The peripheral nervous system consists of numerous individual nerves, nerve trunks, nerve plexuses, and ganglia. This chapter discusses the blockade of somatic peripheral nerves. The sympathetic and visceral nerve blocks are discussed separately. The blockade of peripheral somatic nerves is the hallmark of regional anesthesia. This may be done for the facilitation of surgery as a sole technique or in combination with general anesthesia. Peripheral nerve blocks can be continued into the postoperative period via infusion through catheters for the purpose of continued postoperative pain relief. Excellent perioperative analgesia may help reduce the possibility of development of chronic pain.1,2 Additionally, some evidence indicates that regional anesthesia may have a role in reducing the recurrence of disease in patients undergoing oncologic surgery.3
In the field of chronic pain management, peripheral nerve blocks are useful in the diagnosis of pain conditions. At times these may provide pain relief beyond the duration of the local anesthetic itself and hence serve a therapeutic purpose.4 Various adjuvants such as clonidine, steroids, and vasoconstrictors may be added to the local anesthetic to prolong the duration of the nerve block. In some select circumstances, once the pain generating nerve is identified, neurolysis of the nerve via chemical or thermal techniques can be done. Chemical neurolysis is often done with alcohol or phenol, and in general, use of these agents is reserved for patients with terminal illness because of the risk of recurrent pain that may be worse, as well as the risk of permanent neurologic sequelae. Thermal techniques such as medial branch thermal neurotomy and cryoablation of neuromas are useful in the management of chronic pain.5
Historically, peripheral nerve blocks were often performed as a blind technique using surface anatomy landmarks, as well as feel. The introduction of nerve stimulation techniques was instrumental in improving the success of peripheral nerve blockade. With this technology, the proximity of the needle tip to the neural tissue can be objectively verified. Recently, with the introduction of ultrasound, the nerve can be visually identified and a needle placed next to it in real time. The spread of the medication around the nerve can also be visualized in real time. The availability of portable ultrasound machines has led to exponential use of this modality in the performance of peripheral nerve blocks. There has been increased use of ultrasound guidance in the field of chronic pain management as well. Interventional pain management, however, has a strong reliance on fluoroscopy in the performance of peripheral nerve blocks near the spine because bony landmarks serve well to predict the location of the nerve, and ultrasound has limited utility.
The success of a nerve block depends on several factors. First, it is key that the purpose of performing the nerve block is clearly understood both by the patient and the physician. Second, in the case of diagnostic blocks, knowledge of the factors contributing to a false-positive result or a false-negative result is essential, along with attempts to minimize their influence. Third, the physician should have an excellent knowledge of the anatomy of the nerve and the anticipated effects of the block. Fourth, appropriate preparation is done to deal with any untoward effects of the block. Fifth, appropriate technology such as ultrasound, fluoroscopy, etc. is used when needed to improve the technical success of the procedure. Last, the results of the nerve block and inferences thereof should be clearly documented.
INDICATIONS FOR THE USE OF NERVE BLOCKS
Nerve blocks can be broadly divided into three categories, anesthetic blocks to facilitate surgery, diagnostic blocks for identifying the pain generator, and therapeutic blocks for prolonged benefit.
Diagnostic blocks are performed when the cause of a pain condition is suspected but not confirmed. Some examples of these include medial branch blocks to identify facet pain, lateral branch blocks to identify sacroiliac joint pain, ilioinguinal nerve blocks to differentiate ilioinguinal neuralgia from genitofemoral neuralgia, and transversus abdominis plane (TAP) blocks to differentiate abdominal wall somatic pain from visceral abdominal pain.
Blocks are considered therapeutic when prolonged meaningful relief of pain occurs beyond the duration of the nerve block itself or when permanent denervation is the intended outcome such as radiofrequency ablation of the medial branches.4,5
NEUROPHYSIOLOGY AND PHARMACOLOGY
Neuronal membranes are characterized as semipermeable, double-thickness walls composed of lipid molecules with interspaced globular proteins. Small channels allow ions such as sodium and potassium to pass between the internal and external compartments of nerve membranes. Sensory stimulation causes a sudden influx of sodium ions, which results in depolarization of the nerve membrane. Local anesthetics such as lidocaine or bupivacaine produce temporary impairment of conduction of neural impulses by blocking sodium nerve channel conductance and maintaining the nerve in a polarized state.6 This effect on nerve membranes is temporary and reversible. The size of the nerve fiber affects its sensitivity to local anesthetics, with smaller, thinner, unmyelinated fibers being most susceptible. Peripheral nerves are composed of three types of nerve fibers:
A fibers are the largest myelinated somatic nerve fibers. These are further subdivided into motor and sensory. The motor fibers are α, β, and γ fibers and innervate the muscle spindle. The sensory fibers are α (muscle sense, high conduction velocity), β (touch), and γ (pain and cold temperature) fibers.
