Differential epidural block predicts the success of visceral block in patients with chronic visceral abdominal pain.

BACKGROUND AND AIMS 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. PARTICIPANTS All patients with chronic abdominal pain with normal gastrointestinal studies who underwent DNB. SETTING Tertiary Outpatient Pain Management Clinic. DESIGN   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. CONCLUSION 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.