ASRA Pain Medicine Update

Introduction

Regional anesthesia in the pediatric population is gradually becoming a more accepted and requested practice. Large prospective studies by the Pediatric Regional Anesthesia Network (PRAN) and French Language Society of Pediatric Anesthesiologists (ADARPEF) have shown regional techniques are both beneficial and associated with low incidence of complications even when administered when under general anesthesia.^1-5 A comprehensive understanding of the features unique to pediatric patients is necessary to utilize these techniques safely and effectively, especially if a practitioner’s primary practice is in the adult setting. Patient factors including anatomical and physiological differences between children and adults and the types of preexisting neurological disease can have a more profound impact on our littlest patients because the margin of error is much smaller. We highlight some of the “must know” principles to help guide appropriate care.

Anatomic and Physiologic Differences in Pediatric Patients

Understanding the anatomical and physiological differences is crucial for pediatric regional anesthesia to determine the right dose, type of local anesthetic, and block location for optimal outcomes. Neuraxial anesthesia in the form of caudals, epidurals, and spinals are commonly used in infants and neonates for procedures below the umbilicus; there are several important anatomical differences in the spinal column and cord anatomy that are relevant to performing these techniques. In the spinal canal, the conus medullaris ends approximately at the L3 vertebra and does not reach L1 until about 1 year of age. The sacrum is flatter and narrower with incomplete ossification allowing the caudal space to be more easily accessible; however, the dural sac may end more caudally at S4 in small infants increasing the risk of accidental dural puncture.⁵ In addition, the nociceptive fields of neurons are larger and descending inhibitory pathways are immature leading to poorer pain localization and unmodulated pain in ascending spinal pathways. Ultrasound is very useful in these patients to identify anatomical variations and determine the depth of epidural and sacral spaces. Sacral dimples are observed in some patients and may overlie spinal dysraphism or tethered cord; in these instances, an ultrasound or MRI can be useful to visualize the thecal sac to rule out any abnormalities.^6,7

Physiologically, myelinization of nerves is not complete until the age of twelve years and the surrounding fascia and nerve sheaths are looser allowing local anesthetics to spread around nerve fibers and penetrate them more easily causing high quality blockade with lower concentrations of local anesthetic.⁶ Of note, neonates and infants have higher cardiac output leading to faster systemic absorption, potentially increasing the risk of local anesthetic toxicity and decreasing block duration. Amide local anesthetics primarily bind to plasma alpha-1-glycoprotein limiting the free fraction available in the blood and decreasing the risk of systemic toxicity (LAST); however, these protein levels do not reach adult levels until the age of 1 year, potentially increasing the free fraction of local anesthetics in the blood and requiring careful consideration of dosing.⁸ Preservative-free chloroprocaine may be a safer and more effective choice given its rapid liver-independent metabolism and wider safety margin in terms of volume and local anesthetic mass. ⁹ Additionally, neuraxial anesthesia suppresses the stress response to surgery and has limited effect on left ventricular function and mean blood pressure increasing hemodynamic stability during the perioperative period in children up to 8 years of age.^6,10

Pediatric Patients with Preexisting Neurological Disease

Some pediatric patients present for surgery with a preexisting neurological disease. Due to the rarity of many pediatric neurological conditions, a significant portion of information regarding regional anesthesia in these patients relies on anecdotal evidence, limited case series, or is extrapolated from adult literature. The most frequently encountered neurologic diseases include cerebral palsy, spinal muscular atrophy, Charcot-Marie-Tooth disease, mitochondrial disease, and myasthenia gravis.¹¹ These patients often present many times over the course of their lifetime for different procedures. These diseases are often progressive in nature, increasing the importance of reviewing specific pathophysiological considerations for each disease. Cardiorespiratory and developmental comorbidities are frequently present and worsen over time, which impact the perioperative plan increasing the benefits of regional anesthesia.

Regional Anesthesia in the Sedated Patient

In the adult population, regional anesthesia is often performed in awake patients to inform practitioners of potential complications such as nerve injury (via signs of pain and/or paresthesias) or LAST. On the contrary, the majority of regional blocks performed in pediatric patients are performed under general anesthesia. Regional blocks are difficult to perform in awake children due to limited cooperation, inability to communicate symptoms experienced, and a potential for developing or exacerbating psychologic trauma and fear of needles and medical procedures. A large review of the PRAN database assessed the risk of complications across a large multicenter database for regional anesthetics performed in children and observed a very low incidence of transient neurologic deficits and local anesthetic toxicity.^4,12

One notable exception are infant spinals; typically performed in awake infants undergoing minor procedures less than 60 to 90 minutes below the umbilicus such as hernia repairs, circumcision, or lower extremity tenotomies to decrease the risks of airway manipulation, post-operative apnea, and speed the time to discharge and feeding. Infant spinals decrease the use of opioids and supplemental medications in the perioperative period and have gained increased interest in the past several years due to controversial neurocognitive effects of general anesthesia in small children.¹³ They are a great alternative to general anesthesia in appropriately chosen patients.

