Introduction
The role of regional anesthesia in adult practice is well-established. Some of the benefits of regional anesthesia include improvement in postoperative respiratory function and bowel function and a decrease in the hormonal stress response.
Regional anesthesia can be safely and effectively used in children of all ages. The use of regional anesthesia in the pediatric population has been gradually evolving and expanding beyond a few centers. Providing adequate analgesia in children during the perioperative period is critically important for patient and parental satisfaction and may improve surgical outcomes. Prevention of pain should be our goal in all possible patient care scenarios.
Options
Regional anesthesia for the pediatric patient can be classified into central neuraxial blocks and peripheral nerve blocks (PNBs). Central neuraxial blocks include the single injection caudal block, which provides analgesia for 4 to 6 hours, or a continuous epidural block in which a catheter is placed for providing continuous delivery of local anesthetic and adjuvants (e.g., clonidine or opioids) into the epidural space. PNBs can be further classified, based on the location, into upper extremity nerve blocks, truncal blocks, and lower extremity nerve blocks. The selective nature of PNBs has made them an attractive option instead of the caudal technique. The increasing use of ultrasound in the perioperative setting has helped in performing these PNBs and in increasing their success rate.
Evidence
Anand and colleagues in their seminal study demonstrated that neonates could mount a hormonal and metabolic stress response in the immediate postoperative period. They found that this stress response correlated with the degree of surgical stress and affected postoperative morbidity and mortality rates. They further showed that blocking this stress response resulted in less patient morbidity in the postoperative period. Another study looking at neonatal circumcision revealed that performing a dorsal penile nerve block reduced the pain related behavior in neonates compared with application of lidocaine/prilocaine (EMLA) cream or no treatment to the site.
Evidence supporting the use of regional anesthesia in children has been accumulating since the 1980s. There has been particular interest in the use of regional anesthesia for decreasing the incidence of postoperative apnea in expremature infants after surgery. Early reports were of the use of epidural analgesia (caudal approach) as a supplement to general anesthesia for decreasing the use of opioid medications in these infants. A Cochrane review analyzed evidence regarding improvement in perioperative apnea, bradycardia, and oxygen desaturation between a purely regional (spinal or epidural) anesthetic technique and general anesthesia. They did not find a statistically significant difference in the proportion of infants having postoperative apnea or bradycardia (relative risk [RR], 0.69; confidence interval [CI], 0.4, 1.21) or postoperative desaturation (RR, 0.91; CI, 0.61, 1.37). When infants sedated preoperatively were excluded from the analysis, the difference reached statistical significance (RR, 0.39; CI, 0.19, 0.81). In the conclusion, the authors noted that their review was based on analysis of only 108 patients and recommended that larger randomized controlled trials be performed to determine whether there was a difference between regional and general anesthesia. The authors also noted the limitations of the spinal anesthesia technique, including its high failure rate (about 10%) and the limited time of surgical anesthesia (50 to 60 minutes).
A prospective randomized study using general anesthesia and a caudal block in former premature infants having inguinal hernia repair did not show any difference in outcomes between the use of sevoflurane and desflurane. The authors recommended a light general anesthesia with an inhalational agent and a caudal blockade for pain relief for expremature infants having inguinal hernia repair. Currently, no consensus exists regarding the use of regional anesthesia only (spinal or caudal), general anesthesia only, or a combined regional anesthesia and general anesthesia technique for this common procedure in a very vulnerable population.