B fibers are myelinated preganglionic autonomic nerves. B fibers innervate vascular smooth muscle and are the most readily blocked nerve fiber. Successful blockade results in a sympathectomy, with increased warmth caused by increased blood flow and decreased sweating.
C fibers, the thinnest nonmyelinated fibers, are the slowest conducting nerve fibers. They transmit postganglionic pain and temperature sensation.
The two types of pain fibers, Aδ myelinated and nonmyelinated C fibers, have slightly different functions. Aδ fibers transmit sharp pain, while C fibers are responsible for the dull pain and burning sensations that accompany many chronic pain syndromes.
The choice of local anesthetic used will affect the density of the nerve block as well as the duration. Small nerve fibers (Aδ) and unmyelinated fibers (C fibers) can be interrupted with low concentrations of local anesthetic, with minimal effect on the larger myelinated efferent fibers. The subsequent nerve block would produce analgesia without any limb weakness. In contrast, a higher concentration of local anesthetic would produce a motor block, resulting in temporary limb weakness.
The duration of the analgesic effect depends on the choice of local anesthetic used. Lidocaine has a relatively short duration of action compared with bupivacaine, which typically lasts much longer. The addition of a vasoconstrictor such as epinephrine would prolong the duration of the nerve block by decreasing the absorption of the drug into the vascular system.
PRINCIPLES AND GUIDELINES FOR REGIONAL ANESTHESIA AND NERVE BLOCKS
Patients with chronic pain should always undergo a thorough evaluation before any interventional procedure. Patients may have numerous other medical problems that need to be addressed before deciding if a procedure is warranted. Examples of common medical problems include poorly controlled diabetes, asthma, and hypertension, to name a few. Elements of the patient workup and assessment should include:
A history from the patient and any other records or diagnostic studies
Psychological factors if any
Details of type of pain, location, and duration, as well as exacerbating and relieving factors
Medication and allergy review, including details of anticoagulant use with doses and indications (The performing physician should have a good knowledge of the anticoagulants used and the indications for the use. A risk-to-benefit ratio should be done on a case-by-case basis before stopping the anticoagulants and in concert with the primary care physician or the specialist).
Measurement of pain
Physical examination with clear documentation of neurologic findings
COMMUNICATION AND INFORMED CONSENT
Communication with the patient is equally important. The description of the procedure should be discussed, including why it is being performed, alternatives to it, expected outcome, and possible side effects. Sedation may be offered to minimize any discomfort, which should also be discussed. Oversedation and general anesthesia is not recommended as it is useful to maintain communication with the patient. Finally, the postprocedure recovery period should be discussed (e.g., return to work, physical activity).
LIMITATIONS AND CONTRAINDICATIONS OF NERVE BLOCKS
Nerve blocks can play an integral part in a comprehensive approach to pain management, but it is important that limitations are well understood. The placebo response can dramatically affect the positive predictive value.7 The spillover of the local anesthetic from the target structure, thus anesthetizing other structures, can also create false–positive results.8 Failure to appropriately anesthetize the nerve can give rise to false-negative results. Other causes of false-negative results include vascular uptake of the local anesthetic, improper technique, and inadequate amount of active agent to create nerve blockade. The results of the block need to be carefully interpreted. The mere absence of pain relief after successful blockade of the painful area does not necessarily imply psychogenic pain but may point toward a more central pain generator.9 Improper patient selection, psychological factors, compensation, and litigation issues can also create complexities in the interpretation of the results of a nerve blockade.
CONTRAINDICATIONS TO PERFORMING NERVE BLOCKS
Absolute contraindications are as follows:
Infection at the proposed site of injection
Local anesthetic allergy (Allergies to ester local anesthetics (procaine, tetracaine, and chloroprocaine) are known; however, these solutions are rarely used for regional nerve blocks. Amide local anesthetic allergy (lidocaine, bupivacaine, and ropivacaine) is rare. Some patients may report an allergic reaction after a dental procedure. Further investigation may be warranted to see if it was a true local anesthetic allergy or simply a reaction to epinephrine).
