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Peripheral Stimulator Needle
Peripheral Stimulator Needle
Nerve stimulation can be used for many types of nerve blocks and has become the defacto standard of care in most areas.peripheral stimulator needle It alters signals from your nerves and helps to control pain. At Las Vegas Sports & Spine Center, we offer a variety of treatments for pain management, including peripheral nerve stimulation.
A peripheral stimulator needle is an electrical device that has a tip with a small current generator that is connected to a constant current source.peripheral stimulator needle This type of needle can be used to locate the site of a nerve in preparation for a regional anesthetic block. It is also a useful tool for monitoring the effectiveness of a local anesthetic block.
When used for localization purposes, a nerve stimulator needle should have an insulated tip to minimize interference with surface anatomy.peripheral stimulator needle It should have a long pulse duration (eg, 1 ms) to ensure adequate current density and spatial discrimination. The needle should be inserted at an angle to avoid direct contact with the nerve. It is possible to use a noninsulated needle for localization; however, it requires higher current amplitudes and may elicit a motor response that may be due to the current leaking from the shaft of the needle.
If a motor response is unexpectedly elicited by a needle that is not close to the nerve, extra caution should be exercised as this can indicate an intimate needle-nerve relationship. The needle is then slightly withdrawn to abolish the response and distance the needle from the nerve. Alternatively, the needle can be connected to the stimulator and the current intensity adjusted until no further motor response is elicited. This technique is most commonly utilized with ultrasound-guided blocks.
It is important to verify the circuit to the stimulator as soon as the needle is inserted. The machine should have a flashing light or audible bleep to alert the operator that the connection is complete. It is also a good idea to test the threshold current on the nerve stimulator before the procedure begins. A value below 0.5 mA is generally considered ideal for most nerves.
The electrode-to-skin impedance and the geometry of the needle tip are major contributors to the threshold current. A shorter pulse duration has a higher frequency content and has more impact on the threshold current than a longer pulse. A typical 0.1-ms impulse has a frequency content of 10 kHz and its harmonics.
The constant current generator on the nerve stimulator adjusts the voltage to match the varying resistance of the needle tip and the electrode-to-skin interface. It does this automatically by utilizing Ohm’s law. The resulting constant current provides optimal stimulation of A-type pain fibers and reduces the likelihood of stimulating C-type pain fibers. The minimum required current intensity to evoke a motor response is known as the rheobase. A chronaxy is the double of the rheobase current that is necessary to achieve a motor response. A typical chronaxy is 50-100 ms.
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