Regional anesthesia is becoming more popular in the field of pediatric anesthesia. Improvements in ultrasound (US) technology and research into the safety and efficacy of these techniques have made pediatric regional anesthesia a growing field that continues to improve the practice of pediatric anesthesia. We will discuss the conduct of regional anesthesia blocks in the pediatric population and potential complications and their management (Table 1).
Local Anesthetic Systemic Toxicity (LAST)
Although regional anesthesia is very safe in the pediatric population, it is important to recognize the potentially significant undesirable side effects that can occur. LAST is a very rare but potentially lethal complication of regional anesthesia that occurs due to systemic absorption or an intravascular injection of a local anesthetic. Its sequelae occur secondary to the effects on sodium channels of highly vascular organ systems such as the central nervous system and the cardiovascular system.1 The incidence has been reported to be 0.4 to 3.7 in 10,000 peripheral nerve blocks2,3 and 0.7 to 1.8 per 10,000 epidurals.4,5
The pediatric population is at risk for LAST for a number of reasons. Local anesthetic concentrations leading to cardiovascular depression are half those of an adult.6 Decreased levels of α-1 glycoprotein in neonates cause an increased concentration of free drug compared with that in adults or older children.7 This is even more significant in preterm infants. Furthermore, clearance mechanisms, specifically those utilized in the metabolism of amide local anesthetics, are immature until about 3 to 6 months of age, warranting a 30% decrease in both bolus and infusion doses of these agents in infants younger than 6 months of age.8–11 A malnourished child has decreased total body protein and will therefore have an increased concentration of local anesthetic in its free and active form. Conversely, a morbidly obese child should not simply receive an increased dose due to his or her larger size. Rather, the dosing should be performed on the basis of the lean body weight.
Local anesthetic infiltration into areas with increased perfusion will result in a greater rate of uptake12 and higher blood concentrations than comparable doses in less vascular locations. A useful mnemonic to remember the degree of absorption in adults (in the order of highest absorption to the least) is ICE Block (Intercostal, Caudal, Epidural, peripheral nerve Blocks). Further studies are indicated to assess whether this is also true in our pediatric population.13 The local anesthetic rate of absorption tends to be swifter in the pediatric population compared with adults. After an ilioinguinal nerve block, bupivacaine concentrations in children <15 kg were double those measured in older children.14 However, local anesthetic administration for spinal anesthesia leads to very small blood concentrations, even in the neonate population.10
Generally, the co-administration of epinephrine with local anesthetic prolongs the duration of a block and decreases its rate of uptake. A concentration of 5 μg/mL epinephrine is often utilized, and should not exceed 10 μg/mL. Historically, it has been taught that epinephrine should not be used in blocks where end artery constriction could cause ischemia, such as penile and digital blocks. However, recent debate indicates that further investigation may be warranted.15,16 Because of a combination of factors, including the increased resting heart rate of young children, the age-dependent variation in the reactivity of the cardiovascular system to epinephrine, and the fact that many blocks are performed under general anesthesia, the usefulness and reliability of a test dose in the pediatric population are controversial.17 Therefore, the European Society of Regional Anaesthesia and Pain Therapy-American Society of Regional Anesthesia and Pain Medicine (ESRA-ASRA) taskforce recommends that a test dose be performed at the discretion of the anesthesia provider.18
Signs and Symptoms
Central nervous system toxicity occurs through blockade of sodium channels, inhibiting depolarization and preventing neuronal transmission. This first occurs with inhibitory pathways and then subsequently affects excitatory ones. Excitatory signs include nervousness, muscle twitching, and an endpoint of tonic-clonic seizures; these symptoms may be masked in an intubated, sedated patient, making electrocardiographic signs the first clinical indication of toxicity.