Relative contraindications are as follows:
Blood clotting abnormalities secondary to intrinsic disease or extrinsic use; management is decided case by case
Patients with systemic infection or hemodynamic instability
Situations in which a single or continuous nerve block may mask other pathology, such as limb ischemia from a compartment syndrome that may develop after fractures or crush injuries
PERFORMANCE AND ASSESSMENT OF NERVE BLOCKS
The physician performing the procedure should possess the technical knowledge, experience, and expertise pertinent to the specific procedure. Knowledge of relevant anatomy, potential side effects, and complications of the procedure are essential in preventing adverse outcomes. The expertise to handle immediate serious complications related to the nerve block is also critical. Appropriate technology such as nerve stimulator, fluoroscopy, and ultrasonography should be available as needed to improve the technical success of the procedure.
Discomfort during the procedure may be minimized by using short-acting opioids such as fentanyl. Anxiolytics or short-acting agents such as midazolam are also useful intravenous (IV) medications for minimizing anxiety or discomfort during needle placement. Excess sedation may make accurate assessment of diagnostic or therapeutic blocks difficult.
Appropriate monitoring and resuscitation equipment should be available to manage the effects of the block or any untoward complications. Thus, an IV line should be in place when a large amount of local anesthetic is to be used. Additional intralipid and resuscitation equipment should be available.10 These preparations may not be needed when a low-volume block such as an occipital nerve block is being performed.
Before and after regional anesthesia, baseline pain measurements should be obtained. Various indicators or scales such as the visual analog scale can be used to help document baseline pain level and response to treatment.11 For more specific nerve blocks, additional information may be helpful. For somatic nerve blocks, sensory and motor deficits should be consistent with the anticipated region or dermatome blocked.
The duration and onset of the physiologic effect of the block and its correlation with the duration of pain relief are important for several reasons. If the duration of pain relief is shorter than expected, it may indicate inaccurate needle placement, an incomplete or partial nerve block, or possibly an alternate pain source. If the duration is longer than expected or the onset much quicker than expected, a potential placebo effect should be considered.
SIDE EFFECTS AND COMPLICATIONS OF REGIONAL ANESTHESIA
Effects of the block may include physiological sequelae or side effects such as hypotension after sympathectomy or dizziness after occipital nerve block. Vagal stimulation can cause syncope; this is often seen in young patients. Other effects may relate to complications of the nerve block such as direct needle injury (pneumothorax after intercostal nerve block) or intravascular injection (seizure during a stellate ganglion block), and these remain specific to each block.
Large volume of local anesthetic can cause cardiac arrest, and intralipids should be available to manage this catastrophic complication when large volumes of local anesthetic are to be used.10 To safeguard against this, intermittent aspiration should be done to rule out intravascular placement. When using fluoroscopy, real-time contrast injection is useful in detecting this. When using ultrasound, the local anesthetic spread around the needle tip should be visualized in real time.
NEEDLE PLACEMENT AND POSITIONING
Utmost care should be taken when positioning the patients, and all pressure points should be checked. This is especially important in older individuals.
Needle advancement should be done slowly and incrementally in a goal-directed fashion. This is to reduce patient discomfort and to help minimize multiple redirections. This can take some practice. When approaching important structures, only small changes should be made. If the patient reports pain, determination as to local pain versus paresthesia is important. One necessitates more local anesthetic, whereas the other may require needle withdrawal or redirection. One important point is to refrain from injecting anything if the patient reports pain when the needle is in the vicinity of an important neural structure and to rather gently withdraw it. When using ultrasound the more perpendicular the needle is to the beam, the better it is visualized.12,13
The skin of the face is supplied by the three divisions of the trigeminal nerve. The scalp is supplied by various divisions of the occipital nerve posteriorly and the auriculotemporal nerve in the temporal region. The branches from the dorsal rami of the cervical nerves supply the neck posteriorly, and the branches of the superficial cervical plexus supply the neck anteriorly. Various neuralgia can affect these nerves. In addition, different branches can be peripherally blocked for the provision of surgery such as dental surgery. Blockade of superficial pericranial nerves may also provide relief to patients with intractable headache.4
The trigeminal nerve consists of three divisions: the ophthalmic nerve (V1), maxillary nerve (V2), and mandibular nerve (V3). These three branches supply sensation to most of the face. Trigeminal nerve blocks are used mainly to treat severe pain from trigeminal neuralgia and various malignancies affecting the face.
Gasserian Ganglion Block (Fig. 84-1)
Trigeminal nerve block. (Adapted with permission from MediClip, Williams & Wilkins.)
