title: Differential epidural block predicts the success of visceral block in patients with chronic visceral abdominal pain.
abstract: OBJECTIVE
  Differential thoracic epidural regional block, also known as a differential neural block (DNB), involves the placement of an epidural catheter placed in the thoracic epidural space to achieve appropriate anesthesia in a dermatomal distribution. This is a retrospective case series evaluating how well a DNB may predict success of subsequent visceral blockade in patients with chronic abdominal pain of visceral origin.
  
  
  METHODS
  Of 402 patients who had a DNB performed for unexplained abdominal pain from January 2000 to January 2009, 81 patients were found to have results consistent with visceral pain and thus underwent subsequent visceral blockade. Basic demographic data, years of chronic pain, history of psychosocial issues, initial visual analog scale (VAS) pain score, pain location, and medication usage were documented in our electronic medical record database. Parameters regarding DNB and visceral blocks also were documented. Descriptive statistics were computed for all variables. The positive predictive value (PPV) for DNB for whom visceral block was successful (at least a 50% reduction in VAS) was calculated. Additionally, subjects with successful visceral blocks were compared to those with unsuccessful visceral blocks.
  
  
  METHODS
  All patients with chronic abdominal pain with normal gastrointestinal studies who underwent DNB.
  
  
  METHODS
  Tertiary Outpatient Pain Management Clinic.
  
  
  METHODS
  Retrospective Cohort Study.
  
  
  RESULTS
  Mean age of patients was 46 (± 15) years, 73% were female, and median duration of pain was 5 years. 67% of subjects were taking opioid analgesics. PPV of DNB was 70.4%. Only factor found to be statistically significant with visceral block success was baseline VAS with higher scores associated with DNB predictive success (6.8 ± 1.7 vs. 5.5, 1.8; P = 0.004). Use of membrane stabilizing medications was significantly more common in subjects for whom visceral block was not successful (46% vs. 25%; P = 0.058). Area underneath curve (AUC) for VAS was found to be 0.70 (95% CI: 0.57, 0.82), which signifies fair discrimination.
  
  
  CONCLUSIONS
  Differential neural block is fairly predictive of subsequent visceral block success in patients with chronic abdominal pain of visceral origin. An initial VAS ≥ 5 provides a sensitivity of 93%, which implies that VAS < 5 may predict unsuccessful visceral block. Contrarily, a value of ≥ 8 would provide a specificity of 92% and may be used to predict success of subsequent visceral block.
authors.affiliation: Digestive Disease Institute, Cleveland Clinic, Cleveland, OH, USA. rizkm@ccf.org
authors.forename: Maged K
authors.initials: MK
authors.lastname: Rizk
authors.forename: Reda
authors.initials: R
authors.lastname: Tolba
authors.forename: Leonardo
authors.initials: L
authors.lastname: Kapural
authors.forename: Justin
authors.initials: J
authors.lastname: Mitchell
authors.forename: Rocio
authors.initials: R
authors.lastname: Lopez
authors.forename: Ramatia
authors.initials: R
authors.lastname: Mahboobi
authors.forename: Bruce
authors.initials: B
authors.lastname: Vrooman
authors.forename: Nagy
authors.initials: N
authors.lastname: Mekhail
mesh_terms: D015746:Abdominal Pain / Q000628:therapy*; D000328:Adult; D015360:Analgesia, Epidural / Q000379:methods*; D019540:Area Under Curve; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D010147:Pain Measurement; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D059265:Visceral Pain / Q000628:therapy*