A high index of suspicion for toxicity should be held for any cardiovascular change after the administration of a local anesthetic. Cardiovascular changes associated with LAST can be divided into 3 phases. First, the initial excitatory phase is marked by hypertension and tachycardia. This is followed by the intermediate phase, which is best characterized by myocardial depression and hypotension. On electrocardiogram, this may be characterized by ectopy. Finally, the terminal phase occurs with peripheral vasodilation and profound hypotension accompanied by bradyarrhythmias including but not limited to sinus bradycardia, conduction blockade, asystole, and ventricular tachycardia.1,19
Management of LAST
The first focus of LAST management should be on airway management (ventilation with 100% FiO2 is recommended), seizure suppression (preferably with a benzodiazepine as it is recommended to avoid propofol due to its myocardial depressive properties), and alerting the nearest facility with cardiopulmonary bypass capabilities.19
According to the ASRA, it is recommended to avoid vasopressin, myocardial depressants, and further local anesthetic administration during resuscitative efforts. It is also recommended to reduce the dose of epinephrine to 1 mcg/kg.19
Finally, lipid emulsion therapy should be initiated. It remains uncertain how lipid emulsion works, although several hypotheses have been theorized. The lipid sink hypothesis is one of the more popular ones; it works by binding the offending toxin, thereby pulling it from the target tissue, reversing toxicity, and improving responsiveness to resuscitative efforts. Therapy starts with a bolus of 1.5 mL/kg of 20% lipid emulsion, which can be repeated twice for unrelenting cardiovascular collapse. This is followed by a maintenance infusion of 0.25 mL/kg/min. The rate can be doubled for persistent hypotension and should be continued for 10 minutes after circulatory stability is attained. The administration should not exceed 10 mg/kg over the first 30 minutes.19 Recent data have shown improved management of LAST with the use of a checklist.20
Upper Extremity Blocks
Axillary and supraclavicular blocks are the predominant techniques for brachial plexus regional anesthesia in the pediatric population. However, utilization of US has facilitated the reemergence of the interscalene approach as a feasible method. As more evidence has emerged on their safety, the utilization of peripheral catheters has become more prevalent.21
No evidence exists implicating regional anesthesia in delayed diagnosis or an increased incidence of acute compartment syndrome. Frequent evaluation and reduced infusion rates are still recommended in this subset of patients.18
An interscalene regional technique takes place at the level of the brachial plexus distal roots to proximal trunks and provides good coverage for shoulder or upper arm surgery. This block can often spare the inferior trunk and thus the ulnar nerve distribution area.22 This can be mitigated by utilizing a larger volume of local anesthetic or injecting at a lower level.23 In addition, there is nearly always hemidiaphragm paresis with this block.24 A single shot or a catheter with a continuous infusion can be utilized.
The interscalene block is often performed with the patient in a sitting position or supine with an elevation of the head of the bed and the head turned away from the side that is going to be blocked. The probe should be placed in a transverse oblique plane at the level of the cricoid cartilage on the posterolateral border of the clavicular head of the sternocleidomastoid, just over the external jugular vein. At this level, the brachial plexus can be found as 3 round hypoechoic structures lateral to the carotid artery and internal jugular vein, in between the anterior and middle scalene muscles.25
This block occurs at the distal trunk to proximal trunk level and provides coverage for surgeries of the hand, forearm, elbow, and arm. The intercostobrachial nerve is spared in this block and so an additional block should be performed for coverage of the medial portion of the proximal arm. The utilization of nerve stimulation of the middle trunk or visualization with US has been associated with improved success rates.26 US has improved safety with visualization of anatomy and needle placement.27 Hemidiaphragm paresis is still possible, but less likely than with an interscalene technique.28 Both a single shot and a catheter with a continuous infusion are feasible with this approach.
The supraclavicular block is performed in the supine or the semi-sitting position with the head of the bed elevated and the patient’s head turned away from the side on which the block is being performed. The transducer should be positioned in the transverse plane just behind the middle third of the clavicle. Tilting the probe caudally, the proceduralist should obtain a view of the subclavian artery in cross section. The brachial plexus is seen as an assemblage of hypoechoic rounded structures posterior and superficial to the subclavian artery and superficial to the first rib and the parietal pleura (Fig. 1). Color doppler should be performed before needle insertion to rule out large vessels in the anticipated trajectory of the needle. The plexus can be accessed using an in-plane approach, minimizing the risk of pneumothorax or intravascular injection. Often a single injection of local anesthetic is adequate for this technique; however, multiple injections surrounding the plexus can be administered to ensure spread.27 Preexisting nerve injury should be assessed before block placement through a basic test of nerve function with a “thumbs up” sign (radial nerve), flexion of the proximal interphalangeal joint (median nerve), and scissoring of the fingers (ulnar nerve).29
This regional technique takes place at the level of the brachial plexus branches and is best suited for surgeries and procedures of the distal upper extremity. Straightforward landmarks and the less complicated nature of the block make it accessible and well suited for any number of procedures. Color doppler utilization may facilitate the recognition of vascular structures.
