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

Abstract

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.

Reversible Conduction Block in Peripheral Nerve Using Electrical Waveforms

“…New electrode chemistries that increase the effective surface area of an electrode while maintaining the geometric area of the electrode have been evaluated for this purpose. Platinum black, for example, which is produced by electroplating platinum on platinum, has an effective surface area more than two orders of magnitude larger than bare platinum [60]. Other materials such as Iridium oxide (IrOx) and carbon ink have also been used [61].…”

“…The phases do not need to be at the same current level, as long as the total charge is equal. The CBPC waveform using high charge capacity materials and biphasic waveforms can have a blocking phase as long as tens of seconds long [62]. …”

“…Several different high capacitance electrode chemistries have been tested on the rat sciatic nerve to demonstrate both blocking ability and nerve integrity [60,61]. Proximal and distal stimulation (PS and DS) electrodes were placed on the sciatic nerve with a monopolar blocking electrode in between.…”

Autonomic Nervous System and Neurocardiac Physiopathology

“…• Transcutaneous electrical nerve stimulation (TENS) [142][143][144] • Bioelectronic block [145][146][147][148] • Spinal cord stimulation (SCS) [118,[149][150][151][152] • Vagal nerve stimulation (VNS) [78,153,154] • Renal nerve denervation [155][156][157] • Cardiac decentralization and carotid body ablation [158][159][160][161][162] • Cardiac conditioning (ischemia, exercise) [21,163,164] Table 1. Management strategies that target the autonomic nervous system.…”

“…are used in ischemic heart disease patients to abate reflex activation of peripheral ganglia [118,147,148,174,177,178]. Application of electric current by stimulation/suppression of action potential propagation along nerves modulates neuron and organ function [145,179]. Blockade of action potential propagation is produced by either kHz frequency alternating current or direct current; these protocols are used repeatedly and safely in patients [145,147,180].…”