Caudal block is the most commonly performed regional anesthetic technique in children because it is easily learned, reliable, and effective. Caudal block is adequate for all lower extremity and many lower abdominal surgeries. It is not recommended for surgeries above the T9 dermatome (umbilical cord). It is commonly performed in anesthetized children in the lateral decubitus position but can also be performed in the prone position. A short bevel hypodermic needle of the smallest diameter (22- to 25-G needle) is typically used for this block. Specially designed caudal needles with a short bevel and a stylet are available. The sacral hiatus is palpated, and the needle is placed in the most proximal part of the sacral hiatus at a 45- to 60-degree angle to the skin. After the needle pierces the sacrococcygeal membrane, the needle is advanced a further 2 to 5 mm to ensure epidural location. Advancing the needle further may increase the risk of vascular puncture or intrathecal placement. The French-Language Society of Pediatric Anesthesiologists (ADARPEF) study prospectively examined their experience with 24,409 regional anesthetics in the early 1990s. Caudal blocks accounted for about 60% of the procedures performed, all other peripheral blocks accounted for about 20%, and local infiltration accounted for 20%. They reported a complication rate for all blocks to be 0.9 per 1000, and all the complications were minor. A follow-up to this initial report found that, of the nearly 30,000 regional blocks, caudal blocks accounted for 34% of blocks, whereas PNBs accounted for the other 66%. This highlighted the increasing use of peripheral nerve techniques in children. Complications were again noted to be minor with a rate of 1.2 per 1000 blocks; central blocks had a higher complication rate. Fifteen patients developed cardiac toxicity from the local anesthetic, 10 had inadvertent spinal taps, and five developed temporary nerve injuries. In another audit of all 10,163 epidurals placed in the United Kingdom over a 1-year period, 56 complications were noted in this cohort, yielding an incidence of 1 in 189. Five of these were graded as serious (incidence of 1 in 2000), and one was persistent at 12 months (incidence of 1 in 10,000). Two patients developed an epidural abscess, one developed a postdural puncture headache requiring a blood patch, one developed meningism, and another one developed cauda equina syndrome secondary to an incorrectly administered dose (three times the intended bolus) of local anesthetic.
Eyres and colleagues were the first to measure blood levels of bupivacaine after caudal administration in children. Recent data show that blood levels are within safe limits when 1 mL/kg of 0.25% bupivacaine or 0.2% ropivacaine are used for caudal block placement. Both 0.2% ropivacaine and 0.125% or 0.25% bupivacaine have been extensively used to perform the caudal block. Ropivacaine has a lower incidence of motor blockade and a safer profile compared with bupivacaine in case of accidental intravascular injection. A dose of about 1 mL/kg to a maximum of 25 mL is adequate for most indications.
Bosenberg and colleagues were the first to describe successful placement of a thoracic epidural catheter via the caudal route. Subsequent studies showed this technique to be reliably successful when a styleted epidural catheter was used. The technique has a higher success rate when performed in children younger than 1 year of age. Bosenberg and colleagues also studied the pharmacokinetics of 0.2% ropivacaine infusion in neonates and infants and found that the plasma levels of ropivacaine were below the suggested toxic level of 0.375 mgL. However, neonates did show a higher concentration than the infants for unbound ropivacaine levels. On the basis of their observation, the authors advocate the use of a dose of 0.2 mg/kg/hr for infants younger than 180 days old and 0.4 mg/kg/hr for infants older than 180 days ( Figure 70-1 ). Meunier and colleagues evaluated the pharmacokinetics of bupivacaine during an epidural infusion in neonates and infants. They looked at an infusion rate of 0.375 mg/kg/hr for 48 hours and found two infants to have a blood level greater than 0.2 mg/L ( Figure 70-2 ). On the basis of this observation, they recommended a dose of 0.3 mg/kg/hr for infants younger than 4 months of age and a dose of 0.375 mg/kg/hr for infants older than 4 months of age.
As demonstrated by the French study, PNBs are gaining in popularity in the pediatric population, and increasing data are emerging to demonstrate feasibility, efficacy, and safety in this population. Several studies in children have demonstrated the safety, feasibility, and efficacy of PNBs. The advantages of PNB include efficient, site-specific analgesia, a decrease in the need for opioids, and consequently, a decrease in opioid-related side effects. Early reports of regional anesthesia in pediatric practice used the fascial clicks (pops) technique to deposit the local anesthetic in the desired plane. This was followed by the use of peripheral nerve stimulators to elicit a motor response when the needle was in close proximity to the nerve. This technique is limited to the major motor nerves (e.g., femoral and sciatic) and was not applicable to blocks such as the ilioinguinal block and penile block, which are commonly performed in children. The problem with the anatomic and nerve stimulator–based approaches was that they did not provide any information regarding the relation of the nerve to the adjoining structures, location of other important neurovascular structures in the region, or provide any feedback regarding the spreading of local anesthetic in relation to the nerve. The use of ultrasound to perform PNB has permitted the practitioner to have a clear visualization of the nerve and surrounding structures and provides visual confirmation of the spreading of local anesthetic relative to the nerve.
