Participants and randomization
atrioventricular block, colorectal cancer, head injury, dementia, cardiac arrhythmia, Parkinson’s disease
ATRIOVENTRICULAR BLOCK, COLORECTAL CANCER, SEIZURE DISORDERS, CARDIAC ARRHYTHMIA, ATRIAL FIBRILLATION
All patients were recruited from the Department of Colorectal Surgery, Korea University Guro Hospital by the research staff.The inclusion criteria were as follows: patients scheduled to undergo elective laparoscopic colorectal cancer surgery, between the ages of 65 and 90 years, with an American Society of Anesthesiologists (ASA) physical status I–III. The exclusion criteria were as follows: history of neuromuscular, neurological, or psychological diseases (i.e., dementia, Parkinson’s disease, seizure disorders, head injury); abuse of alcohol or illicit drugs or chronic use of psychoactive medication; significant cardiac arrhythmia (i.e., atrial fibrillation, or atrioventricular block exceeding 1Patients were randomly assigned to two groups (1:1 ratio) without being aware of the assigned group to receive remifentanil infusion guided by SPI (SPI group) or by clinical judgment based on hemodynamic parameters (conventional group). Patients were assigned at random by a single investigator. A web-based (