Pediatric regional anesthesia has gone through significant development in recent years with advances in safety information, pharmacology, and block techniques. There is an increasing interest in regional anesthesia in pediatrics beyond the common caudal, epidural, or spinal. With improvements in equipment that are specific to children and the addition of ropivacaine as a proven local anesthetic, pediatric regional anesthesia, and specifically peripheral nerve blockade, should continue to gain popularity. The last literature reviews in major anesthesia journals on pediatric regional anesthesia were published more than a decade ago (1,2).
The popularity of regional anesthesia as a supplement to general anesthesia in children has grown out of recognition of its advantages beyond simple avoidance of general anesthesia. Suggested benefits include the decreased intraoperative requirement for general anesthetics, less of a need for the use of parenteral opioids thereby limiting the incidence of respiratory depression, and limitation of stress hormone responses (1,3,4). Improved postoperative analgesia and shortened recovery for outpatient surgery have provided further impetus for refinement of techniques that can be used safely in combination with general anesthesia in children.
The goal of these techniques that specifically and peripherally target the location of the surgery is to minimize the undesirable side effects of central blocks such as urinary retention, hypotension, and muscle weakness in unaffected areas. Additionally, when compared with central regional blockade, peripheral nerve blocks may be associated with a decreased incidence of serious sequelae as demonstrated in a large-scale study by the French-Language Society of Pediatric Anesthesiologists, which led the authors to suggest that peripheral blocks be used more often in place of central blocks when appropriate (5). The following review will discuss the safety and the unique differences between adults and children that influence the anesthetics and techniques of peripheral nerve blockade in children.
A common misconception is that performing blocks on anesthetized patients, particularly in children, is not safe. The anesthesia literature that has provided safety data on pediatric regional anesthesia has concluded that, overall, these techniques have extremely small complication rates (5–11). The limitation to these reports is that they typically only include information on the central neuraxis blocks. An exception to this limitation was demonstrated by the report from the French-Language Society of Pediatric Anesthesiologists (5). This one-year study of 24,409 regional blocks in children revealed a complication rate of 1.5 per 1000 in the 60% of children receiving central blocks, and 0 per 1000 in the 38% of children who received peripheral nerve blocks. The authors concluded that these findings should renew the interest in peripheral techniques by anesthesiologists who have sufficient experience in their usage. A subsequent editorial showed the pitfalls with the French study, such as selection bias and lack of efficacy data on the peripheral nerve blocks (12). This same editorial, however, also reconfirmed the advantages of decreased urinary retention and increased duration of analgesia by using a peripheral nerve block.
Certain inherent features of pediatric anatomy and physiology add an additional level of safety to regional anesthesia and specifically to peripheral nerve blockade. These features include a lack of hypotensive response from a sympathectomy produced by the local anesthetic, which is often seen in adults, but only rarely in children. This effect may be a result of either the immature sympathetic nervous system in children younger than five–eight years or a result of the relatively small intravascular volume in the lower extremities thereby limiting venous pooling (13). Although this is a phenomenon of central blockade, it is reassuring to know that severe hypotension should not occur as a result of accidental epidural spread from either a lumbar plexus or paravertebral block. The presence of loose perineurovascular sheaths offers another advantage to regional anesthesia in children by allowing a wider spread of local anesthetic for a large area of analgesia from a single injection site. This should theoretically decrease the chance of inadvertent local anesthetic overdose that may occur with multiple injections.
Pharmacology and Physiology
When performing regional techniques in pediatric patients, one should keep safety in mind and be aware of the differences between adults and children with regard to pharmacology, physiology, and appropriate dosing. Perhaps the most important difference between adult and pediatric pharmacology is the increased risk of toxicity when using local anesthetics in the younger age groups. Infants younger than two months are particularly at risk because of immature hepatic metabolism and decreased plasma proteins such as albumin and α-1-acid glycoprotein (14). This age-effect results in increased serum concentrations of the unbound amide local anesthetics, particularly bupivacaine and ropivacaine, which are normally 90% protein-bound (15). Infants also have decreased levels of plasma pseudocholinesterase that theoretically could increase the risk of toxicity with ester local anesthetics (16,17). This does not appear to be clinically relevant as the half-life of ester anesthetics such as chloroprocaine is still within the ranges of adult patients. All children may be at increased risk of local anesthetic toxicity because of the rapid increase in blood levels of local anesthetic that may occur as a result of the relatively higher cardiac output and regional blood flow that are present in this age group (18,19). Although the routine use of epinephrine for test dosing is controversial because of its lack of total reliability, the addition of epinephrine to the local anesthetic solution may be used to decrease the rapid vascular uptake that can occur at the site of injection. This effect was illustrated in a study that compared plain bupivacaine with bupivacaine and epinephrine 1:200,000 (5 μg/mL) for a fascia iliaca compartment block (20). The maximum plasma concentration in the plain bupivacaine group was 1.1 μg/mL and peaked at 20 minutes compared with a level of 0.35 μg/mL in the bupivacaine with epinephrine group, which peaked at 45 minutes. Also, because the vast majority of children receive regional blocks while under general anesthesia and are unable to describe the prodrome that occurs from intravascular injection of local anesthetic, epinephrine 1:200,000 may aid in detecting the inadvertent intravascular delivery of local anesthetic before neurologic or cardiac sequelae (21). In the presence of halothane, the use of epinephrine as a test dose has been shown to be most reliable when the patient has received atropine, 10 μg/kg, before the test (22). This addition of atropine may depress the parasympathetic tone and thus enhance the sympathetic accelerator effect of epinephrine. This effect of atropine was not present when tested in a similar fashion in the presence of sevoflurane (23). In both studies, an increase in heart rate of 10 bpm was found to be an indication of intravascular injection, whereas using the older criteria of 20 bpm would result in a large number of false negatives of intravascular injection. A 25% increase in T wave amplitude has been shown to be as reliable an indicator as heart rate increase (24). Whether or not epinephrine has been added to the local anesthetic, it is important to remember that there is no good substitute for meticulous attention to the electrocardiogram for ST-T wave changes and slow, incremental dosing (25). Aspiration of blood, although helpful if present, is not reliable, and it is unknown what the relationship between a negative aspiration and the possibility of a positive test response may be when performing a peripheral nerve block in children.
