Peripheral Nerve Blocks for Children
Contents
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HEAD & NECK BLOCKS
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TRUNK BLOCKS
The use of peripheral nerve blocks has been regaining significant popularity in the daily practice of most anesthesiologists. Despite the trend towards increase in the use of regional anesthesia and nerve blocks in adults, peripheral nerve blocks in children remain underutilized. Common reasons include the concern of neurologic complications and the lack of technical skills required for successful use of peripheral nerve blocks. Although performance of PNBs in anesthetized adults is often debated, such practice is well accepted in pediatric patients. A large prospective database collected in France demonstrated no increased incidence of complications when regional anesthesia, particularly when peripheral nerve blocks were performed under general anesthesia.1 The incidence of regional anesthesia related complications in one study was less than 0.9/1000 anesthetic procedures performed. When used with skill, the success and complications of performance of peripheral nerve blocks in children should not be significantly different from those in the adults. In addition, the equipment used for PNBs in children is similar to that used in adults (see Chapter 17). Although most peripheral nerve blocks are performed in an operating room environment, the use of regional anesthesia in children extends to an emergency department 2 as well as in an intensive care unit setting.3;4 The key to success of peripheral nerve blockade in children is the proper knowledge of the anatomy, pharmacology, equipment used for regional anesthesia and effective use of pre-procedure sedation and analgesia.
The use of a reliable nerve stimulator is required to locate motor nerves for blockade. A nerve stimulator with adequate current output capable of eliciting percutaneous stimulation (e.g., 5 mA/1msec) for surface mapping is suggested.
Clinical pearls
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The use of muscle relaxants should be avoided when using a nerve stimulator for motor blockade.
It is crucial to remember that when using a nerve stimulator for motor blockade, the use of muscle relaxants should be avoided and either a deep inhalation induction with placement of an endotracheal tube under general anesthesia or the use of a laryngeal mask airway is preferred. Occasionally, it may be feasible to perform a nerve block in an older child with IV sedation without the use of general anesthesia. The negative electrode is attached to the needle (black to block) and the positive is attached to the patient (positive to patient). Once a needle is placed close to a nerve or a plexus and proper stimulation is obtained, the current output is decrease to maintain the motor response at 0.4-0.2 mA to assure intimate needle-nerve relationship. Objective monitoring of the injection pressures during injection of local anesthetic to decrease the risk of intraneural injection may offset some of the concerns about the use of regional anesthesia in patients under general anesthesia.5
Due to the concomitant use of general anesthesia in children, the intraoperative efficacy of nerve blocks is often assessed indirectly using hemodynamic parameters and the required depth of anesthesia. Most regional techniques used in children are primarily used for the purpose of providing postoperative pain control rather than surgical anesthesia. Peripheral nerve blocks are also utilized in children for chronic painful conditions such as chronic headaches or CRPS.1
The
section "A" of this chapter describes the use of local anesthetic
solution in greater detail. It is imperative however, to remember that
the dosage of local anesthetic solutions should be based on a mg/kg
basis and not based on total volume utilized as is the practice in
adult regional anesthesia. Sensory blocks including head and neck
blocks require very small volumes of local anesthetic solution. The
dosage should be adjusted downwards in infants and neonates due to the
decrease in protein binding and α-1 acid glycoprotein allowing a
greater amount of the free fraction of the drug in the systemic
circulation. The addition of epinephrine to the local anesthetic
solution may offer an additional advantage by (i) revealing
intravascular placement particularly in the child under general
anesthesia.6 and (ii) by prolonging local anesthetic action when used
for peripheral nerve blockade.
The addition of sodium bicarbonate may offer the advantage of
decreasing pain on injection and potentially facilitate a more rapid
onset of local anesthetic action.7 The addition of other additives
including clonidine and fentanyl has also been explored in the
pediatric population. Clonidine may be effective in prolonging the
analgesic effects of local anesthetic solutions.8-10 However, caution
has to be exercised to avoid clonidine in infants and neonates due to
the higher incidence of hypotension and excessive sedation in this
population. Other local anesthetic solutions including
ropivacaine11,12 and levobupivacaine13 are effective for providing
adequate analgesia when used for peripheral nerve blocks.
CLINICAL PEARLS
Maximum dose of local anesthetics
The maximum dose of bupivacaine is 2.5 mg/kg plain and 3.5 mg/kg with epinephrine. The duration of bupivacaine varies from 2-16 hours, depending on the application.
The maximum dose of 2-chloroprocaine is 8 mg/kg plain and 10 mg/kg with epinephrine. The duration of chloroprocaine is 1-1.5 hrs
The maximum dose of lidocaine is 5 mg/kg plain and 10 mg/kg with epinephrine. The duration of lidocaine is 2-3 hrs.
Volume of local anesthetic for common blocks
Axillary block – 0.2-0.6 mL/kg
Interscalene block – 0.33 mL/kg
Femoral block – 0.5 mL/kg
Sciatic block – 0.15-0.2 mL/kg
The most common method for nerve localization is using a stimulating needle (sheathed needle) with the needle pointed in the direction of the nerve. Due to the need for identifying the location of the nerve prior to puncture, pediatric patients benefit from the use of surface stimulation or surface mapping.14 This allows approximation of the site for needle insertion and decrease the need for multiple needle insertion during nerve localization. Surface mapping can be used to facilitate a variety of superficial nerve block procedures such as axillary, radial, median and ulnar nerve blocks at the axilla and the elbow, as well as for femoral and popliteal fossa blocks. Higher current amperage and/or current duration is required (usually about 5 mAmps/1 msec) in order to percutaneously stimulate. A relative moist surface either using alcohol swabs or lubricating jelly allows for better contact of the negative electrode.
Ultrasonography has been introduced into anesthesia practice for over a decade. In the recent years however, the interest for the use of this technology to aid in nerve localization has significantly increased.15-17 Although ultrasound may be useful for nerve localization, one of the main benefits is to provide visualization of the dispersion of the local anesthetic within the desired tissue plains. Ultrasound has been shown to provide adequate landmarks for determining the location of nerves in children along with a discriminatory approach to evaluating nerve location and anatomical variations in infants and children.18 This technology however, requires a significant training and skill for its successful implementation. At the time of the publication of this text there are relatively few practitioners who are adequately skilled and comfortable with the use of ultrasound in children for peripheral nerve blockade. The reader is referred to the Chapter 52 for detailed discussion on this topic.
Sedation prior to performance of peripheral nerve blocks in children is imperative for successful use of nerve blocks. While the performance of regional anesthesia and peripheral nerve blocks in adults is often debated, heavy sedation or general anesthesia prior to administration of nerve blocks in children is a standard and accepted practice. The collective opinion of pediatric anesthesiologists has been highlighted in an editorial which encourages the need to continue to perform regional techniques in children under general anesthesia.19
Peripheral nerve block in children can be topographically divided to cover all areas of the body. (Table-1) A short description of the anatomy followed by the technique for performance of nerve blocks will be described in this chapter.
HEAD & NECK BLOCKS
The use of nerve blocks for various head and neck procedures is gaining popularity, particularly in the pediatric population. Most of these blocks are sensory nerve blocks which are easy to administer (field blocks) and virtually devoid of complications. They can however provide quality analgesia in the postoperative period, facilitating immediate postoperative recovery and pain management. Most of the innervation for the face and scalp are derived from the trigeminal nerve (Cranial V) and the cervical plexus (C2-C4).
The supraorbital and supratrochlear nerves are branches of the 1st division of the trigeminal nerve that exit from the supraorbital foramen. The supraorbital nerve provides sensory innervation to the anterior portion of the scalp except for the midportion of the forehead which is innervated by the supratrochlear nerve. This block can be utilized for frontal craniotomies20 as well as for minor surgical procedures including excision of scalp nevus.21
Technique
The supraorbital nerve can be easily blocked as it exits from the supraorbital foramen. This can be easily correlated in the patient to the midpoint of the pupil, FIGURE 1. Once the foramen is located, a subcutaneous injection of local anesthetic solution (1-2mL of 0.25% bupivacaine with 1:200,000 epinephrine) is injected. Once the local anesthetic solution is injected, gentle pressure is maintained to decrease the formation of a hematoma. Complications are rare with this block.
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Figure 1. Supraorbital nerve block. The supraorbital foramen is located and a local anesthetic (1-2mL of 0.25% bupivacaine with 1:200,000 epinephrine) is injected subcutaneously. |
The 2nd division of the trigeminal nerve is also referred to as the maxillary division of the trigeminal nerve. It exits from the
maxillary foramen or the infraorbital foramen which is located about 2 cm from the midline and is usually aligned with the midpoint of the pupils. The nerve provides the sensory supply to the upper lip, the choana, maxillary sinus, part of the nasal septum and the tip of the nose. This block can be used to provide analgesia for cleft lip surgery22, nasal septal repair23 and endoscopic sinus surgery.24-26
Technique
There are two approaches to the maxillary division of the trigeminal nerve.
Extraoral route: The needle is directed into the infraorbital foramen from an external location of the nerve. The foramen is located externally and a 27-G needle is inserted into the foramen. After aspiration to rule out intravascular injection, 1 to 2 mL of local anesthetic solution is injected.
Intraoral route: The nerve is accessed through the sub-sulcal area in the buccal mucosa, FIGURE 2. This is our preferred modality for blocking the infraorbital nerve. The upper incisor or the second bicuspid on the side to be blocked is located; a needle is passed through a sub-sulcal route towards the location of the infraorbital foramen. After careful aspiration, local anesthetic solution is injected. For infants scheduled for cleft lip repairs, we use 0.5mL of local anesthetic solution for each side, for older children and adolescents; we use 1.5 mL to 2 mL of local anesthetic solution. The upper lip is likely to remain numb for several hours after the block and can be disconcerting to patients and older children. Care should also be provided to prevent biting of the upper lip during the emergence period from anesthesia.
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Figure 2. Infraorbital nerve block. A needle is passed through a sub-sulcal route towards the location of the infraorbital foramen. For infants undergoing cleft lip repair, 0.5-1mL of local anesthetic solution is injected on each side. |
The mandibular division of the trigeminal nerve provides analgesia for the lower jaw, lower lip and portions of the tempo-parietal portions of the scalp. The most common nerve targeted in children is the mental nerve which exits from the mental foramen which is located at the level of the midline in line with the pupil and the supraorbital and infraorbital foramen.
Technique
An intraoral route is again preferred for placement of this nerve block. The needle is directed at the level of the lower incisor towards the infraorbital foramen; 1.5 mL of local anesthetic solution is injected after careful aspiration. Gentle massage of the area is carried out after the injection.The greater occipital nerve is a branch of cervical root C2. The nerve pierces the aponeurosis and traverses medial to the occipital artery inferiorly and crosses over to the lateral aspect of the artery superiorly by the nuchal line as it innervates the posterior portions of the scalp. This can be used for providing an adequate nerve block of the scalp for posterior fossa craniotomies as well as for patients with chronic occipital neuralgia.20
Technique
The occipital protuberance is palpated. The midline is identified and the occipital artery is palpated. A 27-G needle is inserted and a subcutaneous injection of local anesthetic solution is performed. (1.5 to 2 mL of 0.25% bupivacaine with 1:200,000 epinephrine). The area is massaged gently after the injection. Complications are rare with this technique.Superficial Cervical Plexus Block
This is a pure sensory nerve which is derived from C2-C4 nerve roots. The superficial cervical plexus wraps around the belly of the sternocleidomastoid at the level of the cricoid and divides into 4 different branches, the lesser occipital supplying the posterior auricular area; the great auricular supplying the mastoid area and the pinna; transverse cervical supplying the anterior portion of the neck; and the superficial cervical supplying the skin over the shoulder in a cape like distribution over the shoulder joint. Blockade of the superficial cervical plexus can provide good postoperative analgesia for tympano-mastoid surgery27, otoplasty28, thyroid surgery29, and for procedures performed on the anterior portion of the neck.30 The use of this nerve block decreases the use of opioids in the perioperative period thereby decreasing the incidence of nausea and vomiting.27
Technique
The technique is essentially identical to that in the adult patient. The clavicular head of the stenocleidomastoid is identified. A line drawn from the cricoid cartilage to intersect the posterior border of the tenocleidomastoid is identified. A subcutaneous injection of local anesthetic solution (1to 2 mL of 0.25% bupivacaine with epinephrine 1:200,000) is performed. Caution has to be exercised while injecting due to the close proximity of the nerve to the external jugular vein. Deep injections should be avoided to prevent the potential injection into the deep cervical plexus with associated adverse effects including recurrent laryngeal nerve paralysis, paralysis of the hemi-diaphragm and Horner’s syndrome from unilateral sympathetic ganglion blockade. Complications, although rare are related to deep cervical plexus blockade and intravascular injection. The reader is referred to Chapter 23 for more for detail description of the technique.
A complete review of the anatomy of the brachial plexus is provided in Chapters 3 and 25. There are multiple approaches to the brachial plexus in children. Although the interscalene block is often used in adults for most surgical procedures of the shoulder, this approach is used infrequently in children. This is due to the increased incidence of complications associated with the use of the interscalene approach, particularly in children who are under general anesthesia.25. The most common approach to the brachial plexus in children include the parascalene approach, the infraclavicular approach and the axillary approach.
Local anesthetic dose for upper extremity blocks
Local anesthetic dosing for upper extremity peripheral nerve blockade is based on weight. Children younger than five to eight years old should receive 0.3-0.5 milliliters per kilogram (mL/kg) of bupivacaine 0.25% or ropivacaine 0.2%. Older children may require larger concentrations such as 0.3-0.5 mL/kg of bupivacaine 0.5% or ropivacaine 0.5%. Epinephrine 1:200,000 should be added for detection of inadvertent intravascular injection.(1) For continuous infusion through a peripheral nerve block catheter, the suggested dose of local anesthetic is 0.2 milligrams per kilogram per hour (mg/kg/h) of ropivacaine 0.1% or levobupivacaine 0.125% in newborns or infants and 0.3-0.4 mg/kg/h of ropivacaine 0.1% or levobupivacaine 0.125% in older children.(2) The maximum dose of ropivacaine for continuous central infusion is 0.4 mg/kg/h and care should be taken to ensure that the child does not receive more than this amount.
This is an approach that has been used extensively in children.31 This gives the operator the flexibility to approach the plexus without less risk of complications noted with the conventional interscalene approach to the brachial plexus. The roots and the trunks of the brachial plexus are blocked in this position and hence it provides good postoperative analgesia for surgery performed on the shoulder, hand and arm. Landmarks are the posterior border of the sterno-cleidomastoid muscle, the midpoint of the clavicle and the cricoid cartilage, C6. An imaginary line is drawn between the Chassignaic’s tubercle and the midpoint of the clavicle. The needle is inserted perpendicularly at the junction of the upper 2/3rd and lower 1/3rd of this imaginary line and directed in the antero-posterior plane until twitches are obtained. 0.2mL/kg to a maximum of 10 mL local anesthetic solution is injected after careful aspiration.
Complications
Intravascular injection, intraneural injection and consequent brachial plexus injury.The infraclavicular approach allows an easy approach to the block of the brachial plexus and it is suitable for placement of a catheter for continuous plexus anesthesia.
Technique
Classic approach: The midpoint of the clavicle is determined. The axillary artery is palpated in the axilla. Alternatively, ultrasound can be used to localize the plexus, FIGURE 3. A stimulating needle is directed from the midpoint of the clavicle to towards the axillary artery at an angle of 45 degrees to the skin. An initial stimulation of the pectoralis muscle is noted and as the needle approaches the brachial plexus, the flexion or extension of the wrist and elbow are noted. The current is decreased to 0.2 to 0.3 mA and if a twitch response is still present, after careful aspiration, 0.2 mL of local anesthetic solution to a maximum of 15 mL is injected. This approach is also uniquely suitable for insertion of a catheter and administration of continuous brachial plexus block. The catheter is inserted 3-4 cm beyond the tip of the needle (Figure 4) and secured to the anterior chest wall, FIGURE 5.
