title: Comparison of C₅₀ for Propofol-remifentanil Target-controlled Infusion and Bispectral Index at Loss of Consciousness and Response to Painful Stimulus in Elderly and Young Patients.
abstract: BACKGROUND
  In this prospective randomized study, we compared the predicted blood and effect-site C 50 for propofol and remifentanil target-controlled infusion (TCI) and the bispectral index (BIS) values at loss of consciousness (LOC) and response to a standard noxious painful stimulus (LOS) in elderly and young patients, respectively. We hypothesized that the elderly patients will require lower target concentration of both propofol and remifentanil at above two clinical end-points.
  
  
  METHODS
  There were 80 American Society of Anesthesiologists (ASA) physical status I-II unpremedicated patients enrolled in this study, they were divided into elderly group (age ≥65 years, n = 40) and young group (aged 18-64 years, n = 40). Propofol was initially given to a predicted blood concentration of 1.2 μg/ml and thereafter increased by 0.3 μg/ml every 30 s until Observer's Assessment of Alertness and Sedation score was 1. The propofol level was kept constant, and remifentanil was given to provide a predict blood concentration of 2.0 ng/ml, and then increased by 0.3 ng/ml every 30 s until loss of response to a tetanic stimulus. BIS (version 3.22, BIS Quattro sensor) was also recorded.
  
  
  RESULTS
  In elderly group, the propofol effect-site C 50 at LOC of was 1.5 (1.4-1.6) μg/ml, was significantly lower than that of young group, which was 2.2 (2.1-2.3) μg/ml, the remifentanil effect-site C 50 at LOS was 3.5 (3.3-3.7) ng/ml in elderly patients, was similar with 3.7 (3.6-3.8) ng/ml in young patients. Fifty percent of patients lost consciousness at a BIS value of 57.3 (56.4-58.1), was similar with that of young group, which was 55.2 (54.0-56.3).
  
  
  CONCLUSIONS
  In elderly patients, the predicted blood and effect-site concentrations of propofol at LOC were lower than that of young patients. At same sedation status, predicted blood and effect-site concentrations of remifentanil required at LOS were similar in elderly and young patients. BIS were not affected by age. Low-propofol/high-opioid may be optional TCI strategy for elderly patients.
authors.forename: Ning
authors.initials: N
authors.lastname: Yang
authors.forename: Ming-Zhang
authors.initials: MZ
authors.lastname: Zuo
authors.affiliation: Department of Anaesthesiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Yue
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.forename: Yu
authors.initials: Y
authors.lastname: Shi
authors.forename: Xue-Na
authors.initials: XN
authors.lastname: Zhang
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010880:Piperidines / Q000008:administration & dosage* / Q000627:therapeutic use*; D015742:Propofol / Q000008:administration & dosage* / Q000627:therapeutic use*; D011446:Prospective Studies; D000077208:Remifentanil; D014474:Unconsciousness / Q000139:chemically induced*; D055815:Young Adult
chemical_list: D018686:Anesthetics, Intravenous; D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol