Where are We? Ultrasound Confirmation of Interspace after Combined Spinal-epidural Anesthesia for Cesarean: A Quality Control Study

Background: When using a combined-spinal epidural (CSE) technique, the needle must be introduced at an interspace below the level of the conus medullaris to avoid trauma to the spinal cord. In 2000, Felicity Reynolds advanced the notion that “the L2-L3 interspace should not be an option..to allow for human variability.”1 Identification of the interspace by palpation has been shown to be inaccurate, with even experienced operators miscalculating by as many as a four interspace distance from the intended target. 2 Ultrasound on the other hand, has proven to be an easy and effective imaging technique to accurately identify level of insertion. 3

Objective: To use ultrasound as a quality control measure to determine the actual level of CSE insertion in parturients who underwent cesarean delivery

Methods: In this IRB approved study, 61 patients gave verbal consent to undergo ultrasound imaging of their lower spine after cesarean delivery under CSE anesthesia.

Results: In 25% of patients (15/61), CSE was performed at or above the L1-L2 interspace. In 72% of patients (44/61), CSE was performed at or above the Reynolds Zone, i.e., at the L2-L3 interspace or above.

Conclusion: Ultrasound should be considered as a routine tool in identifying interspace prior to administering spinal anesthesia.

1. Reynolds F. Logic in the safe practice of spinal anesthesia. Anaesthesia 2000;55:1045-6. 2. Broadbent CR. Ability of anaesthetists to identify a marked lumbar interspace. Anaesthesia 2000 Nov 55:1122-6. 3. Furness G. An evaluation of ultrasound imaging for identification of lumbar intervertebral level. Anaesthesia 2002;57:277-280.