Chapter 68. Peripheral Nerve Blocks

The interruption, interference, or blockade of painful stimuli has been used in the management of pain for several decades. Acute, chronic, and postoperative pain can be diminished with various types of regional anesthesia or specific nerve blocks. In the setting of chronic pain management, various peripheral nerve blocks can be diagnostic, prognostic, or therapeutic in nature. A nerve block involves the injection or infusion of a short- or long-acting local anesthetic around a peripheral sensory nerve, motor nerve, or sympathetic nerve plexus. In addition to local anesthetic, a steroid preparation may be added to decrease any suspected inflammatory process. Neurolytic nerve blocks can be performed utilizing various techniques including chemical, heat, or cold. Chemical agents such as alcohol or phenol are used for the selective destruction of nerves. Pulsed radiofrequency and cryoanalgesia cause neurolysis via heat or cold lesioning. Advances in fluoroscopic imaging and computed tomography (CT) scanning allow direct visualization and targeting of specific nerves and nerve plexuses. Other improvements include the use of nerve stimulators during interscalene and axillary blocks or sensory and motor nerve stimulation performed during radiofrequency procedures to assist in accurate needle placement.

Nerve blocks are generally most useful when a specific nerve or limb is affected. Neuropathies with bilateral or multiple areas of involvement may benefit from other forms of neuromodulation including pharmacologic management, transcutaneous electrical stimulation (TENS), or spinal cord stimulation.1,2

Successful treatment outcomes involve numerous factors including proper patient selection, understanding the anatomy, side effects, and potential complications of each specific nerve block. A comprehensive approach to chronic pain management has been shown to produce superior outcomes.3 Nerve blocks, when appropriate, should be considered part of the overall multidisciplinary treatment plan.

Patients selected for nerve block therapy or regional anesthesia should have an accurate diagnosis for the origin of their pain. In some instances nerve blocks may aid in the diagnosis of certain acute and chronic conditions. The relief of pain comes from the interruption of nociceptive or pain sensory pathways, sympathetic blockade, or somatosensory blockade. Regional anesthesia may be used to interrupt the afferent limb of abnormal reflexes that contribute to the pathogenesis of some pain syndromes. Regional anesthesia may block efferent sympathetic outflow, which contributes to postoperative, post-traumatic, and chronic pain syndromes with sympathetic involvement such as complex regional pain syndrome (CRPS) or postherpetic neuralgia.4

A complete history and physical evaluation of the patient should be performed including review of laboratory studies, imaging studies, medications, and allergies. Psychiatric and psychosomatic assessment should be carried out when appropriate. Special attention should be paid to anticoagulant medications, sensory loss or motor weakness on physical examination. Complaints of sexual dysfunction, and bowel or bladder problems should also be noted. Any abnormal findings should be documented and may require further evaluation prior to any interventional nerve blocks.

The choice of local anesthetic (LA) 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 LA, 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 LA would produce a motor block resulting in temporary limb weakness. This type of block can be therapeutic in some instances, for example, frozen shoulder, by allowing manipulation and increased range of motion.

The duration of the analgesic effect depends on the choice of LA used (For information on local anesthetics amino esters and amino amides, see Appendix C). Lidocaine has a relatively short duration of action compared with bupivicaine, 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. The choice of local anesthetic is also important when considering the anatomic site of the nerve block. For example, lidocaine may be a better choice for nerve blocks in the head and neck region. Owing to its short duration of action any possible adverse affects would be short-lived.

Finally, it can be difficult to differentiate between somatic, visceral, and sympathetic pain. There may be overlapping symptoms, for example, a peripheral nerve injury leading to sympathetic nervous system stimulation. Due to the complexity of some chronic pain syndromes, nerve blocks or regional anesthesia can be used for diagnostic, prognostic, or therapeutic purposes.5

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 bupivicaine 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 delta (δ), beta (β), and gamma (γ) fibers that transmit motor and pressure sensation. The thinner Aδ fibers transmit pain and temperature sensation.
• 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 due to increased blood flow and decreased sweating.
• C fibers, the thinnest nonmyelinated fibers, are the slowest conducting nerve fibers. They transmit post-ganglionic 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.