Axillary blocks can be performed in the supine position with the arm extended to 90 degrees. The probe is placed on the medial portion of the arm just distal to the humerus insertion of the pectoralis major, perpendicular to the anterior axillary fold. The biceps brachii and the coracobrachialis will be seen laterally. Sliding the US up and down should bring the anechoic pulsatile axillary artery and the conjoined tendon into view, and also show a short-axis view of the branches of the brachial plexus.30 Reports show multiple injections to be better than a solitary injection for this technique.31 Locating the radial nerve is key in the effectiveness of this block, whereas identification of the ulnar nerve is not as essential if the other nerves have been identified.32 The median nerve is usually superficial and can be found between the artery and biceps brachii. Typically, the ulnar nerve lies medial and superficial to the artery, and the radial nerve is found deep to the artery and midline. The musculocutaneous nerve commonly runs between the biceps brachii and coracobrachialis at this level.30
Blockade of the Anterior Trunk
US has been paramount in truncal blocks in the pediatric population due to the tight anatomic relationships between nerves and critical abdominal structures. Providing coverage to the inguinal region, the ilioinguinal/iliohypogastric block is one of the most commonly utilized regional techniques of the anterior trunk.33 The rectus sheath block is a popular technique for periumbilical procedures.
Ilioinguinal/Iliohypogastric Nerve Block
This regional technique is appropriate for procedures of the inguinal region such as an inguinal herniorrhaphy. US has been shown to improve the effectiveness of this technique and reduce the local anesthetic volume needed.34 The recommended volume is 0.1 mL/kg of an appropriately dosed local anesthetic; however, the concentration of the solution can be adjusted on the basis of weight-based dosing and desired density of the block.
The block is often performed in the supine position by placing the probe just medial to the anterior superior iliac spine. The ilioinguinal nerve can be seen between the internal and the external oblique muscles at this level. The risks of inadvertent colonic puncture and transient femoral nerve palsy have been reported with this block using the landmark technique35,36 and can be mitigated with the use of US.
Rectus Sheath Block
This block is best used for periumbilical surgery or procedures involving dermatomes 9 to 11. It can be performed as a single-shot injection or a catheter can be placed for continuous infusion. Dosing with 0.1 mL/kg levobupivacaine per side has been shown to be sufficient.37
With the patient supine, the US probe should be positioned in the transverse position just lateral to the umbilicus. The rectus sheath lies between the rectus abdominus and the posterior rectus sheath. Superficial displacement of the rectus abdominus muscle from the posterior rectus sheath should be seen with hydrodissection37 (Fig. 2).
Transversus Abdominis Plane Block
This technique is best suited for infraumbilical procedures of the anterior abdominal wall and is useful in patients with either a contraindication to neuraxial blockade or as a rescue procedure after failed neuraxial blockade. It can be performed as a single-shot block or a catheter can be placed for continuous infusion.
The patient is most often in the supine position, and the US probe can be placed along the lateral aspect of the abdomen at the midaxillary line between the costal margin and the iliac crest. From superficial to deep, the abdominal wall layers visualized are the fascia, external oblique, internal oblique, and transversus abdominis muscles. Using an in-plane technique, a needle is inserted from lateral to medial to hydrodissect the plane between the transversus abdominis and the internal oblique muscles (Fig. 3). Dosing of 0.2 mL/kg 0.25% bupivacaine per side is sufficient for this block.38
Erector Spinae Block
First described in 2016, this technique can be utilized for acute or chronic pain of the thorax, and for regional anesthesia for cardiac surgery. It can be carried out both as a single-shot injection and a catheter with a continuous infusion. It is theorized to work through diffusion of local anesthetic to the ventral and dorsal rami of the spinal nerves.
