HAND BLOCKS/ANATOMY Median Nerve The median nerve provides sensation to the lateral two-thirds of the palm of the hand, palmar surfaces of the lateral three and one-half digits and their finger tips. The palmar branches of the median digital nerves extend dorsally over the digit to supply the dorsum of the thumb, the index, the middle finger and lateral half of the ring finger distal to the interphalangeal joint and including the nail and the nail bed. The median nerve enters the hand through the carpal tunnel, deep to the flexor retinaculum, between the tendons of the flexor digitorum superficialis and the tendon of the flexor carpi radialis. The median nerve sends cutaneous sensory fibers to the entire palmar surface and sides of the thumb, index finger, middle and lateral half of the ring finger, and the dorsum of these digits distal to their proximal interphalangeal joints ( Fig 32-4).
FIG. 32-4. The cutaneous distribution of anesthesia with block of major nerves of the wrist.
Ulnar Nerve The ulnar nerve can be blocked at the elbow or the wrist to provide anesthesia to the medial aspect of the hand and the small finger, including its nail and nail bed. Just proximal to the wrist, the ulnar nerve gives off a palmar cutaneous branch, which passes superficially to the flexor retinaculum and palmar aponeurosis to supply the skin of the ulnar side of the palm (see Fig; 32-4). It also gives off a dorsal cutaneous branch that supplies the ulnar half of the dorsum of the hand, the small finger, and the ulnar half of the ring finger. The ulnar nerve ends by dividing into a superficial and a deep branch. The superficial branch supplies cutaneous fibers to the anterior surfaces of the small finger and the ulnar half of the ring finger. In the small finger, the dorsal digital nerve extends to the tip of the digit. In the median nerve distribution, the volar nerve supplies the dorsum of the digit distal to the proximal interphalangeal joint ( Fig. . . . 32-5).
FIG. 32-5. The dorsal digital nerve extends to the tip of the digit in the small finger. In areas of the median nerve distribution (i.e., the ring finger), the volar nerve supplies the dorsum of the digit distal to the interphalangeal joint.
Radial Nerve The radial nerve provides sensation to the lateral two-thirds of the dorsum of the hand, the proximal aspect of the dorsum of the thumb and index finger and lateral aspect of the dorsum of the middle finger, excluding the nails and nailbeds of these digits. The superficial branch of the radial nerve is the direct continuation of the radial nerve along the anterolateral side of the forearm and is entirely sensory. It pierces the deep fascia near the dorsum of the wrist to supply skin and fascia over the lateral two thirds of the dorsum of the hand, the dorsum of the thumb, and proximal parts of the lateral one and one-half fingers (see Fig.
HAND BLOCKS/TECHNIQUE For lacerations of the hand, regional blocks at the wrist are performed at the level of proximal volar skin crease ( Fig 32.-6.). The median nerve is anesthetized by inserting a 27-gauge needle perpendicular to the skin between the tendons of the palmaris longus and flexor carpi radialis muscles at the midpoint of the distal volar crease. A regional block of the ulnar nerve is accomplished by passing the needle between the ulnar artery and the flexor carpi ulnaris. Once inserted, the needle is moved fanwise transversely until paresthesia is elicited. When paresthesia occurs, the needle is held in place and 5 to 10 mL of 1 percent lidocaine with epinephrine (1:100,000) is injected slowly.
The superficial rami of the radial nerve can be blocked by raising the subcutaneous ring with 5 to 10 mL of 1 percent lidocaine with epinephrine (1:100,000) beginning at the level of the tendon of the extensor carpi radialis and extending around the radial border of the wrist dorsal to the styloid process ( Fig 32-7).
FINGER BLOCKS Digital Nerve Block The digital nerve block provides excellent anesthesia for fingers and toes and has a more rapid onset although it is as painful a block as the metacarpal block. It is commonly used for laceration repair, incision and drainage of paronychia, finger or toenail removal or repair. Preparation with EMLA or Ethyl Chloride can minimize the pain of injection for these blocks. Epinephrine is contraindicated for this block. Contraindications to performing this block are any compromise to the digits' blood supply. Complications are few, however, large volumes of anesthetic can result in a 'compartment' syndrome. Each digit is supplied by a palmar (volar) and dorsal digital nerve on each side of the digit, superficial to the digital arteries ( Fig 3,2-8^).