Diagnostic Injections and Nerve Blocks

Diagnostic injections and nerve blocks can help determine or differentiate:

• The anatomic location or main pain generator. Examples include trigger point injections, neuromas, or joint injections.
• Cervical or lumbar disc versus facet joint mediated pain.7
• Central (spinal cord or brain) versus peripheral sources of nociception.
• Local pain sources versus referred pain (i.e., facet joint pain referred into hips).
• Somatic versus visceral pain (intercostal nerve blocks will affect somatic afferent nerves in trunk wall without affecting visceral nerves).
• Sympathetic versus somatic nerve injury or dysfunction in upper or lower extremities.
• Selective nerve root blocks can help better define cervical, thoracic, or lumbar radicular pain.
• Pain that may be psychogenic in origin (i.e. differential spinal or epidural).

Prognostic Nerve Blocks

Nerve blocks can be used prognostically before a more permanent neurolytic procedure is performed. Duration of relief from the prognostic nerve block should be noted as well as any sensory or motor deficits. Several prognostic blocks may be indicated before proceeding with certain neurodestructive procedures due to possible placebo effect.8 To aid in accuracy, these blocks should be performed under fluoroscopic or CT scan guidance.9 Examples of prognostic blocks include:

• Cervical and lumbar medial branch nerve block prior to radiofrequency rhizotomies.
• Selective nerve root blocks prior to pulsed radiofrequency of the dorsal root ganglion.
• Intercostal blocks prior to pulsed radiofrequency.
• Celiac plexus block prior to alcohol neurolysis.
• Saddle block prior to neurolytic spinal.
• Trial spinal cord stimulation prior to permanent implantation.
• Epidural or intrathecal morphine trial prior to placement of a permanent pump.

Therapeutic Nerve Blocks

Therapeutic nerve blocks are typically performed after or in conjunction with diagnostic blocks that have established the nature and location of the pain. These blocks can be beneficial in both acute and chronic pain states. Examples include:

• Intraoperative and postoperative intercostal blocks for post-thoracotomy pain.
• Interscalene blocks followed by physical therapy for frozen shoulder.
• Continuous infusions around peripheral nerves (i.e., interpleural, intercostal, brachial plexus, or epidural catheters).
• Continuous sympathetic blockade to increase blood flow to an ischemic limb.

It may be of benefit to the practitioner and patient if a set of general guidelines is followed to assure optimal outcomes prior to initiating any form of regional anesthesia or specific nerve blocks.

Patient Assessment

Chronic pain patients 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, or 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.
• Details of type of pain, location, duration, as well as exacerbating and relieving factors.
• Physical examination documenting any numbness, weakness, and bowel, bladder, or sexual dysfunction.
• Pain measurement tools including visual analog scale (VAS), Beck Depression Inventory, and McGill Pain Questionnaire.
• Psychological assessment and Minnesota Multiphasic Pain Inventory (MMPI).
• Medication and allergy review.

Communication and Informed Consent

Communication with the patient and family members 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. The physician should also highlight possible risks prior to obtaining informed consent. Sedation, either intravenous or intramuscular, may be offered to minimize any discomfort and this may also be discussed. Finally, the post-procedure 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 may have a limited role in certain chronic pain syndromes. Diffuse musculoskeletal pain and peripheral or diabetic neuropathies will generally not benefit from specific nerve blocks. Late-stage CRPS or crush injuries may require more extensive treatments. Damaged tissue, crushed nerves, or pain covering several dermatomes will require some form of systemic treatment. Complex pain patients with no obvious neurologic abnormalities or deficits may have other factors influencing their overall condition and these factors will need to be explored as well. For example, it has been well documented that gender, psychological, cultural, and environmental factors all, or in part, can play a role in pain perception, pain behavior, and treatment outcome.10,11

Contraindications to Performing Nerve Blocks

Absolute contraindications are as follows:

• Infection at the proposed site of injection. This can include decubitus ulcers, fungal, or parasitic skin infections.
• Blood clotting abnormalities secondary to intrinsic disease, aspirin, warfarin, or heparin.
• LA allergy. Allergies to ester LAs (procaine, tetracaine, and chloroprocaine) are known; however these solutions are rarely used for regional nerve blocks. Amide local anesthetic allergy (lidocaine, bupivicaine, and ropivivaine) is rare. Some patients may report an allergic reaction that followed a dental procedure. Further investigation may be warranted to see if it was a true LA allergy or simply a reaction to epinephrine.
• A patient with dementia or some other form of altered mental status (i.e., drugs, alcohol, etc.).
• A patient unwilling to agree to the procedure or who does not sign an informed consent form.
• A pregnant patient if fluoroscopy is being used.

