Epidural electrical stimulation test versus local anesthetic test dose for thoracic epidural catheter placement: a prospective observational study.

Purpose: This study examined the concordance between epidural electrical stimulation test (EEST) and local anesthetic (LA) test dose to indicate correct thoracic epidural catheter position. The relationship between the test results and epidural postoperative analgesia was also assessed.

Methods: This prospective observational cohort study was done in patients receiving thoracic epidural analgesia for abdominal surgery. After insertion, the epidural catheter was tested using a nerve stimulator to elicit a motor response. The LA test dose was then administered, and sensory block to ice and pinprick was assessed. The primary outcome was the presence/absence of motor response to EEST and sensory block to test dose. Concordance of responses was assessed using kappa statistics, and their predictive power of postoperative epidural analgesia was evaluated.

Results: Sixty-eight thoracic epidural catheters were inserted, of which 62 were used perioperatively. The kappa agreement between EEST and LA test dose responses was moderate at 0.42 (95% confidence interval [CI], 0.18 to 0.67). Positive responses to EEST and LA test dose were observed in 62 (100%) and 50 (81%) patients, respectively, while 52 patients (84%) showed adequate analgesia postoperatively. The sensitivity (95% CI) of EEST and LA test dose to predict adequate postoperative epidural analgesia was 1 (0.93 to 1) and 0.79 (0.65 to 0.89), respectively, and the positive predictive values (95% CI) of EEST and LA test dose were 0.84 (0.75 to 0.93) and 0.82 (0.71 to 0.92), respectively.

Conclusion: Following thoracic epidural catheter insertion, the responses to the EEST and LA test dose showed "moderate" agreement. The EEST has a higher sensitivity than the LA test dose to predict adequate epidural analgesia following abdominal surgery, however, both tests have a comparable positive predictive value.