Encephalography guidance of anesthesia to alleviate geriatric syndromes (Engages-Canada) study in cardiac surgery patients: a pragmatic, randomized clinical trial

Abstract

Introduction Postoperative delirium (POD) is a syndrome characterized by an acute onset of fluctuating confusion, disorganization and inattention. POD is frequent in the cardiac surgery population (incidence between 11-50%), and associated to complications such as increased risk of falls, prolonged hospital stay, functional decline and increased morbidity and mortality. Risk factors for POD are often non-modifiable, such as age, male sex, underlying cognitive or psychiatric conditions, while risk factors more specific to the cardiac surgery population include the type of surgery, cardiopulmonary bypass time, transfusions, and mechanical ventilation time15-18. Recent studies suggest that the use of a processed EEG for titration of anesthesia may reduce the incidence of POD. Burst suppression, or the pathological patterns of high-voltage electrical activity alternating with periods of quiescence may be associated with POD. Our primary objective is to demonstrate whether guiding anesthesia depth using an EEG monitor to avoid episodes burst suppression can result in a decreased incidence and severity of delirium in the cardiac surgery population. Secondly, we want to examine contributing risk factors and sequelae of delirium. Methods ENGAGES-Canada is an ongoing multi-center, double-blinded, randomized controlled trial across 4 Canadian sites. Patients included are those over the age of 60 scheduled for elective cardiac surgery with cardiopulmonary bypass. Exclusion criteria are pre-operative delirium, illiteracy, history of awareness, and planned surgery within five days of index surgery. Using an anesthesia protocol for EEG-guided anesthesia to avoid burst suppression, patients are randomized to the intervention or the control group (non-utilization of the monitor). The primary outcome is defined as the incidence of postoperative delirium, assessed using the Confusion Assessment Method (CAM) or CAM-ICU, coupled with chart review from day 1 to 5. Secondary outcomes include the effect of known risk factors on the incidence of delirium and 30-day and 1-year patient-reported outcomes of health-related quality of life and prevention of falls. Results Current enrollment includes 600 patients, out of a target population of 1200. An interim analysis was performed at 570 patients. The incidence of delirium across all subjects was 17.5% when considering CAM alone. Patients in the EEG-blinded group spent more cumulative time in burst suppression than those guided by EEG: median 317 seconds versus 136 seconds in the blind and guided groups respectively. Discussion ENGAGES-CANADA is the first RCT to examine whether avoidance of burst suppression using EEG guidance can decrease the incidence and severity of delirium in a cardiac surgery population.