Relative contraindications include:

• Patients with systemic infection, severely debilitated, or hypovolemic individuals.
• Situations where a single or continuous nerve block may mask other pathology, such as limb ischemia from a compartment syndrome that may develop following fractures or crush injuries.

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 to preventing adverse outcomes, as well as being able to deal with them should they arise. Various aids can assist accurate needle placement such as fluoroscopy, with or without contrast solutions, peripheral nerve stimulators, CT scanning, and Doppler technology have all been used.12

Discomfort during the procedure may be minimized by using short-acting opioids such as fentanyl. Anxiolytics or short-acting agents such as midazolam or propofol are also useful intravenous medications for minimizing anxiety or discomfort during needle placement. Excess sedation may make accurate assessment of diagnostic or therapeutic blocks difficult. For diagnostic or prognostic blocks, a small amount of LA should be used (e.g., for diagnostic medial branch nerve blocks 0.3 mL to 0.5 mL of LA would be appropriate and prevent spread to other surrounding structures). Gentle needle placement under fluoroscopic guidance and anesthetizing the skin with LA or a freezing spray (e.g., ethyl chloride) will help to ensure patient comfort.

Before and following regional anesthesia, baseline pain measurements should be obtained. Various indicators or scales such as the visual analog scale (VAS) can be used to help document baseline pain level and response to treatment.13 For more specific nerve blocks, additional information may be helpful. Skin temperature measurements prior to and following sympathetic nerve blockade may be recorded. An increase in temperature of the affected extremity is typically due to vasodilatation and increased blood flow following the temporary sympathectomy. 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 is 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, potential placebo effect should be considered. For these reasons, which can cause uncertainty in interpretation, it is advisable to repeat blocks using LAs with different durations of action.14 Neural blockade followed by physical or occupational therapy can also assist in assessing the success of various blocks. Additional documentation can include decreased pain response or increased range of motion measurements.

Side Effects and Complications of Regional Anesthesia

Before regional anesthesia or a specific nerve block is initiated, certain issues need to be addressed. When performing the actual injection or infusion of LA, continuous monitoring of patient physiologic indices should occur as dictated by the American Society of Anesthesiology guidelines. Monitoring should include electrocardiography, blood pressure, and pulse oximetry. Verbal contact with the patient is important to detect changes in level of consciousness or sensorium. Patient monitoring after the procedure should continue for at least 30 minutes to detect any delayed complications. Examples of a delayed complication include inadvertent subdural injection following a lumbar epidural injection or a pnemothorax that can occur following intercostal nerve blocks. These complications can present with delayed hypotension and motor block in the case of a subdural injection15 or shortness of breath with cardiopulmonary collapse in the case of a severe pneumothorax.16

Needle Placement and Positioning

Needle placement is not entirely risk-free and great care should be taken even when utilizing fluoroscopic guidance. Observation of the patient is important to detect increased pain during needle placement. Increased pain during needle placement may necessitate the use of more LA to anesthetize the needle trajectory, needle redirection, or repositioning of the fluoroscopy unit for a “tunnel vision view.” Anterior-posterior fluoroscopic views show needle direction, whereas lateral views are required to gauge needle depth. A “heavy hand” will not be overcome by giving the patient large amounts of intravenous sedation. In addition, large amounts of intravenous sedation may cause untoward side effects including nausea, vomiting, and hypotension. Oversedation may result in unwanted patient movement due to inability to follow commands, and any altered mental status may be difficult to distinguish from LA toxicity. Nerve injury or more severe consequences can occur if the patient is unable to respond during actual needle placement or during injection of the LA solution.