FIG. 32-8. Digital nerve block. A. Cross section. (From Yaster M et al: Pediatric Pain Management and Sedation Handbook. St. Louis, Mosby, 1997, p 183. Used by permission.) B. Positions for needle (see text).
TECHNIQUE A 27- or 30-gauge needle is inserted through the skin into one side of the extensor tendon of the affected finger just proximal to the web ( Fig,
32-86,1). After aspirating, approximately 1 mL of 1 percent lidocaine or 0.25% bupivacaine is injected superficially into the subcutaneous tissue lying on the dorsal surface of the extensor tendon to block the dorsal digital nerve. The needle is then advanced toward the palm until its tip is palpable beneath the volar skin at the base of the finger, just distal to the web (Fig. 32:8B). After aspirating, another 1 mL of the anesthetic solution is injected to block the volar digital nerve.
Before removing the needle, it is redirected across the extensor tendon to the opposite side of the finger and approximately 1 mL of the anesthetic solution is injected into the tissue overlying the other dorsal digital nerve ( Fig 32-8C). Five minutes later, the needle is reintroduced in the anesthetized skin on the opposite side of the finger and the same technique is repeated (Fig 32-8D). The total volume of the anesthetic agent should not exceed 4 mL. Epinephrine must not be used as an adjunct to lidocaine because it may result in irreversible ischemic injury to the finger.
Metacarpal Block Metacarpal blocks can be used to anesthetize either the index, long, ring, or small finger although digital blocks are preferred. The block is performed on each side of the affected finger by inserting a 27-gauge needle at a 90° angle to the dorsum of hand approximately 1 cm proximal to the metacarpophalangeal joint midway between each metacarpal bone. The needle is then advanced at a 90° angle to the skin until its tip is at the level of the lateral volar surface of the metacarpal head or until resistance of the palmar aponeurosis is detected. After aspirating, 3 mL of 1 percent lidocaine is injected slowly.
ANKLE BLOCKS/ANATOMY These regional nerve blocks are used for anesthesia of surgical procedures of the foot. There are 5 nerves which supply sensation to the foot. Most foot blocks involve a block of at least two nerves. It is unusual in the ED setting to have need to block the whole foot. The sole of the foot is a commonly injured area. Regional nerve blocks are the preferred LA technique. Local infiltration directly into the sole is extremely painful and difficult to perform effectively and is not recommended. Buffered lidocaine 1%, or bupivacaine 0.25% are the LA agents of choice. Epinephrine is contraindicated, and these blocks should not be used in patients with peripheral vascular disease, or traumatic circulatory compromise.
The sensory innervation of the plantar surface of the foot is primarily the two main branches of the tibial nerve (posterior tibial and sural nerves) which lie posteriorly, and a small contribution from the saphenous nerve medially over the arch. The sensory innervation of the dorsum of the foot is predominantly from the two main branches of the common peroneal nerve (the superficial and deep peroneal nerves), with contribution from the sural nerve laterally and the saphenous nerve medially.
The saphenous nerve is the only branch of the femoral nerve below the knee. It becomes subcutaneous at the medial side of the knee joint and then follows the saphenous vein to a site anterior to the medial malleolus. It provides sensory innervation to the skin over the medial malleolus extending to the skin over the medial side of the foot to the base of the great toe.
The superficial peroneal nerve becomes the dorsal digital nerves. It descends toward the ankle in the lateral compartment, entering the ankle just lateral to the extensor digitorum longus, and provides the cutaneous supply to the dorsum of the foot and all five toes, except for the adjacent sides of the first and second toes (deep peroneal nerve) and lateral side of the fifth toe (sural nerve) (see Fjg._ .32-9). It is most commonly located lateral to the extensor digitorum longus at the level of the lateral malleolus superficially. It also supplies the peroneus longus and brevis. The sensory supply of the deep peroneal nerve is limited to the 1 cm area of web space between the first and second toes. Thus, blocks of the deep peroneal nerve are not reasonable or practical to perform.
