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A 25 kg, nine-year-old female presents for contracture release involving osteotomy of her right ankle. Her past medical history is significant for cerebral palsy (CP) with moderate developmental delay.
Objectives
1. Discuss how regional anesthesia use and timing differs in pediatric populations compared to adult populations.
2. Evaluate the safety data of performing regional anesthesia in the unconscious pediatric patient.
3. Review medication dose for a single-injection peripheral block.
4. Describe medication infusion by peripheral nerve and epidural catheter.
5. Discuss placement and management of a caudal catheter. Include discussion of local anesthetic and adjunct choices.
1. Discuss how regional anesthesia use and timing differs in pediatric populations compared to adult populations
In pediatrics, regional anesthesia (RA) is most often used in combination with general anesthesia (GA). Nerve blocks placement occurs with the child unconscious due to the safety concerns of performing regional anesthesia in an awake and uncooperative child [1]. Although this necessitates two anesthetics, RA adds benefit by decreasing dose exposure to GA and providing excellent control of postsurgical pain. Placement of RA may occur before or after the surgery, depending on the type of procedure, location of the nerve block, and location of a perineural catheter. In small children, catheters may conflict with the surgical field, necessitating placement at the end of the surgery.
Most peripheral nerve blocks (PNBs) and neuraxial techniques utilized in adults have been used in children of all ages [2]. Major differences include the size and location of the nerves as well as the proximity to adjacent critical structures. A sciatic block with or without blockade of the saphenous branch of the femoral nerve is a good choice for this child due to anticipated incisions over the lateral ankle and possibly the medial malleolus. Multiple sciatic approaches, including gluteal, infragluteal, and popliteal are appropriate, but a popliteal approach may be preferable for surgery below the knee. Saphenous nerve analgesia will be needed if an incision is also made over the medial malleolus and can be approached as a femoral nerve block or via blockade at the adductor canal (Table 14.1). Alternatively, epidural analgesia can be used. However, recent large studies demonstrate a lower failure rate and more favorable risk profile for PNBs when compared to neuraxial blocks [3–4]. The RA technique providing adequate analgesia with the best safety profile should be chosen.
Common peripheral nerve blocks of the lower extremity.
| Block | Technique |
|---|---|
| Sciatic; popliteal | 1. Indication: surgical trespass to the bones, muscle, and anterolateral skin of the lower extremity (LE) 2. Patient position: prone, lateral, or supine 3. Technique: ultrasound guided: a. High-frequency (10–15 MHz) linear transducer b. Place in popliteal fossa. Identify popliteal vein, artery, and tibial branch of sciatic nerve c. Scan cephalad until the peroneal nerve enters from lateral to join the tibial nerve to form the sciatic nerve d. In-plane approach, at the level where the two individual nerves join to form the sciatic nerve to maximize surface area for LA spread e. Needle: 21 or 22G × 5 to 10 cm (depending on size of child) 4. Technique: landmark: a. Identify the popliteal triangle: biceps femoris laterally, semitendinosus and semimembranous medially, and gastrocnemius/popliteal crease caudally; caudal 1/3 of posterior thigh b. Just below apex of triangle and 0.5 to 1.0 cm lateral advance an insulated block needle attached to nerve stimulator until a sciatic-mediated twitch is elicited c. Needle: 21 or 22G × 5 cm |
| Saphenous; adductor canal | 1. Indication: surgical trespass to the anteromedial skin of the lower leg 2. Patient position: supine, lower leg slightly abducted 3. Technique: ultrasound guided: a. High-frequency linear transducer (10–15 MHz) b. Place transducer on the anterior surface of mid thigh c. Identify vastus medialis and scan medially until sartorius muscle is identified. Femoral artery branch should be visualized at this level d. Periarterial infiltration on lateral and medial sides of artery |
Neuraxial anesthesia and PNB can be used as a sole anesthetic in pediatric patients, but is not common except in neonates and young infants. Pure RA techniques are commonly used in the youngest infants to avoid all exposure to GA and to decrease postoperative apnea and other complications in former preterm infants [5].
There are many special considerations when caring for patients with CP [6]. The use of RA for pain management may be especially important in preverbal and developmentally delayed children, due to the challenges of assessing pain in these patients. Regional anesthesia use in CP patients results in lower pain scores and fewer respiratory complications when compared to opioid analgesia [7–8]. Patients with CP often have scoliosis and contractures, making positioning for block placement challenging. Abnormal anatomy from contractures and muscular atrophy also make the use of localizing techniques such as nerve stimulation or ultrasound (US) essential for both nerve location and the identification of adjacent critical structures. Additionally, hypothermia develops quickly in these patients due to poor thermal regulation; thus exposure to cold operating rooms during block insertion should be avoided. If the patient has a history of seizures, current antiepileptic therapy must be determined. Sodium valproate may increase bleeding due to platelet dysfunction, thrombocytopenia, or von Willebrand factor deficiency, which may affect the choice of regional technique [6].
