Regional anesthesia and pain relief in children

Published on 07/02/2015 by admin

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Last modified 22/04/2025

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Regional anesthesia and pain relief in children

Robert J. Friedhoff, MD

Regional anesthesia in the pediatric patient has been undergoing a revival since the early 1990s. These advances have been particularly advantageous for the pediatric patient undergoing outpatient surgery. Regional anesthesia is usually provided along with general anesthesia in the pediatric patient because a regional anesthetic technique can provide prolonged and predictable intraoperative anesthesia and postoperative analgesia. Performance of the nerve block after the induction of anesthesia but prior to the beginning of the operation allows the concentration of general anesthetic agents to be reduced once the block is established. The clinician should be familiar with the anatomic, physiologic, and pharmacologic differences between adult and pediatric patients.

Anatomy

In pediatric patients, target nerves are smaller, closer to other anatomic structures (vessels), and closer to the skin. The caudal extent of the dura and spinal cord extends approximately two interspaces lower in an infant than in an older child or adult, down to S3 to S4 and L3, respectively, but by the time the child is 12 months of age, the anatomy is similar to that of an adult. The epidural fat is more gelatinous and less fibrous in an infant, favoring the spread of local anesthetic agents and the passage of epidural catheters, but by 8 years of age, the child’s epidural space is similar to an adult’s.

Physiology

Clinically significant decreases in blood pressure secondary to sympathectomy from central neuraxis blockade are rare in children younger than 8 years of age.

Pharmacology

The potential for local anesthetic toxicity is increased in infants due to their reduced binding proteins (α₁-acid glycoprotein), resulting in an increased concentration of free local anesthetic drug. Maximum recommended doses for commonly used local anesthetic agents are found in Table 196-1.

Table 196-1

Maximum Recommended Doses for Commonly Used Local Anesthetic Agents

Drug	Dose (mg/kg)
Lidocaine*	3.0
Bupivacaine	2.6
Ropivacaine	3.0

^*With epinephrine 6 mg/kg.

Cooperation

Essentially all regional techniques, with the exception of spinal anesthesia for the high-risk premature infant, are performed in a heavily sedated or anesthetized patient. The use of a peripheral nerve stimulator can be very helpful in performing some of the nerve blocks. The use of ultrasound in identifying nerves can be of benefit in certain circumstances (see later).

Test doses

Use of epinephrine to detect unanticipated intravascular injection in patients under inhalation anesthetics is unreliable and controversial. If used, it is recommended that the local anesthetic agent be injected slowly and with frequent aspiration. Observing the electrocardiographic tracing for changes during injection is recommended.

Topical blocks

EMLA cream is a combination of prilocaine and lidocaine that can be placed on the skin and covered with a transparent film dressing at least 1 h before an invasive procedure (e.g., needlestick, circumcision, separation of preputial adhesions).

Lidocaine iontophoresis requires approximately 10 min but also entails an apparatus that provides a tingly sensation, which can be troublesome to the pediatric patient.

Specific techniques

Ilioinguinal/iliohypogastric nerve block

Indication

Ilioinguinal or iliohypogastric nerve blocks are used during hernia repairs and orchidopexy.

Technique

The key to performing an ilioinguinal or iliohypogastric nerve block is to identify the anterior superior iliac spine and place a 23-gauge needle 1 to 2 cm (1 fingerbreadth) medial and inferior to it, feeling the “pop” as the needle passes through the fascia, and then fanning the local anesthetic from lateral to medial. The wound edge is infiltrated prior to surgical closure, or alternatively, the local anesthetic agent can be instilled prior to closure (enough to fill the wound after dissection). Use of ultrasound can confirm the proper needle placement and deposition of drug.

Drug

The most commonly used local anesthetic agent in an ilioinguinal or iliohypogastric nerve block is bupivacaine, 0.25% to 0.5%, at a dose of 2 to 10 mL, depending on the size of the patient.

