title: Risk Factors for and Prediction of a Difficult Neuraxial Block: A Cohort Study of 73,579 Patients from the Danish Anaesthesia Database.
abstract: BACKGROUND
  A difficult neuraxial block (DNB) may be associated with complications. The aims of this study were to estimate the prevalence of DNB, assess patient-related and organizational factors associated with DNB, and evaluate the diagnostic accuracy of an accumulated risk score for predicting DNB.
  
  
  METHODS
  A consecutive cohort of 73,579 patients was retrieved. A predefined DNB score and information on patient-related and organizational factors were included in the analyses. Logistic regression analysis was performed. We evaluated the diagnostic accuracy of an accumulated weighted point score of the patient-related risk factors of DNB.
  
  
  RESULTS
  The prevalence of DNB and abandoned neuraxial block was 3.9 (95% confidence interval [95% CI], 3.7-4.0) and 0.2 (95% CI, 0.16-0.22), respectively. Body mass index of 35 or higher and previous DNB were associated with DNB, with 3.23 (95% CI, 2.87-3.65) and 2.00 (95% CI, 1.33-3.00), respectively. However, the remaining patient-related covariates were associated with DNB with substantial lower odds ratios. The diagnostic accuracy of an accumulated sum score demonstrated an area under the curve of 0.62 (95% CI, 0.61-0.64), a positive predictive value of 5%, and a positive likelihood ratio of 1.4.
  
  
  CONCLUSIONS
  Despite of strong statistical association between DNB and the tested risk factors, the low odds ratios and estimates of the diagnostic test indicate that the clinical impact using an accumulated risk sum score is limited.
authors.affiliation: From the *Department of Anaesthesiology and Intensive Care, Nordsjællands Hospital, Hillerød, and †Copenhagen Trial Unit, Centre for Clinical Intervention Research, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors.forename: Line
authors.initials: L
authors.lastname: Stendell
authors.forename: Lars H
authors.initials: LH
authors.lastname: Lundstrøm
authors.forename: Jørn
authors.initials: J
authors.lastname: Wetterslev
authors.forename: Theis S
authors.initials: TS
authors.lastname: Itenov
authors.forename: Charlotte V
authors.initials: CV
authors.lastname: Rosenstock
mesh_terms: D000368:Aged; D000758:Anesthesia / Q000009:adverse effects* / Q000639:trends; D015331:Cohort Studies; D016208:Databases, Factual / Q000639:trends; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000009:adverse effects*; D011183:Postoperative Complications / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D011237:Predictive Value of Tests; D012307:Risk Factors