Ultrasound Guidance
Ultrasound is becoming an important aspect of modern medicine. It is providing practitioners with a tool to directly visualize structures within the body and helps diagnose pathology or direct therapy. It is noninvasive and has minimal potential side effects. Compared with the other techniques in modern radiology, it is very portable. Ultrasound helps in localizing the neural structures and in guiding the needle to the intended target. It increases success rates, increases the speed of onset of the block, and lowers the volume of local anesthetic needed for PNB. Ultrasound machines are cheaper and simpler to use than before, the user interface has been simplified, and many are preprogrammed to optimize visualization of nerves and vasculature. Despite its ease of use, basic training is necessary to ensure safety and increase efficacy. Higher frequency settings improve the image resolution (the ability to distinguish two adjacent objects). However, as the frequency increases, more of the ultrasound beam is absorbed by the medium, and the beam cannot penetrate deeper structures. For this reason, higher frequencies (e.g., 7.5 to 15 MHz) are used to provide good detail of superficial structures such as the interscalene brachial plexus and the femoral nerve, whereas lower frequencies (3 to 7.5 MHz) are useful in imaging deeper structures like the sciatic nerve and the infraclavicular brachial plexus. In children, because of their smaller size, the higher frequency transducers can be used to image the sciatic nerve and the infraclavicular brachial plexus and will provide better resolution images.
Role of Regional Anesthesia Technique by Anatomic Region
Abdominal Wall Blocks
Ilioinguinal/Iliohypogastric Nerve Block
The most common block that has been studied in pediatric regional anesthesia is the ilioinguinal/iliohypogastric (IL/IH) nerve block for inguinal hernia repair. The original technique described was the single or double pop technique in which the local anesthetic was placed in a plane between the internal oblique muscle and the transversus abdominis muscle medial to the anterior superior iliac spine. Despite some modifications, the landmark-based technique of needle placement has been associated with bowel injury and does have a high failure rate. One study used ultrasound to assess the placement of local anesthetic by the landmark-based technique. The authors found that the local anesthetic was placed in the correct plane between the internal oblique and transversus abdominis muscles only 14% of the time. Another finding in the same study was that 86% of the IL/IH blocks were rated as clinically adequate. The same group found that, by using ultrasound guidance, the exact location of the needle tip in relation to the IL/IH nerve in the correct fascial plane could be identified, and the volume required to produce a clinically significant block was considerably small (0.075 mL/kg of local anesthetic). On the basis of these studies, it is our recommendation that ultrasound guidance be used to increase the efficacy and safety of the IL/IH block in the pediatric population.
Rectus Sheath Block
The rectus sheath block provides analgesia for umbilical surgeries and other midline abdominal procedures. Local anesthetic is placed around the terminal branches of the ninth, tenth, and eleventh intercostal nerves. One approach is to place the local anesthetic in a plane between the rectus abdominis muscle and the posterior rectus sheath. Ultrasound guidance facilitates placement of the local anesthetic in this plane. In a prospective randomized study comparing ultrasound-guided rectus sheath block with local anesthetic infiltration, our group found a statistically significant decrease in the amount of opioid medication used in the rectus sheath block group. Two techniques, the out-of-plane technique and the in-plane technique for needle placement have been described for this block. Anesthesiologists can choose from either of these techniques based on their comfort level with a particular approach. We would recommend ultrasound guidance for performing rectus sheath block, as the risk of injuring the epigastric vessels or entering the peritoneal cavity does exist with the blind approach.
