Current Threshold for Nerve Stimulation Depends on Electrical Impedance of the Tissue: A Study of Ultrasound-Guided Electrical Nerve Stimulation of the Median Nerve

Sauter, Axel R.; Dodgson, M. S.; Kalvøy, Håvard; Grimnes, Sverre; Stubhaug, Audun; Klaastad, Øivind

doi:10.1213/ane.0b013e3181957d84

Cited by 55 publications

(33 citation statements)

References 19 publications

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“…Typical examples are measurements and stimulations in anaesthesiology and neurology (Tsui et al 2004) (Sauter et al 2009) (King et al 1998) The goal for this study was to develop a method to describe the sensitivity field for needle electrodes in an ongoing project concerning a new method for anatomical needle positioning in the clinic ). The description of sensitivity field will furthermore be important in an ongoing resuscitation project using bioimpedance measurements to confirm intravascular needle position.…”

Section: Introductionmentioning

confidence: 99%

Impedance-based tissue discrimination for needle guidance

Kalvøy¹,

Frich²,

Grimnes³

et al. 2009

Physiol. Meas.

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Measurement of electrical impedance can discriminate between tissues of different electrical properties. A measurement system with adequate spatial resolution focused on a volume around the tip of a needle or other invasive clinical equipment can be used to determine in which type of tissue the tip is positioned. We have measured the sensitivity zone of a needle electrode with an active electrode area of 0.3 mm 2 , and measured impedance spectra in porcine tissue in vivo. Small electrode impedance data will be influenced by electrode polarization impedance (EPI) at low frequencies. To refine existing methods for needle guidance with higher spatial resolution, we have used multivariate analysis and new interpretations of EPI, and tissue data gathered with selected needle electrodes. The focus of this study is on discrimination between muscle and fat/subdermis for drug administration, but our results also indicate that these refinements will facilitate new clinical applications for impedance-based needle guidance in general.

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Section: Introductionmentioning

confidence: 99%

Impedance-based tissue discrimination for needle guidance

Kalvøy¹,

Frich²,

Grimnes³

et al. 2009

Physiol. Meas.

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“…In addition, it has also been suggested that electrical impedance influences the threshold current required when using nerve stimulation. 12,[15][16][17] Given that peripheral nerve blocks are generally performed with the guidance of nerve stimulation and that currently available stimulators display resistance, this study serves as a reminder for clinicians to utilize this information for such uses as detection of intravascular placement of the stimulating electrode. The adjuvant use of ultrasound also benefits from a test injection of D5W, given that the observed spread enables prediction of the local anesthetic spread without adding to the total local anesthetic volume or altering the threshold currents used for nerve stimulation.…”

