The effects of general anaesthesia on nerve‐motor response characteristics (rheobase and chronaxie) to peripheral nerve stimulation

Abstract

SummaryUsing a simple surface nerve stimulation system, I examined the effects of general anaesthesia on rheobase (the minimum current required to stimulate nerve activity) and chronaxie (the minimum time for a stimulus twice the rheobase to elicit nerve activity). Nerve stimulation was used to elicit a motor response from the ulnar nerve at varying pulse widths before and after induction of general anaesthesia. Mean (SD) rheobase before and after general anaesthesia was 0.91 (0.37) mA (95% CI 0.77-1.04 mA) and 1.11 (0.53) mA (95% CI 0.92-1.30 mA), respectively. Mean (SD) chronaxie measured before and after general anaesthesia was 0.32 (0.17) ms (95% CI 0.26-0.38 ms) and 0.29 (0.13) ms (95% CI 0.24-0.33 ms), respectively. Under anaesthesia, rheobase values increased by an average of 20% (p = 0.05), but chronaxie values did not change significantly (p = 0.39). These results suggest that threshold currents used for motor response from nerve stimulation under general anaesthesia might be higher than those used in awake patients.

Implant- and anesthesia-related factors affecting threshold intensities for vagus nerve stimulation

“…6C). The increase in PT under general anesthesia is also consistent with other peripheral nerve stimulation studies, which show the stimulation threshold of muscle contraction (end-organ) increases with general anesthesia, possibly as a result of inhibition of nicotinic acetylcholine receptors at the neuromuscular junction 69–71 . In addition to the effect of anesthesia on ANS, they also affect the cardiovascular system, specifically the heart.…”

“…Factors influencing the generated electrical field include electrode geometry 21 22 , electrode orientation relative to the stimulated neural elements 17, 21, 23 , and stimulation parameters 11, 21 . Finally, the state of a subject or the end-organ at the time of stimulation affects the stimulation threshold 24 . For example, general anesthesia has distinct effects on the nervous system and multiple end-organs, altering stimulation thresholds through several mechanisms 24 .…”

“…Finally, the state of a subject or the end-organ at the time of stimulation affects the stimulation threshold 24 . For example, general anesthesia has distinct effects on the nervous system and multiple end-organs, altering stimulation thresholds through several mechanisms 24 . Factors affecting stimulation thresholds in brain stimulation 2, 11 21 , spinal cord stimulation 23 , and somatic peripheral nerve stimulation, such as tibial or ulnar nerve 18, 20, 24 are relatively well-studied.…”

“…For example, general anesthesia has distinct effects on the nervous system and multiple end-organs, altering stimulation thresholds through several mechanisms 24 . Factors affecting stimulation thresholds in brain stimulation 2, 11 21 , spinal cord stimulation 23 , and somatic peripheral nerve stimulation, such as tibial or ulnar nerve 18, 20, 24 are relatively well-studied. There is much less data on factors affecting stimulation thresholds in vagus nerve stimulation (VNS), an established neuromodulation therapy in epilepsy and depression 1, 25, 26 , and currently under study in a variety of cardiovascular, immune, and metabolic disorders 27–30 .…”

Implant- and anesthesia-related factors affecting cardiopulmonary threshold intensities for vagus nerve stimulation

“…Factors influencing the generated electrical field include electrode geometry [22,23], electrode orientation relative to the stimulated neural elements [14,22,24], and stimulation parameters [11,22]. Finally, the state of a subject or the end-organ at the time of stimulation affects the stimulation threshold [25]. For example, general anesthesia has distinct effects on the nervous system and multiple end-organs, altering stimulation thresholds through several mechanisms [25].…”