Abstract
In the last decade, burst suppression has been increasingly studied by many to examine whether it is a mechanism leading to postoperative cognitive impairment. Despite a lack of consensus across trials, the current state of research suggests that electroencephalogram (EEG) burst suppression, duration and EEG emergence trajectory may predict postoperative delirium (POD). A mini literature review regarding evidence about burst suppression impact and susceptibilities was conducted, resulting in conflicting studies. Primarily, studies have used different algorithm values to replace visual burst suppression examination, although many studies have since emerged showing that algorithms underestimate burst suppression duration. As these methods may not be interchangeable with visual analysis of raw data, it is a potential factor for the current heterogeneity between data. Even though additional research trials incorporating the use of raw EEG data are necessary, the data currently show that monitoring with commercial intraoperative EEG machines that use EEG indices to estimate burst suppression may help physicians identify burst suppression and guide anesthetic titration during surgery. These modifications in anesthetics could lead to preventing unfavorable outcomes. Furthermore, some studies suggest that brain age, baseline impairment, and certain medications are risk factors for burst suppression and postoperative delirium. These patient characteristics, in conjunction with intraoperative EEG monitoring, could be used for individualized patient care. Future studies on the feasibility of raw EEG monitoring, new technologies for anesthetic monitoring and titration, and patient-associated risk factors are crucial to our continued understanding of burst suppression and postoperative delirium.
Highlights
Burst suppression was first discovered by Derbyshire et al (1936) and consists of alternating episodes of isoelectric flat EEG periods with bursts of slow waves, including systemic and quasiperiodic variation where high voltage and isoelectric periods have variations between and within bursts (Figure 1) (Swank and Watson, 1949; Niedermeyer et al, 1999; Ching et al, 2012; Amzica, 2015; Purdon et al, 2015b)
postoperative delirium (POD) results in longer hospital stays, increased need for long-term care, loss of functional independence, reduced cognition, and death (American Geriatrics Society Expert Panel on Postoperative Delirium in Older Adults, 2015)
Analysis of propofol-remifentanil general anesthesia maintenance in a non-cardiac surgery study found that independent factors associated with suppression ratio (SR) were advanced age, history of coronary artery disease, and male gender (Besch et al, 2011)
Summary
Burst suppression was first discovered by Derbyshire et al (1936) and consists of alternating episodes of isoelectric flat EEG periods with bursts of slow waves, including systemic and quasiperiodic variation where high voltage and isoelectric periods have variations between and within bursts (Figure 1) (Swank and Watson, 1949; Niedermeyer et al, 1999; Ching et al, 2012; Amzica, 2015; Purdon et al, 2015b). There are many controversies about burst suppression, including its relation to postoperative delirium (POD)—the postoperative onset of acute change from baseline attention, fluctuating awareness, and disturbances in cognition representative of acute brain failure. Burst Suppression: Mini Review (American Geriatrics Society Expert Panel on Postoperative Delirium in Older Adults, 2015). POD results in longer hospital stays, increased need for long-term care, loss of functional independence, reduced cognition, and death (American Geriatrics Society Expert Panel on Postoperative Delirium in Older Adults, 2015). It costs about $150 billion in the U.S annually, even though it is preventable in up to 40% of patients (American Geriatrics Society Expert Panel on Postoperative Delirium in Older Adults, 2015). This review will explore the current methods used to evaluate burst suppression, its origins and proposed mechanisms, relation to cognitive outcomes, role of medications, and associated risk factors, to present the current understanding of intraoperative burst suppression and its consequences
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