Early Detection of the Effect of Epidural Local Anesthetic by Temperature Change on the Big Toe

Traditionally, placement of the epidural catheter is based on hand feel of passing through the ligamentum flavum as well as "loss of resistance" while injecting the air through the needle. However, both are subjective and not necessarily encountered consistently. Moreover, the onset of sensory block is usually slow, thus making confirmation of catheter position a tough task and may delay the turnover of the operating room. The only way to confirm the catheter position objectively without delaying surgery is to find a reliable indicator within minutes of local anesthetic injection. In this study, we try to use the change of temperature in the big toe as a surrogate indicator of correct epidural catheterization.