Peripheral nerve blocks, with the exception of intercostal blockade, should decrease the risk of toxicity from increased uptake when compared with central neuraxis blocks. The following blocks are in order of increasing speed of absorption:
- 1. Peripheral nerve blocks of the lower extremity,
- 2. Peripheral nerve blocks of the upper extremity,
- 3. Caudal blocks,
- 4. Epidural blocks,
- 5. Intercostal nerve blocks,
- 6. Interpleural analgesia, and
- 7. Topical airway applications.
To prevent the occurrence of neurologic and cardiac side effects, maximal dosing guidelines should be strictly followed. The maximum recommended doses of the amides most commonly used in children are presented in Table 1. Ropivacaine has yet to have appropriate pediatric dosing established, although it appears to be nearly equipotent to bupivacaine in central and peripheral blockade (26–29).
Inherent physiologic properties in children result in a decreased minimum anesthetic concentration required to block impulse conduction (30). In younger children, particularly infants, nerves have a thinner myelin sheath, a smaller fiber diameter, and a shorter internodal distance. For these reasons, it is possible to produce an adequate surgical block by using smaller concentrations of local anesthetics in children compared with adults. Although strict age criteria for achieving the adult minimum anesthetic concentration are yet to be established, clinical experience suggests that the smaller concentrations provide sufficient surgical block for children who are younger than the early school ages. The larger concentrations are required for adequate surgical analgesia in the older children and adolescents. Future study to determine the ages and concentration requirements would help to clarify this issue.
Regardless of the local anesthetic chosen or the volume, acetaminophen or a nonsteroidal may be a useful adjunct to improve postoperative analgesia. For example, rectal acetaminophen 35–40 mg/kg or ketorolac 0.5–1 mg/kg will provide additional analgesia without sedating effects and will result in less postoperative nausea and vomiting (31–33). Specific guidelines and further recommendations on adjunctive therapy, although an important part of the overall regional anesthesia experience, are beyond the scope of this review.
Despite the risks of increased toxicity in children, the use of the appropriate equipment should help decrease the risk of injury. Although not proven that a nerve stimulator decreases the risk of neuropathy in anesthetized children, we recommended the use of one to improve the success rate with peripheral nerve blocks. When used in combination with insulated needles, the ability to locate a peripheral nerve in children becomes more reliable despite the relatively small size and variability in anatomy, in our experience. A 1- or 2-inch insulated needle will suffice for the vast majority of peripheral nerve blocks in children, with the exception of sciatic block in older children that will require a 4-inch needle. The nerve stimulator is set at 1 to 1.2 mA (higher if using noninsulated needles) and frequency at 2 Hz for repetitive outflow until the desired nerve is stimulated as seen by muscle response. Once the response is seen, voltage is decreased to less than 0.5 mA, and the tip of the needle should be “fine tuned” so that adequate but not intense muscle response is still present. If one finds that the muscle group shows very strong contractions with stimulation at less than 0.4 mA, the needle should be withdrawn slightly and readjusted carefully on the chance that the tip is intraneural. In anesthetized children, intraneural injections will not be easily detected, so one should look carefully for signs such as increased heart rate or intense muscle response at very low voltage, i.e., 0.2 mA. Not all of the blocks in this review will require a nerve stimulator or an insulated needle for success. An experienced regionalist may even be able to locate the sciatic nerve by using the anterior approach merely by loss of resistance (34).
With an understanding of anatomy and pharmacology, and the appropriate equipment, pediatric anesthesiologists are able to perform safe and effective peripheral nerve blocks in an efficient manner. A variety of peripheral nerve blocks will be presented along with possible indications, basic techniques, and potential complications.
Upper Extremity Nerve Blocks
The brachial plexus is formed mainly of C5-8 and T1 and innervates those muscles that supply the shoulder, arm, and hand. The axillary nerve block may be used for such common pediatric operations as syndactyly release or finger reimplantation (35). To perform the procedure by using a one-injection technique and nerve stimulator, the axillary artery is palpated, and the needle is inserted immediately superior to the artery high in the axilla. The needle should be at a 45 degree angle pointing cephalad toward the midpoint of the clavicle and advanced until there is evidence of nerve stimulation seen distally (Fig. 1). This block may also be successfully performed without the use of the nerve stimulator by using the distinct “pop” into the periplexus sheath as the indicator of success. After local anesthetic injection, the arm should be adducted with distal pressure held on the artery. This improves cephalad spread by releasing the pressure of the head of the humerus from the fossa. Because there is a 40%–50% chance of missing the musculocutaneous nerve when performing an axillary block and many procedures require its analgesia because of its sensory innervation of the lateral forearm, this nerve may be blocked as it passes through the body of the coracobrachialis muscle. By using the same insulated needle from the axillary block, the coracobrachialis muscle is grasped, and the needle is inserted directly into the belly of the muscle while looking for biceps stimulation. Once seen and maintained at less than 0.5 mA, local anesthetic may be injected.
