title: Pupillary effects of high-dose opioid quantified with infrared pupillometry.
abstract: BACKGROUND
  The pupillary light reflex is a critical component of the neurologic examination, yet whether it is present, depressed, or absent is unknown in patients with significant opioid toxicity. Although opioids produce miosis by activating the pupillary sphincter muscle, these agents may induce significant hypercarbia and hypoxia, causing pupillary constriction to be overcome via sympathetic activation. The presence of either "pinpoint pupils" or sympathetically mediated pupillary dilation might prevent light reflex assessment. This study was designed to determine whether the light reflex remains quantifiable during opioid-induced hypercarbia and hypoxia.
  
  
  METHODS
  Ten volunteers were administered remifentanil with a gradually increasing infusion rate and intermittent boluses, until the increasing respiratory depression produced an oxyhemoglobin saturation of 85% or less with associated hypercarbia. Subjects' heart rate, blood pressure, respiration, and transcutaneous carbon dioxide level were continuously recorded. Arterial blood gases and pupillary measures were taken before opioid administration, at maximal desaturation, and 15 min after recovery.
  
  
  RESULTS
  The opioid-induced oxygen desaturation (≤ 85%) was associated with significant hypercarbia and evidence of sympathetic activation. During maximal hypoxia and hypercarbia, the pupil displayed parasympathetic dominance (2.5 ± 0.2 mm diameter) with a robust quantifiable light reflex. The reflex amplitude was linearly related to pupil diameter.
  
  
  CONCLUSIONS
  Opioid administration with significant accompanying hypercarbia and hypoxia results in pupil diameters of 2 to 3 mm and a reduced but quantifiable pupillary light reflex. The authors conclude that the pupillary examination and evaluation of the light reflex remain useful for neurologic assessment during opioid toxicity.
authors: From the Departments of Anesthesia and Perioperative Care and Surgery (M.D.R.), Department of Anesthesia and Perioperative Care ( J.R.F.), Department of Anesthesia and Perioperative Care (M.L.), University of California, San Francisco, California; Department of Pediatrics, University of California, Fresno, California ( J.M.L.); and Department of Anesthesia, University of California, San Diego, California (S.S.).
authors: Mark D
authors: MD
authors: Rollins
authors: John R
authors: JR
authors: Feiner
authors: Jessica M
authors: JM
authors: Lee
authors: Sameer
authors: S
authors: Shah
authors: Merlin
authors: M
authors: Larson
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D001341:Autonomic Nervous System / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002245:Carbon Dioxide / Q000097:blood; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D010100:Oxygen / Q000097:blood; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology; D011680:Pupil / Q000187:drug effects*; D012025:Reflex, Pupillary / Q000187:drug effects*; D000077208:Remifentanil; D012131:Respiratory Insufficiency / Q000139:chemically induced / Q000503:physiopathology
chemical_list: D000701:Analgesics, Opioid; D010880:Piperidines; D002245:Carbon Dioxide; D000077208:Remifentanil; D010100:Oxygen