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Regional Anesthesia in Children
Key Points
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Over the last three decades, regional anesthesia in pediatrics has become an integral part of everyday practice.
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Regional anesthesia appears as a viable option for treating intraoperative and postoperative pain control in children.
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In recent years, there has been an upsurge in the use of peripheral nerve blockade in infants and children.
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Large pediatric databases have contributed pertinent data on the safety of peripheral nerve blockades.
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Peripheral catheter techniques are becoming routine practice with data substantiating their use in pediatric patients.
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The efficiency and safety of these techniques may facilitate early ambulation with improved pain management and includes treatment at home and improved rehabilitation of children.
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Landmark techniques and nerve stimulation localization, which were commonly used for regional anesthesia in children, are being replaced by ultrasound guidance.
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The benefits of the ultrasound-guided regional technique are visualization of targeted nerves and spaces, the spread of injected local anesthetic, and improved safety of the blocks.
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The use of ultrasound guidance for performing peripheral nerve blocks permits the decrease of local anesthetic doses, decrease in number of punctures, and increase in the onset time and duration of sensitive block.
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To avoid local or systemic toxicity, the dose of local anesthetic, in terms of volume and concentration, should be carefully calculated. The introduction of lipid rescue has decreased the incidence of serious complications associated with the use of regional anesthesia.
Acknowledgment
The editors and publisher would like to thank Drs. Christophe Dadure, Chrystelle Sola, Bernard Dalens, and Xavier Capdevila for contributing a chapter on this topic in the prior edition of this work. It has served as the foundation for the current chapter.
The authors would like to thank John Hajduk for his help with copyediting the manuscript.
Introduction
Pediatric regional anesthesia and the research into techniques and applications have followed its use in adults. The adaptation of the pediatric practitioners to several well-described blocks and their use in children have clearly allowed us to explore opportunities for adapting the use of these blocks in even low birth weight neonates. Emerging data from both Europe and North America support the universal acceptance and utilization of regional anesthesia in infants and children. In addition, the introduction of Enhanced Recovery After Surgery (ERAS) protocols in children is now gaining acceptance as standardized methods for the delivery of postoperative analgesia.
The use of ultrasound guidance for regional anesthesia has opened several avenues for regional anesthesia techniques. In addition, a recent Cochrane Review demonstrated the effectiveness of ultrasound guidance as well as the opportunity to reduce the local anesthetic dosage for regional techniques (see ref. below).
Relevant Differences Between Children and Adults
Anatomic Differences
Change in Body Size Resulting From the Growth Process
The most obvious difference between children and adults is body size. “Normal” full-term neonates weigh 3 to 3.5 kg, with a height of 50 cm, and within 10 to 15 years they will multiply their weight by more than 12 (>1200%) and their height by more than 3 (>300%). During the early stages of development the spinal cord occupies the spinal canal entirely, but later the growth of vertebrae exceeds that of the cord, and the last spinal nerves, the cord, and its envelopes are contained within the spinal canal. At birth the dura mater ends at the level of the third or fourth sacral vertebra and the cord (conus medullaris) at the L3 or L4 level. It is only at the end of the first year of life that the adult level is attained—that is, L1 for the conus medullaris and S2 for the dural sac.
Anatomic relationships and landmarks are constantly changing with growth throughout infancy and childhood, which interferes with regional procedures and requires a working knowledge of the developmental anatomy and the assistance of accurate techniques for localization of anatomic spaces and nerve trunks.
Congenital malformations, genetic disorders, and consequences of fetal and neonatal asphyxia (cerebral palsy) are observed in the pediatric population resulting in surgical procedures that are done to facilitate mobility or adaptation to normal childhood life.
The main pediatric anatomic and physiologic factors that can influence indications for performance of regional block procedures are listed in Table 76.1 .
