Impact of thoracic epidural catheter threading distance on analgesia during the first 24 hours following thoracotomy: a randomized controlled trial

Abstract

The purpose of this prospective randomized controlled trial was to determine the impact of thoracic epidural catheter threading distance on analgesia quality after thoracotomy. 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. 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. 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.