Ultrasound-guided carotid sheath block for carotid endarterectomy: a case series of the spread of injectate

Introduction: We aimed to show the spread of local anesthetic following an ultrasound-guided, double-injection technique of a carotid sheath block before carotid endarterectomy. Methods: The study included 15 patients scheduled for elective carotid endarterectomy. The carotid sheath block was performed after ultrasound-guided localization of the carotid bifurcation (level C4 - C6) at the posterior border of the sternocleidomastoid muscle. A mix of 7.5 mL ropivacaine 0.75%, 7.5 mL prilocaine 1% and 3 mL iopromidum was injected at the base of the carotid bifurcation. An additional 15 mL of the mixture was administered subcutaneously at the surgical incision line. Thirty minutes after the block, a computed tomography scan of the head, neck region and upper thorax was performed to reconstruct a 3-D distribution of the injectate. Results: All patients achieved C2-C4 dermatomal sensory blockade. None required conversion to general anesthesia. The injectate spread ranged from the vertebral body of C1 to the vertebral body of T3. The mean volume of distribution was 97 +/- 13 mL, the craniocaudal spread 138 +/- 19 mm, dorsoventral 57 +/- 8 mm and coronal 53 +/- 8 mm. The mean carotid artery circumference contact was 252 degrees +/- 77, with four patients (27%) presenting with a ring formation (360 degrees) around the carotid artery. Conclusions: Ultrasound-guided carotid sheath block provided an extensive spread of local anesthetic. A complete ring formation of local anesthetic around the artery does not seem necessary for a successful anesthesia. The resulting nerve blockade thus appears sufficient for surgery, with minor risks compared to blind methods.