The complications of axillary block in children include hematoma and secondary nerve compression (36). For this reason, a transarterial approach is not recommended unless firm pressure is held on the artery for at least five minutes after the block is performed. The two-injection technique may also not be ideal in children as it can result in a relative distortion of anatomy with the first injection, an increased risk of arterial puncture, or inadvertent delivery of increased volumes of local anesthetic (35).
A brachial plexus block that was designed for use in children is the parascalene block (35). This approach will provide analgesia for surgery of the shoulder joint and has advantages over an interscalene approach by avoiding major structures in the neck. The use of the parascalene block decreases the chance of vascular injection and spares the phrenic nerve. This latter advantage is especially important in infants who depend on their diaphragm for respiratory function. The child should be placed supine with a roll under the shoulders and with the arm down to the side. The head should be extended and turned opposite the side to be blocked. A line is drawn between the midpoint of the clavicle and the transverse process of C6 (Chassaignac’s tubercle). The needle should be inserted perpendicular to the skin at the junction of the upper two thirds and lower one third of this line near the external jugular vein (Fig. 2). A nerve stimulator is used to determine the depth of the brachial plexus, which should be 7 to 30 mm below the skin, depending on the age of the patient (35). Complications of the parascalene approach include puncture of the external jugular vein, pneumothorax, and Horner’s syndrome (<5%).
Dosing of upper extremity blocks depends on the age and size of the patient. As a general rule, dosing consists of 0.3–0.5 mL/kg bupivacaine 0.25% or ropivacaine 0.2% in children younger than five–eight years. In older children, the larger concentrations may be required, i.e., 0.3–0.5 mL/kg bupivacaine 0.5% or ropivacaine 0.5%. Epinephrine 1:200,000 (5 μg/mL) should be added to the local anesthetic for the reasons previously discussed. Bupivacaine and ropivacaine should provide at least eight hours of analgesia.
Lower Extremity Nerve Blocks
Lower extremity blocks include those of the lumbar plexus (L1-4) and sciatic (L4-S3) nerves and are generally used for orthopedic and plastic surgery procedures. The femoral nerve block is extremely simple to perform and may be used for a variety of cases, such as femoral shaft fractures (without using nerve stimulation so that additional pain with movement is not incurred) or in conjunction with a sciatic block for distal extremity surgery (37,38). The child should be placed supine with the feet rotated outward. The femoral artery is palpated just below the inguinal ligament. The needle is inserted with a slight cephalad angle to the skin at 0.5–1 cm below the inguinal ligament and 0.5–1 cm lateral to the artery (Fig. 3). A distinct pop should be felt as the needle pierces the fascia lata. The quadriceps will then contract demonstrating a distinct “patellar kick” a nerve stimulator is used. If a nerve stimulator is not used, a fan technique can result in great success with this block. One must keep in mind that the femoral vessels are in close proximity, and frequent aspiration for blood should be performed to detect and avoid intravascular injection. Holding distal pressure during injection may result in cephalad spread of the local anesthetic in the femoral sheath resulting in a “three-in-one” block of femoral, lateral femoral cutaneous, and obturator nerves. Prolonged analgesia for femur fractures in trauma patients may be accomplished by using continuous peripheral nerve catheters and continuous infusion of local anesthetic (39).
If increased spread is needed beyond the femoral nerve, a popular pediatric block, the fascia iliaca compartment block should be considered. The fascia iliaca block is relatively simple to perform and provides anesthesia of the femoral (100%), lateral femoral cutaneous (90%), and obturator (75%) nerves by a spread of anesthetic behind the fascia iliaca. It is effective in more than 90% of children when compared with a three-in-one block, which has unreliable spread and is only 20% effective (40). The fascia iliaca block may be used in addition to IV sedation to perform muscle biopsies in children with suspected malignant hyperthermia. To perform the fascia iliaca compartment block, the needle is inserted 0.5–1 cm below the junction of the lateral one third and medial two thirds of the inguinal ligament (Fig. 4). Rather than nerve stimulation, a loss of resistance technique may be used to feel entry through the fascia lata, and again as the needle penetrates the fascia iliaca. If there is no resistance to injection, local anesthetic is then delivered with digital pressure held distally to encourage cephalad spread.
Femoral nerve and fascia iliaca blocks pose little risk beyond inadvertent vascular puncture. If the femoral artery is entered, pressure is held for at least five minutes to prevent a hematoma. It is important to identify the inguinal ligament and avoid structures within this area.
The lumbar plexus block will provide analgesia of lumbar nerves L1-4 and may be used for operations on the hip and thigh, such as femoral plate insertion or removal. This block anesthetizes the distal branches of the plexus including the iliohypogastric, ilioinguinal, and genitofemoral nerves that innervate the surgical sites of many pediatric procedures in the groin area. The lumbar plexus is found in the psoas compartment with fascia that is derived from the fascia iliaca and is best approached in children by using the procedure described by Winnie et al. (41) rather than the more medial approach of Chayen (42). The child is placed in the lateral decubitus position with knees and thighs flexed. Two lines are drawn: 1) between the two iliac crests, and 2) parallel to the spinous processes and through the ipsilateral posterior superior iliac spine. The needle should be inserted at 90 degrees to the skin at the intersection of these lines and will traverse through the quadratus lumborum (Fig. 5). If contact is made with the transverse process, the needle should be directed slightly cephalad. The ideal nerve stimulation should appear as a strong contraction of the quadriceps muscles comparable to that seen with a femoral nerve block.