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Figure 3. Infraclavicular block. Shown is localization of the plexus using ultrasound-guided technique. |
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Figure 4. Infraclavicular block. Insertion of the catheter. |
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Figure 5. Infraclavicular block. The catheter is secured to the anterior chest wall. |
Complications
Although rare, the cupola of the lung is in close proximity to the passage of the needle. Hence caution has to be exerted while placing the needle. Intravascular injection is a complication that is potential due to the close proximity of the subclavian vessels.Axillary approach to the brachial plexus
The axillary approach to the brachial plexus is the most commonly used approach in children and adolescents. It is used for procedures on the arm and the hand. The primary advantage of the axillary approach is the ease of placement and the relatively lower risk of complications. However, there is a 40–50% potential of missing the musculocutaneous nerve with this approach due to the proximal exit of this nerve from the axillary sheath. Hence while performing a block using this approach, the musculocutaneous nerve should be blocked separately when analgesia of the biceps and anterior forearm is sought.
Technique
There are several techniques for placing the axillary block. The commonly used approaches include (i) trans-arterial approach; (ii) nerve stimulation approach. Although reports of greater success with the trans-arterial approach is seen in adults33, this approach is not often used in children. This is due to the higher incidence of vessel spasm and potential for ischemia in children as opposed to adults. Surface mapping can be used to approximate the location of the plexus or nerve of interest (FIGURE 6) .14 More recently, ultrasonography has been used for identifying the nerves in the axillary sheath.34 Although multiple methods have been reported in adults, the simple common method of using a single injection technique seems to be very effective in children.35 The patient is positioned with the arm abducted 90 degrees. The elbow is flexed and the arm is placed above the head. After surface mapping to locate the position of the nerve, a stimulating needle is inserted superior to the axillary artery at an angle of 30 degrees with the tip pointed towards the midpoint of the clavicle, FIGURE 7. A ‘pop’ may be felt as the needle enters the axillary sheath. After eliciting the response to nerve stimulation at 0.4 mA, local anesthetic solution is injected. A volume of 0.2 to 0.4mL/kg is recommended up to a maximum of 20 mL. When the musculocutaneous nerve and hence to augment its block, the needle is directed above the pulse of the axillary artery and toward the belly of the corocobrachialis muscle. Contraction of the biceps confirms placement of the needle close to the musculocutaneous nerve.
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Figure 6. Axillary brachial plexus localization using surface stimulation. |
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Figure 7. Axillary brachial plexus block. Once the brachial plexus is approximated using surface stimulation, nerve stimulator technique is used to accomplish blockade. |
Complications
Complications from axillary nerve block are uncommon. If the axillary artery is punctured, a hematoma could form. This can be prevented by applying pressure for about 5 minutes after puncture of the vessel.Digital nerve blocks are provided for analgesia of the fingers and toes. It is an ideal block for provision of analgesia for simple procedures like trigger finger release, ingrown toenail excisions as well as for foreign body removal and minor lacerations requiring suturing. We have used them successfully for blocking pain following laser therapy for warts in children.51 This technique is addressed in Chapter 30.
HandAnatomy
The common digital nerves of the hand are derived from the median and ulnar nerves and divide in the palm to supply the fingers. All digital nerves are always accompanied by digital vessels. The median nerve provides three digital nerves. The first divides into the three palmar digital nerves that supply the side of the thumb; the second common digital nerve supplies the web space between the index and middle finger and the third common palmar digital nerve communicates with the ulnar nerve to supply the web space between the middle and ring finger. These then become the proper digital nerves that supplies the skin of the distal phalynx. There are smaller digital nerves derived from the radial and ulnar nerve that supply the dorsum of the fingers. The four dorsal digital nerves are located on the ulnar side of the thumb, the radial side of the index finger, adjacent to the index and middle fingers. All digital nerves terminate in two main branches (i) supplying the skin under the finger tips and (ii) supplying the pulp under the nail.Technique
The digital nerves are blocked using non-epinephrine containing solution on each side of the finger at the bifurcation between the metacarpal heads. A dorsal or volar injection will accomplish similar results. A needle is inserted into the webspace between the thumb and the index finger to a distance of about 1 cm. A second needle is inserted into the thenar eminence on the radial aspect of the thumb. For the other fingers, the needle is inserted between the metacarpal heads. A needle is inserted proximal to the thenar webspace at the distal palmar crease. After aspiration, 1 mL of local anesthetic solution (without epinephrine) is injected.Complications
Large volumes of local anesthetic solutions are contraindicated because they can cause vascular compromise.Anatomy
The digital nerves to the feet are derived from the plantar cutaneous branch of the tibial nerve. The proper digital nerve of the toe supplies the medial aspect of the great toe. The three common digital nerves split into two proper digital nerves each. The first supplies the adjacent areas of the great and second toes, the second supplies the adjacent sides of the second the third toes and the third supplies the adjacent sides of the third of fourth toes. Each of these terminates at the tip of the toe. A branch from the superficial peroneal nerve supplies the dorsum of the foot. These are derived from tow nerves; (i) the dorsal cutaneous nerve divides into two branches, a medial branch supplying the great toe and a lateral branch supplying the adjacent sides of the second and third toes and (ii) the intermediate dorsal cutaneous nerve that passes along the lateral part of the foot supplying the lateral aspect of the foot and communicating with the sural nerve. The two dorsal digital terminal branches supply the adjacent parts of the third and fourth toes and another branch supplying the adjacent sides of the fourth and fifth toe.Technique
It is easy to block the digital nerves by accessing the webspace on the dorsolateral aspect of the foot. It is best to avoid these blocks in children who may have compromised blood flow to the toes. Vasoconstrictors are to be avoided for all these blocks.