The patient is often optimally sitting or in a lateral decubitus position for this block. The US probe should be placed just lateral to the spinous process in longitudinal orientation. The trapezius, rhomboid major, and erector spinae muscles can then be identified. Hydrodissection of the interfascial plane between rhomboid major and erector spinae should occur.39
Thoracic Wall Blocks
This regional approach is best suited for lateral thoracic wall surgery or breast procedures, and is most often performed as a single-shot injection. For this technique, the probe is placed at the anterior axillary line at the level of the fourth rib. Dosing of 0.2 mL/kg levobupivacaine 0.25% can be infiltrated between pectoralis major and minor. Then, attention should be focused on the midclavicular line at the level of the second rib. Moving the probe laterally, the serratus anterior and pectoralis minor will come into view. Another 0.2 mL/kg can be administered between serratus anterior and pectoralis minor (Fig. 4).40
Serratus Anterior Plane Block
This novel technique will provide coverage for procedures involving the breast and lateral thoracic wall and is most often performed as a single-shot technique. Best positioning is either sitting or supine with the head elevated and with the arm extended above the head. Landmarks are the latissimus dorsi, serratus anterior, ribs, and pleura. The transducer should be applied at the midaxillary line at the level of the clavicle. Ribs should be counted down to the fourth and fifth interspace from the clavicle. At this point, the transducer should be tilted posterior until the latissimus dorsi is identified. The local anesthetic can either be injected deep to serratus anterior or in the fascial plane between the latissimus dorsi and the serratus anterior. Dosing of 0.4 mL/kg 0.125% levobupivacaine is appropriate for this approach.41
Role of Regional Anesthesia in Cardiac Anesthesia
The incidence of congenital heart disease in the United States is ~1% of children born annually, with an estimated 44,000 surgical procedures performed to treat or palliate these conditions.42 Cardiac surgery is associated with significant cost and morbidity, including, but not limited to, postoperative pain, respiratory complications, and prolonged hospitalization. Postoperative pain control is essential not only to alleviate discomfort but also to attenuate respiratory complications, reduce the neuroendocrine response to physiological stress, and help prevent intensification of neuronal pain pathways.43,44
Answers have long been sought to identify the best mechanism to control postoperative pain in cardiac surgery, with the traditional and most common method being high-dose, intravenous opiate therapy. Opiate therapy remains controversial, despite its effectiveness in alleviating pain, due to the severe side-effect profile that includes hemodynamic instability, respiratory depression, habituation, and narcotic dependence potential. Evidence supports that even small, discrete dosing of opiates can lead to long-term dependency and neurohormonal consequences.
Multimodal analgesic options have been historically evaluated and used to mitigate the consequences of high-dose opioid therapy in congenital cardiac surgery. The use of regional anesthesia in pediatric cardiac surgery provides an option to contribute toward an effective multimodal approach for pain management while potentially reducing opioid consumption and associated complications. In a systematic review, Monahan and colleagues reported that the addition of regional anesthetic techniques in children undergoing cardiac surgery reduced postoperative pain up to 24 hours in comparison with systemic analgesia. However, this review did not find a difference in any other outcomes, including the incidence of nausea and vomiting, duration of tracheal intubation, length of intensive care unit (ICU) stay or total hospitalization, blood loss, infection, incidence of reoperation, or death.42
Different regional anesthetic techniques have been explored in pediatric cardiac surgery, including both neuraxial blockade and superficial or peripheral nerve blocks.45 Neuraxial techniques may be preferred if the primary goal is to attenuate the stress response of surgery and cardiopulmonary bypass. The reduction in systemic inflammatory markers with the use of neuraxial techniques may have beneficial long-term effects, but these outcomes remain to be elucidated. Guay and colleagues examined the effect of neuraxial anesthesia in comparison with general anesthesia as it related to postoperative 30-day mortality and morbidity in the adult population for any type of surgical procedure (not limited to just cardiac surgery). The results of this study identified a decrease in mortality rate of 2.5% when neuraxial anesthesia was used alone, but the risk of perioperative pneumonia may be decreased even when neuraxial techniques are used along with general anesthesia.43 This finding may be extrapolated to the pediatric population, although no formalized study has been published. Notably, no study or direct evidence exists that early extubation and the associated hemodynamic profile of spontaneous ventilation have observable benefits in this complex pediatric patient population, particularly in the early postoperative period.46 The limited studies that exist show a positive trend in early extubation times, better pain control, and decreased incidence of respiratory depression, but no notable difference in ICU or hospital length of stay.47,48
If a reduction in pain is the only desired outcome, then peripheral nerve block techniques may be more advantageous with the avoidance of a dural puncture in a patient who will receive systemic heparinization. Clinicians have been specifically cautious of neuraxial techniques because of the risk of systemic anticoagulation and subsequent hematoma formation; however, no study to date has identified any potential increased risk of caudal hematoma formation or other neurological sequelae. In a study by Suresh et al49 that included the analysis of the Pediatric Regional Anesthesia Network (PRAN) database and 18,650 children who received a caudal block, an incidence of 0.6% was found for blood aspiration during block placement, with no long-term or permanent sequelae identified in any of the patients.