Complications should be rare when performing the lumbar plexus block as described. Epidural spread may occur if the needle is placed too medially and has been found to occur at a 90% incidence when using the more medial approach (42). Use of the nerve stimulator should help avoid this undesirable result by localizing nerve stimulation to the ipsilateral branches of the lumbar plexus. One must also adhere to the expected depth of the lumbar plexus to avoid the retroperitoneal structures (42).
To provide analgesia for distal lower extremity procedures, a sciatic nerve block (derived from L4-S3) must be used. The posterior approach is a modification of the classical approach with simplified landmarks and is typically easier and more reliable in children than the lateral or anterior approach (43). To perform the posterior sciatic block, the child is placed in the lateral decubitus position with the legs flexed at the knee and hip. The point of needle insertion in children is at the midpoint of a line drawn between the tip of the coccyx and the greater trochanter of the femur (Fig. 6). The needle should be perpendicular to the skin and advanced medially and upward toward the lateral border of the ischial tuberosity until a muscle twitch is seen in the foot. When performed in conjunction with a lumber plexus block, the positioning of the child remains the same, and the lower extremity can be blocked in its entirety.
One potential complication related specifically to the posterior approach to the sciatic is the possibility of piercing the nerve if it is trapped against the ischium. This same concern was raised in the past with intragluteal injections, particularly in neonates (44,45). The sciatic nerve damage that occurred in these reports was not related to the posterior approach to the sciatic nerve, and none of them were from local anesthetic; thus, the concern should not apply to this block (46).
Another approach to the sciatic nerve that is gaining popularity in pediatrics is the popliteal fossa block. The advantage to this approach is its distal blockade and relative ease of performance. This technique is often described as being performed in the prone position; however, because of the ease of positioning in most children, it may be performed simply by lifting the supine child’s leg with the knee and thigh flexed (47,48). The apex of the popliteal fossa triangle (formed by the biceps femoris tendon laterally and semimembranous and semitendinous tendons medially) is identified, and this triangle is divided into medial and lateral halves (Fig. 7). The point of needle insertion is 1 cm lateral to this line, 1 to 2 cm proximal to the popliteal crease, and lateral to the popliteal artery. A blunt insulated needle, directed perpendicular to the skin or with a slight cephalad angle, is advanced until a distinct pop and muscle stimulation corresponding to either the tibial or common peroneal nerves are obtained. There remains controversy among regionalists as to the efficacy of this block as the tibial and common peroneal nerves separate proximal to the fossa. Using relatively larger volumes of local anesthetic (0.75–1 mL/kg) may make this block more successful by promoting spread via the epineural sheath to both branches of the bifurcated nerve (49).
Dosing requirements for lower extremity blocks are typically higher than those of the brachial plexus. Volumes of 0.5–1 mL/kg of 0.25% bupivacaine or 0.2% ropivacaine in children younger than five–eight years may be used with the higher range reserved for lumbar plexus anesthesia. One can increase the concentration in older children to 0.5% bupivacaine or 0.5% ropivacaine with particular care not to exceed maximal allowable doses. Epinephrine 1:200,000 should be added to the solution. If a combination of two nerves or more are to be blocked, one must determine the maximal allowable dosage of the local anesthetic to be used and not exceed that amount. It is important to remember that the toxicities of different local anesthetics are additive. The duration of analgesia is dependent on the local anesthetic used and should be similar to that of the upper extremity blocks.
Continuous Peripheral Nerve Blockade
Continuous peripheral nerve blockade may prolong analgesia for extensive surgical procedures or be used therapeutically for improvement in perfusion of an extremity. This involves the placement of a catheter into the perineural sheath to allow for repeated injections or a continuous infusion. For this purpose, the insulated needle can be used as described with the nerve stimulator to locate the peripheral nerve. Once this has been accomplished, the initial bolus dose of the local anesthetic is administered. There are then several options on how to place a catheter depending on the equipment available and the size of the patient. One may use a standard single-lumen central line kit (3F or 4F catheter) and the Seldinger technique to place the catheter in the sheath. A 3F polyethylene catheter can be placed over a 0.018-inch wire that has been passed through a 22-gauge insulated needle or a 4F catheter can be placed over a 0.021-inch wire that has been passed through a 20-gauge insulated needle (50). Alternatively, there are commercially available kits (B. Braun Medical, Inc. Bethlehem, PA) that provide an 18-gauge insulated Touhy needle and 20-gauge catheter to deliver continuous analgesia (51). Several lengths of Touhy needles are available in these kits to allow for easier placement of these catheters in many ages, although it may still be difficult to manage an 18-gauge Touhy in the very small patient.
The dosing for these continuous catheters must be calculated with particular attention to maximal allowable infusion rates of local anesthetic as demonstrated in Table 1. For example, a typical 70-kg adult may receive 10 mL/h of ropivacaine 0.2% in a peripheral nerve catheter. If this amount is then converted on a per kilogram basis for a 10-kg child, the rate would be 1.4 mL/h of 0.2% ropivacaine. This would deliver 2.8 mg/h (or 0.28 mg · kg−1 · h−1) to the 10-kg child, which is well below the maximum of 0.4 mg · kg−1 · h−1 recommended for central blocks (52). This example, of course, requires extrapolation of adult data to pediatrics and ropivacaine data from bupivacaine recommendations. Previous experience with continuous infusions of local anesthetics in peripheral nerve catheters in children have recommended a starting rate of 0.15 mL · kg−1 · h−1 of bupivacaine 0.25% (50). Although uptake of local anesthetic from continuous peripheral nerve catheters in children is not yet known, systemic uptake is less from peripheral nerves when compared with central blocks, therefore the margin of safety should be improved. There remains much work to be done in the area of postoperative pain control using localized approaches in children.
