of interscalene block are possible.
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Anesthesia and analgesia · Jul 1993
Randomized Controlled Trial Clinical TrialNerve stimulator polarity and brachial plexus block.
To determine whether needle polarity significantly affects nerve stimulation during peripheral nerve block, we performed a randomized double-blinded study of 10 patients undergoing axillary block for upper extremity surgery. Using an insulated needle, we determined the minimum current necessary to elicit muscle contraction with positive and negative needle polarity at two needle placements: (A) where stimulation was first observed and (B) where stimulation was maximal. At Position A, stimulation required significantly more current when the needle was positive (2.32 +/- 0.45 mA, mean +/- SEM) than when it was negative (1.05 +/- 0.23 mA, P < 0.001). ⋯ The mean ratio of positive to negative threshold stimulation current at Position B (3.11 +/- 0.20) was significantly greater than that at Position A (2.37 +/- 0.19, P < 0.05). Our results emphasize the importance of attaching the negative terminal of the nerve stimulator to the stimulating electrode. Use of the positive terminal could lead to abandoning a block if stimulation were not obtained at a low enough current; alternatively, motor contraction might not be observed before neural contact or vascular puncture.