TL;DR: ⚪ Clean null — EEG-guided anesthesia reduced EEG suppression time by 66% but did NOT reduce postoperative delirium (18.15% vs 18.10%) in older cardiac surgery patients — confirms the original ENGAGES trial.
1. Publication
- Title: Electroencephalography-Guided Anesthesia and Delirium in Older Adults After Cardiac Surgery: The ENGAGES-Canada Randomized Clinical Trial
- Acronym: ENGAGES-Canada
- Year & Journal: JAMA, published June 10, 2024 (332(2):112-123)
- Citation: Deschamps A, Ben Abdallah A, Jacobsohn E, et al; Canadian Perioperative Anesthesia Clinical Trials Group. JAMA. 2024;332(2):112-123. doi:10.1001/jama.2024.8144
2. Context & Rationale
Background: EEG suppression during general anesthesia is an accepted marker of deep anesthesia and has been associated with postoperative delirium risk in some studies, though results are inconsistent. The original ENGAGES trial (US, non-cardiac surgery) found no benefit from EEG-guided anesthesia; ENGAGES-Canada tested this specifically in cardiac surgery.
Research Question/Hypothesis: In older adults undergoing cardiac surgery, does EEG-guided anesthetic administration (minimizing EEG suppression) reduce postoperative delirium incidence compared with usual care?
3. Design & Methods
- Study Type: Multicenter, pragmatic, evaluator- and patient-blinded RCT
- Population: 1140 patients ≥60y undergoing cardiac surgery (562 EEG-guided, 569 usual care analyzed)
- Intervention: EEG-guided anesthesia — clinicians encouraged to decrease volatile anesthetic to limit EEG suppression
- Comparator: Usual care
- Blinding: Evaluator- and patient-blinded
- Statistical Power & Follow-Up: Primary: postoperative delirium incidence, days 1-5. Secondary: ICU/hospital LOS, medical complications, 30-day mortality.
4. Key Results
1131 patients analyzed.
Outcome | EEG-Guided | Usual Care | Effect Size | 95% CI | Notes |
Postoperative delirium, days 1-5 (primary) | 18.15% (102/562) | 18.10% (103/569) | Diff 0.05pp | −4.57 to 4.67 | No significant difference |
Time in EEG suppression | Median 4.0 min | Median 11.7 min | — | — | 66% reduction — intervention delivered as intended |
ICU/hospital LOS, medical complications, 30-day mortality | No significant difference | No significant difference | — | — | No safety penalty either direction |
5. Internal Validity Assessment
Large (1140-patient), multicenter, evaluator- and patient-blinded RCT with confirmed intervention delivery (66% reduction in EEG suppression time). Overall: Strong — clean null result with confirmed physiological separation between arms, ruling out "the intervention wasn't delivered" as an explanation.
6. External Validity Assessment
Canadian, multicenter cardiac surgery population ≥60y — broadly representative of older cardiac surgery patients at risk for delirium.
7. Strengths & Limitations
Strengths: Large, well-blinded, pragmatic design; confirmed on-target physiological effect (reduced EEG suppression); consistent with the original US ENGAGES trial in non-cardiac surgery.
Limitations: Cannot exclude that other EEG-guidance thresholds or different anesthetic protocols might show benefit; delirium assessment timing (once daily) may have missed transient episodes.
8. Interpretation & Practice Impact
Does not support EEG-guided anesthetic administration for preventing postoperative delirium in older cardiac surgery patients — confirms and extends the original ENGAGES trial's null finding to the cardiac surgery population specifically.
9. Controversies & Subsequent Evidence
An accompanying JAMA editorial ("Anesthesia Dose and Delirium — A Picture Coming Into Focus," Berger, Neuman) and a JCVA commentary ("Has This 'Burst' the Bubble of Processed EEG?") both address the now-consistent null findings across both ENGAGES trials, suggesting processed-EEG-guided anesthesia titration may not be the answer to postoperative delirium prevention that observational data had suggested.
10. Summary & Executive Takeaway
Summary: ENGAGES-Canada randomized 1140 older cardiac surgery patients to EEG-guided or usual-care anesthesia. Despite a 66% reduction in EEG suppression time with EEG guidance, postoperative delirium incidence was identical (18.15% vs 18.10%), with no differences in LOS, complications, or mortality.
Overall Takeaway: EEG-guided anesthesia to minimize EEG suppression does not reduce postoperative delirium in older cardiac surgery patients, confirming and extending the original ENGAGES trial's null result — processed EEG monitoring for delirium prevention appears unlikely to be the practice-changing tool earlier observational data suggested.
11. Bibliography
- Wildes TS, Mickle AM, Ben Abdallah A, et al. Effect of Electroencephalography-Guided Anesthetic Administration on Postoperative Delirium (ENGAGES). JAMA. 2019;321(5):473-483.
- Berger M, Neuman MD. Anesthesia Dose and Delirium—A Picture Coming Into Focus [editorial]. JAMA. 2024;332(2):107-108.