Ilioinguinal/Iliohypogastric Nerve Blocks
Peripheral nerve blockade for procedures in the inguinal region includes primarily ilioinguinal and iliohypogastric (ILIH) nerve blocks. ILIH nerve blocks have been shown to provide excellent postoperative pain control for inguinal herniorrhaphy and orchiopexy and allow for earlier ambulation and urination with no lower extremity weakness (53–59). Additionally, blood levels of local anesthetics have been shown to be well below the toxic threshold in children with ILIH blocks for either unilateral or bilateral inguinal procedures (60).
The ilioinguinal and iliohypogastric nerves both originate from the first lumbar nerve root and pass anteriorly near the anterior superior iliac spine before branching to innervate the tissues of the inguinal region and upper scrotum. Blockade of these nerves is generally performed simultaneously by locating a point 1 cm superior and 1 cm medial to the anterior superior iliac spine (1,61). A 22- or 25-gauge, blunt-tipped needle is first directed posterolaterally to contact the inner aspect of the ileum and then withdrawn slightly. Local anesthetic is then continually injected as the needle is withdrawn to the subcutaneous tissue. By redirecting and advancing the needle toward the pubic symphysis, a characteristic “pop” is felt as the external oblique muscle is penetrated. Local anesthetic is then injected in a fan-shaped manner into the body of the muscle and surrounding subcutaneous tissue and may be redirected toward the umbilicus. Alternatively, the nerves can be anesthetized surgically by infiltrating local anesthetic into the muscles at the lateral aspect of the inguinal incision before closure, often in combination with infiltration of the incision. Unfortunately, this is generally performed at the end of the procedure to avoid distortion of the anatomy, eliminating the intraoperative advantages of a regional anesthetic technique combined with general anesthesia.
The ILIH block should be relatively free of complications when used with attention to underlying structures and care to avoid the inguinal area. Transient femoral nerve block is an uncommon side effect, and colonic perforation has been reported (62,63).
Penile Nerve Block
Nerve blockade for procedures on the penis includes dorsal penile nerve block, subcutaneous ring block, and topical anesthesia. The most common operation on the penis is newborn circumcision. Unfortunately, many circumcisions are performed on newborns without the benefit of anesthesia (64,65). Recent investigations have shown that the stress response of awake newborns to circumcision is less when performed with some form of anesthesia and that ring block is more effective than either dorsal penile nerve block or application of a eutectic mixture of local anesthetic cream before newborn circumcision (66–69). For older children under general anesthesia, dorsal penile nerve block is as effective for postoperative pain control as caudal blockade with fewer adverse effects and blood levels of local anesthetic well below the toxic range (70–72). Dorsal penile nerve block has also been described as an effective alternative to general anesthesia in children age 6–17 years (73). Subcutaneous ring block similarly provides effective postoperative analgesia after penile surgery and should result in a lower incidence of complications compared with other techniques (74).
The principle innervation of the penis is via the two dorsal penile nerves, which are branches of the pudendal nerves derived from the sacral plexus. The penile nerves travel near the dorsal penile arteries in the vicinity of Buck’s fascia to innervate the glans and the distal two thirds of the body of the penis. The ilioinguinal and genitofemoral nerves supply a small portion of the innervation of the base of the penis and are derived from the lumbar plexus. These nerves need not be blocked for a simple circumcision.
Several techniques have been described for blocking the dorsal penile nerves. The most important potential complications are damage to dorsal vascular structures and the formation of a compressive hematoma. Subcutaneous ring block is technically easy and is unlikely to cause a compressive hematoma. It is performed by infiltrating local anesthetic circumferentially around the base of the penis, forming a visible wheal as the block is performed (74). Generally, 1–5 mL of local anesthetic is required. Care must be taken to keep the needle subcutaneous, to avoid obvious blood vessels, and to never use epinephrine-containing local anesthetic. The duration of analgesia is dependent on the local anesthetic used. Bupivacaine 0.25%–0.5% may provide 6–12 hours of analgesia or more (70,71,75).
Perhaps the most interesting prospect in regional anesthesia is the use of paravertebral nerve blocks (PVB). This block has emerged as an excellent alternative to general anesthesia in adults for management of breast cancer surgery and herniorrhaphy (76,77). It is also an ideal adjunct with general anesthesia in children who undergo urologic surgery or thoracotomies (78,79). Postoperative morphine requirements have been shown to be significantly lower by using a continuous PVB when compared with a continuous epidural catheter in children after renal surgery (79).
To perform a PVB in children, it is important to review the expected depth of the paravertebral space (80). Because of the variation of size in children, one should not only be aware of the expected depth, but also use a loss of resistance technique to find the space rather than judge the location by depth alone (81). The child is placed in the lateral position. The tips of the spinous processes are marked at the levels that need to be blocked for the proposed surgery. Although the distance from the anatomic midline to point of puncture is 2–3 cm in adults, a rule of thumb in children is that the distance from the midline to the point of lateral puncture should correspond to the distance from one spinous process to another. There are also formulas available that are based on body weight (80). The formula for distance from spinous process to paravertebral space in mm = 0.12 × body weight (kg) + 10.2 and the formula for depth in mm = 0.48 × body weight (kg) + 18.7. A small-gauge Touhy needle or spinal needle with stylet and blunt point may be used. The needle is inserted perpendicular to the skin on the ipsilateral side at the measured distance lateral to midline and at the level of the marked spinous process (Fig. 8). The needle is then advanced until the corresponding transverse process is contacted. The needle is “walked” over the top of the process, a syringe is attached, and a loss of resistance to saline technique is used to identify the paravertebral space after traversing the costotransverse ligament. The loss of resistance is similar to, but not as defined as, the piercing of the ligamentum flavum when performing an epidural.