SOLE OF FOOT BLOCK (SURAL NERVE, POSTERIOR TIBIAL NERVE AND SAPHENOUS NERVE) The three nerves which supply the sole of the foot are the posterior tibial nerve via its medial and lateral plantar branches (medial and lateral sole) and medial calcaneal branch (the heel), the sural nerve (posterolateral sole) and the saphenous nerve (small area, medially over the arch) ( Fig . 32-9).
The posterior tibial nerve is located along the medial aspect of the ankle, lying between the medial malleolus and the Achilles tendon, just posterior and slightly deeper than the posterior tibial artery ( Fig 3.2:10) and gives off the three terminal branches, medial calcaneal branch, and medial and lateral plantar nerves. The sural nerve travels with the short saphenous vein (Fig 32:10), posterior and inferior to the lateral malleolus, it terminates as the dorsal lateral cutaneous nerve. The saphenous nerve follows the great saphenous vein to the medial malleolus.
FIG. 32-10. Posterior view of the left foot demonstrating the sites for tibial and sural nerve blocks.
Technique This block is best performed with the patient in the prone position. The posterior tibial nerve is blocked as it passes posterior to the medial malleolus, the tibial artery is palpated just posterior to the medial malleolus ( Fig 32:10). Buffered lidocaine 1% (or bupivacaine 0.25%) is injected with a 30-gauge needle lateral to the tibial artery and just anterior to the medial border of the Achilles tendon, at the level of the upper border of the medial malleolus. A syringe with a 25-gauge needle is then introduced at 90° to the skin, just lateral and posterior to the tibial artery ( Fig... 32:10). Once paresthesia is elicited and after careful aspiration to ensure no inadvertent intravascular access, 3 to 5 mLs of LA is injected. If no paresthesia is encountered, then 5 to 7 mLs of LA should be injected as the needle is withdrawn. Onset of anesthesia should occur within about 5 to 10 minutes if paresthesia has been elicited and in about 30 minutes if it is not elicited. The sural nerve is blocked between the lateral malleolus and the Achilles tendon (Fig 32-10). It is superficial, lying just anterior to the short saphenous vein. Buffered lidocaine 1% (or bupivacaine 0.25%) is injected with a 30-gauge needle just lateral to the Achilles tendon 1 cm above the lateral malleolus. A 25-gauge needle is then introduced into this area and 3 to 5 mLs of LA is injected subcutaneously as the needle is withdrawn. The saphenous nerve lies superficially between the medial malleolus and the anterior tibial tendon (Fig 32-11) and is blocked anteriorly by infiltration of 3 to 5 mLs of LA between these landmarks as the needle is withdrawn.
FIG. 32-11. Deep peroneal, saphenous, and superficial peroneal nerve blocks.
DORSUM OF FOOT BLOCK Regional block of the dorsum of the foot has fewer ED applications than blocks for the sole of the foot, as direct infiltration of the dorsum is more easily performed. The sensory innervation of the dorsum of the foot is primarily supplied by the superficial peroneal nerve, with contribution from the deep peroneal nerve over the first web space, the sural nerve laterally extending to the lateral malleolus, and the saphenous nerve medially over the arch and the medial malleolus (Fig 32-11).
TECHNIQUE This block is best performed with the patient in the supine position. With a 30-gauge needle a small wheal of LA is raised just above the level of the talocrural joint in the midline anteriorly, between the extensor digitorum longus and the extensor hallucis longus. The superficial peroneal nerve is then blocked by infiltration of 5 mLs of buffered lidocaine 1% (or bupivacaine 0.25%) in a large wheal extending from this point just superior to the talocrural joint at the anterior border of the tibia to the lateral malleolus (Fig 3.2.-1.1). The deep peroneal nerve can be blocked by infiltrating 5 mLs of buffered lidocaine 1% (or bupivacaine 0.25%)
between the tendons of the tibialis anterior and the extensor hallucis longus also just above the talocrural joint. However, the area supplied by the deep peroneal nerve is so small a digital block or local infiltration would achieve the same effect. Saphenous and sural nerves are described above.
