title: Evaluation of experimental pain tests to predict labour pain and epidural analgesic consumption.
abstract: BACKGROUND
  The aim of this study was to determine whether experimental pain tests (EPTs) using heat, pressure, and i.v. cannulation before induction of labour reliably predict epidural analgesic use and pain intensity during labour.
  
  
  METHODS
  Fifty healthy women with singleton, term pregnancies admitted for scheduled induction of labour comprised the study population for this prospective case-controlled study. Heat and pressure threshold, tolerance, and suprathreshold VAS pain ratings were determined using a Medoc thermal sensory analyser and Somedic pressure algometer, respectively, after admission before induction of labour. Verbal pain scores (VPS 0-10) were determined during peripheral 18 G i.v. placement. Response outcomes included time to epidural request, pain at epidural, labour pain [area under the curve (AUC) and worse score], and epidural local anaesthetic use. Bivariate analysis followed by forward-backward multiple regression modelling was performed to determine relationships between EPTs and labour pain response measures.
  
  
  RESULTS
  Heat tolerance was significantly correlated with worst labour pain (r=0.33, P=0.025) and pain with i.v. cannulation was correlated with time to epidural request (r=0.33, P=0.025). Multiple linear regression analysis found that labour pain AUC could be predicted with suprathreshold heat VAS, heat tolerance, and pressure tolerance (R(2)=0.26; P=0.007). There were strong correlations among the various pre-labour QSTs.
  
  
  CONCLUSIONS
  Pre-labour EPTs were not very reliable at predicting the labour pain experience. Consistent with postoperative studies, suprathreshold and tolerance tests appear more useful than the threshold for predicting labour pain responses. Pain rating during i.v. cannulation (an easy, rapid, point-of-care test) showed some utility as an EPT.
authors.affiliation: Department of Anesthesia, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94305, USA. bcarvalho@stanford.edu
authors.forename: B
authors.initials: B
authors.lastname: Carvalho
authors.forename: M
authors.initials: M
authors.lastname: Zheng
authors.forename: L
authors.initials: L
authors.lastname: Aiono-Le Tagaloa
mesh_terms: D000328:Adult; D015360:Analgesia, Epidural / Q000379:methods*; D016362:Analgesia, Obstetrical / Q000379:methods*; D000700:Analgesics / Q000008:administration & dosage* / Q000627:therapeutic use*; D019540:Area Under Curve; D015331:Cohort Studies; D005260:Female; D006358:Hot Temperature; D006801:Humans; D048949:Labor Pain / Q000175:diagnosis*; D007751:Labor, Induced; D016014:Linear Models; D008875:Middle Aged; D010147:Pain Measurement / Q000379:methods*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011312:Pressure; D055815:Young Adult
chemical_list: D000700:Analgesics