2. Evaluate the safety data of performing regional anesthesia in the unconscious pediatric patient
In adult populations, placement of RA under GA has been highly discouraged due to concerns of masking early warning signs of complications such as local anesthetic systemic toxicity (LAST) and nerve trauma [9–10]. Regional anesthesia placement in an awake infant or child is often not feasible due to lack of cooperation; consequently, nerve block placement in children under GA is the standard of care [1, 9–10]. In 2014, a multicenter analysis using the Pediatric Regional Anesthesia Network Database demonstrated no difference in morbidity or mortality whether RA was administered in awake or anesthetized children. This was true of both neuraxial and PNBs [11]. Similarly, the use of neuromuscular blocking drugs at the time of placement of RA did not affect outcomes [11]. Local anesthetic systemic toxicity was more common in young children and neurologic complications occurred most often in older children; yet both were rare events. When neurologic deficits did occur as the result of RA, they were most often transient and resolved within six months [11]. Controversy still exists about the safety of performing interscalene blocks in children under GA or heavy sedation due to risk of catastrophic complications. The American Society of Regional Anesthesia and Pain Medicine guidelines recommend placement of interscalene nerve blocks in awake or lightly sedated patients [9]. However, a recent study of nearly 400 interscalene blocks placed under GA in pediatric patients reports no associated complications [12].
In adult populations, the use of US guidance has decreased the incidence of LAST and post-block neuropraxias [13]. Pediatric-specific data addressing changes in the incidence of infrequent complications as a result of increased US use is still lacking. US guidance is associated with improved block efficacy and decreased local anesthetic (LA) doses [14].
3. Review medication dose for a single-injection peripheral block
Both amide and ester LAs have been used for PNBs (Table 14.2). Amides are most commonly used for single bolus injections and the choice of drug depends on desired speed of onset, duration of action, drug safety profile, and type of block to be performed [15–16].
Local anesthetics.
| Drug | Maximum dose (mg/kg) | Duration of action (min) |
|---|---|---|
| 2,3 Chloroprocaine | 20 | 30 |
| Lidocaine | 5 | 90–200 |
| Bupivacaine | 2.5 | 180–600 |
| Ropivacaine | 3 | 120–240 |
LA dose in children is calculated by weight, and commonly expressed as milliliters per kilogram (Table 14.3). Lean body mass is used for the weight when calculating the pediatric dose and age-specific pharmacokinetics of LAs must be considered when administering the drug. In general, children have a higher volume of distribution, imparting some protection against LAST. Although young infants and neonates have decreased plasma proteins resulting in increased unbound plasma levels of LA, adult hepatic function is achieved by three to six months of age [15–16]. Children with CP and other significant comorbidities may be malnourished and have hypoalbuminemia, which results in increases in unbound LA. The maximum dose of local anesthetics should be calculated prior to placement of multiple nerve blocks in a single patient to avoid LAST.
Single bolus dose for nerve block.
| Bupivacaine 0.25% | Ropivacaine 0.2% | Maximum bolus | |
|---|---|---|---|
| Upper extremity | |||
| Interscalene | 0.15–0.20 ml/kg | 0.15–0.20 ml/kg | 15 ml |
| Brachial plexus: supraclavicular, infraclavicular, axillary | 0.2–0.25 ml/kg | 0.2–0.25 ml/kg | 20 ml |
| Lower extremity | |||
| Sciatic: popliteal, subgluteal | 0.15–0.20 ml/kg | 0.15–0.20 ml/kg | 20 ml |
| Femoral | 0.2–0.25 ml/kg | 0.2–0.25 ml/kg | 20 ml |
| Adductor canal | 0.2 ml/kg | 0.2 ml/kg | 20 ml |
| Lumbar plexus | 0.25–0.5 ml/kg | 0.25–0.5 ml/kg | 30 ml |
| Truncal | |||
| Epidural; caudal approach | 1 ml/kg | 1 ml/kg | 20 ml |
| Paravertebral | |||
| Unilateral | 0.5 ml/kg | 0.5 ml/kg | 20 ml |
| Bilateral | 0.25 ml/kg | 0.25 ml/kg | 20 ml per side |
| Transversus abdominus plane (TAP) | |||
| Unilateral | 0.5 ml/kg | 0.5 ml/kg | 20 ml |
| Bilateral | 0.25 ml/kg | 0.25 ml/kg | 20 ml per side |
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