Faculty Opinions recommendation of Dynamic Cortical Connectivity during General Anesthesia in Healthy Volunteers.

Abstract Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New Background Recent studies of anesthetic-induced unconsciousness in healthy volunteers have focused on functional brain connectivity patterns, but the protocols rarely parallel the depth and duration of surgical anesthesia. Furthermore, it is unknown whether there is a single functional connectivity pattern that correlates with general anesthesia for the duration of prolonged anesthetic exposure. Methods The authors analyzed electroencephalographic data in 30 healthy participants who underwent induction of anesthesia with propofol followed by 3 h of isoflurane anesthesia at age-adjusted 1.3 minimum alveolar concentration. Functional connectivity was assessed by frequency-resolved weighted phase lag index between frontal and parietal channels and between prefrontal and frontal channels, which were classified into a discrete set of states through k-means cluster analysis. Temporal dynamics were evaluated by the occurrence rate and dwell time distribution for each state as well as the transition probabilities between states. Results Burst suppression was present, with mean suppression ratio reducing from 44.8 ± 32.3% to 14.0 ± 20.2% (mean ± SD) during isoflurane anesthesia (P < 0.001). Aside from burst suppression, eight connectivity states were classified by optimizing the reproducibility of clustering solutions, with each characterized by distinct properties. The temporal progression of dominant states revealed a successive shifting trajectory from the state associated with alpha frontal-parietal connectivity to those associated with delta and alpha prefrontal-frontal connectivity during induction, which was reversed during emergence. Cortical connectivity was dynamic during maintenance period, and it was more probable to remain in the same state (82.0 ± 8.3%) than to switch to a different state (P < 0.001). However, transitions to other states were structured, i.e., occurred more frequently than expected by chance. Conclusions Anesthesia-induced alterations of functional connectivity are dynamic despite the stable and prolonged administration of isoflurane, in the absence of any noxious stimuli. Changes in connectivity over time will likely yield more information as a marker or mechanism of surgical anesthesia than any single pattern.

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Dynamic Cortical Connectivity during General Anesthesia in Surgical Patients

Anesthesiology ◽

10.1097/aln.0000000000002677 ◽

2019 ◽

Vol 130 (6) ◽

pp. 885-897 ◽

Cited By ~ 18

Author(s):

Phillip E. Vlisides ◽

Duan Li ◽

Mackenzie Zierau ◽

Andrew P. Lapointe ◽

Ka I. Ip ◽

...

Keyword(s):

Functional Connectivity ◽

General Anesthesia ◽

Temporal Dynamics ◽

Transition Probabilities ◽

Surgical Patients ◽

Phase Lag ◽

Cortical Connectivity ◽

Single Measure ◽

Connectivity Patterns ◽

Weighted Phase Lag Index

Abstract Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New Background Functional connectivity across the cortex has been posited to be important for consciousness and anesthesia, but functional connectivity patterns during the course of surgery and general anesthesia are unknown. The authors tested the hypothesis that disrupted cortical connectivity patterns would correlate with surgical anesthesia. Methods Surgical patients (n = 53) were recruited for study participation. Whole-scalp (16-channel) wireless electroencephalographic data were prospectively collected throughout the perioperative period. Functional connectivity was assessed using weighted phase lag index. During anesthetic maintenance, the temporal dynamics of connectivity states were characterized via Markov chain analysis, and state transition probabilities were quantified. Results Compared to baseline (weighted phase lag index, 0.163, ± 0.091), alpha frontal–parietal connectivity was not significantly different across the remaining anesthetic and perioperative epochs, ranging from 0.100 (± 0.041) to 0.218 (± 0.136) (P > 0.05 for all time periods). In contrast, there were significant increases in alpha prefrontal–frontal connectivity (peak = 0.201 [0.154, 0.248]; P < 0.001), theta prefrontal–frontal connectivity (peak = 0.137 [0.091, 0.182]; P < 0.001), and theta frontal–parietal connectivity (peak = 0.128 [0.084, 0.173]; P < 0.001) during anesthetic maintenance. Additionally, shifts occurred between states of high prefrontal–frontal connectivity (alpha, beta) with suppressed frontal–parietal connectivity, and high frontal–parietal connectivity (alpha, theta) with reduced prefrontal–frontal connectivity. These shifts occurred in a nonrandom manner (P < 0.05 compared to random transitions), suggesting structured transitions of connectivity during general anesthesia. Conclusions Functional connectivity patterns dynamically shift during surgery and general anesthesia but do so in a structured way. Thus, a single measure of functional connectivity will likely not be a reliable correlate of surgical anesthesia.

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Lung Ventilation and Perfusion in Prone and Supine Postures with Reference to Anesthetized and Mechanically Ventilated Healthy Volunteers

Anesthesiology ◽

10.1097/aln.0b013e3181cf40c8 ◽

2010 ◽

Vol 112 (3) ◽

pp. 682-687 ◽

Cited By ~ 42

Author(s):

Sven Nyrén ◽

Peter Radell ◽

Sten G. E. Lindahl ◽

Margareta Mure ◽

Johan Petersson ◽

...