Section: Discussionmentioning

confidence: 99%

No change in impedance upon intravascular injection of D5W

Chin

Tsui

2010

Can J Anesth/J Can Anesth

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Purpose Electrical impedance increases following test injections of non-conducting solutions around nerves; however, this increase should diminish rapidly with intravascular needle placement, wherein the systemic circulation will dissipate the solution. For this observational study, we hypothesized that the impedance increases significantly at the perineural space after an injection of 5% dextrose in water (D5W), but that it does not increase correspondingly at the intravascular location Methods After Ethics Research Board approval, electrical impedance was measured by a nerve stimulator displaying resistance, StimuplexÒ HNS 12, before and during (30 sec) an injection of D5W 3 mL: 1) during intravenous cannula placement using an insulated stimulating needle sheathed in its plastic cannula, MultiSet NanoLine with 18G needle; and 2) during needle placement (Pajunk 22G insulated) for an ultrasound-guided supraclavicular block in patients undergoing hand surgery. The impedance changes at each location were analyzed and compared. Results Data were collected from 16 patients. Baseline impedance was lower intravascularly (mean 16.5 ± standard deviation 7.2 kX) compared with perineurally (23.5 ± 8.3 kX) (P = 0.037). Peak impedance after intravascular D5W injection was 20.1 ± 6.8 kX, which was not a significant change (P = 0.15). In contrast, peak impedance after perineural D5W injection was 58.6 ± 29.1 kX, an increase of 35.1 ± 26.4 kX (155 ± 117%), and then it reached a plateau of 36.7 ± 19.6 kX. The increase in impedance was significantly greater at the perineural location (P \ 0.0001). Conclusion The absence of a significant increase in impedance upon injection of D5W prior to injection of local anesthetic may provide useful information to warn of intravascular injection. RésuméObjectif L'impe´dance e´lectrique augmente apre`s les injections de test de solutions non conductrices autour des nerfs; toutefois, cette augmentation devrait diminuer rapidement lors d'un positionnement intravasculaire de l'aiguille, situation dans laquelle la circulation syste´mique dissipera la solution. Pour re´aliser cette e´tude observationnelle, nous avons e´mis l'hypothe`se que l'impe´dance augmentait de façon significative dans l'espace pe´rineural apre`s une injection de dextrose a`5 % dilue´e dans de l'eau (D5W), mais qu'elle n'augmentait pas de la meˆme manie`re dans un site intravasculaire. Méthode Apre`s avoir reçu l'approbation du Comited 'e´thique de la recherche, l'impe´dance e´lectrique a e´teḿ esure´e à l'aide d'un stimulateur nerveux affichant la re´sistance, le StimuplexÒ HNS 12, avant et pendant (30 sec) une injection de 3 mL de D5W: 1) pendant le positionnement d'une canule intraveineuse a`l'aide d'une aiguille de stimulation isole´e prote´ge´e par sa canule de plastique, le MultiSet NanoLine avec une aiguille 18G; et 2) pendant le positionnement de l'aiguille (Pajunk 22G isole´e) pour un bloc supraclaviculaire par e´choguidage chez des patients subissant une chirurgie de la main. Les changements d'impe´dance a`c...

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“…This was done recording the voltage drop across a RC low pass filter made with the parallel combination of a 10 Ω resistor and 2.2 μF capacitor (cutoff frequency = 7.2 kHz). The results show that the current sources implemented were able to generate a low frequency current peak value of 2.7 mA in the cathodal phase and a peak value of 2.8 mA in the anodal phase, which is enough to electrically stimulate nerves [10]. The calculated charge shows that the circuit was able to inject over 0.22 μC in the cathodal phase of the stimulation and that this charge was balanced during the anodal phase.…”

Section: Complete Circuit Architecturementioning

confidence: 93%

Charge Counter for Performing Active Charge-Balance in Miniaturized Electrical Stimulators

Becerra-Fajardo

Ivorra

2015

IFMBE Proceedings

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Abstract-Functional Electrical Stimulation (FES) has been explored in order to restore the capabilities of the nervous system in patients that suffer from paralysis. This area of research and of clinical practice greatly benefits from any technological improvement yielding miniaturization. In this regard, we recently proposed and demonstrated an innovative electrical stimulation method based on implanted microstimulators that operate as rectifiers of bursts of innocuous high frequency current supplied by skin electrodes, generating low frequency currents that are capable of stimulating excitable tissues. We envision flexible ultrathin implants (diameters < 300 μm) containing ASICs that have advanced capabilities, such as addressability and current control. As miniaturization is the main aim of this method, the use of bulky DC-blocking capacitors (e.g. 10 µF) to accomplish zero net charge injection and avoid electrochemical tissue and electrode damage is highly inconvenient. As an alternative, here we present an active charge-balance method based on the use of a digital charge quantifier, whose operation is inspired in the functioning of the tipping bucket rain gauge. The system monitors the charge injection, matching the charge injected in the cathodal phase, with the charge injected in the anodal phase, generating a biphasic current waveform that adapts itself to possible current source mismatches. We have implemented a prototype built with discrete components which uses a capacitor of only 100 pF for the charge counter.

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Current Threshold for Nerve Stimulation Depends on Electrical Impedance of the Tissue: A Study of Ultrasound-Guided Electrical Nerve Stimulation of the Median Nerve

Cited by 55 publications

References 19 publications

Impedance-based tissue discrimination for needle guidance

Impedance-based tissue discrimination for needle guidance

No change in impedance upon intravascular injection of D5W

Charge Counter for Performing Active Charge-Balance in Miniaturized Electrical Stimulators

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