Rectus sheath block

Indication

The rectus sheath is a potential space located between the rectus abdominis muscle and the posterior rectus sheath, where thoracic intercostal nerves pass through to provide sensation to the anterior abdominal wall. A rectus sheath block is used most often for repair of an umbilical hernia.

Technique

Using ultrasound guidance, the lateral edge of the rectus sheath is identified bilaterally at the level of the umbilicus, and a 22-gauge B (blunt) or 23-gauge needle is inserted into the rectus sheath while simultaneously feeling and seeing the needle pop through.

Drug

The local anesthetic agent most commonly used in the rectal sheath block is bupivacaine, 0.25% to 0.5%, at a dose of 0.1 mL/kg on each side of the abdomen.

Penile block

Indication

Penile blocks are used during circumcision and hypospadias repairs.

Technique

When performing a penile block, the base of the penis is ringed with a superficial wheal of local anesthetic agent, or, while pulling the penis toward the patient’s feet, a needle is inserted at 90 degrees, just below the symphysis pubis into the dorsum of the penis. A “pop” will be felt as the needle passes through the Buck fascia—this needs to be repeated twice, with half of the drug injected at 11 o’clock and half at 1 o’clock.

Drug

The local anesthetic agent most commonly used in the penile block is bupivacaine, 0.25%, at a dose of 2 to 10 mL, depending on the patient; epinephrine should not be used.

Femoral nerve block

Indication

The femoral nerve block is most commonly used for biopsy of the quadriceps muscle, when the femoral shaft is fractured, or during knee operations.

Technique

The key to performing the femoral nerve block is to remember NAVEL (nerve, artery, vein, empty space, ligament)—the nerve is lateral to the artery. When performing the femoral nerve block, a line is drawn from the anterior superior iliac spine to the pubic tubercle, demarcating the inguinal ligament. Just below (0.5-1.0 cm) the inguinal ligament, an insulated needle attached to a nerve stimulator is placed lateral to the femoral artery pulsations. (The patient must not be paralyzed with a neuromuscular blocking agent.) The twitch monitor is set at 1 per second, and the nerve is stimulated at the lowest possible setting until a twitch is noted in the patella. Ultrasound can be helpful in visualizing the anatomic structures as well.

Drug

The drugs most commonly used in a femoral nerve block are bupivacaine, 0.25% to 0.5%, or ropivacaine, 0.2%, at a dose of 5 to 20 mL, depending on the patient’s size.

Lateral femoral cutaneous nerve block

Indication

The lateral femoral cutaneous nerve is often blocked in conjunction with the femoral nerve.

Technique

A needle is advanced 1 cm below and medial to the inguinal ligament and the anterior superior iliac spine. The drug is injected after “popping” through the fascia lata.

Drug

The local anesthetic agent most commonly used in the lateral femoral cutaneous nerve block is bupivacaine, 0.5%, at a dose of 0.1 to 0.2 mL/kg.

Popliteal fossa block

Indication

The popliteal fossa block is most commonly used for blocks below the knee.

Technique

Correct positioning of most children undergoing a popliteal fossa block involves simply lifting the supine child’s leg with the knee and thigh flexed. 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. 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, is advanced until a distinct pop is felt and muscle stimulation resulting in plantar flexion or dorsiflexion of the foot occurs. Ultrasound can provide visualization of the sciatic nerve bifurcating into the common peroneal and tibial nerves.

Drug

The local anesthetic agent most commonly used in the popliteal fossa block is bupivacaine, 0.25%, at a dose of 0.5 to 1.0 mL/kg.

Axillary block

Indication

An axillary block is used when operations involve the upper extremity.

Technique

As in adults, axillary blocks in children are performed with a nerve stimulator (in patients who have not received a neuromuscular blocking agent). Alternatively, the axillary artery in the axilla can be palpated, and the skin can be punctured with a 20-gauge needle. A 22-gauge B (blunt) needle is then inserted through the puncture site, aiming toward the artery, until a “pop” is felt as the needle goes through the fascia or “septa” of the axillary sheath. Upon demonstration of a negative aspiration, the local anesthetic agent can be injected. Ultrasound can also provide assistance in performing this block.

