Early Detection of Epidural Onset by Temperature Change

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.

Epidural anesthesia loading dose: 17ml 2% xylocaine + 2.3ml sodium bicarbonate + 2ml Rapifen (1088 mcg) + 0.1 mg epinephrine

Inclusion Criteria:

• Body weight:50-90kg,
• American Society of Anesthesiologists physical status classification I-II,
• Under epidural anesthesia for surgery

Exclusion Criteria:

• History of receiving lumbar surgery
• Allergy to alfentanil ,xylocaine, bicarbonate
• Trauma