title: The pupillary light reflex for predicting the risk of hypotension after spinal anaesthesia for elective caesarean section.
abstract: BACKGROUND
  The balance between the sympathetic and parasympathetic systems could be used to predict the onset of hypotension following spinal anaesthesia. The autonomic innervation of the pupil may reflect this balance. The aim of this study was to evaluate the ability of pupillometry to predict the risk of hypotension after spinal anaesthesia for caesarean section.
  
  
  METHODS
  Two hundred patients receiving spinal anaesthesia for caesarean section were recruited. Changes in pupillary diameter, pupillary reaction latency, pupil constriction velocity and maximum and minimum pupillary diameters were measured with a pupillometer (Neurolight®, IDMed) prior to induction of spinal anaesthesia with 10mg bupivacaine and fentanyl 30μg. Hypotension was defined as a systolic blood pressure drop of > 20% compared with the baseline value.
  
  
  RESULTS
  A total of 141 patients (70%) presented at least one episode of hypotension. Pupillary reaction latency can poorly predict hypotension and severe hypotension after spinal anaesthesia. The areas under the receiver-operating characteristic curves were 0.654 (95% confidence interval: 0.584-0.720, P=0.0001) and 0.633 (95% confidence interval: 0.562-0.700, P=0.004) for optimal threshold values of 223 and 231ms, respectively. In multivariate analysis, a baseline systolic blood pressure > 130mmHg (odds ratio: 1.98, P=0.04) and a PRL > 223ms (odds ratio: 3.42, P=0.0002) were independently associated with the risk of spinal anaesthesia-related hypotension.
  
  
  CONCLUSIONS
  Following spinal anaesthesia in patients undergoing caesarean section, though the predictive capacity pupillary reaction latency for the onset of hypotension and severe hypotension is poor, it is nevertheless the strongest predictor of hypotension identified in our study.
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine, Femme-Mère-Enfant Teaching Hospital, hospices civils de Lyon, Claude-Bernard Lyon 1 University, 59, boulevard Pinel, 69677 Bron, France.
authors.forename: Céline
authors.initials: C
authors.lastname: Riffard
authors.affiliation: Department of Anaesthesia, Ben Vien Tu Du Hospital, Ho Chi Minh City, Viet Nam.
authors.forename: Truong Quoc
authors.initials: TQ
authors.lastname: Viêt
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine, Femme-Mère-Enfant Teaching Hospital, hospices civils de Lyon, Claude-Bernard Lyon 1 University, 59, boulevard Pinel, 69677 Bron, France. Electronic address: fp_desgranges@yahoo.fr.
authors.forename: François-Pierrick
authors.initials: FP
authors.lastname: Desgranges
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine, Femme-Mère-Enfant Teaching Hospital, hospices civils de Lyon, Claude-Bernard Lyon 1 University, 59, boulevard Pinel, 69677 Bron, France.
authors.forename: Lionel
authors.initials: L
authors.lastname: Bouvet
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine, Lyon Sud Teaching Hospital, hospices civils de Lyon, Claude-Bernard Lyon 1 University, 165, chemin du Grand-Revoyet, 69495 Pierre-Bénite cedex, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Allaouchiche
authors.affiliation: Department of Anaesthesia, University College London Hospital NHS Foundation Trust, London, UK.
authors.forename: Adrienne
authors.initials: A
authors.lastname: Stewart
authors.affiliation: Department of Anaesthesia and Intensive Care Medicine, Femme-Mère-Enfant Teaching Hospital, hospices civils de Lyon, Claude-Bernard Lyon 1 University, 59, boulevard Pinel, 69677 Bron, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Chassard
mesh_terms: D000328:Adult; D000773:Anesthesia, Obstetrical / Q000009:adverse effects*; D000775:Anesthesia, Spinal / Q000009:adverse effects*; D002585:Cesarean Section / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007022:Hypotension / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology*; D015994:Incidence; D007431:Intraoperative Complications / Q000175:diagnosis*; D010775:Photic Stimulation; D011237:Predictive Value of Tests; D011247:Pregnancy; D011446:Prospective Studies; D012372:ROC Curve; D012016:Reference Values; D012025:Reflex, Pupillary; D012307:Risk Factors; D055815:Young Adult
keywords: Caesarean section; Hypotension; Pupillometry; Spinal anaesthesia