Thesis
Understanding loss of consciousness under general anaesthesia using multimodal neuroimaging
- Abstract:
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Despite major advancements in consciousness science over the past few decades, how anaesthesia causes loss of consciousness remains incompletely understood and the translation from basic science to clinical practice has been limited. Recent concurrent electroencephalography (EEG) and functional magnetic resonance imaging (FMRI) evidence indicates that a state of complete perception loss is achieved under general anaesthesia when slow wave activity in the brain reaches saturation. Slow wave activity saturation (SWAS) is therefore a potentially clinically relevant end point for titration of anaesthesia.
We have developed a prototype system for titrating anaesthesia to SWAS within an individual. The system features EEG and anaesthesia data input, modelling of slow wave power and detection of SWAS, and visualisation of the model output in a graphical user interface. The prototype system was applied in a patient pre-surgery study (Study 1) which focused on clinical translation of SWAS, and a healthy volunteer EEG-MRI study (Study 2) which focused on experimental validation of SWAS.
We successfully applied the prototype SWAS system in twelve patients (Study 1) and twenty-three healthy volunteers (Study 2). No subjects in either Study 1 or Study 2 were behaviourally responsive when held at SWAS and none had recall of events from when they were held at SWAS.
In Study 2, we also acquired measures of cerebral blood flow (CBF), and resting and task-related FMRI data during wakefulness and when held at SWAS. When held at the SWAS state, CBF was significantly elevated compared to wakefulness. Furthermore, we found that the brain was unresponsive to external stimulation when held at SWAS even when controlling for the observed CBF changes. Finally, we found that this was accompanied by disruption of functional connectivity in the thalamocortical system and in known resting state networks. Our findings provide further evidence that SWAS is a state of perception loss and a clinically relevant target for surgical anaesthesia.
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Authors
Contributors
- Institution:
- University of Oxford
- Division:
- MSD
- Department:
- Clinical Neurosciences
- Sub department:
- Clinical Neurosciences
- Research group:
- WIN
- Oxford college:
- St Cross College
- Role:
- Supervisor
- ORCID:
- 0000-0002-6268-487X
- Institution:
- University of Oxford
- Division:
- MSD
- Department:
- Clinical Neurosciences
- Sub department:
- Clinical Neurosciences
- Research group:
- WIN
- Oxford college:
- St Hilda's College
- Role:
- Supervisor
- ORCID:
- 0000-0003-3234-5639
- Institution:
- University of Oxford
- Division:
- MSD
- Department:
- Clinical Neurosciences
- Sub department:
- Clinical Neurosciences
- Research group:
- WIN
- Oxford college:
- Merton College
- Role:
- Supervisor
- ORCID:
- 0000-0003-4134-6115
- Funder identifier:
- https://ror.org/019w4f821
- Funding agency for:
- Warnaby, C
- Grant:
- H2020-FETOPEN-2014-2015-RIA
- Programme:
- Horizon 2020
- Funder identifier:
- https://ror.org/03x94j517
- Funding agency for:
- Warnaby, C
- Grant:
- MR/R006423/1
- Programme:
- Development Pathway Funding Scheme
- Funding agency for:
- Holmgren, J
- Grant:
- N/A
- Programme:
- Aker Scholarship
- DOI:
- Type of award:
- DPhil
- Level of award:
- Doctoral
- Awarding institution:
- University of Oxford
- Language:
-
English
- Keywords:
- Subjects:
- Deposit date:
-
2023-12-17
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