Purpose: The purpose of this prospective randomized controlled trial was to determine the impact of thoracic epidural catheter threading distance on analgesia quality after thoracotomy.
Methods: We randomly assigned 120 elective thoracotomy patients to a thoracic epidural catheter threading distance of 3, 5, or 7 cm (groups 3CM, 5CM, and 7CM, respectively). Epidural bupivacaine 0.1% with fentanyl 2 µg·mL(-1) was administered according to a standardized protocol. Epidural analgesia quality was assessed at 60 min and 24 hr postoperatively for four measures: incidence of non-functioning epidurals; numerical rating score (NRS) < 4 at rest, while coughing, and during wound palpation; cold perception at the wound site; and cumulative dose of analgesic medication used. Our primary hypothesis was that, compared to threading distances of 3 and 5 cm, a threading distance of 7 cm was not inferior at providing an NRS < 4 while coughing at 60 min postoperatively, with a non-inferiority margin of 25% (absolute value) being significant.
Results: The incidence of NRS < 4 while coughing at 60 min was 74% (29/39) in group 7CM compared with 68% (54/80) in the combined 3CM and 5CM groups (absolute difference 7%; 95% confidence interval -11 to 23; P = 0.29). At both 60 min and 24 hr, differences between groups were similar regarding the number of non-functioning epidurals, NRS < 4, and suppressed cold sensation. Analgesic doses were similar in the three groups.
Conclusions: This study found that a thoracic epidural catheter threading distance of 7 cm in the epidural space was not inferior to distances of 3 cm and 5 cm with respect to pain scores at 60 min postoperatively. This study was not powered to examine differences that could have clinical significance that were less than our a priori 25% non-inferiority margin.