In the investigators' institution, the failure rate for thoracic epidural blocks is 23.1%. This stems from the prevalence of trainee operators coupled with the non-specific nature of loss-of-resistance. In the current randomized trial, we will set out to compare conventional and epidural waveform analysis-confirmed loss-of-resistance. The investigators' research hypothesis is that loss-of-resistance combined with epidural waveform analysis will decrease the failure rate of thoracic epidural blocks.

Inclusion Criteria:

• the patients undergoing thoracic epidural catheter insertion for thoracic and abdominal surgery or rib fractures with American Society of Anesthesiologists (ASA) classification 1-3 and body mass index between 18 and 35

Exclusion Criteria:

• adults who are unable to give their own consent
• coagulopathy (assessed by history and physical examination and, if deemed clinically necessary, by blood work up ie platelets ≤ 100, or International Normalized Ratio ≥ 1.4)
• renal failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up ie creatinine ≥ 100)
• hepatic failure (assessed by history and physical examination and, if deemed clinically necessary, by blood work up ie transaminases ≥ 100)
• allergy to local anesthetic (LA)
• pregnancy
• prior surgery in the thoracic spine