Regional Anesthesia in Children: An Overview

Common Nerve Blocks in Pediatric Anesthesia

• Neuraxial anesthesia is the most common type of regional anesthesia performed in the pediatric population.^2,3
  • With over 50 years of experience and safety data, the most common pediatric regional anesthesia procedure to this day is the single-shot caudal block, which is used for any surgical procedure below T10 (level of the umbilicus).
  • The second most common regional block is epidural anesthesia.
  • Spinal anesthesia, despite being commonly used in the adult population, has not been as widely adopted as a sole anesthetic for pediatric surgical procedures.
  • There has been an increase in the use of spinal anesthesia due to recent Food and Drug Administration (FDA) warnings related to the neurodevelopmental impact of general anesthesia in children younger than 3 years.
• Other commonly performed pediatric blocks include:
  • Penile block, indicated for circumcisions, hypospadias repairs, and other distal penile procedures
  • Ilioinguinal/ iliohypogastric block
    • indicated for inguinal and groin procedures
    • ultrasound-guided technique has been shown to be superior in both clinical effectiveness and ease of placement³
• With advances in ultrasound technology, there has been an increase in the acceptance and implementation of several ultrasound-guided nerve blocks in children, such as
  • brachial plexus block
  • femoral block
  • popliteal block
  • transversus abdominis plane (TAP) block
  • quadratus lumborum block
• There is a growing body of literature that demonstrates the effectiveness and superiority of quadratus lumborum block over TAP block in children.⁴ This is due to better spread of local anesthetic and a longer duration of action. The local anesthetic spreads between T7 to L1 with a single injection compared to only three dermatomes with a TAP block.

Important Differences Between Regional Anesthesia in Adults and Children

Anatomy

• Nerve targets are smaller in children, closer to vascular structures, and much closer to the skin than in adult patients.
• The most significant differences in anatomy between adult and young children are appreciated when performing neuraxial anesthesia techniques.
  • In neonates and infants, the conus medullaris is located lower in the spinal column at approximately L3 vertebra (compared to the L1 vertebra in adults), and care must be taken during spinal and epidural anesthesia to avoid injury to the spinal cord.
  • At approximately 2 years of age, the conus medullaris reaches the L1 level.
  • In infants, the sacral hiatus is located more cephalad, and the dural sac ends more caudally; caution should be used to avoid the risk of dural puncture.
  • Fat within the epidural space is less dense, facilitating cephalad spread of local anesthetic, faster onset, and easier advancement of epidural catheter to the lumbar and thoracic space with or without fluoroscopy.^1,2

Physiology

• Incomplete myelination at birth can take up to 12 years to be completed, leading to better penetration of local anesthetic into the nerve fibers and enabling effectiveness with lower concentration of local anesthetic.
• Clinically significant hypotension and bradycardia are rarely seen in children younger than 10 years and are attributed to
  • lower resting sympathetic tone compared to adults; and
  • greater ability to compensate for decreases in systemic vascular resistance.
• Crystalloid administration prior to performing neuraxial anesthesia in children is typically not necessary.

Pharmacology

• Cerebrospinal fluid volume is higher in infants and neonates (4 mL/kg) compared to adults (2 mL/kg) and this accounts for higher local anesthetic requirements and shorter duration of action for spinal anesthesia in infants.⁸
• The volume of distribution of local anesthetics is greater in children than in adults.
  • Children tolerate a higher mg/kg of local anesthetic without reaching a toxic threshold.
  • It is still important to maintain dosages of local anesthetic below the toxic dose of bupivacaine or ropivacaine (3 mg/kg).
• Neonates and small infants younger than 6 months are at the greatest risk for LAST.
  • Decreased plasma concentrations of albumin and other proteins increase the free fraction of local anesthetic in the bloodstream.
  • Immature hepatic function decreases local anesthetic clearance.
  • A decrease in the weight-based dosing by 30-50% is warranted.
• Higher concentrations (0.5% ropivacaine or bupivacaine) are rarely used for epidural or peripheral nerve blocks in children due to incomplete myelination.⁸

Awake vs. Asleep

• Regional anesthesia in pediatrics is typically performed under general anesthesia or deep sedation.
  • Children are typically too anxious and fearful to have regional anesthesia performed while awake.
  • This is different than in adults where regional anesthesia is performed awake or with minimal sedation.
• From a practical standpoint, regional anesthesia procedures are safer under general anesthesia than attempting to perform them in a moving, upset or uncooperative patient.

Risks and Complications of Regional Anesthesia in Children

• The Pediatric Regional Anesthesia Network (PRAN) is a database of over 100,000 pediatric regional nerve blocks that revealed several important data points.^6-8
  • The complication rate of performing blocks under general anesthesia was similar to that of complications of performing blocks awake in adults.
  • The rate of complication is 0-2/10,000 blocks.
  • The most common complication was benign catheter failures, including dislodgements, occlusions, and disconnections (4%).
  • Neurological complications occur at 0.02%. All complications were minor and without permanent sequelae.
  • The incidence of LAST was low (0.05%), with no resultant long-term effects.
• Early neurological signs of LAST in children can be masked by general anesthetics, and the first signs of LAST are arrhythmias and hemodynamical instability.6 Regional Anesthesia in Children: An Overview It is critical to maintain strict adherence to weight-based dosing, use ultrasound technology, and when possible, perform the block in the presence of an experienced practitioner to prevent LAST in the pediatric population.