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Anaesthesia and Intensive Care, Vol. 34, No. 2, April 2006 Anaesth Intensive Care 2006; 34: 240-244 Equipment Ultrasound Guided Deep Cervical Plexus Block D. J. Sandeman*, M. J. Griffiths†, A. F. Lennox‡ Departments of Anaesthesia and Vascular Surgery, Prince of Wales Hospital, Randwick, New South Wales, Australia SUMMARY We describe a new technique for achieving a deep cervical plexus block using a portable vascular access ultrasound scanner (Site~Rite® II, Bard Access Systems, Pittsburgh, PA). Key Words: deep cervical plexus block, ultrasound imaging Regional anaesthesia requires safe and accurate localization of nerves. The block needle must be placed in close proximity to the nerve without injury to the nerve or adjacent structures1 . Alon P. Winnie once predicted: “Sooner or later someone will make a sufficiently close examination of the anatomy in­- volved, so that exact techniques will be developed” 2 . Ultrasonography allows close examination of the anatomical structures for successful regional anaes- thesia. Ultrasound guidance has advantages over the traditional nerve localization techniques of land- marks and nerve stimulation. These include higher success rates, shorter onset times3 , and a decrease in local anaesthetic needs and complications4 . Deep cervical plexus block is a well established regional anaesthetic for operations in the anterior triangle of the neck including awake carotid endarter- ectomy surgery, lymph node biopsy and plastics. Palpation of anatomical landmarks in the neck may be difficult and uncomfortable, particularly with obese patients. Ultrasonography allows precise mapping of the deep cervical plexus. Our technique is described using the Site~Rite® II portable ultra- sound scanner (Bard Access Systems Pittsburgh, PA, U.S.A. ANATOMY The cervical plexus The cervical plexus is formed from the ventral rami of the upper four cervical spinal nerves, supplying motor branches to the diaphragm and neck muscles, and sensation for much of the skin and integument of the neck. The plexus is found at the level of the first four cervical vertebrae deep to the sternocleidomastoid, in the layer superficial to the scalenus medius and levator scapulae5 . The cervical plexus can be further divided into a superficial and deep portion. The super- ficial branches perforate the cervical fascia to supply skin and other integumental structures whilst the deep branches predominantly supply muscle5 . Relationship to vertebral artery The vertebral artery lies in close proximity to the C2, 3 and 4 spinal nerves, allowing it to be used as an ultrasonic landmark for identifying the deep cervical plexus. The vertebral artery arises from the first part of the subclavian artery and ascends vertically through the foramina of all but the seventh cervical vertebrae. At the level of the first cervical vertebra (atlas) it winds behind its lateral mass and enters the skull through the foramen magnum5 . A consistent but rarely mentioned feature of the vertebral artery is the prominent loop it makes between the first and second cervical vertebrae (axis), which allows it to pass from the foramen in the axis to the far more laterally placed foramen in the atlas. The loop, which can be easily viewed with ultrasound, is an accurate landmark for the C2 transverse process and C2 spinal nerve, which are immediately inferior and posterior to the artery. * F.A.N.Z.C.A., M.B., B.S.(Hons), B.Sc., Senior Staff Specialist, Anaesthesia Prince of Wales and Sydney Children’s Hospitals and Senior Conjoint Lecturer University of New South Wales. † M.B., B.S. (Hons), B.Pharm., Visiting Anaesthetist, Prince of Wales and Sydney Children’s Hospitals. ‡ F.R.A.C.S., M.B., B.S., M.Sc., Visiting Vascular Surgeon, Prince of Wales and Sydney Children’s Hospitals. Address for reprints: Dr D. J. Sandeman, Department of Anaesthesia, Prince of Wales Hospital, Randwick, N.S.W., Australia 2031. Accepted for publication on February 3, 2006.