TOE BLOCKS Digital nerve blocks of the toe are used for laceration repair and minor surgical procedures of the toe. Epinephrine must not be used as an adjunct to lidocaine because it may result in irreversible ischemic injury. A 27- or 30-gauge needle should be introduced through the skin on the dorsal aspect of the base of the midpoint of the involved toe (Fig 32.-12). The needle should be angled around the bone until it induces blanching of the skin on the plantar surface. As the needle is withdrawn, approximately 1.5 mL of 1% lidocaine is injected. Before the needle is withdrawn completely from the skin, it should be redirected to the opposite side of the injured toe to inject the local anesthetic agent in a similar manner. The total volume of the injected local anesthetic agent should not exceed 3 mL.
For the hallux (great toe), a modified collar (ring) block is used (see Fig 32-12). The 27-gauge needle is inserted through the skin on the dorsolateral aspect of the base of the toe until it blanches the plantar skin. As the needle is withdrawn, 1.5 mL of 1% lidocaine is injected into the tissues. Before the needle is removed completely from the skin, the needle is passed under the skin on the dorsal aspect of the toe and 1.5 mL of 1% lidocaine is injected as the needle is withdrawn from the skin. The needle is then introduced through the anesthetized skin on the dorsomedial aspect of the toe and advanced until it produces blanching of the plantar skin, at which time the needle is withdrawn and 1.5 mL of 1% lidocaine is injected. Usually, approximately 4.5 mL of 1% lidocaine is needed to anesthetize the hallux.
FACIAL AND ORAL BLOCKS Facial blocks are ideal anesthesia techniques for commonly injured areas such as the forehead, chin, lips, nose, tongue and ear, where local infiltration is often either not possible, extremely painful or results in tissue distortion or potential tissue necrosis. These blocks, as for foot blocks, often require blockade of more than one nerve to provide for adequate regional anesthesia. For all intraoral routes of infiltration, a small amount of 2% viscous lidocaine should be applied to the mucosa prior to injection. For percutaneous routes of infiltration, topical EMLA cream or refrigerant sprays should be applied prior to injection.
Forehead (Trigeminal Nerve, Ophthalmic Branch, Frontal and Supratrochlear Nerves) The sensory innervation of the forehead (anterior aspect from eyebrows extending posteriorly to the lambdoid suture) is supplied by the lateral and medial branches of the frontal (or supraorbital) nerve and the supratrochlear nerve, branches of the ophthalmic branch of the trigeminal nerve ( Fig 32-13). Regional nerve block can be easily achieved by infiltration of 3 to 6 mLs of lidocaine 1% (or bupivacaine 0.25%) with a 27-gauge needle into the skin immediately above the full length of the eyebrow.
FIG. 32-13. Regional blocks of (1) the lateral branch of the frontal nerve, (2) the medial branch of the frontal nerve, and (3) the supratrochlear nerve. Infiltration anesthesia is an alternative approach to anesthetizing lacerations of the forehead.
Lower Lip, Chin (Trigeminal Nerve, Mandibular Branch, Inferior Alveolar and Mental Nerve) Direct infiltration to the lip is very painful and causes tissue distortion which can interfere with the quality of the repair of lacerations. The skin of the chin and lower lip are supplied by the mental nerve (branch of the inferior alveolar nerve). A block of the inferior alveolar nerve as it enters the mandibular foramen, medial and just below the anterior border of the ramus of the mandible is performed by the intraoral route (Fig 32:14). Regional block of the mental nerve can be performed by an intraoral ( Fig 32-15) or extraoral route. The mental foramen is located at the mucosal reflection of the lower lip and the lower gum, just posterior to the first premolar tooth.
TECHNIQUE The landmarks for the inferior alveolar nerve block are the inferior aspect of the vertical ridge of the anterior border of the ramus of the mandible (oblique line), and the oral mucosa 1 cm above the occlusal surface of the third molar tooth. After the mucosal injection site is anesthetized, the oblique line is identified by palpation. A 27-guage needle is inserted just medial to this ridge and 1 cm above the third molar tooth, and slowly advanced along the medial side of the ramus of the mandible to a depth of 2 cm, keeping the syringe in parallel position with the body of the mandible and the occlusal surfaces of the teeth of the lower jaw. While the needle remains in proximity to the medial aspect of the ramus of the mandible, 2 to 4 mLs of lidocaine 1% (with or without epinephrine) is infiltrated after the syringe is rotated over to the premolar region of the opposite side of the mandible, maintaining the same horizontal plane.
