The Sensitivity of Motor Response to Nerve Stimulation and Paresthesia for Nerve Localization As Evaluated by Ultrasound

Background Recommendations regarding the technical aspects of nerve stimulator-assisted nerve localization are conflicting. The objectives of this study were to determine whether the placement of the cutaneous electrode affects nerve stimulation and to determine the duration and intensity of an electrical stimulus that allows nerve stimulation with minimal discomfort. Methods Ten healthy volunteers underwent an interscalene and a femoral nerve block. After obtaining a clearly visible motor response of the biceps (interscalene) and quadriceps (femoral) muscles at the minimal current (0.1 ms, 2 Hz), the position of the cutaneous electrode was varied. Next, the duration of the stimulating current was set at 0.05, 0.1, 0.3, 0.5, or 1.0 ms, in random order. Intensity of the motor response and discomfort on stimulation were recorded. Results The minimal current at which a visible motor response was obtained was 0.32 +/- 0.1 mA (0.23-0.38 mA) for the inter-scalene block and 0.29 +/- 0.1 mA (0.15-0.4 mA) for the femoral block. Changing the position of the return electrodes did not result in any change in the grade of the motor response or in the current required to maintain it. Currents of longer duration caused discomfort and more forceful contraction at a lower current intensity as compared with currents of shorter duration (P < 0.01). When the current was adjusted to maintain the same visible motor response, there was no significant discomfort among studied current durations. Conclusion Site of placement of the cutaneous electrode is not important when constant current nerve stimulators are used during nerve localization in regional anesthesia. There is an inverse relation between the current required to obtain a visible motor response and current duration. Selecting a current duration between 0.05 and 1.0 ms to specifically stimulate sensory or motor components of a mixed nerve does not seem to be important in clinical practice.

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DEVELOPMENT OF MOTOR RESPONSE TO INTRAMURAL NERVE STIMULATION AND TO DRUGS IN RAT SMALL INTESTINE

British Journal of Pharmacology ◽

10.1111/j.1476-5381.1982.tb09251.x ◽

1982 ◽

Vol 76 (4) ◽

pp. 531-540 ◽

Cited By ~ 22

Author(s):

H. MIYAZAKI ◽

A. OHGA ◽

K. SAITO

Keyword(s):

Small Intestine ◽

Nerve Stimulation ◽

Motor Response ◽

Rat Small Intestine ◽

Intramural Nerve

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Ultrasound-Guided Popliteal Block Demonstrates an Atypical Motor Response to Nerve Stimulation in 2 Patients With Diabetes Mellitus

Regional Anesthesia and Pain Medicine ◽

10.1097/00115550-200309000-00021 ◽

2003 ◽

Vol 28 (5) ◽

pp. 479-482 ◽

Cited By ~ 60

Author(s):

Brian D. Sites ◽

John Gallagher ◽

Michael Sparks

Keyword(s):

Diabetes Mellitus ◽

Nerve Stimulation ◽

Motor Response ◽

Ultrasound Guided ◽

Patients With Diabetes ◽

Popliteal Block

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Ultrasound Examination and Localization of the Sciatic Nerve

Anesthesiology ◽

10.1097/00000542-200602000-00017 ◽

2006 ◽

Vol 104 (2) ◽

pp. 309-314 ◽

Cited By ~ 106

Author(s):

Vincent W. S. Chan ◽

Hugo Nova ◽

Sherif Abbas ◽

Colin J. L. McCartney ◽

Anahi Perlas ◽

...

Keyword(s):

Sciatic Nerve ◽

Nerve Stimulation ◽

Low Frequency ◽

Threshold Current ◽

Ultrasound Probe ◽

Nerve Blocks ◽

Low Frequency Ultrasound ◽

Nerve Imaging ◽

Proximal Thigh ◽

Nerve Localization

Background Few studies have examined the use of ultrasound for sciatic nerve localization. The authors evaluated the usefulness of low-frequency ultrasound in identifying the sciatic nerve at three locations in the lower extremity and in guiding needle advancement to target before nerve stimulation. Methods In this prospective observational study, 15 volunteers underwent sciatic nerve examination using a curved ultrasound probe in the range of 2-5 MHz and a Philips-ATL 5000 unit (ATL Ultrasound, Bothell, WA) in the gluteal, infragluteal, and proximal thigh regions. Thereafter, an insulated block needle was advanced inline with the ultrasound beam to reach the nerve target, which was further confirmed by electrical stimulation. The quality of sciatic nerve images, ease of needle to nerve contact, threshold stimulating current, and resultant motor response were recorded. Results The sciatic nerve was successfully identified in the transverse view as a solitary predominantly hyperechoic structure on ultrasound in all of the three regions examined. The target nerve was visualized easily in 87% and localized within two needle attempts in all patients. Nerve stimulation was successful in 100% after two attempts with a threshold current of 0.42 +/- 0.12 (mean +/- SD) eliciting foot plantarflexion or dorsiflexion. Conclusions These preliminary data show that a curved 2- to 5-MHz ultrasound probe provides good quality sciatic nerve imaging in the gluteal, infragluteal, and proximal thigh locations. Ultrasound-assisted sciatic nerve localization is potentially valuable for clinical sciatic nerve blocks.

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