title: Pupillometry to detect pain response during general anaesthesia following unilateral popliteal sciatic nerve block: a prospective, observational study.
abstract: BACKGROUND
  Pupillary reflex dilation appears to be a reliable indicator of response to noxious stimulation even under general anaesthesia. The ability of pupillometry to detect the effects of extremity blocks during continuous infusion of opioids remains unknown.
  
  
  OBJECTIVE
  To explore the performance of pupillometry to detect differences in pupillary reflex dilation response to a standardised noxious stimulus applied to each leg following unilateral popliteal sciatic nerve block during continuous infusion of remifentanil.
  
  
  METHODS
  Prospective, observational study.
  
  
  METHODS
  University hospital anaesthesia department, between June 2010 and December 2010.
  
  
  METHODS
  Twenty-four adult patients undergoing elective foot or ankle surgery under general anaesthesia who requested a peripheral nerve block. Unilateral popliteal sciatic nerve block with 0.75% ropivacaine and 1% lidocaine was performed awake. General anaesthesia was maintained with steady-state infusions of propofol and remifentanil.
  
  
  METHODS
  Video-based pupillometer was used to determine pupillary reflex dilation during tetanic stimulation (60 m, 100 Hz) applied to the skin area innervated by the sciatic nerve for 5 s after the onset of general anaesthesia.
  
  
  RESULTS
  Sensory nerve block led to a blunted maximal pupillary reflex dilation response to noxious stimulation compared with the non-blocked leg: median (interquartile range) change from baseline 2% (1 to 4%) versus 17% (13 to 24%), respectively (P < 0.01). The differences in the response persisted throughout the 5-s stimulus and the recovery phase.
  
  
  CONCLUSIONS
  These results are a proof of concept. The effects of peripheral nerve block can be detected via the measurement of pupillary reflex dilation response to noxious stimulation of the skin in patients receiving remifentanil.
authors.affiliation: Pôle d'Anesthésie-Réanimation, the Centre de Recherche Clinique, Hôpital Michallon, CHU de Grenoble et UJF-Grenoble 1, Grenoble, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Isnardon
authors.forename: Marc
authors.initials: M
authors.lastname: Vinclair
authors.forename: Celine
authors.initials: C
authors.lastname: Genty
authors.forename: Amelie
authors.initials: A
authors.lastname: Hebrard
authors.forename: Pierre
authors.initials: P
authors.lastname: Albaladejo
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Payen
mesh_terms: D000328:Adult; D000577:Amides / Q000008:administration & dosage; D000701:Analgesics, Opioid / Q000627:therapeutic use; D000768:Anesthesia, General / Q000379:methods*; D000842:Ankle / Q000601:surgery; D019540:Area Under Curve; D005260:Female; D005528:Foot / Q000601:surgery; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D059408:Pain Management / Q000379:methods; D010147:Pain Measurement / Q000379:methods*; D010880:Piperidines / Q000008:administration & dosage; D011446:Prospective Studies; D011680:Pupil / Q000187:drug effects / Q000502:physiology*; D012025:Reflex, Pupillary / Q000187:drug effects; D000077208:Remifentanil; D000077212:Ropivacaine; D012584:Sciatic Nerve / Q000473:pathology / Q000601:surgery*; D014741:Video Recording
chemical_list: D000577:Amides; D000701:Analgesics, Opioid; D010880:Piperidines; D000077212:Ropivacaine; D008012:Lidocaine; D000077208:Remifentanil