Damage or irritation to neural structures can range from paresthesias during needle placement to nerve damage or paralysis.17 Care should be taken when injecting near the neural foramen, such as during transforaminal epidural injections or when passing the neural foramen during a lumbar sympathetic block or celiac plexus block. The ulnar nerve lies superficial in the medial epicondyle and may be prone to needle injury. Cauda equina injuries or paralysis may occur following the inadvertent injection of hypertonic saline intrathecally during lysis of epidural adhesions.18 Nerve damage or neuritis can occur from “spill over” during the injection of neurolytic substances. Therefore, small amount of phenol or alcohol should be used, except perhaps in the case of a neurolytic celiac plexus block. Finally, improper needle placement during radiofrequency neurolyis can result in neuritis of a specific nerve root.19

Damage to non-neural structures including bowel perforation or renal damage may also occur. These complications can be avoided or minimized by careful, gentle technique and the use of continuous fluoroscopic guidance. Complications associated with specific nerve blocks are discussed throughout the text. For some procedures, there is a small incidence of a specific complication, such as pneumothorax following intercostal blocks or supraclavicular/infraclavicular brachial plexus blocks. The incidence of discitis following provocative discography has been reported at 0.1% to 1.3% per disc.20 The potential always exists for a needle to puncture a blood vessel resulting in bleeding or a hematoma. Hematomas can be seen following stellate ganglion blocks if the carotid artery is punctured. These usually resolve quickly on their own with minimal side effects. A hematoma within the epidual space is a rare occurrence, with potential serious side effects including paraparesis and paraplegia.21 Discontinuing aspirin or other blood thinners, and checking coagulation studies can help avoid this serious complication. In rare instances a stroke can occur due to arterial spasm, particularly in the cervical region. Bowel perforation can occur due to poor technique following lumbar discography, lumbar sympathetic, hypogastric or impars ganglion blocks. The use of fluoroscopic guidance should be considered medically necessary in terms of standard of care and, in addition, for confirming needle placement when injecting a contrast solution.9,22

Local Anesthetic Effects

Local anesthetics can have a toxic effect on the central nervous system and cardiovascular system. A quick rise in LA blood level can result from inadvertent intravascular injection, rapid absorption into the circulation (e.g., intercostal blocks) or simply the use of an excessive amount of LA. Systemic effects of a LA such as lidocaine include lightheadedness or tinnitus at low concentrations (5 to 10 μg/mL plasma concentration) to seizures, respiratory arrest, and coma at higher concentrations (>15 μg/mL plasma concentration). Bupivicaine, another commonly used LA for nerve blocks, is four times more toxic than lidocaine and can result in ventricular arrhythmia and death from ventricular fibrillation. If epinephrine is used in the LA solution, rapid absorption or intravascular injection will result in tachycardia, hypertension, and palpitations. In general, epinephrine should be avoided, especially in patients with cardiovascular disease.

To help guard against any toxic LA effects, always aspirate prior to injection; in addition, a contrast solution can be injected to rule out intravascular needle placement or intravascular catheter migration. The dose of LA should be kept within acceptable limits (see Appendix C).

Physiologic Effects of Regional Anesthesia

Expected side effects include hypotension following sympathetic or epidural anesthesia and sensory loss or motor weakness following specific somatic nerve blocks. Unexpected effects are numerous and detailed throughout the text. Vagal reactions can occur in extremely anxious individuals, sometimes resulting in severe bradycardia or hypotension. These reactions can be quickly treated with intravenous fluids and intravenous or intramuscular ephedrine. Phrenic nerve block commonly occurs following stellate ganglion or interscalene blocks. If shortness of breath occurs in patients after intercostal nerve blocks, any potential pneunothorax should be ruled out. Patients should always be monitored closely and treated early with supportive care or more aggressive resuscitative measures if the need arises.

Head and Neck

Trigeminal Nerve Block

Anatomy

(Fig. 68-1)

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, excluding the angle of the jaw, which is supplied by the second cranial nerve. Trigeminal nerve blocks are used mainly to treat severe pain from trigeminal neuralgia and various malignancies affecting the face.

