EEG-Guided Anesthesia and Delirium in Elderly Patients After Cardiac Surgery

Research Background

Delirium is a common postoperative complication in elderly patients, particularly after cardiac surgery. Delirium not only leads to cognitive decline but also increases hospitalization time and medical costs. Current preventive measures are limited in effectiveness, calling for further research to find effective prevention methods. During anesthesia, deep anesthesia is considered a significant factor leading to postoperative delirium. EEG (Electroencephalogram) waveform suppression is a biomarker of deep anesthesia. Therefore, researchers propose that using EEG-guided anesthesia to reduce anesthesia depth may lower the incidence of postoperative delirium.

Research Source

This study was conducted by the Canadian Perioperative Anesthesia Clinical Trials Group, with primary authors including Alain Deschamps, MD, PhD, and Eric Jacobsohn, MD, ChB. The study recruited 1,140 patients from December 2016 to February 2022, concluding in February 2023. The results were published in the JAMA journal on June 10, 2024.

Subjects and Methods

Study Design

This study is a multicenter, patient and assessor double-blind, randomized controlled clinical trial involving four hospitals in Canada. The specific randomization method was stratified by hospital, with patients randomly assigned 1:1 to receive either EEG-guided anesthesia or conventional anesthesia. The primary clinical endpoint was the incidence of delirium from postoperative days 1 to 5, with additional records of ICU and hospital stay duration and other serious adverse events (such as intraoperative awareness, medical complications, and 30-day mortality).

Inclusion and Exclusion Criteria

Participants were aged 60 years and above, scheduled for cardiac surgery requiring cardiopulmonary bypass. Exclusion criteria included preoperative delirium, hearing loss, inability to read or write English or French, and a history of intraoperative awareness.

Implementation Steps

1. Random Grouping: Patients were randomly assigned to the EEG-guided anesthesia group (n=567) and the conventional anesthesia group (n=573).
2. Anesthesia Management: Anesthesiologists in the EEG group used EEG monitoring to minimize the use of volatile anesthetics, while anesthesiologists in the conventional group did not use such monitoring.
3. Data Collection and Analysis: Postoperative delirium was assessed daily by trained researchers using the Confusion Assessment Method (CAM) and CAM-ICU to ensure objective and consistent evaluations.

Results

Primary Results

1. Incidence of Delirium: From postoperative days 1 to 5, 102 patients (18.15%) in the EEG-guided group developed delirium compared to 103 patients (18.10%) in the conventional anesthesia group, with no statistically significant difference (difference 0.05%, 95% CI: -4.57% to 4.67%).
2. Anesthetic Dosage and EEG Suppression Time: The median minimum alveolar concentration (MAC) of volatile anesthetics in the EEG-guided group was 0.14 lower than in the conventional group (0.66 vs. 0.80), and EEG suppression time was reduced by 7.7 minutes (from 11.7 minutes to 4.0 minutes).

Secondary Results and Adverse Events

1. ICU and Hospital Stay Duration: There was no significant difference in the median ICU and hospital stay durations between the two groups.
2. Intraoperative Awareness and Other Complications: No patients reported intraoperative awareness, with the incidence of medical complications being 11.3% in the EEG-guided group and 12.7% in the conventional group.
3. 30-Day Mortality: The 30-day mortality rate was 1.4% in the EEG-guided group, lower than 2.3% in the conventional group.

Interpretation and Analysis

Although the EEG-guided anesthesia group had reduced anesthesia depth and EEG suppression time, it did not significantly lower the incidence of postoperative delirium. The impact on other secondary clinical endpoints (such as ICU stay, postoperative complications, etc.) was also insignificant. This suggests that EEG-guided anesthesia does not have a clear advantage in this specific surgical type and patient population.

Conclusion and Value of the Study

The conclusion of this study is that EEG-guided anesthesia does not reduce the incidence of postoperative delirium in elderly cardiac surgery patients. This is inconsistent with some previous small-scale studies and results from non-cardiac surgery patients, indicating a need for further research to investigate the actual effects of EEG-guided anesthesia in different patient groups and surgical types.

Highlights of the Study

1. Large Sample Size and Multicenter Design: Increases the reliability and generalizability of the study results.
2. Rigorous Double-Blind Design: Reduces potential bias.
3. Precise Anesthesia Depth Control: Although the results did not meet expectations, the research methods demonstrated high levels of technical application and data management.

Important Significance

This study is significant for future clinical practice, reminding anesthesiologists to consider other strategies for preventing delirium in elderly cardiac surgery patients. Although EEG-guided anesthesia did not significantly reduce delirium incidence, its precise control of anesthesia depth still helps in understanding and optimizing intraoperative management.

Additional Information

The study also considered the potential long-term cognitive effects of delirium and plans to follow up on the long-term health status of these patients. These data will provide a basis for more effective interventions in the future.