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Use of Color flow Doppler in neuraxial ultrasound to predict epidural location and unilateral or bilateral blockade
Abstract Number: S2D-5
Abstract Type: Case Report/Case Series
INTRODUCTION: Pre-procedural neuraxial ultrasound (US) can decrease risk of epidural failure and improve placement success rates. (1) We describe an approach for real-time confirmation of access to the epidural space (ES) via US and use of color flow doppler (CFD) to predict unilateral or bilateral blockade.
CASE: 36-year-old G3P1 woman presented with history of one-sided epidurals during a previous delivery, prompting US evaluation for epidural placement.
Our technique required two providers, an epidural kit, a curvilinear US probe, a sterile marking pen, and a sterile US cover. Parasagittal views were obtained at the sacrum and moving cephalad to verify the L3-L4 interlaminar space. Transverse views at the L3-L4 space identified midline, posterior (PC) and anterior complexes (AC). Caliper function estimated depth to PC. The midline of each side of the probe was marked, with the intersection representing the interlaminar space where the ES was accessed, and the epidural catheter was threaded. In the transverse view at the epidural insertion site, PC and AC was visualized with CFD, while injecting 3 mL of agitated test dose. Images revealed complete absence of CFD on the right. (Fig 1)
The epidural catheter was secured and despite a bolus of 7 ml of local anesthetic (LA), the patient had left-sided sensory dermatomal coverage. Further bolusing with additional LA improved the unilateral block, however she required subsequent boluses and epidural replacement at a different level. Ultimately she had an uneventful vaginal delivery with bilateral epidural analgesia.
DISCUSSION: Epidural failure rate is about 6.8%. (2) Unilateral epidural blockade is believed to be caused by catheter position or patient anatomy. Though studies have evaluated epidural anatomy for a separation, there is controversy as to whether a separation raphe truly exists. (3)
Epidural injection of test dose typically shows bilateral CFD deep to the PC. We demonstrate US evidence of an anatomic ES separation supporting its existence and its potential to predict presence of unilateral epidurals and decrease time to replacement.
Future studies need to assess this technique's feasibility to confirm subcutaneous or unilateral catheters and its ability to decrease failure rate, forecast epidural replacement, and predict location prior to catheter activation for surgical anesthesia.
1. Perlas, Reg Anesth Pain Med, 2016
2. Pan, IJOA, 2004
3. Arendt, Rev Obstet Gynecol, 2008