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Objective: Validate independent component analysis (ICA) for removal of EMG contamination from EEG, and demonstrate a heuristic, based on the gradient of EEG spectra (slope of graph of log EEG power vs log frequency, 7-70 Hz) from paralysed awake humans, to automatically identify and remove components that are predominantly EMG., Methods: We studied the gradient of EMG-free EEG spectra to quantitatively inform the choice of threshold. Then, pre-existing EEG from 3 disparate experimental groups was examined before and after applying the heuristic to validate that the heuristic preserved neurogenic activity (Berger effect, auditory odd ball, visual and auditory steady state responses)., Results: (1) ICA-based EMG removal diminished EMG contamination up to approximately 50 Hz, (2) residual EMG contamination using automatic selection was similar to manual selection, and (3) task-induced cortical activity remained, was enhanced, or was revealed using the ICA-based methodology., Conclusion: This study further validates ICA as a powerful technique for separating and removing myogenic signals from EEG. Automatic processing based on spectral gradients to exclude EMG-containing components is a conceptually simple and valid technique., Significance: This study strengthens ICA as a technique to remove EMG contamination from EEG whilst preserving neurogenic activity to 50 Hz., (Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.)

The serious impact of electromyogram (EMG) contamination of electroencephalogram (EEG) is well recognised. The objective of this research is to demonstrate that combining independent component analysis with the surface Laplacian can eliminate EMG contamination of the EEG, and to validate that this processing does not degrade expected neurogenic signals. The method involves sequential application of ICA, using a manual procedure to identify and discard EMG components, followed by the surface Laplacian. The extent of decontamination is quantified by comparing processed EEG with EMG-free data that was recorded during pharmacologically induced neuromuscular paralysis. The combination of the ICA procedure and the surface Laplacian, with a flexible spherical spline, results in a strong suppression of EMG contamination at all scalp sites and frequencies. Furthermore, the ICA and surface Laplacian procedure does not impair the detection of well-known, cerebral responses; alpha activity with eyes-closed; ERP components (N1, P2) in response to an auditory oddball task; and steady state responses to photic and auditory stimulation. Finally, more flexible spherical splines increase the suppression of EMG by the surface Laplacian. We postulate this is due to ICA enabling the removal of local muscle sources of EMG contamination and the Laplacian transform being insensitive to distant (postural) muscle EMG contamination., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Study Objective: To determine the potentiation of the neuromuscular blockade induced by a titrated infusion of mivacurium in the presence of isoflurane versus a nitrous oxide (N2O)-opioid anesthesia., Design: An open-label, controlled study., Setting: The inpatient anesthesia service of two university medical centers., Patients: Thirty adults divided into two groups., Intervention: An intravenous infusion of mivacurium during anesthesia with N2O-opioid or N2O-isoflurane., Measurements and Main Results: A neuromuscular blockade was monitored by recording the electromyographic activity of the adductor pollicis muscle resulting from supramaximal stimulation at the ulnar nerve at 2 Hz for 2 seconds at 10-second intervals. The mivacurium infusion rate was significantly less in the presence of isoflurane [4.0 +/- 0.8 micrograms/kg/min (mean +/- SEM)] than during N2O-opioid anesthesia (6.4 +/- 0.6 micrograms/kg/min). The recovery rates did not differ between anesthetic groups. After the termination of the infusion, spontaneous recovery to T4/T1 of at least 0.75 occurred in an average of 17.9 +/- 1.5 minutes, with a mean recovery index (T25-75) of 6.0 +/- 0.7 minutes., Conclusion: Isoflurane anesthesia reduces the infusion rate of mivacurium required to produce about 95% depression of neuromuscular function.

Mivacurium chloride is a new, short-acting nondepolarizing neuromuscular blocking agent presently undergoing clinical evaluation. The neuromuscular effects of mivacurium and suxamethonium given by bolus and infusion were compared in adult patients during nitrous oxide-oxygen-opioid anaesthesia. Neuromuscular block was monitored by recording the compound electromyogram of the adductor pollicis muscle resulting from supramaximal train-of-four stimuli applied to the ulnar nerve. Time to onset of complete block and recovery to T5 were significantly shorter for suxamethonium than for mivacurium (1.0 (0.1) v. 2.5 (0.3) min and 6.4 (0.7) v. 17.5 (1.8) min; mean (SEM]. Conditions for tracheal intubation were similar in the two groups although intubation was performed 0.75-1.3 min later following mivacurium. The infusion rate required to maintain neuromuscular block was 88.6 (10.4) micrograms kg-1 min-1 for suxamethonium and 7.8 (1.2) micrograms kg-1 min-1 for mivacurium. There was a significant negative correlation between recovery to T5 and infusion rate for mivacurium and for suxamethonium. It was equally easy to titrate the infusion rate to the desired degree of block in each group. The recovery index (T25-T75) after the infusion stopped was similar in patients who received mivacurium and those who received suxamethonium.