Gasserian Ganglion

Anatomy

(Fig. 68-2)

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 matter. 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.

Indications

Used for intractable pain from trigeminal neuralgia (tic douloureux) or cancer after conservative treatments have failed. This type of block is recommended when more than one division of the trigeminal nerve is involved. Neurolytic solutions (alcohol, glycerol) and radiofrequency rhizotomy techniques are also used for more permanent blockade or destruction of the nerve.

Complications

The major complication is corneal anesthesia leading to loss of sensation and corneal ulcers. Subarachnoid injection can cause unconsciousness or seizures.

Mandibular Nerve Block

Anatomy

(Fig. 68-3).

The largest of the three divisions is the third division, the mandibular nerve that exits the cranium through the foramen ovale. Below the foramen the mandibular nerve divides into a smaller anterior and larger posterior division. The anterior division innervates the muscles of mastication (lateral pterygoid, temporalis, and masseter muscles). The posterior division is mainly sensory, dividing into the inferior alveolar, lingual, and auricotemporal nerves. The mandibular nerve is both a sensory and motor nerve.

Indications

Trigeminal neuralgia, malignant conditions involving the lower jaw (e.g., Ewing’s sarcoma, osteogenic sarcoma) or cancer of the tongue.

Complications

Neuritis if nerve is traumatized or bleeding into the cheek.

Maxillary Nerve Block

Anatomy

(Fig. 68-4)

After leaving the gasserian ganglion, the maxillary nerve passes along the inferior lateral border of the cavernous sinus. It then exits the middle cranial fossa through the foramen rotundum and enters the pterygopalatine fossa, where it divides into its major branches. The maxillary nerve is a sensory nerve.

Indications

Trigeminal neuralgia, malignancy, or radiation damage to middle third of the face, nasal cavity, and hard palate.

Complications

Bleeding due to highly vascular pterygopalatine fossa. Injections using greater the 1 mL of volume can spread into the orbit and thus affect the oculomotor and abducens nerves, resulting in visual difficulty.

Glossopharyngeal Nerve Block

Anatomy

(Fig. 68-5)

The glossopharyngeal nerve exits the skull through the jugular foramen located posterior to the tip of the mastoid process. The nerve then passes anteriorly between the internal jugular vein and internal carotid artery, coursing medial to the styloid process and lateral to the vagus and spinal accessory nerves. The glossopharyngeal nerve supplies sensation to the posterior one third of the tongue, the palatine tonsils, and pharyngeal wall.

Indications

Glossopharyngeal neuralgia characterized by pain of the throat with possible radiation to the ear and thyroid cartilage area and pharyngeal cancer.

Complications

Dysphagia from paralysis of the pharyngeal muscles and weakness or partial paresis of the tongue. The block should only be performed unilaterally since a bilateral block will produce complete paralysis of the pharyngeal muscles. Weakness in the trapezius muscle can also be seen due to blockade of the spinal accessory nerve.

Occipital Nerve Block

Anatomy

(Fig. 68-6)

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. The lesser occipital nerve arises from the ventral primary ramus to 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.

Indications

Blocking the greater and lesser occipital nerves can be used for diagnostic or therapeutic measures in managing patients with suspected occipital neuralgia or occipital headaches.

Complications

Generally none. Possible seizure if large amount of local anesthetic injected into occipital artery.

Upper Extemity: Shoulder

Brachial Plexus Block

Anatomy

(Fig. 68-7)

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. After dividing into upper, middle, and lower trunks, these nerves enter the axilla between the clavicle and first rib. The trunks then divide into anterior and posterior divisions, which in turn divide into lateral, medial, and posterior cords. Within the axilla, near the lateral border of the axilla, the cords divide into the peripheral nerves of the upper extremity.

• Long thoracic nerve contains fibers from C5, C6, and C7.
• 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.

