title: Does mutual compensation of the cognitive effects induced by pain and opioids exist? An experimental study.
abstract: BACKGROUND
  Studies have demonstrated that both pain and opioids have actions on the central nervous system that may interfere with cognitive function, but their effects have mainly been analysed separately and not as an integrated process.
  
  
  OBJECTIVE
  The objective of this study is to test two hypotheses: (1) the analgesic effect of opioids improves cognitive function by decreasing pain, and (2) pain antagonizes cognitive effects of opioids.
  
  
  METHODS
  Randomized, placebo-controlled, crossover study. Three experiments were conducted with 22 healthy males. Sustained attention, memory and motor function/attention/mental flexibility were evaluated by continuous reaction time (CRT), verbal fluency test (VFT) and trail making test-B (TMT-B), respectively. In the 1st experiment, the cognitive effects of experimental tonic pain of mild and moderate intensities produced by a computer-controlled pneumatic tourniquet cuff were assessed; in the 2nd, the effects of saline solution and remifentanil were assessed in the absence of pain; and in the 3rd experiment, the cognitive effects of moderate pain intensity relieved by remifentanil infusion were assessed followed by increasing pain to moderate intensity during a constant remifentanil infusion.
  
  
  RESULTS
  The first two experiments demonstrated that pain and remifentanil impaired CRT. In the 3rd experiment, remifentanil infusion relieving pain significantly impaired CRT and further deterioration was noted following increasing pain intensity.
  
  
  CONCLUSIONS
  Pain and remifentanil seemed to have additive deleterious cognitive effects. This study represents an initial step to enhance our basic understanding of some of the cognitive effects following a painful stimulus and an opioid infusion separately and combined in a sequence comparable to clinical settings.
authors.affiliation: Section of Palliative Medicine, Department of Oncology, Rigshospitalet Copenhagen University Hospital, Rigshospitalet Dept 4111, Blegdamsvej 9, 2100, Copenhagen, Denmark, geana@rh.regionh.dk.
authors.forename: Geana Paula
authors.initials: GP
authors.lastname: Kurita
authors.forename: Lasse Paludan
authors.initials: LP
authors.lastname: Malver
authors.forename: Trine
authors.initials: T
authors.lastname: Andresen
authors.forename: Romanas
authors.initials: R
authors.lastname: Polianskis
authors.forename: Asbjørn Mohr
authors.initials: AM
authors.lastname: Drewes
authors.forename: Lona
authors.initials: L
authors.lastname: Christrup
authors.forename: Jette
authors.initials: J
authors.lastname: Højsted
authors.forename: Per
authors.initials: P
authors.lastname: Sjøgren
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000009:adverse effects*; D003071:Cognition / Q000187:drug effects* / Q000502:physiology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D006801:Humans; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology; D008606:Mental Processes / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000150:complications* / Q000523:psychology*; D010147:Pain Measurement / Q000379:methods / Q000523:psychology*; D010880:Piperidines / Q000009:adverse effects*; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D000077208:Remifentanil; D055815:Young Adult
chemical_list: D000701:Analgesics, Opioid; D010880:Piperidines; D000077208:Remifentanil