Neurocognitive Disorders After Major Surgery in Elderly

The main objective of the study is to investigate the effect of EEG-guided anesthesia aiming at reducing anesthetic administration and minimizing burst suppression on the EEG during general anesthesia on the incidence of NCD at postoperative day 1 in elderly patients (> 70 years old) undergoing major (expected duration > 1h) non-cardiac surgery compared to standard care.

Secondary objectives are to investigate the effect of EEG-guided anesthesia compared to standard care on:

• neurocognitive disorders at postoperative day 2, 7, 15, 30 and 90,
• perioperative cognitive trajectories,
• postoperative delirium,
• intraoperative consumption of volatile anesthetics, opioids and vasopressors,
• intraoperative hypotension (number of interventions to treat hypotensive events),
• cerebral hypoxemia (assessed by cerebral oximetry),
• cumulative burst suppression duration and cumulative low processed EEG values duration during anesthesia,
• awareness
• postoperative surgical and quality of life / recovery outcomes.

Tertiary objectives are to:

• explore the effect of EEG-guided anesthesia compared to standard care across and within subgroups including different categories of surgical, duration of surgery, preoperative frailty, preoperative presence of depressive symptoms, age and patients with preoperative neurocognitive disorder.
• explore the effect of a possible imbalance in risk factors for postoperative NCD between the two groups on the incidence of postoperative NCD.

Methods

Participants 314 patients 70 years of age or older scheduled for elective major gynecologic, abdominal, urologic, thoracic or orthopedic surgeries via laparoscopy or laparotomy under general anesthesia and an anesthesia time of more than 60 minutes at the institution HMR-CEMTL, who are seen at the preoperative clinic (CIEPC) by internal medicine and/or anesthesiology.

Exclusion criteria: patients with known diagnosis of dementia or other neurological, psychiatric, developmental or medical condition that resulted in severe documented cognitive impairment, emergency surgery, significant auditory or visual impairment that precludes participation in cognitive testing, known allergy or intolerance or other medical condition that precludes the use of prescribed general anesthesia protocol for this study, inability to communicate in French or English will not be included in the present study.

Anesthesia Protocol All patients will undergo general anesthesia with the following: induction with IV slow boluses of lidocaine to numb the vein, propofol 1.5mg.kg-1, remifentanil 1µg.kg-1, rocuronium 0.8mg.kg-1. The maintenance of anesthesia will be based on sevoflurane to reach [0.8-1.2] minimal alveolar concentration (MAC adjusted to age) in the control group, and to achieve a Bispectral index (BIS) of [40-60] in the EEG-guided group (see below). The Nociception level (NOL) index (PMD200™ device, Medasense Biometrics Ltd, Ramat Gan, Israel) and the bilateral cerebral regional oximetry (rSO2) (Invos™, Medtronic, Canada) will be placed and available for both groups throughout the entire anesthesia. Remifentanil infusion will be set between 0.02 and 0.3 µg.kg-1.min-1 to achieve a NOL index of [5-25]. Phenylephrine will be started at 0.2 µg.kg-1.min-1 and adjusted to maintain +/- 20% of the baseline values of the pre-anesthesia mean arterial pressure (MAP). No benzodiazepines or ketamine will be used intraoperatively. An epidural may be placed at the discretion of the anesthesiologist in charge of the patient in the OR. Patients will receive standard prophylaxis against postoperative nausea and vomiting. Hydromorphone PCA (or hydromorphone SC or PO if patient is not a candidate for PCA) for postoperative pain scores < 4/10, or Patient controlled epidural analgesia if an epidural is started in Postoperative anesthesia care unit (PACU). All anesthesia related side effects and quality of analgesia and rehabilitation will be evaluated for 48h.

Intervention Patients will be randomized (1:1) to receive EEG guided anesthesia versus standard of care. Information provided by the BIS (Medtronic, Canada) monitor will guide the volatile anesthetic administration in the EEG-guided group to maintain a BIS value between 40 and 60, a Suppression Ratio (SR; % of time with suppressed brain electrical activity) at 0% or the closest, a direct EEG display without any suppression time and a spectrogram (DSA or density spectral array) with most of the EEG wave frequency within the Alpha (8-12Hz), Theta (4-8Hz) and Delta (0.5-4Hz) frequencies. In the standard of care group, the age-adjusted Minimum Alveolar Concentration (MAC-age) of sevoflurane will be kept at [0.8-1.2] MAC.

Cognitive Assessment Participants will undergo cognitive assessment preoperatively to establish a baseline and then postoperatively to assess change from that baseline at postoperative days 1, 2, 7, 15, 30 and 90.

• The MoCA or the telephone version of the MoCA (T-MoCA) will be administered at each time point depending on patient location (hospital / home).
• Verbal fluency including phonemic and categorical fluency will be administered at each time point
• The Confusion Assessment Method (CAM) will be used to diagnose postoperative delirium at postoperative days 1 and 2.
• The Quality of Recovery-15 (QoR-15) questionnaire will be used at postoperative day 30 and 90 to explore quality of life after anesthesia and surgery.

Significance/Importance This study was designed to explore the effect of EEG-guided anesthesia on perioperative neurocognitive disorders with tight control of intraoperative blood pressure and nociception level. Understanding EEG patterns of anesthesia to individualize titration of hypnotic drugs may help in reducing the incidence of perioperative neurocognitive disorders, particularly in the elderly.

Study Design Prospective monocentric randomized controlled trial.

Subject Population Patients ≥ 70 years old scheduled for major non-cardiac surgery (expected duration ≥1h).

Sample Size Three hundred and fourteen (314 total; 157 per group, 2 groups) will be included in the present study.

Study Duration 2 years.

Study Center Single centre study, at Maisonneuve-Rosemont Hospital (HMR), Centre intégré universitaire de santé et de services sociaux (CIUSSS) de l'Est de l'Ile de Montréal (CEMTL), Montréal, Québec, Canada.

Adverse Events Non expected.