For the oral approach to the mental nerve the lip is retracted with the thumb and index finger (see Fig 32-15). A 27-gauge needle is inserted at the mucosal junction of the lower lip and gum near the mental foramen. 2 ml of lidocaine 1% with epinephrine (1:100,000) is infiltrated taking care that the needle is not introduced into the mental foramen to avoid neural injury. Similarly for the extraoral approach, identification of landmarks, and percutaneous infiltration of 2 mL of LA close to the mental foramen.
Tongue (Trigeminal Nerve, Mandibular Branch, Lingual Nerve) Direct infiltration into the sensate and moving of the tongue is very painful and poorly effective, and a regional block is preferred. The lingual nerve provides sensory innervation to the anterior two-thirds of the tongue, the floor of the mouth and gums. It lies in close proximity to the inferior alveolar nerve at the entrance to the mandibular foramen. The lingual nerve can be blocked by the intraoral route similarly to the inferior alveolar nerve (Fig 32:14).
TECHNIQUE From an intraoral approach the vertical ridge of anterior border of the ramus of the mandible is identified by palpation with the index finger ( Fig 32.-1.5).
After the mucosal injection site is anesthetized topically, the procedure for an inferior alveolar nerve block (same as above) is followed. Infiltration of the LA as the needle is withdrawn will anesthetize the lingual nerve. Alternatively the lingual nerve can be anesthetized by injecting 2 to 3 mLs of LA into the lateral floor of the mouth adjacent to the premolar teeth.
Cheek, Lower Eyelid, Upper Lip and Lateral Aspect of Nose (Trigeminal Nerve, Maxillary Branch, Infraorbital Nerve) The infraorbital nerve supplies sensory innervation to the cheek, lower eyelid, upper lip and lateral aspect of the side of the nose. A regional block of the infraorbital nerve can be performed by an intraoral approach (Fig 32-16,) or extraoral transcutaneous approach. The duration of action is more prolonged with the intraoral approach.
TECHNIQUE To identify the infraorbital foramen, the midpoint of the lower margin of the orbit is palpated, approximately 1 cm inferior to this point the infraorbital nerve exits the infraorbital foramen. For the intraoral approach, a palpating finger is positioned over the infraorbital foramen ( Fig..32-16). The cheek is retracted cephalad with the thumb and index finger and a 27-gauge needle with syringe, held in the other hand directed through the mucosa at the reflection of the upper gum opposite and parallel to the long axis of the upper premolar tooth. The needle is then advanced until it is palpated near the infraorbital foramen, approximately a depth of 2.5 cm. Use caution not to introduce the needle directly into the infraorbital foramen to avoid neural injury and subsequent numbness of the cheek, also use caution not to direct the needle too far superiorly or posteriorly to avoid inadverntently entering the orbit. Aspirate to ensure facial artery and vein are avoided. Instil 2 to 3 mLs of lidocaine 1% (or bupivacaine 0.25%) adjacent to the foramen. The extraoral approach uses the same landmarks for identification of the infraorbital foramen, but with a percutaneous approach. Epinephrine is best avoided due to the proximity of the facial artery.
Nose (Trigeminal Nerve, Ophthalmic Branch, Infratrochlear and External Nasal Nerves; Maxillary Branch, Infraorbital Nerve, Posterior Nasal and Nasopalatine Nerves) The sensory supply of the nose is supplied by both the ophthalmic and maxillary branches of the trigeminal nerve. It is important to note that block of the infraorbital nerve alone will not provide adequate anesthesia of the nose. The mucosal surface of the nose can be anesthetized by topical application of LA spray or gel. The ophthalmic branch of the trigeminal nerve (infratrochlear and external nasal nerves) provides sensation to the majority of the external nose in the midline. These nerves can be blocked by percutaneous infiltration of LA at the sites of their emergence from bony foraminae. The remaining aspects of the nose are supplied by the maxillary branch of the trigeminal nerve, the infraorbital nerve for the lateral aspect (see above for intraoral and extraoral block technique) and the posterior nasal and nasopalatine nerves for the septum and inferior midline. The posterior nasal and nasopalatine nerves are best approached intraorally in the midline from the mucosal surface of the reflection of the upper lip.
