1. Department of Anaesthesia, Russells Hall Hospital, Dudley
Cervical plexus block for Carotid Endarterectomy –an assessment of accuracy and safety under ultrasound
W Thomas and J Paul
Department of Anaesthesia, Russells Hall Hospital, Dudley
Results
Average total volume of LA used was 25 ml and the average additional LA used by surgeon was 3.24 ml (lignocaine 1%). 15 (41%) patients didn’t required any additional LA. 22 (60%) patients had minimal discomfort based on Gloucester score when carotid sheath approached. 13 (35%) patients need additional LA when carotid sheath was approached. All the patients have bilateral diaphragmatic movement on US. There were no complications and all patients had an uneventful recovery.
Introduction
Carotid endarterectomy is often performed by blocking the deep and superficial components of the cervical plexus. Traditional landmark approach can sometimes result in unpredictable block, block failure, direct vascular-puncture or serious neurological complications. These complications are more likely in the region of neck where there is a close proximity of vascular and nerve structures. Ultrasound (US) imaging will allow clear identification of the target nerve and other vital structures, in-line visibility of needle progression and the local anaesthetic (LA) spread allowing us to improve the accuracy and safety of nerve blockade. NICE published a guideline in supporting the use of ultrasound for regional nerve block. We aim to evaluate the efficacy and safety of ultrasound guided cervical plexus block in our hospital.
Figure 1. Superficial Plexus block
Method
We identified 37 patients who underwent carotid endarterectomy under ultrasound guided cervical plexus block between January 2010 to May All cervical plexus blocks were performed by a single experienced anaesthetist. Ultrasonic images of the superficial cervical plexus was identified as hyper-echoic shadows between the posterior border of sternomastoid and scalenus medius muscle (Fig.1). The block was performed by depositing up to 12 ml of 0.5% Chirocaine in the mid, the upper third and middle third of sternomastoid. Deep cervical block was performed by depositing up to 15ml 0.5% Chirocaine at C4, C3, C2 transverse processes. The anterior and posterior tubercles of transverse process of the cervical vertebrae are seen as a double hump on ultrasonic images with the nerve root in between the tubercles (Fig.2). Patients were sedated during the surgical procedure using target controlled propofol infusion. Data collected include the volume of local anaesthetic used, diaphragmatic movement using ultrasound to rule out phrenic nerve block, patient comfort levels at incision and during the surgery using Gloucester Comfort Score and complications of the block. Also noted the additional local anaesthetic used by the surgeon and where it is used.
Figure 2. Deep Cervical Plexus block at C4 Level
Conclusion
In this series of 37 patients who had cervical plexus blocks, there were no complications and the analgesia was effective and supplemental local anaesthetic requirement was minimal. However, being a small series and a single experienced anaesthetist was involved no conclusion can be drawn regarding safety of the procedure. We believe this study improved the awareness and encourage the use of ultrasound guided cervical plexus block among the colleagues. More importantly, ultrasound guided block reduced the technique-related complication rate in these patients.
Gloucester Comfort Scale
1 = Comfortable (talking / comfortable throughout)
2 = Minimal (1 or 2 episodes of mild discomfort without
distress)
3 = Mild (more than 2 episodes of discomfort without
4 = Moderate (significant discomfort experienced several
times with some distress )
5 = Severe (frequent discomfort with significant distress)
References
Roessel T, Wiessner D, Heller A et al. High-Resolution Ultrasound-
Guided High Interscalene Plexus Block for Carotid Endarterectomy.
Reg Anesth Pain Med. 2007; 32 (3): 247–253.
(2) NICE guideline: Ultrasound-guided regional nerve block (Jan 2009)