Ultrasound-assisted middle thoracic epidural catheter placement utilizing the most dorsal sites of bilateral transverse process roots as anatomical landmarks: A cadaveric observational study and a clinical randomized controlled trial.

Study objective: We developed an innovative method for ultrasound-assisted thoracic epidural catheter placement and assessed its potential to reduce procedural duration for trainees.

Design: A cadaveric observational study and a clinical randomized controlled trial.

Setting: Sapporo Medical University Hospital.

Patients: A total of 52 adult patients scheduled for thoracic or abdominal surgery and four cadavers.

Interventions: Patients were randomly assigned to either group receiving conventional palpation (conventional group) or combination of the ultrasound examination and conventional palpation (ultrasound group).

Measurements: The primary outcome was total procedure time (sum of skin marking time and needling time) by trainees. The secondary outcomes were (1) skin marking time, (2) needling time, (3) multiple skin punctures, (4) needle redirection, (5) complications, and (6) failed cases.

Main results: Through dissection of four cadavers, the most dorsal site of the transverse process root was identifiable by ultrasound and the reliable indicator of the interlaminar space. We devised ultrasound-assisted middle thoracic epidural catheter placement utilizing the most dorsal sites of bilateral transverse process roots as anatomical landmarks. Trainees in the ultrasound group had significantly longer skin marking time and significantly shorter needling time than those in the conventional group (107 [87-158] vs 46 s [34-54] s, p < 0.001 and 197 [156-328] vs 341 [303-488] s, p = 0.003). Consequently, there was no significant difference between the two groups in total procedure time (326 [263-467] s vs 391 [354-533] s, p = 0.167). Moreover, the probability of trainee failure in epidural anesthesia was significantly lower in the ultrasound group (2/26 [17.7 %] vs 10/26 [38.5 %], p = 0.019).

Conclusions: Our novel technique for thoracic epidural catheter placement resulted in expedited needling and enhanced success rates among trainees, although there was no significant difference between total procedure time when using ultrasound guidance and that when using conventional palpation.