Transversus Abdominis Plane (TAP) Block
The TAP bock provides analgesia for the anterior abdominal wall. The classic TAP block is performed by placing the local anesthetic in a plane between the internal oblique muscle and the transverse abdominis muscle in the lumbar triangle of Petit (a space bound by the iliac crest, latissimus dorsi muscle, and the external oblique muscle). Evidence regarding the efficacy of TAP block for providing analgesia after abdominal surgery has been variable: some trials have shown superior analgesia compared with a placebo TAP block, whereas others have failed to show additional analgesic efficacy. In the pediatric population, one prospective randomized trial showed a decrease in opioid use in patients who received a TAP block compared with a placebo injection in patients undergoing open appendectomy. Another prospective randomized trial in children found that the IL/IH block provides better analgesia compared with the TAP block for surgery in the inguinal region. No pediatric study has compared the TAP block to epidural analgesia, which is a common technique used for postoperative analgesia for open abdominal procedures.
A recent study points to the need for performing a upper intercostal TAP block in addition to the classic TAP block to cover T7 to T12 dermatomes. In this study, the classic TAP block was seen to provide a sensory block in the T10 to T12 dermatomes. A cadaver study of infiltration of aniline dye using ultrasound guidance as in a classic TAP block found good coverage of segmental nerves at the T10 to L1 level.
Lower Extremity Nerve Blocks
Orthopedic procedures are the most common procedures performed on the lower extremity. Regional anesthesia for lower extremity procedures sometimes requires the performance of more than one nerve block to achieve adequate analgesia depending on the location of the surgery. For knee surgery and procedures above the knee joint, a femoral nerve block is required. Additionally, a sciatic nerve block is required for procedures involving the posterior aspect of the thigh, whereas an obturator nerve block is recommended for procedures involving the medial thigh. For procedures below the knee area, the sciatic nerve block covers most of the area, except the cutaneous area over the medial aspect of the shin, which requires a saphenous nerve block.
Femoral Nerve Block
A femoral nerve block is typically performed just caudad to the inguinal ligament. The femoral artery is located by palpation or with ultrasound guidance, and the femoral nerve is located lateral to the artery. The femoral nerve lies underneath two fascial layers, the superficial fascia lata and the deeper fascia iliaca. The nerve typically lies over the iliacus and psoas muscles, but anatomic variations have been documented where the nerve lies underneath muscular slips from the iliacus muscle. As the nerve passes into the thigh, it divides into an anterior and a posterior division and quickly arborizes. Using the origin of the lateral circumflex femoral artery, a branch of the femoral artery, as a guide for placement of the femoral block may help in the performance of the femoral nerve block before it ramifies and may avoid risk of injury to this branch of the femoral artery. Using ultrasound compared with nerve stimulation to place the femoral nerve block in pediatric patients has been shown to increase the mean duration of analgesia provided by the block (508 versus 335 minutes) and decrease the volume of local anesthetic (0.2 mL/kg versus 0.3 mL/kg) required for the block. For procedures where prolonged analgesia (beyond 10 to 12 hours) may be beneficial (e.g., anterior cruciate ligament repair and tumor excisions), a catheter can be placed in the proximity of the femoral nerve to infuse local anesthetic continuously for 48 to 72 hours postoperatively. Our group reported the role of patient and family education and continued follow-up in successful implementation of a continuous PNB program in the pediatric population.
Lumbar Plexus Block
A few pediatric studies have reported that the lumbar plexus block provides excellent postoperative analgesia after hip and femoral shaft surgeries. The duration of analgesia provided by the lumbar plexus block was greater than that of a caudal block. The use of ultrasound guidance to aid in placement of this nerve block has been described in children. An observational study evaluated the landmarks for placing lumbar plexus block in pediatric patients. In this study, the authors found that the point at three quarters of the distance from the midline of a line connecting the L4 vertebrae to a paramedian line through the posterior superior iliac spine to be feasible for placing a lumbar plexus block. With the use of ultrasound guidance, the lumbar plexus appears as an ovoid structure consisting of hypoechoic dots (fascicles) within the posterior part of the psoas major muscle. Complications related to the lumbar plexus block include renal hematomas, epidural placement, intrathecal placement, and injury to intra-abdominal structures. These should be considered in the risk–benefit analysis when the lumbar plexus block is selected.