Consent and Assent for Pediatric Regional Anesthesia

Finally, while adult patients provide consent for their own medical procedures, it is crucial to recognize that parents or legal guardians give consent for medical procedures on their children. The ability to which children can affirmatively agree with that decision making is termed assent.¹⁴ There are several factors to consider when determining a child’s ability to give appropriate assent including age, cognitive development, complexity of decision making, and understanding of the benefits and risks of specific medical procedures.¹⁵ Assent is often obtained in children as early as 7 years or older. Regardless, age appropriate discussion of medical information should be offered and the child’s opinion solicited regarding anesthetic options.¹⁶ As children transition to adolescence they should be treated as if they have decision making capacity; it becomes increasingly important to prioritize their preferences by offering information aligned with genuine informed consent similar to an adult patient, but also taking into consideration their emotional, psychological and intellectual ability that may impact their decision making.¹⁵  

Overall, regional anesthesia has proven beneficial to the perioperative experience of children and their families with the appropriate balance between risks and benefits. With the benefits of ultrasound, a greater number of regional techniques can be safely and reliably utilized in children with appropriate training and precautions. 

References

1. Walker BJ, Long JB, Sathyamoorthy M, et al. Complications in pediatric regional anesthesia: an analysis of more than 100,000 blocks from the pediatric regional anesthesia network. Anesth 2018;129:721-32. https://doi.org/10.1097/ALN.0000000000002372
2. Ecoffey C, Lacroix F, Giaufré E, et al. Epidemiology and morbidity of regional anesthesia in children: a follow-up one-year prospective survey of the French-language Society of Pediatric Anesthesiologists (ADARPEF). Ped Anesth 2010;20(12):1061-1069. https://doi.org/10.1111/j.1460-9592.2010.03448.x
3. 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 & Anal 1996;83(5):904-912. https://doi.org/10.1097/00000539-199611000-00003
4. Taenzer AH, Walker BJ, Bosenberg AT, et al. Asleep versus awake. RAPM 2014;39(4):279-283. https://doi.org/10.1097/aap.0000000000000102
5. Suresh S, De Oliveira GS. Local anesthetic dosage of peripheral nerve blocks in children: analysis of 40121 blocks from the pediatric regional anesthesia network database. BJA 2018;120(2):317-322. https://doi.org/10.1016/j.bja.2017.10.019
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7. Lam DKM, Corry GN, Tsui BCH. Evidence for the use of ultrasound imaging in pediatric regional anesthesia. RAPM 2016;41(2):229-241. https://doi.org/10.1097/aap.0000000000000208
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10. Wolf AR. Effects of regional analgesia on stress responses to pediatric surgery. Ped Anesth 2011;22(1):19-24. https://doi.org/10.1111/j.1460-9592.2011.03714.x
11. Cung S, Ritz ML, Masaracchia MM. Regional anesthesia in pediatric patients with preexisting neurological disease. Ped Anesth 2021;31(5):522-530. https://doi.org/10.1111/pan.14152
12. Dalens B, Albert N. Asleep or awake rethinking safety [editorial]. RAPM 2014;39(4):267-268. https://doi.org/10.1097/aap.0000000000000111
13. Ebert KM, Jayanthi VR, Alpert SA, et al. Benefits of spinal anesthesia for urologic surgery in the youngest of patients. J of Ped Urology 2019;15(1):49.e1-49.e5. https://doi.org/10.1016/j.jpurol.2018.08.011
14. Tait AR, Voepel-Lewis T, Malviya S. Do they understand (part II): assent of children participating in clinical anesthesia and research. Anesth 2003;98:609-614. https://doi.org/10.1097/00000542-200303000-00006
15. Carollo DS, Mann DG. The ethics of pediatric informed consent. ASA Monitor 2018;82(11):10-13.
16. Katz A, Webb SA. Informed consent in decision-making in pediatric practice. Ped 2016;138(2);e20161485. https://doi.org/10.1542/peds.2016-1485