There is a paucity of studies comparing various peripheral nerve blocks in the pediatric cardiac population. Biswas et al50 reported in a case series the utilization of a serratus plane block for thoracotomy pain relief in aortic coarctation repair that showed a decrease in postoperative opioid requirements, and decreased ICU stay and overall hospitalization in comparison with control groups that received systemic intravenous opioids. Turkoz et al51 reported similar findings utilizing paravertebral blocks for analgesic management during aortic coarctation repair. In a randomized-controlled trial of 30 children, Chaudhary et al52 reported decreased 24-hour fentanyl consumption, overall lower pain scores, and earlier time to extubation in children undergoing median sternotomy with parasternal intercostal nerve blocks compared with conventional systemic opioid administration. Similar to findings in the adult studies, paravertebral blocks continue to show promise in mitigating pain and improving outcomes for pediatric patients undergoing thoracotomy and median sternotomy. Thoracic paravertebral nerve blocks have shown promising results in pectus excavatum repair, specifically with less opioid consumption, decreased pain scores, and improved incidence of postoperative behavioral disturbances. In a comparison of thoracic paravertebral block with thoracic epidural block for pediatric cardiac surgery, a study by El-Morsy et al53 showed comparable results in terms of pain and pulmonary function, but fewer complications in the paravertebral group. Complications in this particular study included block failure, vomiting, urinary retention, and hypotension.
Although no specific modality has shown consistent findings to alter the course of analgesic management, the addition of a regional anesthetic technique to a multimodal anesthetic plan may result in individual benefits to pediatric patients. The potential for reduced pain scores, less opioid consumption, early extubation, and fewer respiratory complications may serve unique benefits to the pediatric cardiac patient that may outweigh any perceived inherent risks.
Central Neuraxial Blocks
Epidural anesthesia, particularly the caudal nerve block, is a popular anesthetic technique to provide anesthesia and analgesia for a number of surgical procedures. The efficacy of this technique has been established to provide analgesia for major orthopedic procedures of the lower extremities and hip, abdominal and genitourinary procedures, and thoracic surgery, including thoracotomies. The safety of epidural anesthesia, in particular, has been examined in prospective national audits that determined an incidence of severe complications at 1:2000, with an incidence of persisting sequelae at 12 months of 1:10,000.54 Safety concerns in terms of the placement of epidurals in children asleep versus awake have been largely debunked, favoring the placement of epidural anesthesia in asleep patients.55 This accepted practice and standard of care has been supported by advisory practice guidelines established by ASRA that have delineated that the benefits of placing epidural anesthesia in a cooperative and immobile patient outweigh any perceived risks.56
Notable differences do exist in epidural neuraxial techniques between children and adults. The intercristal line between the posterior superior iliac spines crosses higher in adults at the L3-L4 interspace while crossing lower at L5-S1 in infants. The depth from the skin to the epidural space is more variable in pediatric patients than adults with a generally shorter distance, allowing for the use of a shorter epidural needle. The epidural space tends to have less fat, greater cerebrospinal fluid production, and greater degree of nonmyelination that may allow for increased cephalad spread, and a greater rate of onset and toxicity. In addition, higher cardiac output in children, particularly neonates and infants, may allow for greater systemic absorption and potential for systemic toxicity. The choice of a local anesthetic agent can be complicated by decreased hepatic metabolism and decreased plasma protein binding of drugs in the infant population that allows for greater fractions of plasma drug concentrations and subsequent higher likelihood of toxicity. A review by Veneziano and Tobias57 examined the role of chloroprocaine, an amino-ester local anesthetic, as an alternative local anesthetic in the neonatal and infant population that shows greater safety margins in providing appropriate analgesia in this fragile population. Given that chloroprocaine is metabolized in an ultra-fast mechanism through plasma cholinesterases, this local anesthetic shows promise in providing a safer alternative to other local anesthetics (ropivacaine, bupivacaine).
