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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.)

The first global harmonized standards for in vitro diagnostic (IVD) products are nearing completion. Six of these standards are mandated for the IVD Directive. Part II of this two-part article continues with a report on the current status of these standards and reflects on the lessons learned so far from international standardization activity.

Performance claims are the vehicle by which a manufacturer communicates the analytic capabilities of its methods to laboratory users and to regulatory agencies. Claims describe the expected performance of an analytic system. To be useful, claims must be meaningful, achievable, and verifiable. To ensure consistent interpretation, they must be stated in clear, unambiguous terms. There are no specific guidelines for stating claims. Consequently, comparing the performance of one system to another is difficult. Claims fall into three categories: clinical utility, analytical performance, and boundary conditions. This article focuses on the three basic analytical performance characteristics, precision, accuracy, and specificity, and describes how they are established, validated, maintained, and monitored by manufacturers and how they can be verified by end users. Precision claims describe the inherent variability of the system. They differ in the components of variance included, ranging from the short-term variables within a single run to the long-term variables experienced over time, such as lot changes, calibrations, instrument drift, and environmental fluctuations. Precision may be stated either as typical user experience or as the minimum performance expected. Accuracy claims describe the degree to which the results will approximate the true values. They are more difficult to establish and verify, given the lack of objective standards for many analytes. For this reason, few manufacturers make true accuracy claims, relying instead on comparisons with other marketed methods. A notable exception is cholesterol, for which a model reference system has been established to help laboratories ensure accuracy. External proficiency testing is handicapped by matrix effects from imperfect survey fluids. Specificity claims describe the method's freedom from interference and cross-reactivity. They are based on screening tests by the manufacturer, augmented by feedback from users. There are no agreed-on criteria for what constitutes clinically significant interference, and no consistent approach for disclosing interference information. The National Committee for Clinical Laboratory Standards, Villanova, Pa, is beginning to develop guidelines to promote greater consistency in performance claim statements.

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.

The neuromuscular and cardiovascular effects of mivacurium were studied in 90 adult patients during nitrous oxide-oxygen-isoflurane (n = 45, ISO group) and nitrous oxide-oxygen-narcotic (n = 45, BAL group) anesthesia. Neuromuscular blockade was measured using electromyographic activity of the adductor pollicis muscle after supramaximal stimulation of the ulnar nerve at 2 Hz for 2 seconds at 10-second intervals. To estimate dose-response relations, three subgroups of nine patients in the ISO group received mivacurium doses of 0.025, 0.03, and 0.04 mg/kg, respectively. Similarly, three subgroups of nine patients in the BAL group received mivacurium doses of 0.03, 0.04, and 0.05 mg/kg, respectively. The ED50 and ED95 of mivacurium in each group were estimated from linear regression plots of log dose vs probit of maximum percentage depression of neuromuscular function. The estimated ED50 values for the ISO and BAL groups were 0.029 and 0.041 mg/kg, respectively. The estimated ED95 values for the ISO and BAL groups were 0.045 and 0.058 mg/kg, respectively. Recovery indexes were measured in 26 patients who received ED95 or greater doses of mivacurium in either the ISO or BAL groups. The recovery index was shorter in the BAL group (5.5 +/- 1.6 minutes [n = 10]), than in the ISO group (7.4 +/- 3.0 minutes [n = 16]). The addition of isoflurane (0.5-0.75% end-tidal concentration) to nitrous oxide-narcotic anesthesia augments the degree of neuromuscular blockade from a given dose of mivacurium and also prolongs the recovery index.