Keyword(s):

Mechanical Ventilation ◽

General Anesthesia ◽

Healthy Volunteers ◽

Photon Emission ◽

Vertical Direction ◽

Emission Computed Tomography ◽

Mechanically Ventilated ◽

Supine Posture ◽

Controlled Mechanical Ventilation ◽

Prone Posture

Background The literature on ventilation (V) and lung perfusion (Q) distributions during general anesthesia and controlled mechanical ventilation in supine and prone position is contradictory. The authors aimed to investigate whether V, Q, and ventilation to perfusion ratio (V/Q ratio) matching in anesthetized and mechanically ventilated volunteers are gravity dependent irrespective of posture. Methods Seven healthy volunteers were studied at two different occasions during general anesthesia and controlled mechanical ventilation. One occasion studied ventral to dorsal V and Q distributions in the supine posture and the other in the prone posture. Imaging was performed in supine posture at both occasions. A dual radiotracer technique and single photon emission computed tomography were used. V and Q were simultaneously tagged with Tc-Technegas (Tetley Manufacturing Ltd., Sydney, Australia) and In-labeled macroaggregates of human albumin (TechneScan LyoMAA, Mallinckrodt Medica, Petten, The Netherlands), respectively. Results No differences in V between postures were observed. Q differed between postures, being more uniform over different lung regions in prone posture and dependent in supine posture. The contribution of the vertical direction to the total V/Q ratio heterogeneity was larger in supine (31.4%) than in prone (16.4%) (P = 0.0639, two-tailed, paired t test) posture. Conclusions During mechanical ventilation, prone posture favors a more evenly distributed Q between lung regions. V distribution is independent of posture. This results in a tendency toward lower V/Q gradients in the ventral to dorsal direction in prone compared with supine posture.

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Breath isoprene concentrations in persons undergoing general anesthesia and in healthy volunteers

Journal of Breath Research ◽

10.1088/1752-7155/6/4/046004 ◽

2012 ◽

Vol 6 (4) ◽

pp. 046004 ◽

Cited By ~ 9

Author(s):

Cyrill Hornuss ◽

Armin Zagler ◽

Michael E Dolch ◽

Dirk Wiepcke ◽

Siegfried Praun ◽

...

Keyword(s):

General Anesthesia ◽

Healthy Volunteers

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Network Efficiency and Posterior Alpha Patterns Are Markers of Recovery from General Anesthesia: A High-Density Electroencephalography Study in Healthy Volunteers

Frontiers in Human Neuroscience ◽

10.3389/fnhum.2017.00328 ◽

2017 ◽

Vol 11 ◽

Cited By ~ 23

Author(s):

Stefanie Blain-Moraes ◽

Vijay Tarnal ◽

Giancarlo Vanini ◽

Tarik Bel-Behar ◽

Ellen Janke ◽

...

Keyword(s):

General Anesthesia ◽

Healthy Volunteers ◽

High Density ◽

Network Efficiency

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Awake vs. anesthetized: layer-specific sensory processing in visual cortex and functional connectivity between cortical areas

Journal of Neurophysiology ◽

10.1152/jn.00923.2014 ◽

2015 ◽

Vol 113 (10) ◽

pp. 3798-3815 ◽

Cited By ~ 44

Author(s):

Kristin K. Sellers ◽

Davis V. Bennett ◽

Axel Hutt ◽

James H. Williams ◽

Flavio Fröhlich

Keyword(s):

Visual Cortex ◽

Functional Connectivity ◽

General Anesthesia ◽

Sensory Processing ◽

Local Field ◽

Local Field Potential ◽

Field Potential ◽

Cortical Layers ◽

Cortical Connectivity ◽

Sensory Responses

During general anesthesia, global brain activity and behavioral state are profoundly altered. Yet it remains mostly unknown how anesthetics alter sensory processing across cortical layers and modulate functional cortico-cortical connectivity. To address this gap in knowledge of the micro- and mesoscale effects of anesthetics on sensory processing in the cortical microcircuit, we recorded multiunit activity and local field potential in awake and anesthetized ferrets ( Mustela putoris furo) during sensory stimulation. To understand how anesthetics alter sensory processing in a primary sensory area and the representation of sensory input in higher-order association areas, we studied the local sensory responses and long-range functional connectivity of primary visual cortex (V1) and prefrontal cortex (PFC). Isoflurane combined with xylazine provided general anesthesia for all anesthetized recordings. We found that anesthetics altered the duration of sensory-evoked responses, disrupted the response dynamics across cortical layers, suppressed both multimodal interactions in V1 and sensory responses in PFC, and reduced functional cortico-cortical connectivity between V1 and PFC. Together, the present findings demonstrate altered sensory responses and impaired functional network connectivity during anesthesia at the level of multiunit activity and local field potential across cortical layers.

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