Use of High Surface Area Electrodes for Safe Delivery of Direct Current for Nerve Conduction Block

Neuromodulation: Technology at the Neural Interface

2014

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217

231

Objectives The features and clinical applications of balanced-charge kilohertz frequency alternating currents (KHFAC) are reviewed. Preclinical studies of KHFAC block have demonstrated that it can produce an extremely rapid and reversible block of nerve conduction. Recent systematic analysis and experimentation utilizing KHFAC block has resulted in a significant increase in interest in KHFAC block, both scientifically and clinically. Materials and Methods We review the history and characteristics of KHFAC block, the methods used to investigate this type of block, the experimental evaluation of block, and the electrical parameters and electrode designs needed to achieve successful block. We then analyze the existing clinical applications of high frequency currents, comparing the early results with the known features of KHFAC block. Results Although many features of KHFAC block have been characterized, there is still much that is unknown regarding the response of neural structures to rapidly fluctuating electrical fields. The clinical reports to date do not provide sufficient information to properly evaluate the mechanisms that result in successful or unsuccessful treatment. Conclusions KHFAC nerve block has significant potential as a means of controlling nerve activity for the purpose of treating disease. However, early clinical studies in the use of high frequency currents for the treatment of pain have not been designed to elucidate mechanisms or allow direct comparisons to preclinical data. We strongly encourage the careful reporting of the parameters utilized in these clinical studies, as well as the development of outcome measures that could illuminate the mechanisms of this modality.

Section: Characteristics Of Khfac Blockmentioning

confidence: 99%

Reversible Nerve Conduction Block Using Kilohertz Frequency Alternating Current

Kilgore

Neuromodulation: Technology at the Neural Interface

2014

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217

231

“…Platinum black has a high effective surface area relative to the geometric surface area, resulting in a significant reduction in the effective charge density when current is delivered through the electrode. Platinum black can be applied using several techniques including electroplating [38] and sputtering [39], but electrodeposition produces a surface with a higher charge capacity [40, 41]. We demonstrated previously that this method can be used to produce electrodes with charge capacities in excess of 10 mC, allowing for DC block to be applied for ten seconds or more before irreversible reactions begin based on in vitro electrochemical measurements and in vivo experiments on the sciatic nerve in rats [30].…”

Section: Introductionmentioning

confidence: 99%

Continuous Direct Current Nerve Block Using Multi Contact High Capacitance Electrodes

Vrabec

IEEE Trans. Neural Syst. Rehabil. Eng.

Acker

et al. 2017

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Charge-balanced direct current (CBDC) nerve block can be used to block nerve conduction in peripheral nerves. Previous work demonstrated that the CBDC waveform could be used to achieve a 10% duty cycle of block to non-block repeatedly for at least two hours. We demonstrate that the duty cycle of this approach can be significantly increased by utilizing multiple electrode contacts and cycling the CBDC waveform between each contact in a “carousel” configuration. Using this approach, we demonstrated in an acute rat sciatic nerve preparation, that a 30% duty cycle complete block can be achieved with two contacts; and a 100% duty cycle block (>95% complete block) can be achieved with four contacts. This latter configuration utilized a four second block plateau, with three seconds between successive plateaus at each contact and a recharge phase amplitude that was 34% of the block amplitude. Further optimization of the carousel approach can be achieved to improve block effectiveness and minimize total electrode length. This approach may have significant clinical use in cases where a partial or complete block of peripheral nerve activity is required. In one example case, we achieved continuous block for 22 minutes without degradation of nerve conduction. Future study will be required to further optimize this technique and to demonstrate safety for chronic human use.

“…The ability to use DC alone without causing onset makes it a desirable choice for nerve block if the nerve damage can be mitigated. High capacitance electrodes with a CBDC waveform show promise in providing safe DC delivery [18, 47]. The purpose of this study was to demonstrate the feasibility of platinum black electrodes for repeatable direct current nerve block with a duration of at least 2 s.…”

Section: Introductionmentioning

confidence: 99%

Characterization of high capacitance electrodes for the application of direct current electrical nerve block

Vrabec

Wainright

et al. 2015

Med Biol Eng Comput

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Direct current (DC) can briefly produce a reversible nerve conduction block in acute experiments. However, irreversible reactions at the electrode–tissue interface have prevented its use in both acute and chronic settings. A high capacitance material (platinum black) using a charge-balanced waveform was evaluated to determine whether brief DC block (13 s) could be achieved repeatedly (>100 cycles) without causing acute irreversible reduction in nerve conduction. Electrochemical techniques were used to characterize the electrodes to determine appropriate waveform parameters. In vivo experiments on DC motor conduction block of the rat sciatic nerve were performed to characterize the acute neural response to this novel nerve block system. Complete nerve motor conduction block of the rat sciatic nerve was possible in all experiments, with the block threshold ranging from −0.15 to −3.0 mA. DC pulses were applied for 100 cycles with no nerve conduction reduction in four of the six platinum black electrodes tested. However, two of the six electrodes exhibited irreversible conduction degradation despite charge delivery that was within the initial Q (capacitance) value of the electrode. Degradation of material properties occurred in all experiments, pointing to a possible cause of the reduction in nerve conduction in some platinum black experiments.