Caudal nerve blocks are the most commonly used regional anesthesia technique in pediatric surgical patients.58 The popularity of the caudal nerve block largely stems from the readily palpable landmarks (sacral hiatus) in children coupled with the relative ease of nerve block insertion. The caudal block can provide analgesia from mid-thoracic (T6) to sacral dermatomal levels in a weight-based and volume-based calculation (mL/kg) that shows a duration of 4 to 6 hours depending on the local anesthetic used. Caudal nerve blocks can provide superior analgesia for a number of surgical procedures including lower extremity, genitourinary, and lower abdominal procedures including hernia repairs.
In addition to the single injection technique, the caudal block can be augmented by the insertion of a catheter threaded to the desired dermatomal level. Catheter tip location can be confirmed by fluoroscopy with contrast media, electromyography, electrocardiography, or ultrasonography.
Suresh and colleagues found an overall incidence of complications to be 1.9%. The most common complications in their analysis were block failure, blood aspiration, and intravascular injection, with no temporary or permanent sequelae identified.59
Lower Extremity Nerve Blocks
Few historical studies have compared the use of lower extremity peripheral nerve blocks to traditional pain control including parental and oral medications. The trend in the emerging body of evidence supports that the utilization of peripheral nerve blocks results in lower pain scores and less postoperative opioid consumption.59 Studies supporting the safety and efficacy of peripheral nerve blocks, particularly lower extremity nerve blocks, have been strengthened by the large body of patient studies from the PRAN database. Walker and colleagues examined 45,324 peripheral nerve blocks in the pediatric patient population, determining that the most common peripheral nerve blocks were femoral (n=8936), sciatic (n=3263), and popliteal (n=2929) blocks.58 The most recent data analysis of this large sample set shows a 30% to 40% lower risk estimate compared with previous assessments of pediatric regional anesthesia audits. In particular, no cases of LAST or other serious complications (cardiac arrest, seizures, or serious infections) were associated with lower extremity nerve blocks in this analysis. Comparison of peripheral nerve catheters with single-injection blocks did not show a difference in neurological complications, with an overall incidence found to be 2.4:10,000.58
Historically, the femoral nerve block (Fig. 5), in particular, has been described as a nerve block that could be placed successfully by palpation and landmarks; however, the introduction of ultrasonography has further increased the safety and efficacy. In addition, direct visualization of the neurovascular bundle allows for the possibility of less local anesthetic application to achieve the desired effect without increasing the possibility of LAST.
The utilization of lower extremity nerve blocks allows analgesia to be compartmentalized to the lower half of the body depending on the specific surgical site. Lower extremity nerve blocks can include, but are not limited to, femoral, sciatic, popliteal, saphenous, and/or adductor canal, tibial, ankle, and lumbar plexus blocks. The saphenous nerve block has gained popularity in the adult population in part due to its relative motor-sparing effect on the quadriceps muscle group, allowing some postoperative mobility. At present, no studies have examined the efficacy of the saphenous nerve block in pediatrics. Variations in nerve distribution to the lower extremity can result in patchy distributions of anesthesia from the saphenous nerve block, and additional supplementation may be needed depending on the surgical procedure (Fig. 6).60
The introduction of the lumbar plexus block has allowed for analgesia directed at the ipsilateral groin, hip, and thigh. Mastery of this nerve block may allow for more consistent analgesic coverage compared with other lower extremity nerve blocks. Ultrasonography of the lumbar plexus can be challenging, especially as patient age increases.61 Selective utilization of this block may require a risk-benefit analysis over adequately achieving anesthesia through selective blocks of the desired peripheral nerves or a caudal/neuraxial block (Figs. 5, 6).
