Regional anesthesia and pain relief in children

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CHAPTER 196

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

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

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Regional anesthesia and pain relief in children

Regional anesthesia and pain relief in children

Anatomy

Physiology

Pharmacology

Cooperation

Test doses

Topical blocks

Specific techniques

Ilioinguinal/iliohypogastric nerve block

Indication

Technique

Drug

Rectus sheath block

Indication

Technique

Drug

Penile block

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