241 Anaesthesia and Intensive Care, Vol. 34, No. 2, April 2006 The spinal nerves are consistently located posterior to the vertebral artery as they exit the gutter in the cervical transverse processes. TECHNIQUE The patient is placed supine with the head turned away from the operative side. Having aseptically prepared the neck and covered the probe with the sterile Site~Rite® II cover, the ultrasound probe is placed along a line joining the mastoid process and Chassaignac’s tubercle. Starting at the mastoid process, the probe is moved caudally until the vertebral artery loop is visible. Under ultrasound guidance the 50 mm Braun Stimuplex® A needle is advanced until contact is made with the transverse process (postero-inferior Figure 1: Left vertebral artery angiogram clearly demonstrating the loop above the C2 vertebrae. Top arrow points to the loop of left vertebral artery above body of C2. The bottom arrow points to the position of C2 spinal nerve below vertebral artery. Figure 2: Left vertebral artery and C2 spinal nerve. Top arrow points to left vertebral artery loop. Centre arrow points to C2 spinal nerve. Bottom arrow points to the transverse process C2. Figure 3: Left cervical vertebral artery. Arrows point to spinal nerves C2, 3, 4 postero-lateral to the vertebral artery. Deep Cervical Plexus Block
242 Anaesthesia and Intensive Care, Vol. 34, No. 2, April 2006 to the artery), then after negative aspiration, 5 ml of local anaesthetic is injected. The choice of local anaesthetic agent must take into account the type and anticipated duration of surgery, and the recom- mended safe dose. The operator continues to move the probe caudally until a cross-sectional view of the vertebral artery is obtained between the C2 and 3 transverse processes. As the probe is moved further caudally, the cross- sectional view is lost at the position of the C3 trans- verse process. This locates the injection point for C3 spinal nerve. The needle is again advanced under ultrasound guidance until the transverse process is contacted, whereafter negative aspiration a further 5 ml of local anaesthetic is injected. The C4 spinal nerve is blocked similarly over the C4 transverse process. From an anatomical point of view, the ultrasound provides advantages to the classical palpation method. Firstly, the path of vertebral artery from the C2 to C4 transverse foramina provides the antero-posterior (AP) position for needle placement. Secondly, the loop of the vertebral artery above the C2 vertebra and loss of cross-sectional images at C3 and C4 provide the cranio-caudal position for needle placement. Finally, utilization of the Site~Rite® needle guide facilitates placement of the needle onto the C2 trans- verse process under direct vision, avoiding inadver- tent arterial injection. DISCUSSION Our work on the deep cervical plexus block has Figure 4: Site~Rite® II 7.5 MHz probe in sterile sheath and needle holder. Figure 5: Left vertebral artery sonogram. Top arrow: vertebral artery loop between C1 and C2 vertebrae. Bottom arrow: body and transverse process of C2. Figure 6: Cross-sectional view of vertebral artery between C2 and C3 vertebrae. D. J. Sandeman, M. J. Griffiths, A. F. Lennox
243 Anaesthesia and Intensive Care, Vol. 34, No. 2, April 2006 utilized the vascular access Site~Rite® II 7.5 MHz probe, which is designed for depths of 1.5 to 4 cm. Increasing frequency increases image resolution but reduces depth penetration. Conversely, lower probe frequency provides greater depth of tissue penetra- tion but poorer image resolution6,7. There are many ultrasound systems available specifically designed for regional anaesthesia. The Site~Rite® II system is widely available in anaesthesia departments and can be utilized for the deep cervical plexus block without the added expense of more sophisticated systems. structures facilitates accurate needle placement and avoids inadvertent vertebral artery puncture. In our experience, the Site~Rite® II ultrasound also gives satisfactory images of the vertebral artery, even in obese patients where palpation of the traditional landmarks for the deep cervical plexus block are very difficult. The C2 spinal nerve lies immediately inferior and posterior to the loop of the vertebral artery between C1 and C2 vertebrae. The vertebral artery is most vulnerable to inadvertent injection at this point. The C3 and C4 spinal nerves exit the gutter of the transverse processes slightly posterior to the vertebral artery. At this point the vertebral artery is also shielded from needle puncture by the bone of the transverse process. Vertebral artery injection is therefore virtually impossible during blocking of the C3 and C4 spinal nerves if the needle is positioned immediately over the transverse process. Ultrasonography allows identification of position and depth of the vertebral artery. We anticipate that this identification will result in reduced inadvertent injection into adjacent structures such as the verte- bral artery, radicular arteries and dural cuff. We also anticipate improved cervical region structure identifi- cation with the use of more sophisticated ultrasound devices which are becoming increasingly available. We recommend that the C2 spinal nerve should not be blocked unless the vertebral artery is imaged above the C2 vertebra using ultrasonography. We further recommend that in the absence of ultrasound, injections should only be made at the C3 and C4 transverse processes as vertebral artery injection is unlikely. In summary, by using ultrasound imaging to place needles in close proximity to regional nerves, several studies have shown greater reliability and a decreased incidence of adverse effects2-4. The vertebral artery and the C2-4 spinal nerves are in close anatomical proximity. Mapping of the vertebral artery allows accurate needle placement during deep cervical plexus block. Our technique utilizes ultrasound to accu- rately map the anatomy of the vertebral artery. This information makes deep cervical plexus block a relatively safe and simple procedure, with anticipated greater reliability and reduced potential for adverse effects. The skills involved are an adaptation of those required for vascular access using the portable ultra- sound imaging and can be learned rapidly. We are currently designing a prospective ran- domized trial comparing ultrasound guided deep cervical plexus block with the traditional landmark guided block. Figure 7: High definition ultrasound and Doppler flow study of right vertebral artery. Top arrow: loop of left vertebral artery between C1 and C2 vertebrae. Bottom arrow: position of C2 spinal nerve. The Site~Rite® II is a rudimentary vascular access ultrasound device which provides only black and white images without colour flow Doppler. An ex- perienced ultrasonographer using a high definition duplex ultrasound scanner with colour flow Doppler confirmed that the images obtained by the Site~Rite® II were indeed the vertebral artery. The Site~Rite® II allows the vertebral artery to be clearly visualized from the first to the fourth cervical vertebrae. Knowledge of the anatomical relation- ship between the vertebral artery and surrounding Deep Cervical Plexus Block