Saphenous Nerve Block
Saphenous nerve block is useful as a supplement to the sciatic nerve block for foot and ankle surgery. In a study comparing saphenous nerve blocks performed using a perifemoral approach, transsartorial approach, block at the medial femoral condyle, and below-the-knee field block, the perifemoral and trans-sartorial approaches were seen to be superior. In the trans-sartorial method the sartorius muscle is identified, and the saphenous nerve is located underneath it. The femoral artery runs with the saphenous nerve in the proximal thigh and should be avoided. We prefer to perform the block at a more distal location to avoid the femoral artery.
Sciatic Nerve Block
The sciatic nerve block is used for procedures involving the posterior aspect of the lower extremity and for most procedures below the knee in children. Recent reports in adult and pediatric patients have shown the feasibility of ultrasound guidance for this technique. One prospective study in pediatric patients showed that the use of ultrasound guidance increased the duration of postoperative analgesia by 30%. In addition, the amount of local anesthetic needed in the ultrasound group was decreased. Another study has shown that ultrasound guidance decreases the time to completion of the nerve block and is associated with fewer needle passes for block completion. The sciatic nerve block can be performed at gluteal, subgluteal, midthigh, or popliteal regions on the basis of the area involved in the surgery. Sciatic nerve block has been associated with a higher incidence of motor block. For this reason, a lower concentration of local anesthetic is preferred if a motor block is undesirable. Popliteal sciatic nerve blocks placed under ultrasound and nerve stimulation guidance with the use of a current of less than 0.5 mA (2 Hz, 0.1 msec) to place the nerve block resulted in intraneural injection in 16 of the 17 patients studied. Postoperative follow-up with the use of electrophysiologic testing revealed no injury to the sciatic nerve secondary to the intraneural injection. These data, although limited because of a small sample size, highlight the risk of intraneural and subepineural injection; a possible increased risk of injury exists when low-current intensity (less than 0.5 mA) is used in the placement of a sciatic nerve block with the popliteal approach.
Upper Extremity Nerve Blocks
PNBs along the brachial plexus are used to provide postoperative analgesia for upper extremity procedures. Commonly used techniques in children are the interscalene, infraclavicular, and axillary blocks, depending on the location of the surgery.
Interscalene Brachial Plexus Block
A case series of severe neurologic complications after interscalene blocks performed under general anesthesia led to recommendations against performing this block in patients under general anesthesia. As almost all regional anesthesia in pediatric patients is performed under deep sedation or general anesthesia, this created a safety concern regarding performance of this block in children. Ultrasound guidance has been seen in recent reports to be superior to nerve stimulation in performance of the interscalene block and provides a means of visualizing the spread of the local anesthetic. The use of ultrasound guidance may allow us to safely perform this block in a pediatric population.
Supraclavicular Nerve Block
The ultrasound-guided supraclavicular nerve block has been described in pediatric patients for upper extremity surgery. In the supraclavicular region, the brachial plexus is identified medial to the clavicle, posterolateral to the subclavian artery, and superficial to the first rib. In a prospective study in pediatric patients, infraclavicular nerve block and supraclavicular nerve blocks had similar efficacy and duration of block.
Infraclavicular Nerve Block
The infraclavicular nerve block has been described in the pediatric population for elbow surgery. An advantage of this block is that all the branches of the brachial plexus are still together. The use of ultrasound guidance was seen to help in successful placement of this block in pediatric patients. The use of ultrasound guidance for this block has been shown to have a better success rate compared with the nerve stimulation technique. Continuous perineural infusion with the use of the infraclavicular approach was seen to provide superior postoperative analgesia compared with a supraclavicular approach for distal upper extremity surgery.
Axillary Nerve Block
The axillary nerve block has been described for distal arm and hand procedures. Studies have found the ultrasound-guided axillary nerve block to have a similar or improved success rate compared with nerve stimulation–guided axillary nerve block. One study of the ultrasound-guided axillary nerve block found that the ability to detect needle-to-nerve contact was 74.5% with the nerve stimulation technique and 38.2% with the use of a paresthesia technique. The authors concluded that the low sensitivity of either technique might increase the number of attempts needed to successfully place an axillary nerve block.
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