Blockade of the radial, ulnar, and median nerve can be accomplished at the level of the wrist. The advantage with these peripheral blocks is the absence of motor blockade. They are primarily used for surgery on the hand e.g., syndactaly repair. These are performed in conjunction with general anesthesia since tourniquet pain cannot be eliminated with this block alone. The reader is referred to Chapter 29 for more information on the technique, which is essentially identical to that in adults. The discussion bellow outlines some specifics that relate to application of the wrist blocks in the pediatric patient.
The radial nerve is a superficial sensory nerve proximal to the radial head. The radial nerve divides into two branches, a thenar branch and a dorsal branch. This division takes place proximal to the distal end of the radius. This block is performed for children undergoing trigger thumb release or minor surgical procedures involving the thumb and index finger.
Technique
The anatomical ‘snuff box’ is identified. Approximately 2 cms. proximal to the anatomical snuff box, local anesthesia is infiltrated subcutaneously. A volume of 2 mL is adequate to provide good analgesia in the postoperative period.Complications
Rare.The median nerve is located between the tendons of the palmaris longus and the flexor carpi radialis (FCR). The nerve is usually blocked at the level of the flexor retinaculum. One of the important anatomical advantages of blocking the median nerve at the wrist is the presence of a bursa at the level of the flexor retinaculum. This bursa encompasses the median nerve and hence blockade of this nerve can be carried out without damage to the nerve.
Technique
The tendons of the flexor carpi radialis and the palmaris longus are identified. Flexion of the wrist will be able to identify the tendons. A 27-G needle is inserted at the medial border of the palmaris longus tendon. A ‘pop’ is felt as the bursa is entered. 2 mL of local anesthetic solution is injected. Smaller quantities are required for younger children and infants.The palmar cutaneous branch of the ulnar nerve accompanies the ulnbar artery to the wrist. It perforates the flexor retinaculum and ends in the palm communicating with the median nerve.
Technique
The nerve is easily blocked at the wrist. The flexor carpi ulnaris tendon is identified. The nerve is blocked under the flexor carpi ulnaris tendon, just proximal to thepisiform bone. A 27_G needle is passed under the flexor carpi ulnaris, proximal to the pisiform bone, about 0.5cm. After aspiration 2 mL of local anesthetic solution is injected.
The lumbar and sacral plexus supply the lower extremity.
The lumbar plexus is contained in the psoas compartment and consists of a small portion of T12 and lumbar nerves L1-L4. The femoral nerve, lateral femoral cutaneous nerve and the obturator nerves are branches of the lumbar plexus that supply most of the thigh and the upper leg. The lower leg is innervated by the sacral plexus which is derived from the anterior rami of the L4, L5, S1, S2 and S3. This plexus gives rise to the sciatic nerve which is the largest nerve in the body.
Local anesthetic doses for lower extremity blocks
Lower extremity nerve blocks generally require more local anesthetic solution than upper extremity nerve blocks. Children younger than five to eight years old can receive 0.5-1 mL/kg of bupivacaine 0.25% or ropivacaine 0.2%. Older children may require larger concentrations such as 0.5-1 mL/kg of bupivacaine 0.5% or ropivacaine 0.5%. Epinephrine 1:200,000 is typically added for detection of inadvertent intravascular injection.(1) If multiple nerve blocks are to be performed, the maximum allowable dose of local anesthetic should not be exceeded when the amount is calculated for both blocks. For continuous infusion through a peripheral nerve block catheter, the suggested dose of local anesthetic is 0.2 mg/kg/h of ropivacaine 0.1% or levobupivacaine 0.125% in newborns or infants and 0.3-0.4 mg/kg/h of ropivacaine 0.1% or levobupivacaine 0.125% in older children.(2)
This is the most commonly performed lower extremity peripheral nerve block in children. It is used for providing pain relief following femoral fractures.4;36-38 The femoral nerve is located at the level of the crease at the groin, lateral to the pulsation of the femoral artery. Surface mapping for locating the position of the nerve prior to utilizing a sheathed needle.
Technique
The technique is similar to that in the adult, see Chapter 35. Femoral artery pulse is located and the needle is inserted immediately lateral to the pulse to elicit quadriceps muscle contraction. The nerve stimulator is initially set at 1 mA and then reduced to 0.4mA while observing the quadriceps contraction. Surface mapping electrode can also be used to approximate the location of the nerve. Once the location of the needle is stabilized, and after careful aspiration to prevent intravascular injection, local anesthetic solution is injected. A volume of 0.2mL/kg to 0.3mL/kg is injected.Complications
Intravascular injection can be prevented by carefully aspirating prior to injection and injecting graduated doses. The risk of intraneural injection can be reduced by localizing the nerve with a nerve stimulator (>0.2 mA). More recently, the use of injection pressure monitoring has been suggested to add additional information in preventing intra-neural injections.39Lateral femoral cutaneous nerve
The lateral femoral cutaneous nerve is derived from L3, L4 segments of the lumbar plexus. It is a pure sensory nerve that passes superficially along the lateral border of the iliac crest as it exits into the fascia iliaca compartment to supply the lateral aspect of the thigh. It is useful for providing analgesia for surgery on the lateral aspect of the thigh including muscle biopsies40 and graft excisions. This technique is also similar to that in the adult (see Chapter 40). It is a relatively easy block to perform with very few side effects and hence easily applicable in the pediatric population.