Potential complications of the PVB include pneumothorax (<1%), vascular puncture, and hypotension (81). The latter complication should rarely be seen in children because of a lack of sympathectomy response in patients younger than five years. This was confirmed by Lonnqvist et al. (82) as no hypotension was observed in the 48 children in the study who received a PVB.
To use this block successfully in children, one may use a single injection of 0.5 mL/kg bupivacaine 0.25% or ropivacaine 0.2% with epinephrine at the desired level. If using multiple levels in children, it is important not to exceed the maximal allowable dosage. A maximum of 5 mL per level is more than enough local anesthetic in even the largest child when multiple levels are to be blocked individually. If placing a catheter in the paravertebral space, dosing has been effective by using an infusion of bupivacaine 0.25% with 1:200,000 epinephrine at a rate of 0.25 mL · kg−1 · h−1 (81).
Although regional anesthesia is commonly practiced in adult patients, there remains some hesitation in applying these practices to children. With improvement in technique and refinement in equipment, these valuable techniques can now be applied to even our youngest patients. As with adult patients, regional anesthetic techniques and peripheral nerve blockade can be used instead of general anesthesia, as an adjunct to general anesthesia as a means of controlling the surgical stress response and avoiding the use of IV opioids, or to simply provide postoperative analgesia. Additionally, the improvement in regional blood flow after peripheral nerve blockade can be used as a therapeutic tool in specific problems where there are alterations of regional blood flow, e.g. digital reimplantation. Postoperatively, peripheral nerve blocks in children are particularly promising in that their prolonged duration when compared with central blocks should allow for a smoother recovery with an increased duration of the pain-free period. The advent of sustained-release local anesthetics should also increase the popularity of peripheral nerve blockade. Hopefully, appropriate clinical trials will be conducted to confirm our observations and experience.
1. Yaster M, Maxwell LG. Pediatric regional anesthesia. Anesthesiology 1989; 70:324–38.
2. Dalens B. Regional anesthesia in children. Anesth Analg 1989; 68:654–72.
3. Kehlet H. Epidural analgesia and the endocrine-metabolic response to surgery-updates and perspectives. Acta Anaesthesiol Scand 1984; 28:125–7.
4. McNeely JK, Farber NE, Rusy LM, Hoffman GM. Epidural analgesia improves outcome following pediatric fundoplication. Reg Anesth 1997; 22:16–23.
5. Giaufre E, Dalens B, Gombert A. Epidemiology and morbidity of regional anesthesia in children: a one-year prospective survey of the French-Language Society of Pediatric Anesthesiologists. Anesth Analg 1996; 83:904–12.
6. Broadman LM. Complications of pediatric regional anesthesia. Reg Anesth 1996; 21:64–70.
7. Broadman LM, Rice LJ. Neural blockade for pediatric surgery. In: Cousins MJ, Bridenbaugh PO, eds. Neural blockade in clinical anesthesia and management of pain. 3rd ed. Philadelphia: JB Lippincott, 1996:.
8. Bosenberg AT, Ivani G. Regional anesthesia-children are different. Paediatr Anaesth 1998; 8:447–50.
9. Krane EJ, Dalens BJ, Murat I, Murrell D. The safety of epidurals placed during general anesthesia. Reg Anesth Pain Med 1998; 23:433–8.
10. Goldman LJ. Complications in regional anaesthesia. Paediatr Anaesth 1995; 5:3–9.
11. Pietropaoli JA, Keller MS, Smail DF, et al. Regional anesthesia in pediatric surgery: complications and postoperative comfort level in 174 children. J Pediatr Surg 1993; 28:560–4.
12. Berde C. Regional anesthesia in children: what have we learned? Anesth Analg 1996; 83:897–900.
13. Dohi S, Naito H, Takahashi T. Age related changes in blood pressure and duration of motor block in spinal anesthesia. Anesthesiology 1979; 50:319–23.
14. Thomas J, Long G, Moore G, Morgan D. Plasma protein binding and placental transfer of bupivacaine. Clin Pharmacol Ther 1975; 19:426–34.
15. Lee A, Fagan D, Lamont M, Tucker GT, et al. Disposition kinetics of ropivacaine in humans. Anesth Analg 1989; 69:736–8.
16. Zsigmond EK, Downs JR. Plasma cholinesterase activity in newborns and infants. Can Anaesth Soc J 1971; 18:278–85.
17. Finster M. Toxicity of local anesthetics in the fetus and newborn. Bull NY Acad Med 1976; 52:222–5.
18. Eyres RL, Bishop W, Oppenheim RC, Brown TCK. Plasma bupivacaine concentrations in children during caudal epidural analgesia. Anaesth Intensive Care 1983; 11:20–2.
19. Eyres RL, Hastings C, Brown TCK, Oppenheim RC. Plasma bupivacaine concentrations following lumbar epidural anaesthesia in children. Anaesth Intensive Care 1986; 14:131–4.
20. Doyle E, Morton NS, McNicol LR. Plasma bupivacaine levels after fascia iliaca compartment block with and without adrenaline. Paediatr Anaesth 1997; 7:121–4.
