Protocol for the Electroencephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes (ENGAGES) study: a pragmatic, randomised clinical trial

Abstract

Introduction: Postoperative delirium, arbitrarily defined as occurring within 5 days of surgery, affects up to 50% of patients older than 60 after a major operation. This geriatric syndrome is associated with longer intensive care unit and hospital stay, readmission, persistent cognitive deterioration and mortality. No effective preventive methods have been identified, but preliminary evidence suggests that EEG monitoring during general anaesthesia, by facilitating reduced anaesthetic exposure and EEG suppression, might decrease incident postoperative delirium. This study hypothesises that EEG-guidance of anaesthetic administration prevents postoperative delirium and downstream sequelae, including falls and decreased quality of life.

Methods and analysis: This is a 1232 patient, block-randomised, double-blinded, comparative effectiveness trial. Patients older than 60, undergoing volatile agent-based general anaesthesia for major surgery, are eligible. Patients are randomised to 1 of 2 anaesthetic approaches. One group receives general anaesthesia with clinicians blinded to EEG monitoring. The other group receives EEG-guidance of anaesthetic agent administration. The outcomes of postoperative delirium (≤5 days), falls at 1 and 12 months and health-related quality of life at 1 and 12 months will be compared between groups. Postoperative delirium is assessed with the confusion assessment method, falls with ProFaNE consensus questions and quality of life with the Veteran's RAND 12-item Health Survey. The intention-to-treat principle will be followed for all analyses. Differences between groups will be presented with 95% CIs and will be considered statistically significant at a two-sided p<0.05.

Ethics and dissemination: Electroencephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes (ENGAGES) is approved by the ethics board at Washington University. Recruitment began in January 2015. Dissemination plans include presentations at scientific conferences, scientific publications, internet-based educational materials and mass media.

Trial registration number: NCT02241655; Pre-results.

Keywords: ANAESTHETICS; EDUCATION & TRAINING (see Medical Education & Training); GERIATRIC MEDICINE.

Figure 1

Stylized common EEG patterns from frontal EEG channel seen with progressively increasing anaesthetic depth. BIS, bispectral index.

Figure 2

Flow diagram showing design overview for ENGAGES study.

Figure 3

Flow of participants.

Figure 4

The anaesthesia monitor is configured for the EEG-guided arm such that the raw EEG waveform as well as the non-proprietary numerical values are displayed by the monitor, including the burst suppression ratio (SR) and the spectral edge frequency (SEF). The EEG filter is turned off so the low frequency slow delta waves (with a frequency of about 0.5 Hz) are clearly visible. Turning off the filter allows EEG waves ≤2 Hz to be seen. The filter is a bandpass filter from 2 to 70 Hz with a notch to eliminate 60 Hz alternating current electrical noise. With the filter off, the system has a bandwidth of ∼0.25– 100 Hz.

Figure 5

The anaesthesia monitor is configured for the control arm such that all the EEG and BIS parameters are hidden, and only the signal quality index (SQI) of the EEG montage is visible.

Figure 6

The design elements of the ENGAGES trial that tend to be pragmatic (markers placed towards the periphery) and elements that tend to be explanatory (markers placed towards the centre). This figure was generated from a median determination for each criterion (using a 1 to 5 ordinal scale from explanatory to pragmatic) from 18 independent raters on the study team. Aside from the intensity of patient follow-up and the expertise needed to deliver the EEG-guided protocol, the ENGAGES study fulfils the criteria for a pragmatic clinical trial.

Figure 7

ENGAGES trial organization.