Head and Neck Blocks
Infraorbital Nerve Block
The infraorbital nerve supplies the sensory innervation to the upper lips, the maxillary sinus area, and parts of the nasal septum, and is often used successfully for infants and children undergoing cleft lip repair or sinus surgery.62 The infraorbital nerve is the terminal branch of the trigeminal nerve (V2) and it exits the skull at the infraorbital foramen. Using a landmark technique, the provider everts the upper lip, inserts a needle above the left upper incisor, and then advances it toward the infraorbital foramen. Adverse effects include residual numbness of the upper lip (distressing to some children) and development of a small hematoma at the site of injection.
Superficial Cervical Plexus Block
The superficial cervical plexus supplies sensory innervation to the neck, the pinna, and the mastoid area. With US guidance, the sternocleidomastoid is identified at the level of the cricoid cartilage (C6), and a needle is inserted along the posterior border of the sternocleidomastoid, where the local anesthetic is injected (Fig. 7). This technique is often used for children undergoing mastoid repair surgery and for cochlear implants.63 Serious adverse effects can occur from injection into a blood vessel, but the use of US technique decreases the risk.
Suprazygomatic Maxillary Nerve Block
The suprazygomatic maxillary nerve block is an alternative approach to a maxillary nerve block, and when used bilaterally, is effective in the management of cleft palate repair in children. The suprazygomatic approach is preferred because it limits needle insertion trajectory, thereby avoiding inadvertent intraorbital puncture through the infraorbital fissure. This block is performed under US guidance and enables direct visualization of needle positioning and spread of the local anesthetic solution. The US probe is placed over the maxilla and under the zygomatic bone, inclined at 45 degrees in the frontal and horizontal planes. The pterygopalatine fossa is visualized, with the maxilla anterior and greater wing of the sphenoid posterior. After puncture at the frontozygomatic angle, at the junction of the upper edge of the zygomatic arch and the posterior orbital rim, the needle is advanced to the greater wing of the sphenoid. The needle is then withdrawn several millimeters and redirected toward the nasolabial fold, progressing in the direction of the pterygopalatine fossa, and the internal maxillary artery is identified (Fig. 8). Advancement through the temporalis muscle is noted with loss of resistance and signifies appropriate puncture depth. After aspiration for blood, US can be used to observe the spread of local anesthetic in the pterygopalatine fossa and should be observed clearly in most cases.64
The paravertebral block is a well-described technique to provide analgesia in dermatomal distribution for chest wall and thoracic surgeries. Several approaches to the paravertebral nerve block (PVNB) have been described in children65 and adults.66 After positioning the patient laterally for single PVNB or prone for bilateral PVNB, the desired thoracic level is identified using surface landmarks. A linear US probe is placed in a transverse orientation over the midline of the spine and desired dermatome. The spinous process is characteristically hyperechoic and looks like an inverted v. After identification of the spinous process, the probe is moved laterally to reveal the tip of the transverse process, in the same view as the parietal pleura. Here, a hyperechoic structure is identified as the internal intercostal membrane, connecting the edge of the internal intercostal muscle to the lower edge of the transverse process. Using an in-plane technique, a needle is inserted lateral to the edge of the US probe and advanced, at an angle, from lateral to medial until the needle tip is through the internal intercostal membrane, between the parietal pleura and the acoustic shadow of the transverse process (Fig. 9). Needle position is confirmed by downward depression of the pleura with injection. Paravertebral nerve blocks may be performed as single injections or catheters may be placed for infusions. This block is useful when motor blockade or hypotension must be avoided or to avoid the epidural space when coagulopathy is suspected.
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