The gasserian or trigeminal ganglion lies within the medial cranial fossa across the superior border of the petrous temporal bone. The posterior two-thirds is fully covered by dura mater. This posterior portion lies within a small recess called Meckel's cave. This invagination of the dura surrounding the posterior two-thirds of the ganglion allows direct continuity with the cerebrospinal fluid.
This block is used for intractable pain from trigeminal neuralgia and involves neurolysis of one or two divisions of the trigeminal nerve via thermal radiofrequency lesioning or glycerol rhizotomy. Neurodestructive procedures are usually reserved for older individuals who are poor surgical risks and have intractable pain unresponsive to multiple neuropathic medications. The V1 branch is not a candidate for neurolysis because of the risks of corneal insensitivity.
The foramen ovale is visualized on an anteroposterior view of the skull. The entry point for the needle is lateral to the lateral margin of the mouth medial to the masseter muscle.14 A 22-gauge, 10-cm needle is advanced to the foramen ovale in the plane of the pupil and directed cephalad toward the auditory meatus. As the foramen is entered, a mandibular paresthesia is perceived.
Subarachnoid injection can cause unconsciousness or seizures. The internal carotid artery lies medially at this location. Radiofrequency ablation of V1 will lead to corneal anesthesia, leading to loss of corneal sensation and corneal ulcers.
Mandibular and Maxillary Nerve Block at the Coronoid Notch
The trigeminal nerve divides into three branches that can be individually blocked at the coronoid notch. The V3 division is posterior at the pterygoid plate, whereas the V1 and V2 divisions are anterior. The mandibular nerve splits to form two divisions. The anterior division supplies the muscles of mastication, and the posterior division is sensory to the jaw, tongue, and the teeth, forming the alveolar, auriculotemporal, and lingual nerves. The maxillary nerve is mainly a sensory nerve to the nasal cavity, upper teeth, and middle of the face.
This block is used for diagnosis and treatment of neuralgia of these nerves or in trigeminal neuralgia. It provides the ability to block individual nerves. Anesthesia to the areas of nerve innervation can also be provided.
The coronoid notch is identified by having the patient open and close the mouth. A 25-gauge, 3.5-in needle is advanced through the midpoint of the coronoid notch inferior to the zygomatic arch to contact the pterygoid plate. If both the nerves are to be blocked, an injection with 7 to 10 mL of local anesthetic may be performed here. For the mandibular nerve, the needle is then slightly withdrawn and directed posteriorly and inferiorly and about 1 cm deeper to block the V3 branch; 3 to 5 mL of local anesthetic is injected here. To block the V2 nerve, the needle is redirected in a similar fashion but anteriorly and superiorly. Higher volumes injected at this anterior location can also block the V1 nerve.
Particulate steroids should not be used.
Possible complications include spread to additional nerves, intravascular injection, hematoma, and bleeding.
Supraorbital and Supratrochlear Nerve Block
This is a peripheral branch of the V1 division with sensory innervation to the forehead.
This block is used for diagnosis and treatment of neuralgia of the nerve and in management of patients with chronic intractable migraine often requiring multiple blocks in the management.15
The skin is cleaned with alcohol. The supraorbital notch is identified by palpation, and a 30-gauge, 1-in needle is advanced to this location. A total of 1 to 2 mL of local anesthetic is injected in a fan-shaped manner. To block the supratrochlear nerve, the needle is then advanced medially to the apex of the nose, and local anesthetic is injected here as well. Do not mix with steroids, as steroids can leave a mark on the face resulting from lipoatrophy.16
Possible complications include local bruising and neuritis.
This is a peripheral branch of the V2 division with sensory innervation to the region below the eye.
This block is used for the diagnosis and treatment of neuralgia of the nerve and management of intractable headaches.15
The infraorbital ridge of the maxillary bone is identified, and the foramen is palpated. A 30-gauge, 1-in needle is advanced to this location. A total of 1 to 2 mL of local anesthetic is injected in a fan-shaped manner. Do not mix with steroids, as steroids can leave a mark on the face resulting from lipoatrophy.16
Possible complications include local bruising and neuritis.
Auriculotemporal Nerve Block
This is a peripheral branch of the V3 division with sensory innervation to the area of the temple, external auditory canal, tympanic membrane, and a few articular branches to the temporomandibular joint.
This block is used for the diagnosis and treatment of auriculotemporal neuralgia and in the management of chronic intractable migraine often requiring multiple blocks in the management.15
Field block in the region of the auriculotemporal nerve as it emerges above the zygomatic arch. A total of 1 to 2 mL of local anesthetic is injected. Do not mix with steroids, as steroids can leave a mark on the face resulting from lipoatrophy.16
Possible complications include local bruising and neuritis.