Technique
The anterior superior iliac spine is identified. A point 1.5 inches below and medial to the anterior superior iliac spine is identified. After careful aseptic preparation of the area, a blunt needle is introduced into the marked site. An initial ‘pop’ is felt as the needle enters the skin and the fasia lata, a second ‘pop’ is felt as the needle enters the fascia iliaca compartment. Once the needle is lodged in this space, loss of resistance can be easily felt as the local anesthetic solution is injected. A total volume of 0.2mL to 0.3 mL of the local anesthetic solution is injected.Complications
It is very rare to see complications with this block. A hematoma can form at the site of injection especially if a superficial blood vessel is damaged as the needle enters.The sacral plexus comprises the sciatic nerve and provides the innervation to the posterior thigh and the leg and most part of the foot except the medial portion which is innervated by the femoral nerve. There are a number of techniques used in children for sciatic nerve block. We will address two main methods, the infragluteal approach and the popliteal fossa approach.
Infragluteal sciatic nerve block
This is an easy block to perform in children under general anesthesia since it can be performed either in the lateral position or in the supine position with elevation of the limb. The nerve is easily localized for this technique. The infragluteal line where the gluteal crease is present is marked. The biceps femoris tendon is identified and a point inferior to the gluteal crease just medial to the biceps femoris tendon is delineated. A sheathed needle connected to a nerve stimulator is introduced in an anterior plane and cephalad at an angle of 60 to 70 degrees. Inversion of the foot is indication of blockade of the tibial nerve.45 The current is reduced to 0.4mA and if inversion is still present the local anesthetic solution is injected. If eversion is noted, the needle is withdrawn to skin and is inserted medially. If the biceps femoris tendon is contracting, the needle is drawn back to the skin and the needle is inserted medially away from the muscle belly of the biceps femoris tendon. Plantar flexion is also an indicator of placement of adequate block although this yields a potential for a failed blockade.45 A volume of 0.5mL/kg to a maximum of 20 mL is injected into the space. On initial injection of 1mL of local anesthetic solution, the twitch disappears and confirms placement of the needle in the right location.
Complications
Absence of complete block especially if plantar flexion or dorsiflexion are only present without eversion. Intravenous injections are also a complication.The popliteal fossa block is our preferred method for blocking the sciatic nerve. There are two approaches to the sciatic nerve in the popliteal fossa, a lateral approach, and, a posterior approach. The popliteal fossa is a diamond shaped area with the superior triangle formed by the tendons of the semitendinosis, semimbranosus medially and the biceps femoris tendon laterally.46 The sciatic nerve divides into the common peroneal nerve and the tibial nerve. The common peroneal nerve exits the popliteal fossa laterally and the tibial nerve exits medially. The branching of the sciatic nerve takes place about 5 to 8 cms above the popliteal crease. A common epineural sheath is present that envelops both the tibial and the common peroneal nerve that may lead to complete blockade of both the branches.47
Lateral approach to the popliteal fossa
Because anesthetized children are typically in the supine position, the lateral approach to popliteal block is particularly advantageous. Although the use of this technique has been well described in children48 and adults16;49, it has not gained wide popularity in children.
Technique
After induction of anesthesia and placement of a laryngeal mask airway or mask and strap outfit, the knee is flexed on the side of the block. The biceps femoris tendon is identified and the needle is placed between the vastus lateralis and the biceps femoris tendon at an angle of about 30 degrees about 5 to 6 cm above the popliteal crease, FIGURE 8. If the femur is encountered without a twitch response, the needle is pulled back to the skin and inserted at a caudal angle to pass behind the shaft of the femur, FIGURE 9. A response to nerve stimulation at 0.4mA, usually plantar or dorsiflexion and eversion or inversion confirms the position of the needle and its proximity to the sciatic nerve. Since at this spot the needle is expected to be above the point where the sciatic nerve bifurcates into the common peroneal and tibial nerve, response of either tibial (TN) or common peroneal nerve (CPN) is adequate. Cadaveric studies have shown a wide variation of the position of the sciatic nerve division in adult cadavers.50 This may further vary in children. After aspiration to rule out intravascular placement, local anesthetic solution is injected. A total volume of 05mL/kg is injected with a maximum volume of 20mL. Alternatively, perineural catheter can be inserted using a similar technique to provide long-lasting analgesia, Figure 10. The catheter can be conveniently secured at this position, Figure 11.
