Postoperative delirium is common in patients undergoing cardiovascular surgery and associated with poor outcomes. However the pathogenesis of postoperative delirium is poorly understood. Multichannel electroencephalogram is a recognized tool for identifying neurophysiologic states during anesthesia, sleep, and arousal. The aim of the current study is to evaluate the mechanisms and predictors of postoperative delirium in patients undergoing cardiovascular surgery using electroencephalogram.
age of at least 18 years
normal cognitive function at the time of enrollment evidenced by a Mini-Mental State Examination (MMSE) score of more than 24 of 30
Chinese Mandarin as the native language
providing informed consent
pre-existing delirium assessed according to the Confusion Assessment Method (CAM)
history of neurological or psychiatric disease
impaired vision or auditory function which may effect the assessments
unwillingness to participate in the study
Patients undergoing cardiovascular surgery
Cohort
Prospective
Not listed
Incidence of postoperative delirium
The incidence of postoperative delirium was determined according to the Confusion Assessment Method (CAM) diagnostic algorithm. The algorithm consists of four clinical criteria: (1) acute onset and fluctuating course, (2) inattention, (3) disorganized thinking, and (4) altered level of consciousness. To define a patient as having delirium, both the first and the second criteria have to be present, as well as either the third or the fourth criteria. The CAM-ICU will be used for patients who are intubated in the postoperative period.
Relative power of each brain waves
Electroencephalogram data were acquired using a 32-channel electroencephalogram recording system (Brain Products, Germany). A 5 min, baseline, eyes-closed recording was conducted at the preoperative holding room when the patient was at rest. Recording of electroencephalogram was commenced before the start of anesthetic induction and was stopped before discharge of the patient from the operating room. We defied delta (1 to 3 Hz), theta (4 to 7 Hz), alpha (8 to 12 Hz), and beta (13 to 40 Hz) frequency bands. And then, the relative power of each frequency bands to the total power of the sum is calculated.
Duration of delirium
Severity of delirium
Delirium severity is evaluated both as the peak (highest) and sum Confusion Assessment Method - Severity (CAM-S) score over all hospital days. The CAM-S includes two forms: a Short Form (CAM-S Short Form, based on the 4-item algorithm, the sum of score ranging from 0 to 7, with 7 being the most severe) and a Long Form (CAM-S Long Form, based on the 10-item CAM instrument, the sum of score ranging from 0 to 19, with 19 being the most severe).
Worst daily pain scores at rest
Pain scores will be collected three times daily using a numeric rating scale (0, no pain, to 10, worst possible pain).
Biomarkers
Identify biomarkers (such as Ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1), brain-derived neurotrophic factor (BDNF), and metalloproteases-9 (MMP-9) )of delirium and neural damage through changes in circulating plasma proteins and molecules
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