Drug

The local anesthetic agents most commonly used in the axillary block are bupivacaine, 0.25%, or ropivacaine, 0.2%, with epinephrine, 1/200,000, at a dose of 0.5 mL/kg.

Caudal block

Single-shot caudal block

Indication

The single-shot caudal block is used most often in operations with an operative field below the diaphragm.

Technique

With the patient in the lateral decubitus position (left lateral for a right-handed clinician, right lateral for a left-handed clinician) and the knees flexed up into the abdomen, the thumbnail is used to palpate and identify the two sacral cornua above the gluteal fold. Using aseptic technique, a 22-gauge Jelco, 22-gauge B-bevel needle, or a 23-gauge needle is placed at 45 degrees to the skin and advanced until a “pop” is felt through the sacrococcygeal ligament. The needle is then lowered, parallel to the skin, and advanced 1 cm. After ascertaining that aspiration for blood and cerebrospinal fluid is negative, the local anesthetic agent is slowly injected while observing the electrocardiogram for T-wave changes. Injection of the local anesthetic agent should be easy; any resistance indicates incorrect needle placement.

Drug

The local anesthetic agents most commonly used in the single-shot caudal block are bupivacaine, 0.125% to 0.25%, or ropivacaine, 0.2%, with the dose dependent upon the patient’s age and the location of the incision: penile operation, 0.5 to 0.8 mL/kg; inguinal operations, 1.0 mL/kg up to 20 mL. Other analgesic agents such as the α-adrenergic agonist clonidine (dose of 2 μg/kg) or preservative-free ketamine (dose of 0.5 mg/kg) can be added to the bupivacaine solution to prolong the duration of the block for an additional 3 to 12 h. Adverse effects include sedation and minor hypotension.

Continuous caudal block

Indication

The continuous caudal block is used most often for prolonged pain relief after operations. The catheter tip is placed at the level of the incision.

Caution

The dressing for a continuous caudal block, which is in the sacral area, must be kept clean, and access must be maintained to the site; therefore, the patient cannot have a spica cast.

Technique

The technique for a continuous caudal block is similar to that of a single-shot caudal block. The caudal space is identified under sterile technique, and then either an 18-gauge angiocatheter or a Crawford needle is advanced. The epidural catheter is then threaded through the needle for 3 cm or to the level of the incision. A sterile transparent film dressing is applied.

Drug

The choice of drug for a continuous caudal block is dependent upon catheter position and the operation.

Lumbar epidural block

Indications

Indications and contraindications for lumbar epidural blocks are similar to those in adults.

Technique

Techniques for performing a lumbar epidural block in children are similar to those used in adults. For patients weighing less than 30 kg, a 2-inch, 18-gauge Weiss or Crawford needle can be used.

Drug

The drugs most commonly used in a lumbar epidural block are lidocaine, bupivacaine, fentanyl, morphine (Duramorph), or hydromorphone, depending on the patient and the operation.

Spinal block

Indication

A spinal block is used most often in high-risk neonates who were born prematurely and are having lower abdominal operations.

Technique

The spinal block should be placed, if possible, with the patient in the sitting position, upright, with special attention to the head so as not to flex it and obstruct the airway. The depth of the subarachnoid space is about 0.7 cm in premature infants and 1.0 cm in full-term infants. It is best to avoid sedation, if possible, including ketamine, to prevent postoperative apnea. Placing the blood pressure cuff on a lower extremity will avoid stimulating the restless infant.

Drugs

The drug most commonly used in a spinal block is tetracaine, 1 mg/kg, plus dextrose.

Newer techniques

The use of ultrasound-guided blocks in pediatric patients has some advantages (e.g., shorter block performance time, faster onset time, higher success rates, longer block duration, and less volume of anesthetic used) over the traditional nerve stimulation techniques, but improved safety has been shown to be beneficial only while performing an ilioinguinal nerve block.

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