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Figure 8. Popliteal
sciatic block - landmarks for the lateral approach. |
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Figure 9. Popliteal sciatic block; lateral approach: Needle insertion. |
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Figure 10. Popliteal block; lateral approach: Catheter insertion. |
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Figure 11. Popliteal block; lateral approach: Securing the catheter. |
Complications
Sparing of one of the branches of the sciatic nerve especially if the division takes place proximally.46 Intravascular injection may be a complication if caution is not exercised prior to injection of the local anesthetic solution.Posterior approach to the popliteal fossa
Although the classic teaching of posterior approach to the popliteal fossa entails placing the patient prone and marking the tendons comprising the ‘diamond’ of the fossa, this may not be needed in the pediatric population due to their weight and the ability to lift the leg easily. We prefer keeping the patient supine and then localizing each individual nerve, tibial nerve and the common peroneal nerve by surface mapping, Figure 12. Once each nerve is identified, they are individually blocked using a stimulating needle. The tibial nerve is localized with the presence of inversion and plantar flexion (internal nerve= inversion); the common peroneal nerve is localized by the presence of eversion and dorsiflexion.(external nerve= eversion). The total volume can also be reduced to 0.2mL/kg since individual nerves blocked will require less local anesthetic solution. This is particularly valuable in infants where toxicity can be seen at lower doses of local anesthetic solution.
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Figure 12. Popliteal sciatic block; posterior approach. The needle is inserted between the tendons of the biceps femoris (laterally) and semitendinosus muscles. |
This is a very common and easy block to perform for children undergoing foot surgery. The disadvantage of this block is the absence of pain relief during tourniquet application. However, since most procedures are performed under general anesthesia, the presence of adequate pain relief in the postoperative period can be achieved using this block. There are five main nerves to be blocked, the posterior tibial nerve; deep peroneal, superficial peroneal; saphenous and sural nerve. All of the nerves are distal branches of the sciatic nerve except for the saphenous nerve which is a branch of the femoral nerve. Since the nerves are superficial, they do not require much volume. Epinephrine should be avoided in the local anesthetic solution since end arteries are present at the site of injection. The reader is referred to Chapter 39 for illustrations and detailed description.
This is the largest nerve that supplies the plantar aspect of the foot. This is an important nerve to be blocked for any foot surgery. We routinely used surface mapping with a current of 5 mA to locate the tibial nerve prior to injection. The nerve is located behind the posterior tibial pulsation below the medial malleolus. A 27-G needle is advanced to the bone and slightly withdrawn to avoid injection into the periosteum. 5 to 8 mL of local anesthetic solution is injected. Alternatively, a sheathed needle can be used and plantar flexion or inversion can be elicited prior to injection.
This is the distal cutaneous branch of the femoral nerve. It is located superficially anterior to the medial malleolus. A superficial ring injected along the medial malleolus and 5mL of local anesthetic solution is injected. Caution has to be exercised to avoid intravascular injection since the saphenous vein courses alongside the nerve. The saphenous nerve supplies the sing over the medial aspect of the leg bellow the knee and ankle.
This innervates the first web space of the foot.. It can be blocked by depositing local anesthetic solution lateral to the externsor hallucis longus tendon. The needle is advanced until the periosteum of the tibia is encountered, drawn back slightly and then 2 to 3 mL of local anesthetic solution is injected.
This supplies the sensory supply to the dorsum of the foot. It is superficial and can be easily blocked by injecting a superficial ring of local anesthesia between the lateral malleolus and the extensor hallucis longus tendon.
This supplies the sensory innervation to the lateral aspect of the foot. It can be easily blocked by injecting local anesthetic solution between the lateral malleolus and the calcaneus.
The ankle block is a very easy block to perform and has very few side effects. If performed carefully, it can provide excellent analgesia for foot surgery.
TRUNK BLOCKS
For most hernia surgery in children, a caudal block is the block of choice. However, if there is a relative contraindication to a caudal block due to the presence of a sacral dimple or if the child is obese and the caudal space is not easily identified, an ilioinguinal nerve block is utilized.
Anatomy: The ilioinguinal and iliohypogastric nerves originate from the T12 (subcostal nerve) and L1 (ilioinguinal, iliohypogastric) nerve roots of the lumbar plexus. These nerves pierce the internal oblique aponeurosis 2 to 3 cm medial to the anterior superior iliac spine. It travels between the internal oblique and the external oblique aponeurosis. Here it accompanies the spermatic cord and is part of the neurovascular bundle to the genital area.Technique
A line is drawn between the umbilicus and anterior superior iliac spine. The line is divided into thirds. The point where the lateral third meets with the medial 2/3rds is where the needle is inserted. The needle is advanced towards the inguinal canal and passed in until a pop is felt, Figure 13. Local anesthetic solution is injected into the area after aspiration. Alternatively, an ilioinguinal nerve block can be performed can by having the surgeon flood the site of surgery with 10 mL of local anesthetic solution.
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Figure 13. Ilioinguinal block. The needle is inserted at the point where the lateral third meets with the medial 2/3rds of the line connecting the umbilicus with the anterior-superior iliac spine. |
Complications
Complications of the ilioinguinal nerve block is relatively safe. Perforation of the bowel wall can occur and has been reported.52 Occasional femoral nerve blockade can occur while this block is placed.53The rectus sheath block was first described in 1899 for surgery performed around the umbilcal area. It is useful particularly in children for umbilical area surgery.
