title: Failure of subarachnoid blocks.
abstract: OBJECTIVE
  Due to the discomfort caused to patients, failure of subarachnoid blocks that happen occasionally even when properly conducted be the most capable professionals have been described since Bier. However, the concept of failure and especially identification of the causes vary. The objective of this report was to identify the causes of this discomfort through a systematic review of publications with a significant number of patients.
  
  
  BACKGROUND
  The analysis was divided in three topics: anatomy and its variations; anesthetic agent, focusing on drug selection, its solutions, and additions to achieve the most appropriate result of the proposed surgery; and the dose, discussing concentration, volume, or gravimetric dose, to obtain the most adequate result regarding the intensity of the blockade and its duration.
  
  
  CONCLUSIONS
  Failures are more commonly secondary to technical factors: adequate anatomic assessment, judicious choice of the needle and puncture site, care when storing the drugs, dose adequacy, and baricity, besides proper patient positioning during and after the puncture, and they all should be adequate for the surgical objective.
authors.affiliation: Gerente Médico de Farmacovigilância do Laboratório Cristália.
authors.forename: Hugo
authors.initials: H
authors.lastname: Praxedes
authors.forename: Antonio Leite
authors.initials: AL
authors.lastname: Oliva Filho
mesh_terms: D000775:Anesthesia, Spinal / Q000379:methods; D006801:Humans; D013346:Subarachnoid Space; D017211:Treatment Failure