title: The epidural blood patch. Resolving the controversies.
abstract: OBJECTIVE
  To review the literature regarding epidural blood patch (EBP) to generate conclusions relating to the controversial issues surrounding its application.
  
  
  METHODS
  A Medline search was made for relevant publications using keywords epidural blood patch, prophylactic epidural blood patch, dural puncture, and postdural puncture headache. Bibliographies of retrieved articles were hand-searched for relevant articles. Case series and comparative trials were emphasized in the analyses. These were culled and those deemed relevant were reviewed.
  
  
  RESULTS
  The majority of the literature consists of observational reports: there are few comparative studies. Headache most likely results from cerebrospinal fluid (CSF) loss leading to intracranial content shift and traction on pain sensitive structures; cerebrovascular alterations may be implicated. An EBP with 10-15 ml blood is indicated and effective therapy for severe headache after dural puncture. There is conflicting evidence regarding larger volume blood injections or delaying EBP for 24 hr or more after the diagnosis of postdural puncture headache (PDPH). Efficacy of EBP is related to a "patch effect" as well as transmission of increased epidural space pressure to the CSF space. Previous estimates of EBP efficacy were overgenerous; persistent symptomatic relief can be expected in 61-75% of patients with initial EBP. Patching with non-blood solutions, although initially effective, is associated with a high incidence of headache recurrence. Prophylactic injection of saline or blood decreases the incidence of severe headache after dural puncture.
  
  
  CONCLUSIONS
  Blood-patching is an effective treatment of PDPH but further research is required regarding its mechanisms and prophylaxis.
authors.affiliation: Department of Anesthesiology, University of Ottawa and the Ottawa Hospital, Ontario, Canada. pduffy@anesthesia.org
authors.forename: P J
authors.initials: PJ
authors.lastname: Duffy
authors.forename: E T
authors.initials: ET
authors.lastname: Crosby
mesh_terms: D000767:Anesthesia, Epidural / Q000009:adverse effects*; D017217:Blood Patch, Epidural; D000075202:Contraindications; D006261:Headache / Q000209:etiology* / Q000628:therapy*; D006801:Humans