Indications

There are four approaches to blocking the nerves of the brachial plexus. The interscalene, supraclavicular, and infraclavicular approach will provide anesthesia for the entire arm including the shoulder. The axillary approach can be used for anesthesia between the hand and elbow. Continuous infusions of local anesthetic through a catheter can also be used for prolonged block of the various peripheral nerves of the brachial plexus. Indications for brachial plexus block include:

• Anesthesia for upper extremity surgery
• Postoperative pain relief and rehabilitation
• Differentiate sympathetic pain from peripheral nerve injury
• Manipulation of frozen shoulder or wrist injuries
• Continuous sympathetic nerve blockade to improve blood flow to the affected extremity (i.e., Raynaud’s)
• Phantom limb pain
• Differentiate pain of peripheral neuralgia verses a more central origin (i.e., brachial plexus avulsion).

Complications

For interscalene approach: epidural or intrathecal injection, inadvertent vertebral artery or intravenous injection, and recurrent laryngeal and phrenic nerve block.

For supraclavicular approach: phrenic nerve block, cervical sympathetic block, and 0.5% to 6.0% incidence of pneumothorax.

For axillary approach: intravascular injection with seizure incidence 1.5% and axillary artery damage.

Suprascapular Nerve Block

Anatomy

(Fig 68-8)

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.

Indications

Used to treat arthritis or bursitis of the shoulder joint in addition to intra- and periarticular injections. Diagnostically, to confirm suprascaplular nerve irritation or entrapment.

Side Effects

Paralysis of the supraspinatus and infraspinatus muscles.

Complications

Pneumothorax from the needle being advanced past the upper border of the scapula. Direct nerve injury.

Upper Extremity: Elbow and Wrist

Median Nerve Block

Anatomy

(Fig. 68-9)

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 palmoris longus tendon.

Indications

Used to supplement a brachial plexus block or as diagnostic and therapeutic block and the elbow or wrist (i.e., carpal tunnel).

Technique and Landmarks

Medial and lateral epicondyles of the humerus and medial to the brachial artery.

Complications

Direct nerve injury.

Ulnar Nerve Block

Anatomy

(Fig. 68-10)

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.

Indications

Used to supplement brachial plexus anesthesia or as diagnostic and therapeutic block for ulnar nerve injury such as compression or entrapment neuropathies.

Complications

Direct nerve injury.

Radial Nerve Block

Anatomy

(Fig. 68-11)

The posterior cord (C5 to T1) gives rise to the radial nerve.

Indications

Used to supplement a brachial plexus block or as diagnostic and therapeutic block for radial nerve injury (i.e., humeral fracture).

Complications

Direct nerve injury.

Pelvis

Ilioinguinal and Iliohypogastric

Anatomy

(Fig. 68-12)

The ilioinguinal and iliohypogastric nerves originate from the L1 nerve root. A small contribution from T12 can also exist. The iliohypogastric nerve courses between the transverse and external oblique abdominal musculature. It divides into lateral and anterior cutaneous branches at the level of the iliac crest. The lateral branch provides sensation to the posterolateral gluteal area. The anterior branch sends sensory fibers to the skin of the abdomen around the pubis.

The ilioinguinal nerve is typically smaller. It lies slightly lateral to the iliohypogastric nerve, traversing the internal oblique muscle following the spermatic cord into the inguinal canal. Sensation is provided to the inner thigh, upper part of the scrotum in men and mons pubis and lateral labia in women.

Indications

Inguinal hernia operations and to diagnose and treat postherniorrhapy nerve entrapment.

Technique

Mark 1 in. medial to the anterior superior iliac spine and draw a line between this area and the umbilicus. A 25-gauge 1½—in. needle can be used to inject 8 to 10 mL of local anesthetic solution fanwise in an up and down direction.

Complications

Bleeding if femoral artery or vein is punctured.

Lateral Femoral Cutaneous

Anatomy

(Fig. 68-13)

The lateral femoral cutaneous nerve is formed from the posterior divisions of L2 and L3 within the psoas muscle. It passes into the thigh slightly medial to the anterior superior iliac spine and beneath the inguinal ligament. It provides sensation to the anterolateral thigh and buttock.

Indications

Diagnosis and treatment of meralgia paresthetica.

Technique

Approximately 1 in. medial to the anterior iliac spine and just inferior to the inguinal ligament. A 25-gauge 1½-in. needle is inserted perpendicular to the skin advanced slowly until a paresthesia is obtained. Then 5 mL to 10 mL of local anesthetic solution can be injected.

