Introduction
Regional anesthesia in pediatric patients has recently gained popularity. It has a documented protective effect in reducing noxious surgical stress, provides superior analgesia, and reduces the minimum alveolar concentration of volatile anesthetic agents. Well-established evidence proves that inadequate analgesia in the neonate results in biobehavioral changes and modulates future pain responses in childhood. For example, former neonatal intensive care patients exposed to noxious stimuli demonstrate an exaggerated response to pain in the primary somatosensory cortex, and anterior cingulate cortex, and insult on functional magnetic resonance imaging studies. Regional anesthesia also facilities minimal airway instrumentation thus allowing a spontaneously breathing patient for some surgical procedures.
1 Table 24.1 outlines the advantages of regional anesthesia in children.
In addition to providing pain coverage with minimal to no opioid use, regional anesthesia is generally safe. These techniques should only be performed by specialized pediatric anesthesiologists. Mild sedation to general anesthesia is employed in pediatric regional anesthesia because children tend to be less cooperative than their adult counterparts.
2Advances in ultrasound technology have allowed practitioners to provide adequate postoperative pain relief, therefore reducing opioid consumption, the incidence of postoperative nausea and vomiting, and respiratory complications (
Table 24.2). The French-Language Society of Pediatric Anesthesiologists (ADARPEF) published large prospective studies demonstrating the safety of regional anesthesia performed under general anesthesia in children. Complications are reported at a rate of 0.12% with a 95% confidence interval. In that percentage, complications were four times greater in children <6 months old receiving a caudal block (1.9% of 18 650 caudal blocks).
3,
4Additional data from the Pediatric Regional Anesthesia Network registry and the UK National Pediatric Epidural Audit support a low incidence of complications of regional anesthesia in children. Common complications were related to catheter malfunctions such as disconnection, displacement, and disconnection. Other complications related to neuraxial anesthetic techniques were transient neurological defect (2.4 in 10 000) without permanent sequelae, two cases of epidural abscesses, one case of postdural puncture headache, and five cases of severe neuropathy/radiculopathy with resolution over a 10-month period.
5
Technical Considerations of Ultrasound Use in Children
Safe performance of increased use of regional anesthesia in the pediatric population requires adequate integrated training in needling techniques and ultrasound imaging.
6High-frequency ultrasound probes of 10-15 MHz are recommended in children. The active transducer surface length should be between 25 and 30 mm. Nerve appearance can be variable; the nerve diameter and frequency and angle of the ultrasound beam can determine whether the nerve appears as a hypo- or hyperechoic structure. Generally, neural structures like plexuses that are more central and compact structures tend to generate more hypoechoic images. On the contrary, peripheral terminal nerves have a more hyperechoic appearance. The in-plane (IP) technique is preferred in pediatric regional anesthesia. This IP technique facilitates visualization of the entire length of the needle during block placement.
7
Anatomical and Physiological Differences Between Pediatric and Adult Patients
Anatomical, physiological, and pharmacokinetic differences exist in neonates, infants, older children, and adults. Increased systemic absorption and accumulation of local anesthetics are more likely to occur in infants secondary to their increased cardiac output and immature hepatic function (
Table 24.3).
Local Anesthetics
Local anesthetics are lipid-soluble weak bases that work by binding the voltage-dependent sodium channel. This binding prevents effective depolarizing of the cell membrane and blocks conduction of afferent pain signals and efferent motor transmission. Local anesthetics also block potassium and calcium channels at higher concentrations.
Local anesthetics are classified as esters or amides. Ester local anesthetics are rapidly metabolized by plasma pseudocholinesterases, whereas amides require cytochrome P-450 enzymes from the liver for metabolism. The hepatic biotransformation necessary for amide local anesthetics is immature at birth. In contrast, plasma pseudocholinesterases are present in neonates.
Human serum albumin and alpha-1-acid glycoprotein (AGP) are two proteins in the blood to which local anesthetics bind. Although concentrations of AGP are low in the serum, it is the primary protein that binds local anesthetics. At birth, the concentration of AGP is low. Infants and neonates have a higher free fraction of local anesthetics than adults. This possibly increases their risk of systemic local anesthetic toxicity.
A rare and catastrophic life-threatening complication of local anesthetics is local anesthetic systemic toxicity (LAST). The majority of cases occur in infants with an incidence of 0.76-1.6:10 000. Early recognition of LAST is challenging because most often children receiving regional anesthesia are sedated or under general anesthesia. According to the ADARPEF study, one case of LAST resulted in convulsions. Similarly, the UK epidural audit reported two respiratory failures and one seizure.
8Rapid identification of LAST is necessary to avoid circulatory collapse and death. LAST causes acute neurological and cardiovascular manifestations (
Table 24.4). Airway management,
oxygenation, ventilation, and life support are the initial steps of LAST treatment. Further treatment requires lipid resuscitation with the lipid emulsion Intralipid. Recent guidelines from The Society of Pediatric Anesthesia and the ESRA/ASRA joint committee limit the maximum cumulative amount of lipid resuscitation therapy to 10 mL/kg.
Table 24.5 outlines the treatment of LAST in pediatric patients according to Society of Pediatric Anesthesia guidelines.
The local anesthetics of choice in pediatric regional anesthesia are levobupivacaine and ropivacaine. Amide local anesthetics tend to have greater lipid solubility, greater stability to hydrolysis, a longer duration of action, and a lower incidence of allergic reactions. ESRA/ASRA joint committee suggests the use of preservative-free intrathecal morphine or clonidine to improve both the duration of blocks and the quality of analgesia. For peripheral nerve blocks, alpha-2-agonists, clonidine and dexmedetomidine, improve postoperative analgesia compared with plain local anesthetic.
9
Get Clinical Tree app for offline access