Ear (Trigeminal Nerve, Mandibular Branch, Auriculotemporal Nerve; Cervical Plexus C2 and C3; Greater Auricular Nerve and Mastoid Branch of Lesser Occipital Nerve) The sensory innervation to the external ear is supplied anteriorly by the auriculotemporal nerve (mandibular branch of the trigeminal nerve), and posteriorly by the greater auricular nerve and the mastoid branch of the lesser occipital nerve (branches of the cervical plexus). Direct infiltration of the pinna should be avoided due to the risk of tissue necrosis. Regional block of the ear is achieved by infiltration of lidocaine 1% (or bupivacaine 0.25%) via a 27- or 30-gauge needle at the base of the ear from an inferior and superior direction both anteriorly and posteriorly ( Fig 3.2,-1.7.and Fig 3,2,-,1,,,7B)
FIG. 32-17. A. Sensory nerve supply of the auricle. B. Technique of regional anesthesia of the auricle.
FEMORAL NERVE BLOCK Femoral nerve block is an effective technique for relieving pain of a femoral shaft fracture and is useful in the multitrauma patient when minimizing narcotics is important. The femoral nerve is lateral to the femoral artery at the inguinal ligament and innervates the anterior thigh, the periosteum of the femur, and the knee joint (Fig 32-.18).
FIG. 32-18. A. Regional block of the femoral nerve. (Adapted from Nichols DG et al: Golden Hour: The Handbook of Advanced Pediatric Life Support, 2d ed. St. Louis, Mosby Yearbook, 1996, p 335. Used by permission.) B. Sensory innervation of the skin and femur by the femoral nerve is depicted in the shaded area. (From Yaster M et al: Pediatric Pain Management and Sedation Handbook. St. Louis, Mosby, 1997, p 176. Used by permission.)
Technique Bupivacaine, 0.5 mL/kg (maximum 1 mL/kg, or 25 mL) of a 0.25 percent solution, is suggested as the preferred LA agent because of its longer duration of action. The usual adult dose is 10 to 20 mL. A sterile field is prepared over and surrounding the femoral triangle. The femoral artery is located midway between the anterior superior iliac crest and the pubic tubercle. The femoral artery is compressed 1 to 2 cm below the inguinal ligament with the nondominant hand. A weal of local anesthetic is raised in the skin and subcutaneous tissues lateral to the artery; the needle is then introduced 60° to the skin lateral and parallel to the femoral artery. A double loss of resistance or "pop" is felt as the needle traverses the fascia overlying the femoral nerve. Onset of anesthesia is 10 to 20 min, and the duration is 3 to 8 h.
INTERCOSTAL BLOCK Intercostal block is valuable for the management of pain after chest trauma (typically rib fracture) or discomfort from a chest tube. It is a simple block; however, caution should be exercised due to the rapid and high systemic absorption of local anesthetic at this site. Contraindications are local soft tissue disease and contralateral pneumothorax. Complications include pneumothorax and systemic toxicity. The intercostal nerves run anteriorly within the neurovascular bundle along the inferior portion of the rib. Addition of epinephrine enhances the safety of this block. The dosage range for an adult is 3 to 5 mL per segment (child, 1 to 3 mL) 1% lidocaine or 0.25% bupivacaine. To perform this procedure, the landmarks are the palpable intercostal spaces and the midaxillary line. The intercostal space is identified by palpation. On the upper margin of this space the inferior border of the upper rib is palpated. At the mid or posterior axillary line the needle is inserted and advanced at a 90° angle until the rib is reached. The needle is withdrawn slightly and redirected caudally to the inferior aspect of this upper rib (Fig 32:19).
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FIG. 32-19. Intercostal nerve block. (From Nichols DG et al: Golden Hour: The Handbook of Advanced Pediatric Life Support, 2d ed. St. Louis, Mosby Yearbook, 1996, p 336. Used by permission.)
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