Complications

Bleeding if femoral artery or vein punctured. Pain at injection site.

Sciatic Nerve Block

Anatomy

(Fig. 68-14)

The sciatic nerve contains most of the sensory and sympathetic fibers of the leg. It is the largest nerve in the body originating from anterior divisions of L4, L5, S1, S2, and S3. This nerve leaves the pelvis through the sciatic notch below the piriforms muscle, then courses between the greater trochanter of the femur and ischial tuberosity. In the thigh it branches to the hamstring and adductor magnus muscles before dividing into the common peroneal and tibial nerves behind the head of the fibula.

Indications

For surgery or manipulation of the leg below the knee. Diagnostic and therapeutic block for sciatic nerve injury (i.e., trauma or hip fracture) piriformis syndrome.

Complications

Hematoma in buttocks or nerve damage.

Femoral Nerve Block

Anatomy

(Fig. 68-15)

The femoral nerve is formed by the dorsal divisions of the anterior rami of the second (L2), third (L3), and fourth (L4) lumbar segments. It emerges from the psoas muscle and is primarily responsible for extension of the thigh. It passes into the thigh underneath the inguinal ligament and just lateral to the femoral artery. The femoral nerve sends branches to the sartorius, quadriceps femoris, and pectinus muscles along with sensory branches to the skin overlying anteromedial thigh. It terminates in the lower leg as the saphenous nerve, which supplies sensation to the skin on the medial aspect of the leg.

Indications

Can be combined with a sciatic nerve block for surgical manipulation of the leg. Diagnosis of femoral nerve damage or entrapment.

Technique

See Appendix A.

Complications

Intravascular injection, or hematoma. Nerve injury.

Lower Extremity: Knee

Common Peroneal Nerve Block

Anatomy

(Fig. 68-16)

The common peroneal and the tibial nerve are the two major peripheral branches of the sciatic nerve. This nerve enters the lower leg behind the head of the fibula, where it then courses laterally around the neck of the fibula before dividing into the deep peroneal and superficial peroneal nerves.

Indications

Generally used in combination with tibial and saphenous nerve blocks for analgesia of the lower leg.

Complications

Injury to nerve adjacent to neck of fibula.

Tibial Nerve Block

Anatomy

(Fig. 68-16)

After branching off from the sciatic nerve, this nerve courses through the popliteal fossa into the lower leg deep between the heads of the gastronemius muscle which it supplies. This nerve becomes superficial at the ankle passing between the medial malleolus and Achilles’ tendon before dividing into the lateral and medial plantar nerves. It supplies sensation to the skin of the heel and medial sole of the foot.

Indications

Supplement inadequate sciatic block for lower extremity interventions.

Complications

Neuritis tibial nerve.

Lower Extremity: Ankle

Tibial Nerve

See previous section for discussion.

Deep Peroneal Nerve Block

Anatomy

(Fig. 68-17).

The common peroneal nerve branches into the deep and superficial peroneal nerves. This nerve enters the foot medial to the tendon of the hallucis longus muscle. It supplies fibers to the tarsal and metatarsal joints and the skin adjacent to first and second toes.

Indications

When combined with a tibial nerve block, almost complete analgesia and sympathetic blockade of the foot is possible.

Complications

Injury to nerve.

Superficial Peroneal and Saphenous Nerve Block

(Fig. 68-18)

Anatomy

After branching from the common peroneal, this nerve travels adjacent to the extensor digitorum longus muscle before dividing into terminal branches just above the ankle. It supplies sensation to the dorsum of the foot and first through fifth toes.

Indications

Usually combined with other nerve blocks around the ankle for surgical anesthesia. Therapeutic interventions on foot or toes.

Complications

None.

Sural Nerve Block

Anatomy

(Fig. 68-19)

The sural nerve branches from the posterior tibial nerve entering the foot between the lateral malleolus and the Achilles’ tendon. It provides sensation to posterior lateral aspect of the lower calf, lateral side of the foot and small toe.

Indications

Operative and therapeutic interventions on the foot and toes.

Complications

None.