This is a peripheral branch of the V3 division emerging from the mental foramen with sensory innervation to the anterior mandible.
This block is used for the diagnosis and treatment of neuralgia of the mental nerve.
The foramen lies about 2 cm from the midline and can often be palpated. A 30-gauge, 1-in needle advanced to this location with care taken not to enter the foramen. A total of 1 to 2 mL of local anesthetic is injected in a fan-shaped manner. Do not mix with steroids, as steroids can leave a mark on the face resulting from subcutaneous tissue atrophy.16
Possible complications include local bruising and neuritis.
Glossopharyngeal Nerve Block
The glossopharyngeal nerve exits the skull through the jugular foramen located posterior to the tip of the mastoid process. The glossopharyngeal nerve supplies sensation to the posterior third of the tongue, the palatine tonsils, and the pharyngeal wall.
This block is used for glossopharyngeal neuralgia characterized by clusters of severe lancinating, electric shock–like pain in the oropharynx and tonsils with possible radiation to the ear. It is usually unilateral.17
An imaginary line is drawn from the mastoid process to the angle of the jaw. The styloid process lies just below the midpoint of this line. A 25-gauge, 1.5-in needle is inserted and the styloid process contacted within 3 cm. The needle is withdrawn and inserted posteriorly to lie just past the styloid process and local anesthetic injected here. Do not use particulate steroid because of the embolic risk.
Possible complications include dysphagia from paralysis of the pharyngeal muscles and weakness or partial paresis of the tongue. The block should only be performed unilaterally because a bilateral block will produce complete paralysis of the pharyngeal muscles. Weakness in the trapezius muscle can also be seen caused by blockade of the spinal accessory nerve.
Occipital Nerve Block (Figs. 84-2 and 84-3)
Ultrasound image of the occipital region. The occipital artery (OA) is visualized in the center with the help of color Doppler. The nerve usually lies medial to it. The needle is inserted in an in-plane approach, and real-time injection of local anesthetic is used to block the nerve. The probe is placed horizontally to obtain a cross-section view of the artery. IO, internal oblique; L, lateral; M, medial; ON, occipital nerve; SSC, semispinalis capitis.
Occipital nerve block. (Adapted with permission from MediClip, Williams & Wilkins.)
The greater occipital nerve is formed from the dorsal primary ramus of the second and third cervical nerves. It supplies sensation to the medial-posterior portion of the scalp. This nerve is usually located 2 to 3 cm lateral to the external occipital protuberance and just medial to the occipital artery, which serves as a reliable landmark. A 25 -gauge, 1.5-in needle is identified, and 2 to 5 mL of local anesthetic is deposited in this location. The lesser occipital nerve arises from the ventral primary ramus of the second and third cervical nerves passing along the posterior border of the sternocleidomastoid muscle. It is located approximately 2.5 cm lateral to the occipital artery.
This block is used for the diagnosis and treatment of neuralgia of the nerve and in the management of chronic intractable migraine often requiring multiple blocks.15
The occipital nerve is blocked at the superior nuchal line about one-third of the distance from the external occipital protuberance to the mastoid process. The lesser occipital nerve is blocked as a field block posterior to the mastoid process. An ultrasound-guided occipital nerve block has been described.18
A possible complication is local bruising.
Deep Cervical Plexus Block (Fig. 84-4)
Deep cervical plexus block. The needle is inserted in plane posterior to anterior. The probe is placed transversely between the mastoid and the C6 tubercle to obtain a cross-sectional view of the nerves. A, anterior; AT, anterior tubercle; P, posterior; PT, posterior tubercle; C4 and C5, nerve roots; SA, scalene anterior; SCM, sternocleidomastoid.
The plexus is formed by the ventral rami of C1 to C4. These divide into ascending and descending branches, forming series of three loops called the cervical plexus. Each loop gives a superficial and deep branch. The superficial branches form the superficial cervical plexus. Blockade of the deep cervical plexus blocks both the deep and superficial branches.
This block is used to provide surgical anesthesia over the anterior neck for procedures such as neck dissection, thyroidectomy, and carotid endarterectomy.
