Background and Objectives High-resolution ultrasound imaging (HRUI) allows real-time visualization of peripheral nerves, needle insertion, and the spread of local-anesthetic (LA) solution. We evaluated the feasibility of performing a high interscalene brachial-plexus block for carotid endarterectomy by means of HRUI, thereby limiting the amount of LA to the dose required to sufficiently surround the relevant nerve structures.
Methods The interscalene brachial plexus was localized in the interscalene groove at its most cephalad point in 14 patients undergoing carotid endarterectomy by use of an ultrasound device with a 17.5 MHz transducer. Up to 20 mL of ropivacaine 0.5% was injected.
Results In all patients, HRUI allowed clear delineation of the upper part of the interscalene brachial plexus at the level of the 4th cervical vertebra appearing as 1 hypoechoic, roundish, hypodense node located in a distance of 1.5 ± 0.3 cm to the skin, 1.5 ± 0.2 cm lateral to the common carotid artery, and 0.6 ± 0.2 cm from the transverse process of the spine. Likewise HRUI allowed a clear delineation of minor blood vessels and adjacent anatomic structures, as well as accurate placement of the needle close to the nerves. Real-time observation of LA spread during injection was possible, even in increments of less than 1 mL.
Conclusions High-resolution ultrasonic imaging allows clear depiction of the target tissues and facilitates accurate needle placement during high interscalene brachial-plexus blocks. This technique may minimize the risk of direct puncture-related complications, as well as accidental intravascular injection of LA. The observation of LA spread in all patients, even in small increments of less than 1 mL might enhance safety by limiting the injected LA to the actual demand. Well-placed LA spread could potentially avoid central nervous toxicity caused by intravascular injection or resorption of inadequately high dosages, in particular in nerve blocks of the highly vascularized neck region.
- Interscalene plexus block
- High-resolution ultrasound imaging
- Carotid endarterectomy
- Patient safety
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This work was supported by institutional funding.