Anatomy
The umbilical area is innervated by 10th thoracoabdominal intercostals nerves from the right and the left side. Each nerve then passes behind the costal cartilage and between the transverse abdominus muscle and the internal oblique muscle. The nerve runs between the sheath and the posterior wall of the rectus abdominus muscle and ends as the anterior cutaneous branch supplying the skin of the umbilical area.Technique
The aim of this block is to deposit local anesthetic solution between the muscle and the posterior aspect of the sheath. The technique has been well described by Ferguson et al.54 A 23-G needle is inserted above or below the umbilicus ½ cm medial to the linea semilunaris in a perpendicular plane. The anterior rectus sheath is identified by moving the needle with a back and forth motion until a scratching sensation is felt, the rectus sheath is identified and entered, Figure 14. After the belly of the muscle is entered, the needle si further advanced until the posterior aspect of the rectus sheath is appreciated with a scratching sensation as the needle is moved again with a back and forth motion. Once the sheath is felt, it is entered and local anesthetic solution is deposited posterior to the sheath. The usual depth of needle entry is about 0.5 to 1.5 cm. After aspiration, 0.2 ml/kg bupivacaine 0.25-0.5% is injected on each side.
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Figure 14. Rectus sheath block. A 23-G needle is inserted above or below the umbilicus ½ cm medial to the linea semilunaris in a perpendicular plane. Once the sheath is entered, local anesthetic solution is deposited posterior to the sheath. The usual depth of needle entry is about 0.5 to 1.5 cm. |
If resistance is felt to injection, the needle is advanced deeper since it may be in the body of the muscle. This block can be performed with a greater degree of precision with the assistance of ultrasound as the muscle is readily visualized, Figures 15 and 16. A sharp needle is used in a direction perpendicular to the skin.
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Figure 15. Rectus sheath block. The ultrasound image shows the widening space between the muscle and the posterior aspect of the rectus sheath. |
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Figure 16. Rectus sheath block. As the larger volume of local anesthetic is injected, the space between the muscle and the posterior aspect of the rectus sheath continuous to distend. |
Complications
A lateral approach may not allow appreciation of passage of the needle through the various layers, a superficial injection after passage through the anterior rectus sheath may not allow spread of local anesthetic due to the presence of tendinous bands. Intravascular injection particularly if a large volume is injected directly into the rectus muscle.The nerve supply to the penis is derived from the pudendal nerve and the pelvic plexus. The dorsal nerves of the penis separate at the level of the symphysis pubis to the two dorsal nerves of the penis which supply the sensory innervation to the shaft of the penis.
Technique
Non-epinephrine containing solution is used for providing this nerve block. A needle is inserted in the infrapubic space and a pop is felt as the needle enters the facial compartment, Figure 17. After careful aspiration, the needle is then directed to each one of the sides of the shaft of the penis. An alternative approach is to place a subcutaneous ring block around the base of the penile shaft, Figure 18. Although this is effective in providing analgesia, complications include the presence of a hematoma and a higher incidence of inadequate postoperative pain relief .55 Our preferred approach is to use an injection at the base of the penis.
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Figure 17. Penile nerve block; infrapubic approach. A needle is inserted in the infrapubic space and a pop is felt as the needle enters the facial compartment. After careful aspiration and injection, the needle is then directed to each one of the sides of the shaft of the penis to inject additional local aneshetic. |
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Figure 18. Penile block: Subcutanous ring block. A subcutaneous ring block is accomplished by injecting local anesthetic around the base of the penile shaft. |
Complications
Hematoma formation.Thoracic paravertebral blocks is used to treat postoperative pain after thoracotomy and unilateral Abdominal Surgery (open splenectomy, nephrectomy). Contraindications for this technique are rare. Pediatric (5 cm) epidural kit is used.
Anatomy
Approximate distance to the paravertebral space in children (mm) is 20 + (0.5 x weight in kg). The needle point is typically 1-2 cm lateral to midline; T7-9 level is usually used.Technique
The patient is positioned in the lateral decubitus position in the neutral position, Figure 19. The needle is inserted through the skin, then the stylet is removed a syringe is attached for assessment of the loss of resistance. The needle is advanced until the transverse process is contacted (Figure 20). At this point the needle is advanced 1 cm pass the transverse process. Alternatively, the syringe is advanced until get the loss of resistance is appreciated. A bolus of 0.5-1 ml/kg of 0.25% bupivacaine is injected, followed by infusion of 0.3 ml/kg/hr of bupivacaine 0.125%. The same technique can be used to insert a paravertebral catheter for continuous infusion of local anesthetic, similarly to other continuous nerve block techniques, Figures 21 and 22.
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Figure 19. Thoracic paravertebral block. The patient is positioned in the lateral decubitus position with slight flexion of the back. The arrow points to T7 (tip of the scapulae). |
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Figure 20. Thoracic paravertebral block. The needle is inserted 1-2 cm lateral to the medline and advanced to the transverse process. The needle is then "walked off" superiorly or inferiorly by 1 cm. |
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Figure 21. Thoracic paravertebral block. After the paravertebral space is identified, the catheter is inserted 2-4 cm beyond the tip of the needle |
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Figure 22. Thoracic paravertebral block. The catheter is firmly secured to the patient's back using a locking device. |
SUMMARY
Peripheral nerve blocks can be performed with ease in children and
adolescents. Adequate knowledge of the anatomy of the area along with
appropriate indications and knowledge of complications will facilitate
the use of peripheral nerve blocks in children. The fear of use of
peripheral nerve blocks in children under general anesthesia is not
unfounded but techniques with the use of ultrasound technology can
facilitate better placement of nerve blocks.
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