Agreement between anatomical landmark palpation and preprocedural ultrasound for thoracic epidural level identification in adults: a prospective observational study

Abstract Background Incision-catheter congruency is essential for effective perioperative epidural analgesia. The regularly used landmark-based identification of thoracic interlaminar spaces is often inaccurate. Ultrasound offers a potentially more precise alternative for identifying the desired spaces. Methods In this prospective observational study, 86 adult patients who underwent elective thoracoabdominal surgery with thoracic epidural catheterization were enrolled in the study. The interlaminar space was initially identified using anatomical landmarks and marked by the treating anesthesiologist. Two independent blinded anesthetists subsequently confirmed the level marked using ultrasound. Agreement was defined as an exact match between the landmark- and ultrasound-identified levels. The time taken to perform the ultrasound and the extent of deviation were also noted. Results Landmark-based identification was in agreement with ultrasound findings in 53.5% of patients. The disagreements were one level caudad to the desired space in 25.6%, two levels in 9.3%, and three levels in 1.2%. 10% of the disagreements were one-level cephalad. The mean time for ultrasound identification was 42.8 ± 19.9 s. No interobserver variability was observed in the ultrasound findings. Conclusion Anatomical landmark palpation was in agreement with ultrasound findings for the intended thoracic interspinous level at approximately 53%, and the discrepancies were most often one level and in the caudal direction. Dual blinded ultrasound assessments showed complete inter-observer agreement with a brief scan time (~ 43 s). Ultrasound can be used as an adjunct to confirm the anatomically palpated epidural site in a selected context. Trial registration Registry: ctri.nic.in, CTRI: CTRI/2024/04/065943, Registration date: 18 April 2024.