How to Position a Needle With a Peripheral Nerve Stimulator

How to Position a Needle With a Peripheral Nerve Stimulator

In the early days of regional anesthesia, it was common practice to verify needle placement with a nerve stimulator prior to injection.peripheral stimulator needle Since ultrasound guidance has become more widely available to anesthesia professionals, the use of nerve stimulation has been waning and its utility has been questioned. However, it remains a useful tool for clinicians as part of the regional anesthesia block procedure.

A peripheral nerve stimulator is a small, handheld electrical device that uses an externally applied current to stimulate a peripheral nerve or nerve plexus and produce a defined response (muscle twitch or sensation) to confirm correct needle positioning.peripheral stimulator needle This technique is a critical step in the delivery of effective and safe regional anesthesia blocks.

To ensure proper needle-to-nerve contact, it is important to start with a high current intensity (1.peripheral stimulator needle 0 mA) and advance the needle in the likely direction of the nerve based on anatomic landmarks. As the needle approaches the nerve, the current intensity is gradually decreased and the needle is repositioned if necessary. This process is repeated until the desired muscle response is obtained with a threshold current intensity of 0.2-0.5 mA and a short stimulus duration of 0.1 ms.

The most commonly used peripheral nerve stimulator has a cathode as the needle which makes the needle the negative pole.peripheral stimulator needle If the needle is positive (the anode) it will hyperpolarize the nerve and cause a larger current to be required to depolarize the nerve and elicit an action potential. In this case the threshold current is higher as a result of the increased current requirements and the ability to elicit a response is diminished.

It is also important to understand that the minimum current required to elicit a motor response is not an indication of proximity to the nerve as it can be induced at very low threshold currents and even when the needle is only 4mm from the nerve. In contrast, a needle that is echogenic has the entire shaft insulated except for the tip and allows for precise spatial discrimination when the needle is close to the nerve as demonstrated by the significant decrease in the threshold current with an echogenic needle compared to a noninsulated needle.

The Arrow(r) UltraQuik(r) Tuohy Echogenic PNB Needle is an insulated, echogenic peripheral nerve stimulator needle that helps increase block success by providing better spatial discrimination when the needle is close to a nerve. It features a five grooved ring that improves needle visibility under ultrasound and is designed to help anesthesia professionals optimize their peripheral nerve block procedure. As with all needles, please refer to the manufacturer’s package insert for complete warnings, indications, contraindications, precautions and potential complications.

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