Articles: nerve-block.
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A technique of sciatic nerve block in the popliteal fossa, for operations on the foot and the ankle is described. It is obtained in the patient in prone position with a 12 cm long and insulated 22 G needle, connected to a nerve stimulator. The latter increases the rate of success and acceptance by the patient. This technique was used in 1000 patients between 16 and 88 years of age without any significant complication.
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Anesthesia and analgesia · Dec 1992
Subblocking concentrations of local anesthetics: effects on impulse generation and conduction in single myelinated sciatic nerve axons in frog.
Phenomena seen in axons exposed to subblocking doses serve as the basis for interpreting clinical and behavioral observations during onset and recovery of peripheral nerve block. To delineate the changes in excitability and in impulse conduction caused by subblocking concentrations of local anesthetics (LAs) in myelinated peripheral nerve fibers, LAs were applied to excised frog sciatic nerves while impulse conduction was monitored in single axons. For concentrations ranging from 0.01 to 1.2 times the LA concentration needed to block impulse conduction, three measures of susceptibility to LA were made to quantify the action of the drugs on "resting" fibers (firing rates < or = 0.5 Hz): the increase in the threshold for electrical activation of impulses, the increase in conduction latency reflecting the slowing of impulse conduction in the region exposed to LA, and the "critical blocking concentration" of LA just sufficient to prevent impulse conduction in the recorded fiber. ⋯ Such "use-dependent" increases in threshold and decreases in conduction velocity showed kinetics that were agent specific, lasting 1 s after a burst of impulses for lidocaine and lasting > 10 s for bupivacaine. At low concentrations, within the range of nontoxic plasma concentrations after systemic administration, the predominant actions of LAs on conducting fibers were transient decreases in excitability and conduction velocity in combination with a reduction of intrinsic oscillatory aftereffects of impulse discharge. These effects may degrade decoding of information in discharge patterns without actually blocking conduction of infrequent impulses, suggesting how functional blockade of coordinated movement and perception may occur even without complete blockade of impulse conduction.
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Anesthesia and analgesia · Dec 1992
A rat sciatic nerve model for independent assessment of sensory and motor block induced by local anesthetics.
The purpose of this study was to develop a reliable model to independently quantify motor and sensory block produced by local anesthetics. The sciatic nerve was blocked in 52 rats by injecting 0.2 mL of 0.125%, 0.25%, 0.5%, or 0.75% bupivacaine (n = 13 for each concentration). Accurate needle placement was achieved using a nerve stimulator at 0.2 mA and 1 Hz. ⋯ The intensity of both motor and sensory block measured at 30-min intervals was plotted against time until full recovery to obtain the area under the curve. Intergroup comparisons using analysis of variance showed increasing area under the curve with increasing concentrations of bupivacaine for motor blocks (P < 0.05 for all intergroup comparisons except 0.5% vs 0.75%) and sensory blocks (P < 0.05 for all intergroup comparisons). Normal saline or sham nerve stimulation did not result in any motor or sensory block.