Traditionally, the block is done by multiple injections at C2, C3, C4 or by single injection technique at C4. A line is drawn from the mastoid process to the C6 anterior tubercle. The C2, C3, and C4 transverse processes are marked at 1.5, 3, and 4.5 cm caudad to the mastoid process, respectively. A needle is inserted medially and caudally at these points to contact the transverse process at 1.5 to 2 cm, and 3 to 5 mL of local anesthetic is injected at each point.19 Recently an ultrasound-guided technique has also been described.20,21
Possible complications include epidural or spinal spread and consequent effects, phrenic nerve paralysis, and intravascular injection. Do not use particulate steroid because of the embolic risk.
Superficial Cervical Plexus Block
The superficial branches of the cervical plexus emerge approximately in the middle of the posterior margin of the sternocleidomastoid muscle and provide cutaneous innervation via supraclavicular, transverse cutaneous (anterior), greater auricular, and lesser occipital nerves.
This block is used to provide surgical anesthesia over the anterior neck for procedures such as neck dissection and carotid endarterectomy.
Field block is done in the midsternocleidomastoid region posteriorly. A total of 5 mL of local anesthetic is injected subcutaneously, and then 2 to 3 mL of local anesthetic is injected in a fan-shaped manner superiorly and inferiorly. An ultrasound-guided technique is also described.22
Possible complications include hematoma and bruising if the external jugular vein is injured.
SHOULDER AND UPPER EXTREMITY
The brachial plexus is formed from the ventral primary rami of the fifth (C5), sixth (C6), seventh (C7), and eighth (C8) cervical nerves along with the first thoracic nerve (T1). The C4 and T2 spinal nerves may also contribute to the plexus. These roots pass between the anterior and middle scalene muscles in the neck before passing into the arm. The roots combine to form upper, middle, and lower trunks that subdivide into anterior and posterior divisions. These divisions then form the cords. Within the axilla, near the lateral border of the axilla, the cords divide into the peripheral nerves of the upper extremity.
The long thoracic nerve contains fibers from C5, C6, and C7.
The suprascapular nerve contains fibers from C4, C5, and C6.
Peripheral branches of the lateral cord form the musculocutaneous nerve and lateral root of the median nerve formed from C5, C6, and C7.
Peripheral branches of the medial cord (C8 and T1) form the medial root of the median nerve, the ulnar nerve, and the medial cutaneous branches of the arm and forearm.
Peripheral branches of the posterior cord form the axillary, radial, and subscapular nerves.
Anesthesia for upper extremity surgery
Postoperative pain relief and rehabilitation
Manipulation of frozen shoulder
Continuous sympathetic nerve blockade to improve blood flow to the affected extremity (i.e., Raynaud's disease)
TYPES OF BRACHIAL PLEXUS BLOCKS
Interscalene Block (Fig. 84-5)
Interscalene block. The probe is placed transversely at about the C6 to C7 level to get a cross-sectional view of the nerve roots, and the needle is inserted in plane posterior to anterior. CA, carotid artery; C5 to C7, nerve roots; IJV, internal jugular vein; SA-scalenus anterior; SCM, sternocleidomastoid muscle; SM, scalenus medius.
The roots combine to form upper, middle, and lower trunks that lie in the interscalene groove.
This block is used as anesthesia for surgery on the shoulder, catheters for postoperative pain relief, and for shoulder manipulation in case of frozen shoulder. It is not ideal for forearm surgery because ulnar sparing is seen.
The block is usually done with ultrasound guidance or with the help of a nerve stimulator. A combined technique is often used. With the stimulator technique, a 22-gauge, 1.5-in stimulating needle is inserted into the interscalene groove after rolling of the anterior scalene muscle. The needle is inserted perpendicular to the skin, and stimulation of the brachial plexus is sought. After obtaining stimulation, 10 to 15 mL of local anesthetic is injected here. When using ultrasonography, the probe is placed in transverse plane, and the needle is advanced using an in-plane approach from posterior to anterior; the local anesthetic is deposited between the middle and the lower trunk. With ultrasound guidance, low volumes of local anesthetic can provide adequate coverage and in one study has been shown to allow for shorter procedure times and fewer skin and vascular punctures.23 Lower volumes might decrease the incidence of phrenic nerve blockade.
Possible complications include neuritis, intravascular injection, and phrenic nerve block. Major neurologic complications are rare.
Supraclavicular Block (Fig. 84-6)
Supraclavicular block. The probe is placed transversely posterior (P) to anterior (A) to get a cross-sectional view of the nerve roots, and the needle is inserted in plane posterior to anterior. Infiltration is started in the sheath between the subclavian artery (SA) and the first rib. Br. Pl. Divisions, brachial plexus divisions; SAM, scalenus anterior muscle; SCM, sternocleidomastoid; SV, subclavian vein.
