Identification of epidural space using loss of resistance technique with the combination of liquid and air: a clinical feasibility study

ABSTRACT

BACKGROUND: The loss of resistance technique is the most popular method for identifying the epidural space. Air or liquid is a commonly used medium for this technique. These two media have certain advantages and disadvantages. A liquid filled pressure line connected to an air syringe might have advantages of both air and liquid while preventing the drawbacks of each medium. METHODS: Twenty-five consecutive patients were scheduled to receive an epidural anesthesia for surgery and selected for study. A lidocaine filled pressure line connected to an air syringe allowed for sequential injection of lidocaine and air. The time spent on the procedure, amount of air injected into the epidural space, inadvertent puncture of the dura mater, and rate of anesthetic failure were recorded. RESULTS: The procedure took less than 2 minutes in 22 cases. The average amount of air lost from the syringe during the loss of resistance test was 0.98 +/- 0.23 ml in 22 patients. Volume of the 3-way connected pressure line was 0.95 ml. Therefore, the air volume injected into the epidural space was minimal. In the other 3 cases where previous spinal disease existed, multiple epidural approaches were needed and the procedure took relatively longer with larger injection volumes. There were no complications. CONCLUSIONS: This technique minimized injection of the air into the epidural space during identification but simultaneously, it does not disturb the feel of air compressibility in the syringe.