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Is there a relationship between processed EEG characteristics during anaesthesia and general level of health?

A 2018/2019 Summer Studentship research project

If we can establish a correlation between EEG activity and general health level, such a relationship would help us optimise measures to improve the post-operative outcomes for individual patients.

Student: Rachel Matthews 
Supervisors: Associate Professor Ross Kennedy, Mrs Margie McKellow
Sponsor: TBC

Student prerequisites

Must be a current medical student.

How to apply

Contact the first supervisor, Associate Professor Ross Kennedy, to express your interest:

Tel +64 3 364 0288

Project brief


Processed EEG monitors are being used increasingly during anaesthesia to reduce the risk of awareness and to allow titration and individualisation of drug dosing.  Early devices gave a single number to target and a short segment of a waveform. Newer devices give a derived index, multiple EEG waveforms and a detailed display of the frequency distribution of the EEG.

This frequency display, the spectrogram, conveys information about the energy of the EEG in different frequency bands. It is recognised that the EEG during anaesthesia gets less energetic with age, and we see this.  We have also observed differences in the energy of the EEG between patients of similar age that appears to relate to their overall level of health.

There is increasing interest in predicting and optimising physical and mental recovery after surgery and anaesthesia.

Our hypothesis is that there is a relationship between general physical fitness and the amount of EEG activity as evidenced by the energy of the spectrogram. A secondary hypothesis is that this may be related to outcome, as preoperative fitness is a well-recognised predator of postoperative outcome.


The primary aim of this study is to assess our observation of a correlation between EEG “energy” and general level of health. This study is also a feasibility study for a more detailed investigation of the relationship between EEG “energy” during anaesthesia and changes in physical and cognitive performance after anaesthesia and surgery. The data collected during this study will allow us to superficially explore the effect of a range of covariates on the EEG intensity and on outcomes to help design further studies.


30–60 patients over 65yr in whom the anaesthetist plans to use processed EEG monitoring. No significant dementia and sufficiently fluent in English to give consent and be able to complete the questionnaires. We will exclude patients undergoing intracranial or cardiac surgery and those with neck of femur fractures. Patients will be selected to allow the preoperative assessments to be conducted without delaying surgery.

Preoperatively, we will administer the Montreal Cognitive Assessment (MOCA), WHO disability assessment schedule (WHODAS), Edmonton Frailty assessment and a timed ‘get up & go test’. We estimate this will take around 30 minutes.

Conduct of anaesthesia will be left to the anaesthetist in charge of the case. Processed EEG monitoring with Masimo Sedline. Details of the anaesthetic technique and operation will be recorded with operations stratified as minor, intermediate and major. Physiological and drug data will be recorded electronically. The EEG will be recorded and intensity of spectrogram derived off line. The intensity of the spectrogram will also be scored on an empirical scale.

Follow-up will be at 1 day and 30 days. Patients will be contacted and hospital notes reviewed. WHODAS will be administered and major morbidity recorded.

Student researcher’s component of the study

Our student will communicate with the anaesthetist to ensure that the study protocol complies with their intended treatment of identified patients. The student will consent patients, administer the tests outlined above, and download relevant data from the theatre anaesthetic machines. They will also visit / telephone the patient on post-op days 1 and 30 to ask questions relating to their recovery.