The divisions of the trunks lie in the supraclavicular fossa. A block at this location anesthetizes the entire arm from shoulder to the hand.
This block is used for anesthesia for surgery on the shoulder and arm. The advantage of this block may be less likelihood of phrenic nerve block; however, the interscalene block is still preferred for shoulder surgery.
The block is usually done with ultrasound guidance or with the help of a nerve stimulator. A combined technique is often used. With the stimulator technique, a 22-gauge, 5-cm stimulating needle is inserted perpendicular to the skin and lateral to the subclavian artery in a direction aimed at the first rib. After obtaining stimulation, 10 to 15 mL of local anesthetic is injected here. When using ultrasound the probe is placed in transverse plane, and the needle is advanced using an in-plane approach from posterior to anterior, the local anesthetic is deposited around the brachial plexus divisions. With ultrasound guidance, low volumes of local anesthetic can provide adequate coverage.
Possible complications include neuritis, intravascular injection, and phrenic nerve block, pneumothorax. Major neurologic complications are rare.
Infraclavicular Block (Fig. 84-7)
Infraclavicular block. The probe is placed vertically medial to the coracoid process to get a cross-sectional view of the nerve roots and the subclavian vessels. Medial (M) scanning is done to outline the extent of the pleura medially. The needle is inserted in plane superior to inferior, and infiltration around the posterior cord (PC) is done. Medial cord infiltration may be needed if the medication does not spread there from the PC. L, lateral; LC, lateral cord; MC, medial cord; SA, subclavian/axillary artery; SV, subclavian vein.
The cords of the brachial plexus are formed at and below the clavicle. With this block, the axillary nerve may be spared.
This block is used for anesthesia for surgery on the elbow and forearm. Shoulder and upper arm is spared.
The block is usually done with ultrasound guidance or with the help of a nerve stimulator. Often combined technique is used. With the stimulator technique 22-gauge, 10 cm stimulating needle is inserted perpendicular to the skin 2 cm medial and 2 cm inferior to the coracoid process. Stimulation of the posterior cord is sought. After obtaining stimulation 15-30 mL of local anesthetic is injected here. When using ultrasound the probe is placed in a vertical plane to visualize the cross section of the subclavian artery and the surrounding brachial plexus cords and the needle advanced using an in-plane approach from superior to inferior. The local anesthetic is deposited around the posterior cord from where it spreads to the other cords or these may also be blocked individually. With ultrasound guidance low volumes of local anesthetic can provide adequate coverage.
Possible complications include neuritis, intravascular injection, hematoma, and pneumothorax. Major neurological complications are rare.
Axillary nerve block. The circles drawn outline the nerves. The probe is placed horizontally to get a cross-sectional view of the nerve roots, and the needle is inserted in plane. AA, axillary artery; AV, axillary vein; BP, brachial plexus.
The branches of the brachial plexus lie beyond the axillary fold. At this location musculocutaneous sparing may occur, and a separate injection to cover may be needed.
This block is used for anesthesia for surgery on the forearm and hand. Shoulder and upper arm sparing occurs. Musculocutaneous sparing occurs and is blocked separately.
The block is usually done with ultrasound guidance or with the help of a nerve stimulator. A combined technique is often used. When using ultrasound, the probe is placed in a transverse plane to visualize the cross-section of the subclavian artery and the surrounding brachial plexus branches, and the needle is advanced using an in-plane approach from lateral to medial. The musculocutaneous nerve is blocked separately. With ultrasound guidance, low volumes of local anesthetic can provide adequate coverage.
Possible complications include neuritis, intravascular injection, and hematoma. Major neurological complications are rare.
Suprascapular Nerve Block (Fig. 84-9)
Suprascapular nerve block. (Adapted with permission from MediClip, Williams & Wilkins.)
The suprascapular nerve arises from C4, C5, and C6 contributions from the upper trunk of the brachial plexus. It passes beneath the trapezius muscle to the superior border of the scapula, where it passes through the suprascapular notch. The suprascapular nerve is the major sensory supply to the shoulder joint and motor supply to the supraspinatus and infraspinatus muscles.
This block is used to treat arthritis or bursitis of the shoulder joint in addition to intra- and periarticular injections. It is also used diagnostically to confirm suprascapular nerve irritation or entrapment.
The technique is done with fluoroscopic24 or ultrasound guidance.25 With fluoroscopic guidance, the patient lies in a prone position, and the C-arm image intensifier is tilted cranially and with medial obliquity to visualize the notch. The needle is then directed inferior to the notch and then slid in. With ultrasound guidance, it may be more reliable to block the nerve in a supraclavicular position.25
Possible complications include pneumothorax with improper technique and neuritis.