21. Tanaka M, Nishikawa T. The efficacy of a simulated intravascular test dose in sevoflurane-anesthetized children: a dose-response study. Anesth Analg 1999; 89:632–7.
22. Desparmet J, Mateo J, Ecoffey C, Mazoit X. Efficacy of an epidural test dose in children anesthetized with halothane. Anesthesiology 1990; 72:249–51.
23. Tanaka M, Nishikawa T. Simulation of an epidural test dose with intravenous epinephrine in sevoflurane-anesthetized children. Anesth Analg 1998; 86:952–7.
24. Tanaka M, Nishikawa T. Evaluating T-wave amplitude as a guide for detecting intravascular injection of a test dose in anesthetized children. Anesth Analg 1999; 88:754–8.
25. Freid EB, Bailey AG, Valley RD. Electrocardiographic and hemodynamic changes associated with unintentional intravascular injection of bupivacaine with epinephrine in infants. Anesthesiology 1993; 79:394–8.
26. Koinig H, Krenn CG, Glaser C, et al. The dose-response of caudal ropivacaine in children. Anesthesiology 1999; 90:1339–44.
27. Ivani G, Lampugnani E, Torre M, et al. Comparison of ropivacaine with bupivacaine for paediatric caudal block. Br J Anaesth 1998; 81:247–8.
28. DaConceicao MJ, Coelho L, Khalil M. Ropivacaine 0.25% compared with bupivacaine 0.25% by the caudal route. Paediatr Anaesth 1999; 9:229–33.
29. Kohane DS, Sankar WN, Shubina M, et al. Sciatic nerve blockade in infant, adolescent and adult rats: a comparison of ropivacaine with bupivacaine. Anesthesiology 1998; 89:1199–1208.
30. Benzon HT, Strichartz GR, Gissen AJ, Shanks CA, et al. Developmental neurophysiology of mammalian peripheral nerves and age-related differential sensitivity to local anesthetic. Br J Anaesth 1988; 61:754–60.
31. Birmingham PK, Tobin MJ, Henthorn TK, et al. Twenty-four hour pharmacokinetics of rectal acetaminophen in children: an old drug with new recommendations. Anesthesiology 1997; 87:244–52.
32. Korpela R, Korvenoja P, Meretoja OA. Morphine-sparing effect of acetaminophen in pediatric day-case surgery. Anesthesiology 1999; 91:442–7.
33. Splinter WM, Reid CW, Roberts DJ, Bass J. Reducing pain after inguinal hernia repair in children: caudal anesthesia versus ketorolac tromethamine. Anesthesiology 1997; 87:542–6.
34. McNicol LR. Sciatic nerve block for children. Anaesthesia 1985; 40:410–4.
35. Dalens B. Proximal blocks of the upper extremity. In: Dalens B, ed. Regional anesthesia in infants, children and adolescents. Baltimore: Williams & Wilkins, 1995: 275–312.
36. Merril DG, Brodsky JB, Hentz RV. Vascular insufficiency following axillary block of the brachial plexus. Anesth Analg 1981; 60:162–4.
37. McNicol LR. Lower limb blocks for children. Anaesthesia 1986; 41:27–31.
38. Ronchi L, Rosenbaum D, Athouel A, et al. Femoral nerve blockade in children using bupivacaine. Anesthesiology 1989; 70:622–4.
39. Tobias JD. Continuous femoral nerve block to provide analgesia following femur fracture in a paediatric ICU population. Anaesth Intensive Care 1994; 22:616–8.
40. Dalens B, Vanneuville G, Tanguy A. Comparison of the fascia iliaca compartment block with the 3-in-1 block in children. Anesth Analg 1989; 69:705–13.
41. Winnie AP, Ramamurthy S, Durrani Z, Radonjic R. Plexus blocks for lower extremity surgery. Anesthesiol Rev 1974; 1:11–6.
42. Dalens B, Tanguy A, Vanneuville G. Lumbar plexus block in children: a comparison of two procedures in 50 patients. Anesth Analg 1988; 67:750–8.
43. Dalens B, Tanguy A, Vanneuville G. Sciatic nerve blocks in children: comparison of the posterior, anterior, and lateral approaches in 180 pediatric patients. Anesth Analg 1990; 70:131–7.
44. Combes MA, Clark WK, Gregory CF, James JA. Sciatic nerve injury in infants: recognition and prevention of impairment resulting from intragluteal injections. JAMA 1960; 173:1336–8.
45. Gilles FH, French JH. Postinjection sciatic nerve palsies in infants and children. J Pediatr 1961; 58:195–7.
46. Kytta J, Heinonen E, Rosenberg PH, Wahlstrom T, et al. Effects of repeated bupivacaine administration on sciatic nerve and surrounding muscle tissue in rats. Acta Anaesthesiol Scand 1986; 30:625–9.
47. Kempthorne PM, Brown TCK. Nerve blocks around the knee in children. Anaesth Intensive Care 1984; 12:14–7.
48. Vloka JD, Hadzic A, Koorn R, Thys D. Supine approach to the sciatic nerve in the popliteal fossa. Can J Anaesth 1996; 43:964–7.
49. Vloka JD, Hadzic A, Lesser JB, et al. A common epineural sheath for the nerves in the popliteal fossa and its possible implications for sciatic nerve block. Anesth Analg 1997; 84:387–90.
50. Tobias JD. Continuous femoral nerve block to provide analgesia following femur fracture in a paediatric ICU population. Anaesth Intensive Care 1994; 22:616–8.
51. Steele SM, Klein SM, D’Ercole FJ, et al. A new continuous catheter delivery system [letter]. Anesth Analg 1998; 87:228–34.
