Frontal alpha-delta EEG does not preclude volitional response during anaesthesia: prospective cohort study of the isolated forearm technique

A L Gaskell; D F Hight; J Winders; G Tran; A Defresne; V Bonhomme; A Raz; J W Sleigh; R D Sanders

doi:10.1093/bja/aex170

Frontal alpha-delta EEG does not preclude volitional response during anaesthesia: prospective cohort study of the isolated forearm technique

Br J Anaesth. 2017 Oct 1;119(4):664-673. doi: 10.1093/bja/aex170.

Authors

A L Gaskell^{1

2}, D F Hight², J Winders², G Tran³, A Defresne^{3

4}, V Bonhomme^{3

4

5}, A Raz^{6

7}, J W Sleigh^{1

2}, R D Sanders⁶

Affiliations

¹ Department of Anaesthesia, Waikato Hospital, Hamilton, New Zealand.
² Department of Anaesthesiology, Waikato Clinical School, Waikato Clinical Campus, University of Auckland, New Zealand.
³ Coma Science Group, GIGA research, University and CHU University Hospital of Liege, Belgium.
⁴ Department of Anesthesia and Intensive Care Medicine, CHU University Hospital of Liege, Belgium.
⁵ University Department of Anesthesia and Intensive Care Medicine, CHR Citadelle, Liege, Belgium.
⁶ Department of Anesthesiology, University of Wisconsin School of Medicine and Public Health University of Wisconsin, Madison, WI, USA.
⁷ Department of Anesthesiology, Rambam Health Care Campus, Haifa, Israel.

PMID: 29121278
DOI: 10.1093/bja/aex170

Abstract

Background: The isolated forearm test (IFT) is the gold standard test of connected consciousness (awareness of the environment) during anaesthesia. The frontal alpha-delta EEG pattern (seen in slow wave sleep) is widely held to indicate anaesthetic-induced unconsciousness. A priori we proposed that one responder with the frontal alpha-delta EEG pattern would falsify this concept.

Methods: Frontal EEG was recorded in a subset of patients from three centres participating in an international multicentre study of IFT responsiveness following tracheal intubation. Raw EEG waveforms were analysed for power-frequency spectra, depth-of-anaesthesia indices, permutation entropy, slow wave activity saturation and alpha-delta amplitude-phase coupling.

Results: Volitional responses to verbal command occurred in six out of 90 patients. Three responses occurred immediately following intubation in patients (from Sites 1 and 2) exhibiting an alpha-delta dominant (delta power >20 dB, alpha power >10 dB) EEG pattern. The power-frequency spectra obtained during these responses were similar to those of non-responders (P>0.05) at those sites. A further three responses occurred in (Site 3) patients not exhibiting the classic alpha-delta EEG pattern; these responses occurred later relative to intubation, and in patients had been co-administered ketamine and less volatile anaesthetic compared with Site 1 and 2 patients. None of the derived depth-of-anaesthesia indices could robustly discrimate IFT responders and non-responders.

Conclusions: Connected consciousness can occur in the presence of the frontal alpha-delta EEG pattern during anaesthesia. Frontal EEG parameters do not readily discriminate volitional responsiveness (a marker of connected consciousness) and unresponsiveness during anaesthesia.

Clinical trial registration: NCT02248623.

Keywords: EEG; anaesthesia awareness; anaesthesia general; consciousness.

Publication types

Multicenter Study

MeSH terms

Adult
Anesthesia, General / methods*
Cohort Studies
Consciousness / drug effects*
Electroencephalography / drug effects*
Electroencephalography / methods
Female
Forearm
Humans
Male
Monitoring, Intraoperative / methods*
Prospective Studies
Young Adult

Associated data

ClinicalTrials.gov/NCT02248623