1 Nuffield Department of Anaesthetics, John Radcliffe Hospital, Oxford OX3 9DU, UK. 2 Department of Human Anatomy, Parks Road, Oxford OX1 3PT, UK
Corresponding author. E-mail: jaideep.pandit@physiol.ox.ac.uk
Accepted for publication: June 24, 2003
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Abstract |
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Methods. Superficial cervical plexus blocks (injections just below the investing fascia) were performed using methylene blue (30 ml) in four cadavers. In one additional control cadaver, a deep cervical plexus injection was performed. In a second control cadaver, a subcutaneous injection (superficial to investing fascia) was performed at the posterior border of the sternomastoid muscle.
Results. Anatomical dissection showed that with superficial block there was spread of the dye to structures beneath the deep cervical fascia. In the first control, dye remained in the deep cervical space. In the second control, dye remained subcutaneous.
Conclusions. The superficial cervical space communicates with the deep cervical space and this may explain the efficacy of the superficial block. The method of communication remains unknown. Our findings also indicate that the suitable site of injection for the superficial cervical plexus block is below the investing fascia of the neck, and not just subcutaneous.
Br J Anaesth 2003; 91: 7335
Keywords: anatomy; anaesthetics local; anaesthetic techniques, cervical plexus block; anaesthetic techniques, regional; surgery, carotid endarterectomy
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Introduction |
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One possible explanation for the efficacy of superficial block is if the local anaesthetic crossed the deep cervical fascia to act on the nerve roots. However, the current view is that deep cervical fascia is an impenetrable barrier.3 4 The purpose of this study was to investigate the spread of superficially injected solutions in human cadavers.
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Methods and results |
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Comments |
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Conventional anatomical drawings suggest that the distance between the investing and deep cervical fasciae is large (Fig. 1). Another possible explanation of our result is that, in fact, the two fascial layers are in very close proximity (i.e. the superficial cervical space is a potential, rather than an actual, anatomical space). The two fascial layers are plausibly brought into greater contact by the act of turning the head for the block. Thus, when the injecting needle is placed deep to the investing fascia, it might at the same time and quite easily also pierce the deep cervical fascia.
Our result explains, at least in part, the equal efficacy of the superficial and deep/combined cervical plexus blocks for carotid endarterectomy.1 2 The local anaesthetic enters the same anatomical (deep cervical) space containing the cervical nerve roots in both techniques. It has been suggested that the superficial block carries fewer risks to the patient than does the deep/combined block.7 8 If this is so, the need to perform a deep cervical plexus injection as part of the block does not seem easily justified in the light of our anatomical finding.
Some authors describe the superficial block as a simple subcutaneous injection.9 10 However, the result of our subcutaneous injection (CAD5) suggests that, in fact, this alone is unlikely to be clinically effective. A superficial plexus block should properly involve injection below the investing fascia of the neck (Figs 1 and 2), and it is only then that the injectate enters the deep cervical space.
Our study indicates a number of areas for further research. First, radiological studies in vivo might add to our observations in cadavers. Secondly, clinical studies might examine whether simple subcutaneous injections are indeed ineffective as compared with superficial cervical plexus bocks (i.e. sub-investing fascia injections) for carotid endarterectomy. Thirdly, histological work in tissue specimens might define the ultrastructure and porous properties of the deep cervical fascia.
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References |
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2 Pandit JJ, Bree S, Dillon P, Elcock D, McLaren ID, Crider B. A comparison of superficial versus combined (superficial and deep) cervical plexus block for carotid endarterectomy: a prospective, randomised study. Anesth Analg 2000; 91: 7816
3 Granite EL. Anatomic considerations in infections of the face and neck. J Oral Surg 1976; 34: 3444[ISI][Medline]
4 Moncada R, Warpeha R, Pickleman J, et al. Mediastinitis from odontogenic and deep cervical infections: anatomic pathways of propogation. Chest 1978; 73: 497500[Abstract]
5 Winnie AP, Ramamurthy S, Durrani Z, Radonjic R. Interscalene cervical plexus block: a single-injection technic. Anesth Analg 1975; 54: 3705[Abstract]
6 Esclamado RM, Carroll WR. Extracapsular spread and the perineural extension of squamous cell cancer in the cervical plexus. Arch Otoloaryngol Head Neck Surg 1992; 118: 11578
7 Pandit JJ, McLaren ID, Crider B. Efficacy and safety of the superficial cervical plexus block for carotid endarterectomy. Br J Anaesth1999; 83: 9701
8 Pandit JJ, Satya-Krishna R, McQuay H. A comparison of the complication rate associated with superficial versus deep (or combined) block for carotid endarterectomy. Anesth Analg 2003; 96: S279
9 Prys-Roberts C, Brown BR, Nunn JF. International Practice of Anaesthesia. London: Butterworths, 1996
10 Katz J. Atlas of Regional Anesthesia. Norwalk, CT: Appleton & Lange, 1994