Laboratory evaluation of single-lumen, dual-orifice combined spinal-epidural needles: effects of bevel orientation and modified technique.

ABSTRACT

STUDY OBJECTIVES: To evaluate the success rate of the spinal needle exiting through the spinal needle orifice in two commonly available single-lumen, dual-orifice combined spinal-epidural (CSE) needle kits, and to study the effects of the epidural needle bevel orientation and the modified insertion technique on its success rate. DESIGN: Prospective, randomized study. SETTING: Laboratory. EQUIPMENT Two types of single-lumen, dual-orifice CSE needle kits CSE-Q kit and CSE-S kit. INTERVENTION 20 anesthesiologists and nurse-anesthetists were assigned to select randomly from the two types of CSE kits (CSE-Q and CSE-S). The epidural needle was then placed into a foam device simulating a patient's back and the associated spinal needle was inserted through the epidural needle with the epidural needle bevel oriented randomly upward, downward, left, and right, respectively. The procedures were performed before and after the modified technique was used. The modified technique consisted of (1) aligning the orifice/bevel of the spinal needle in the same direction as the epidural needle bevel, and (2) gently bending the hub of the spinal needle in the direction of the epidural needle bevel while advancing the spinal needle. MEASUREMENTS AND MAIN RESULTS: Success rate of the spinal needle exiting through the spinal needle orifice was measured. Data were collected from 1600 attempts. The modified technique improved the success rate of spinal needle exiting through the spinal needle orifice from 67% to 94 % for the CSE-Q kit and 50% to 81% for the CSE-S kit. Upward orientation of the epidural needle bevel further improved the success rate to 96% and 91% for CSE-Q and CSE-S kits, respectively. CONCLUSIONS: The spinal needle did not always exit through the spinal needle orifice in the CSE kits tested. CSE-Q kits performed better than CSE-S kits. Under the study conditions, the modified technique and the upward orientation of epidural needle bevel significantly improved the success rate of the spinal needle exiting through the appropriate spinal needle orifice.