title: Changes in the Bispectral Index in Response to Loss of Consciousness and No Somatic Movement to Nociceptive Stimuli in Elderly Patients.
abstract: BACKGROUND
  Bispectral index (BIS) is considered very useful to guide anesthesia care in elderly patients, but its use is controversial for the evaluation of the adequacy of analgesia. This study compared the BIS changes in response to loss of consciousness (LOC) and loss of somatic response (LOS) to nociceptive stimuli between elderly and young patients receiving intravenous target-controlled infusion (TCI) of propofol and remifentanil.
  
  
  METHODS
  This study was performed on 52 elderly patients (aged 65-78 years) and 52 young patients (aged 25-58 years), American Society of Anesthesiologists physical status I or II. Anesthesia was induced with propofol administered by TCI. A standardized noxious electrical stimulus (transcutaneous electrical nerve stimulation, [TENS]) was applied (50 Hz, 80 mA, 0.25 ms pulses for 4 s) to the ulnar nerve at increasing remifentanil predicted effective-site concentration (Ce) until patients lost somatic response to TENS. Changes in awake, prestimulus, poststimulus BIS, heart rate, mean arterial pressure, pulse oxygen saturation, predicted plasma concentration, Ce of propofol, and remifentanil at both LOC and LOS clinical points were investigated.
  
  
  RESULTS
  BISLOCin elderly group was higher than that in young patient group (65.4 ± 9.7 vs. 57.6 ± 12.3) (t = 21.58, P < 0.0001) after TCI propofol, and the propofol Ce at LOC was 1.6 ± 0.3 μg/ml in elderly patients, which was significantly lower than that in young patients (2.3 ± 0.5 μg/ml) (t = 7.474, P < 0.0001). As nociceptive stimulation induced BIS to increase, the mean of BIS maximum values after TENS was significantly higher than that before TENS in both age groups (t = 8.902 and t = 8.019, P < 0.0001). With increasing Ce of remifentanil until patients lost somatic response to TENS, BISLOSwas the same as the BISLOCin elderly patients (65.6 ± 10.7 vs. 65.4 ± 9.7), and there were no marked differences between elderly and young patient groups in BISawake, BISLOS, and Ce of remifentanil required for LOS.
  
  
  CONCLUSIONS
  In elderly patients, BIS can be used as an indicator for hypnotic-analgesic balance and be helpful to guide the optimal administration of propofol and remifentanil individually.
  
  
  BACKGROUND
  CTRI Reg. No: ChiCTR-OOC-14005629; http://www.chictr.org.cn/showproj.aspx?proj=9875.
authors.forename: Ning
authors.initials: N
authors.lastname: Yang
authors.affiliation: Department of Anesthesiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Yue
authors.forename: Jonathan Z
authors.initials: JZ
authors.lastname: Pan
authors.forename: Ming-Zhang
authors.initials: MZ
authors.lastname: Zuo
authors.forename: Yu
authors.initials: Y
authors.lastname: Shi
authors.forename: Shu-Zhen
authors.initials: SZ
authors.lastname: Zhou
authors.forename: Wen-Ping
authors.initials: WP
authors.lastname: Peng
authors.forename: Jian-Dong
authors.initials: JD
authors.lastname: Gao
mesh_terms: D000328:Adult; D000368:Aged; D004569:Electroencephalography / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009069:Movement Disorders / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology*; D010880:Piperidines / Q000494:pharmacology; D015742:Propofol / Q000494:pharmacology; D000077208:Remifentanil; D004561:Transcutaneous Electric Nerve Stimulation; D014474:Unconsciousness / Q000503:physiopathology*
chemical_list: D010880:Piperidines; D000077208:Remifentanil; D015742:Propofol