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Brown: Atlas of Regional Anesthesia, 3rd ed., Copyright © 2006 Saunders, An Imprint of Elsevier
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STIMULATING CATHETER TECHNIQUE

The insulated stimulating needle (Fig. 2-2 A [2] [4]) is directed to the peripheral nerve to be blocked with a stimulator current output of 1.5 mA. Adequate needle position is confirmed by observing an appropriate motor response with the nerve stimulatorcurrent output set at 0.3 to 0.5 mA, a frequency of 1 to 2 Hz, and a pulse width of 100 to 300 μsec. The needle is held steady in this position without injecting any solution through the needle. The nerve stimulator negative lead is then clipped to the proximal end of the stimulating catheter, which is in turn advanced through the needle ( Fig. 2-2 B ). The desired motor response should be produced, similar to the response elicited during initial needle placement. Next, the catheter is advanced through the distal end of the needle while seeking to maintain the motor response. If the motor response changes, it usually indicates that the catheter is being directed away from the nerve with advancement. With this paired needle—catheter assembly, the catheter can be withdrawn back into the needle without undue concern about catheter shearing.

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Figure 2-2a  Stimulation catheter placement for infraclavicular block. A, Equipment used with the StimuCath technique. A1. Insulated needle for initial insertion. A2, Electrically isolated catheter that allows stimulation via the catheter tip. A3, “Alligator extension” that allows stimulation via needle and catheter, with catheter stimulation possible with initial catheter insertion and after the Touhy-like end-adapter is placed via the needle and the potential manipulation via the needle if refined catheter positioning is desired.


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Figure 2-2b  B, Block technique with StimuCath. B1, Initial needle placement with stimulation. B2, Placement of catheter into needle without passing the needle tip. B3, Placement of alligator adapter to catheter prior to catheter insertion.


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Figure 2-2c  B4, Advancement of catheter while stimulating the catheter. B5, Finalizing placement of the catheter based on an adequate stimulation pattern.


If refinement in catheter positioning is required, withdraw the distal catheter into the shaft of the needle. Then make a small positioning change of the needle, typically by rotating it clockwise or counterclockwise or by advancing or withdrawing the needle a few millimeters; then advance the catheter again, similar to the earlier catheter-positioning steps. This process may be repeated until the desired motor response is elicited during catheter advancement. The desired motor response should continue as the catheter is advanced 3 to 5 cm along the neural structures.

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