UPPER EXTREMITY: ELBOW AND WRIST
Median Nerve Block (Fig. 84-10)
Median nerve block. (Adapted with permission from MediClip, Williams & Wilkins)
The median nerve, formed from the lateral and median roots of the brachial plexus, contains fiber from C5 through T1. There are no branches in the upper arm, and it descends with the brachial artery, being slightly medial to it at the elbow. It crosses the elbow anteriorly and passes between the two heads of the pronator teres. It courses through the wrist deep to the palmaris longus tendon.
This block is used to supplement a brachial plexus block or as a diagnostic and therapeutic block for carpal tunnel syndrome.26
The nerve can be easily visualized in the forearm and the wrist, and the block is accomplished with ultrasound guidance. A total of 2 to 3 mL of local anesthetic is enough to block the nerve when using ultrasound.
Major neurological complications are rare.
The ulnar nerve is formed from the C7, C8, and T1 roots. At the elbow, it lies behind the medial epicondyle in the ulnar groove.
This block is used to supplement brachial plexus anesthesia27 or as a diagnostic and therapeutic block for ulnar nerve injury such as compression or entrapment neuropathies.
The nerve can be easily visualized in the forearm and the wrist and the block accomplished with ultrasound guidance. A total of 2 to 3 mL of local anesthetic is enough to block the nerve when using ultrasound.
Major neurological complications are rare.
The posterior cord (C5–T1) gives rise to the radial nerve.
This block is used to supplement a brachial plexus block.27 It is also used to diagnose and treat neuralgia.
The nerve can be easily visualized and the block accomplished with ultrasound guidance. A total of 2 to 3 mL of local anesthetic is enough to block the nerve when using ultrasound.
Major neurological complications are rare.
Paravertebral Nerve Block (Fig. 84-11)
Paravertebral block. The probe is placed transversely between the ribs and parallel to the ribs, and the view of the pleura diving under the transverse process is obtained. The needle is inserted in plane lateral (L) to medial (M). When the injectate is in the correct plane, the pleura is seen to push down. TP, transverse process.
In the thoracic area, the paravertebral space is a potential space that surrounds the somatic nerves as they course from the spine to the thoracic wall to form the intercostal nerves. It is bounded laterally by the pleura and medially by the intervertebral foramen. Injection of local anesthetics into this space is efficacious in blocking multiple somatic nerves. In the lumbar area, the anatomy is different, and a block here is essentially a block of the lumbar plexus.
This block is used for intraoperative and postoperative analgesia for breast, thoracic, and upper abdominal surgery. It has been shown that paravertebral block can provide superior analgesia compared with an epidural infusion.28 It can also serve a diagnostic role in distinguishing somatic from visceral pain.
The lumbar paravertebral block is used for intraoperative and postoperative analgesia for hip and leg surgery where epidural or spinal analgesia is either not feasible or not desirable. Postoperative catheter infusions are often used.
This block may be accomplished by landmarks, often with the help of a stimulator to identify the nerve or with ultrasound guidance.
A single injection of 10 to 20 mL of local anesthetic may be done in the midpoint of the incision or multiple injections (2 to 5 mL per site) to cover all the dermatomes. The superior margin of the thoracic spinous process is marked. A needle is inserted perpendicular to all planes and 2.5 cm lateral to the spinous process to contact the transverse process. It is then slightly withdrawn and advanced caudad to lie at the lower edge of the transverse process and then advanced 1 cm past the caudad edge of the transverse process.29,30
Ultrasound guidance can also be used to accomplish this block. The needle is advanced in an in-plane approach to lie ventral to the transverse process and dorsal to the pleura, which is clearly identifiable with the use of ultrasound.31
A lumbar plexus or lumbar paravertebral block is usually accomplished at the L3 or L4 level.32,33 The patient is placed on the side with the side to be blocked being nondependent. A 22-gauge, 10-cm needle is inserted 3 to 4 cm off the midline (4–5 cm at the L4 level) at about the superior margin of the corresponding spinous process, advanced to contact the transverse process, and then walked off cephalad 1.5 cm beyond the transverse process. A total of 20 to 30 mL of local anesthetic solution is injected here. If a twitch monitor is used, a twitching of the thigh muscles can be visualized. The sciatic nerve and the sacral plexus are usually spared, requiring a separate sciatic nerve block.34