Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

1. In this randomized controlled trial, EEG-guided anesthetic administration during surgical interventions did not reduce the incidence of delirium compared to anesthetic administration as usual in elderly patients.

2. There was a small reduction in 30-day mortality in patients who received EEG-guided anesthetic administration

Evidence Rating Level: 1 (Excellent)

Study Rundown:

EEG-guided administration of anesthetics can reduce anesthetic exposure by providing feedback in the form of burst suppression when a patient is excessively anesthetized. For elderly patients who are especially prone to post-operative delirium, it is unclear if reduction in burst-suppression during anesthetic administration might reduce delirium. In this randomized controlled trial, EEG-guided anesthetic administration resulted in a reduction in anesthetic exposure but did not reduce the incidence, duration, or severity of delirium. In exploratory analysis, there was a small reduction in 30-day mortality in patients who received EEG-guided anesthetic administration.

Despite a previous meta-analysis suggesting a benefit of EEG-guided anesthetic administration for delirium risk, this well designed and executed study argues against this conclusion. Importantly, the reduction in anesthetic exposure suggests that the intervention was successful in reducing anesthetic administration, though this does not preclude the possibility that a larger reduction in anesthetic may still improve rates of post-operative delirium. While unexpected, the finding of reduced 30-day mortality deserves increased follow-up to determine if EEG-guided anesthesia is beneficial for this indication.

In-Depth [randomized controlled trial]:

1232 patients (98.5% assessed for the primary outcome) over the age of 60 years were recruited for the Electroencephalography Guidance of Anesthesia to Alleviate Geriatric Syndromes (ENGAGES) trial at a single, US, academic institution across multiple surgical specialties. Patients were excluded if they were unable to provide informed consent, delirious, blind, deaf, illiterate, not fluent in English, had a history of intraoperative awareness, or were scheduled for a second surgery within 5 days of the initial surgery. Patients were randomized to receive EEG-guided anesthetic administration, where dose was titrated down in the setting of burst suppression, and anesthetic administration as usual. While the median duration of midazolam, propofol, opioids, and neuromuscular blocking agents was similar between groups, there was a reduction in median end-tidal volatile anesthetic concentration (difference -0.11 minimum alveolar concentration; CI95 -0.13 to -0.10), median cumulative time with EEG-suppression (difference -6.0 min; CI95 -9.9 to -2.1), and median cumulative time with bispectral index less than 40 (difference -28.0 min; CI95 -38.0 to -18.0). More phenylephrine was administered to the usual care group (p < 0.05). There was no significant difference in the incidence of delirium (difference, 3.0%; CI95 -2.0 to 8.0%) nor delirium incidence on the day of the surgical procedure, time to delirium onset, duration of delirium, and incidence of severe delirium (p > 0.05). Three post-hoc sensitivity analyses did not change this result, and there was no difference in the rate of adverse events. In exploratory analyses, EEG-guided anesthetic administration was associated with a reduced 30-day mortality rate (difference -2.42%; CI95 -4.3 to -0.8%).

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