title: Low-dose remifentanil infusion does not impair natural killer cell function in healthy volunteers.
abstract: BACKGROUND
  Mu opioid agonists suppress natural killer (NK) cell activity in animal models. Studies in human volunteers, however, have yielded conflicting results, with morphine suppressing and fentanyl increasing NK cell activity. This study evaluated the effect of a constant 8-h infusion of remifentanil on NK cell number and function in human volunteers.
  
  
  METHODS
  After IRB approval and informed consent was obtained, 10 healthy volunteers underwent an 11 pm to 7 am infusion of saline, and at least 1 week later an infusion of 0.02-0.04 microg x kg(-1) min(-1) remifentanil. Blood was collected at 7 am for measurement of NK cell cytotoxicity using a (51)Cr release assay and measurement of NK cell number using fluorescent flow cytometry.
  
  
  RESULTS
  Median and range of the total NK cell cytotoxicity (KU ml(-1)) was 745.0 (498.3-1483.6) on the control morning and 818.6 (238.5-1454.5) on the morning following the remifentanil infusion. Neither the number of NK cells ml(-1) (2.5 x 10(5) (1.4 x 10(5)-4.2 x 10(5)) vs 2.7 x 10(5) (1.1 x 10(5)-4.4 x 10(5))) nor the cytotoxicity per 1000 NK cells (KU 1000 NK cells(-1)) (3.0 (1.8-5.2) vs 2.9 (0.9-6.7)) changed between the control and remifentanil conditions.
  
  
  CONCLUSIONS
  An 8-h infusion of remifentanil did not affect NK cell activity in normal volunteers. This result differs from previous findings of morphine-induced NK cell activity suppression and fentanyl-induced NK cell activity enhancement in normal volunteers.
authors: Penn State College of Medicine, Milton S Hershey Medical Center, 500 University Drive, H187, Hershey, PA 17033, USA. acronin@psu.edu
authors: A J
authors: AJ
authors: Cronin
authors: N M
authors: NM
authors: Aucutt-Walter
authors: T
authors: T
authors: Budinetz
authors: C P
authors: CP
authors: Bonafide
authors: N A
authors: NA
authors: DiVittore
authors: V
authors: V
authors: Gordin
authors: H G
authors: HG
authors: Schuler
authors: R H
authors: RH
authors: Bonneau
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000494:pharmacology*; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000276:immunology; D018655:Lymphocyte Count; D008297:Male; D010880:Piperidines / Q000494:pharmacology*; D000077208:Remifentanil; D012119:Respiration / Q000187:drug effects; D016037:Single-Blind Method
chemical_list: D000701:Analgesics, Opioid; D010880:Piperidines; D000077208:Remifentanil