52. Berde CB. Acute postoperative pain management in children. ASA Refresher Course Lectures 1995; 225:1–7.
53. Casey WF, Rice LJ, Hannallah RS, et al. A comparison between instillation versus ilioinguinal/iliohypogastric nerve block for postoperative analgesia following inguinal herniorrhaphy in children. Anesthesiology 1990; 72:637–9.
54. Markham SJ, Tomlinson J, Hain WR. Ilioinguinal nerve block in children. Anaesthesia 1986; 41:1098–103.
55. Shandling B, Steward D. Regional analgesia for postoperative pain in pediatric outpatient surgery. J Pediatr Surg 1980; 15:477–80.
56. Hinkle AJ. Percutaneous inguinal block for the outpatient management of post-herniorrhaphy pain in children. Anesthesiology 1987; 67:411–3.
57. Hannallah RS, Broadman LM, Belman AB, et al. Comparison of caudal and ilioinguinal/iliohypogastric nerve blocks for control of post-orchiopexy pain in pediatric ambulatory surgery. Anesthesiology 1987; 66:832–4.
58. Splinter WM, Bass J, Komocar L. Regional anaesthesia for hernia repair in children: local versus caudal anaesthesia. Can J Anaesth 1995; 42:197–200.
59. Fisher QA, McComiskey CM, Hill JL, et al. Postoperative voiding interval and duration of analgesia following peripheral or caudal nerve blocks in children. Anesth Analg 1993; 75:173–7.
60. Epstein RH, Larijanii GE, Wolfson PJ, et al. Plasma bupivacaine concentrations following ilioinguinal-iliohypogastric nerve blockade in children. Anesthesiology 1988; 69:773–6.
61. Dalens B. Nerve blocks of the trunk. In: Dalens B, ed. Regional anesthesia in infants, children and adolescents. Baltimore: Williams & Wilkins, 1995: 461–87.
62. Derrick J, Aun C. Transient femoral nerve palsy after ilioinguinal block [letter]. Anaesth Intensive Care 1996; 24:115.
63. Johr M, Sossai R. Colonic puncture during ilioinguinal nerve block in a child. Anesth Analg 1999; 88:1051–2.
64. Rabinowitz R, Hulbert W. Newborn circumcision should not be performed without anesthesia. Birth 1995; 22:45–6.
65. Wellington N, Rieder M. Attitudes and practices regarding analgesia for newborn circumcision. Pediatrics 1993; 92:541–3.
66. Butler-O’Hara M, Lemoine C, Guillet R. Analgesia for neonatal circumcision: a randomized controlled trial of EMLA versus dorsal penile nerve block. Pediatrics 1998; 101:e5.
67. Stang HJ, Gunnar MR, Snellman L, et al. Local anesthesia for neonatal circumcision: effects on distress and cortisol response. JAMA 1988; 259:1507–11.
68. Hardwick-Smith S, Mastrobattista JM, Wallace PA, Ritchey ML. Ring block for neonatal circumcision. Obstet Gynecol 1998; 91:930–4.
69. Lander J, Brady-Fryer B, Metcalfe JB, et al. Comparison of ring block, dorsal penile nerve block, and topical anesthesia for neonatal circumcision. JAMA 1997; 278:2157–62.
70. Yeoman PM, Cooke R, Hain WR. Penile block for circumcision? A comparison with caudal blockade. Anaesthesia 1983; 38:862–6.
71. Vater M, Wandless J. Caudal or dorsal nerve block? A comparison of two local anaesthetic techniques for postoperative analgesia following day case circumcision. Acta Anaesth Scand 1985; 29:175–9.
72. Sfez M, Yann LM, Mazoit X, Dreux-Broucard H. Local anesthetic serum concentrations after penile nerve block in children. Anesth Analg 1990; 71:423–6.
73. Serour F, Cohen A, Mandelberg A, et al. Dorsal penile nerve block in children undergoing circumcision in a day-care surgery. Can J Anaesth 1996; 43:954–8.
74. Broadman L, Hannallah RS, Belman AB, et al. Post-circumcision analgesia: a prospective evaluation of subcutaneous ring block of the penis. Anesthesiology 1987; 67:399–402.
75. White J, Harrison B, Richmond P, et al. Postoperative analgesia for circumcision. Br Med J 1983; 286:1934.
76. Weltz CR, Greengrass RA, Lyerly HK. Ambulatory surgical management of breast carcinoma using paravertebral block. Ann Surg 1995; 222:19–26.
77. Klein SM, Greengrass RA, Weltz C, Warner DS. Paravertebral somatic nerve block for outpatient inguinal herniorrhaphy: an expanded case report of 22 patients. Reg Anesth Pain Med 1998; 23:306–10.
78. Lonnqvist PA, Olsson GL. Paravertebral vs epidural block in children: effects on postoperative morphine requirement after renal surgery. Acta Anaesthesiol Scand 1994; 38:346–9.
79. Eng J, Sabanathan S. Continuous paravertebral block for postthroacotomy analgesia in children. J Pediatr Surg 1992; 26:556–7.
80. Lonnqvist PA, Hesser AU. Location of the paravertebral space in children and adolescents in relation to surface anatomy assessed by computed tomography. Paediat Anaesth 1992; 2:285–9.
81. Lonnqvist PA. Continuous paravertebral block in children: initial experience. Anaesthesia 1992; 47:607–9.
82. Lonnqvist PA, MacKenzie J, Soni AK, Conacher ID. Paravertebral blockade: failure rate and complications. Anaesthesia 1995; 50:813–5.