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Tracking brain states under general anesthesia by using global coherence analysis.

ABSTRACT: Time and frequency domain analyses of scalp EEG recordings are widely used to track changes in brain states under general anesthesia. Although these analyses have suggested that different spatial patterns are associated with changes in the state of general anesthesia, the extent to which these patterns are spatially coordinated has not been systematically characterized. Global coherence, the ratio of the largest eigenvalue to the sum of the eigenvalues of the cross-spectral matrix at a given frequency and time, has been used to analyze the spatiotemporal dynamics of multivariate time-series. Using 64-lead EEG recorded from human subjects receiving computer-controlled infusions of the anesthetic propofol, we used surface Laplacian referencing combined with spectral and global coherence analyses to track the spatiotemporal dynamics of the brain's anesthetic state. During unconsciousness the spectrograms in the frontal leads showed increasing ? (8-12 Hz) and ? power (0-4 Hz) and in the occipital leads ? power greater than ? power. The global coherence detected strong coordinated ? activity in the occipital leads in the awake state that shifted to the frontal leads during unconsciousness. It revealed a lack of coordinated ? activity during both the awake and unconscious states. Although strong frontal power during general anesthesia-induced unconsciousness--termed anteriorization--is well known, its possible association with strong ? range global coherence suggests highly coordinated spatial activity. Our findings suggest that combined spectral and global coherence analyses may offer a new approach to tracking brain states under general anesthesia.

SUBMITTER: Cimenser A

PROVIDER: S-EPMC3102391 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Tracking brain states under general anesthesia by using global coherence analysis.

Cimenser Aylin A Purdon Patrick L PL Pierce Eric T ET Walsh John L JL Salazar-Gomez Andres F AF Harrell Priscilla G PG Tavares-Stoeckel Casie C Habeeb Kathleen K Brown Emery N EN

Proceedings of the National Academy of Sciences of the United States of America 20110509 21

Time and frequency domain analyses of scalp EEG recordings are widely used to track changes in brain states under general anesthesia. Although these analyses have suggested that different spatial patterns are associated with changes in the state of general anesthesia, the extent to which these patterns are spatially coordinated has not been systematically characterized. Global coherence, the ratio of the largest eigenvalue to the sum of the eigenvalues of the cross-spectral matrix at a given fre ...[more]

PMID: 21555565

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Project description:BackgroundA comprehensive understanding of how anesthetics facilitate a reversible collapse of system-wide neuronal function requires measurement of neuronal activity with single-cell resolution. Multineuron recording was performed in Caenorhabditis elegans to measure neuronal activity at varying depths of anesthesia. The authors hypothesized that anesthesia is characterized by dyssynchrony between neurons resulting in a collapse of organized system states.MethodsUsing light-sheet microscopy and transgenic expression of the calcium-sensitive fluorophore GCaMP6s, a majority of neurons (n = 120) in the C. elegans head were simultaneously imaged in vivo and neuronal activity was measured. Neural activity and system-wide dynamics were compared in 10 animals, progressively dosed at 0%, 4%, and 8% isoflurane. System-wide neuronal activity was analyzed using principal component analysis.ResultsUnanesthetized animals display distinct global neuronal states that are reflected in a high degree of correlation (R = 0.196 ± 0.070) between neurons and low-frequency, large-amplitude neuronal dynamics. At 4% isoflurane, the average correlation between neurons is significantly diminished (R = 0.026 ± 0.010; P < 0.0001 vs. unanesthetized) and neuron dynamics shift toward higher frequencies but with smaller dynamic range. At 8% isoflurane, interneuronal correlations indicate that neuronal activity remains uncoordinated (R = 0.053 ± 0.029; P < 0.0001 vs. unanesthetized) with high-frequency dynamics that are even further restricted. Principal component analysis of unanesthetized neuronal activity reveals distinct structure corresponding to known behavioral states. At 4% and 8% isoflurane this structure is lost and replaced with randomized dynamics, as quantified by the percentage of total ensemble variance captured by the first three principal components. In unanesthetized worms, this captured variance is high (88.9 ± 5.4%), reflecting a highly organized system, falling significantly at 4% and 8% isoflurane (57.9 ± 11.2%, P < 0.0001 vs. unanesthetized, and 76.0 ± 7.9%, P < 0.001 vs. unanesthetized, respectively) and corresponding to increased randomization and collapse of system-wide organization.ConclusionsAnesthesia with isoflurane in C. elegans corresponds to high-frequency randomization of individual neuron activity, loss of coordination between neurons, and a collapse of system-wide functional organization.

Project description:This meta-analysis aimed to analyze and compare the efficacy and safety of remifentanil and dexmedetomidine applied respectively for controlled hypotension under general anesthesia. We searched the Cochrane Library, PubMed, EMBASE, Web of Science, CNKI, SinoMed, Wanfang, and VIP databases, as well as dissertations and conference papers, to obtain randomized controlled trials comparing remifentanil and dexmedetomidine applied respectively for controlled hypotension before August 23, 2021. The primary outcomes included hemodynamic profiles, surgical field score, and blood loss. Extubation time, sedation and pain score at the PACU, and perioperative adverse events were the secondary outcomes. Nine randomized controlled trials with 543 patients (272 in the dexmedetomidine group and 271 in the remifentanil group) were eventually included. This meta-analysis indicated no significant difference between dexmedetomidine and remifentanil in terms of surgical field score, blood loss, minimum values of mean arterial pressure (MD 0.24 with 95% CI [-1.65, 2.13], P = 0.80, I2 = 66%) and heart rate (MD 0.42 [-1.33, 2.17], P = 0.64, I2 = 40%), sedation scores at the PACU (MD -0.09 [-0.69, 0.50], P = 0.76, I2 = 92%), and incidence of bradycardia (OR 2.24 [0.70, 7.15], P = 0.17, I2 = 0%). Compared with remifentanil, dexmedetomidine as the controlled hypotensive agent showed a lower visual analogue score at the PACU (MD -1.01 [-1.25, -0.77], P<0.00001, I2 = 0%) and incidence of shivering (OR 0.22 [0.08, 0.60], P = 0.003, I2 = 0%), nausea, and vomiting (OR 0.34 [0.13, 0.89], P = 0.03, I2 = 0%). However, extubation time was shorter in the remifentanil group (MD 3.34 [0.75, 5.93], P = 0.01, I2 = 90%). In conclusion, dexmedetomidine and remifentanil are both effective in providing satisfactory controlled hypotension and surgical conditions. Dexmedetomidine is better in easing postoperative pain at the PACU and reducing the occurrence of shivering, nausea, and vomiting. Meanwhile, remifentanil is a fast-track anesthesia with a shorter extubation time. Given the limitations of this meta-analysis, further studies are needed for a more definitive comparison of the efficacy and safety of dexmedetomidine and remifentanil.

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Tracking brain states under general anesthesia by using global coherence analysis.

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Tracking brain states under general anesthesia by using global coherence analysis.

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