Table 76.1
Main Anatomic and Physiologic Factors in the Pediatric Period That Can Influence the Selection or Performance of a Regional Block Procedure
| Pediatric Factors (Mainly Infants) | Resulting Danger | Implications for Regional Anesthesia |
|---|---|---|
| Lower termination of spinal cord | Increased risk for direct trauma to the spinal cord | Avoid epidural approaches above L3 whenever possible. |
| Lower projection of dural sac | Increased risk for inadvertent penetration of the dura mater | Check for cerebrospinal fluid reflux, including during caudal approaches. Favor low approaches to the epidural space. |
| Delayed myelinization of nerve fibers | Easier intraneural penetration of local anesthetics | Onset time is shortened, and diluted local anesthetic is as effective as more concentrated anesthetic in adults. |
| Cartilaginous structure of bones and vertebrae | Reduced resistance to penetration by sharp needles Danger of direct trauma and bacterial contamination of ossification nuclei compromising further bone or joint growth |
Avoid use of thin and sharp needles; use short and short beveled ones instead. Do not apply excessive force on needle: if resistance is felt, stop trying to insert the needle farther. |
| Lack of fusion of sacral vertebrae | Persistence of sacral intervertebral spaces | Intervertebral sacral epidural approaches can be performed throughout childhood. |
| Delayed development of curvatures of the spine | Cervical lordosis (3-6 months) Lumbar lordosis (8-9 months) |
Same orientation of epidural needles is appropriate whatever the spinal level before 6 months of age; then adapt needle orientation to spinal flexures. |
| Changing axis of coccyx and absence of growth of sacral hiatus | Sacral hiatus comparatively smaller with increasing age | Identification of sacral hiatus becomes more difficult after 6-8 years (increased failure rate of caudal anesthesia). |
| Delayed ossification and growth of iliac crests | Tuffier line, which joins anterior superior iliac spinous processes, crosses the spine at L5 or lower in infants. | This line passes over L5-S1 interspace instead of L4-L5 interspace. |
| Increased fluidity of epidural fat | Increased diffusion of local anesthetic up to 6-7 years of age | Excellent blockade after caudal anesthesia can be achieved up to 6-7 years of age. |
| Loose attachment of sheaths and aponeuroses to underlying structures | Increased spread along nerve paths with danger of penetrating remote anatomic spaces and blocking distant nerves | Larger volume of local anesthetic is required for epidural blocks because of leakage along spinal nerve roots. Smaller volume of local anesthetic is necessary to produce excellent peripheral blocks. |
| Enzymatic immaturity | Slower metabolism of local anesthetics (usually compensated by other enzyme pathways) | Increased mean body residency time and half-life, with accumulation (especially after repeat injection and continuous infusions of local anesthetic), are characteristic. |
| Increased extracellular fluids | Increased distribution volume and mean body residency time of local anesthetic (and most medications) | Decreased C max occurs after single injection but accumulation occurs with repeat or continuous injections. |
| Low plasma protein content (HSA and AGP) | Competition at nonspecific HSA binding sites Limited capacity of specific binding of local anesthetic by AGP, resulting in increased plasma concentration of the free fraction |
Increased unbound free fraction of all local anesthetic occurs, with greater danger of systemic toxicity |
| Increased cardiac output and heart rate | Increased regional blood flow resulting in increased systemic absorption of local anesthetic | Increased systemic absorption of local anesthetic occurs (decreased T max and shorter duration of blockade). Increased efficacy of epinephrine. Vasoconstriction reduces absorption (thus toxicity) and prolongs duration of blockade. |
| Sympathetic immaturity, diminished autonomic adaptability of the heart, smaller vascular bed in lower extremities | Hemodynamic stability during neuraxial blocks | Fluid preloading and use of vasoactive agents are unnecessary. |
| Delayed acquisition of body scheme and conceptualization, anxiety | Inability of patients to locate precise body areas Concept of paresthesia not understandable Difficult cooperation |
Nerve and space identification requires application of location techniques independent of patient’s cooperation. Heavy sedation or general anesthesia is required in most patients (especially when a “dangerous” technique is planned to avoid detrimental consequences of panic attacks at a critical phase of the block procedure). |
AGP, α 1 -Acid glycoprotein; C max , peak plasma concentration; HSA, human serum albumin; T max, time to reach C max .
Delayed Ossification of Bones and Fusion of Sacral Vertebrae
Bones of neonates, including vertebrae, are mostly cartilaginous. Sharp needles can easily traverse them because cartilage offers little resistance to penetration, and ossification nuclei can be severely damaged, thus compromising further bone and joint development. Consequently, bone contact should be avoided as often as possible during block procedures, especially in infants. This cartilaginous structure also allows easy penetration of radiographs and ultrasound.
Development of Curvature of the Spine
At birth, a single spinal curvature is present and the orientation of epidural needles is the same regardless of the intervertebral space. Flexures, however, are not fixed, and they can be easily counteracted by forced flexion almost throughout childhood because of persistent spinal flexibility, which is a major advantage in the pediatric period (in addition to the absence of osteophytes).
Loose Attachment of Fasciae and Fluidity of Epidural Fat
Fasciae and perineurovascular sheaths are loosely attached to underlying structures (e.g., nerves, muscles, tendons, vessels). This allows extended spread of local anesthetics, resulting in high-quality nerve blockade regardless of the technique but also, occasionally, undesirable spread to distant nerves or anatomic spaces. The epidural fat is very fluid in infants and young children (up to 6-7 years of age). This fluidity combined with the loose attachment of the sheaths surrounding the spinal roots favors consistent leakage of local anesthetics injected within the epidural space; therefore comparatively large volumes of epidural local anesthetics (up to 1.25 mL/kg) are required to reach desired levels of anesthesia.
Delayed Myelinization of Nerve Fibers
Myelinization begins during the fetal period in cervical neuromeres and extends cephalad and caudad, but the process is not finalized before the twelfth year of life. Myelinization is especially poor in infants; the lack of fully developed nerve fibers is the main reason why they are unable to walk. A major pharmacologic consequence of this condition is that local anesthetics can penetrate and block nerve fibers more easily. Diluted solutions of local anesthetics provide the same quality of nerve blockade as with at least twofold more concentrated solutions in adults. Onset time is shortened, but duration of blockade is reduced because trapping of local anesthetics within myelin with subsequent progressive release is reduced and because local circulation and therefore vascular absorption are greater in infants.
Pain Perception
Somatic pain is a subjective sensory experience resulting from the intermixing of three main components : motivational-directive, sensory-discriminatory, and cognitive-evaluative. The motivational-directive component is conveyed by unmyelinated C fibers (“slow” pain or “true” pain). Pain leads to protective reflexes such as autonomic reactions, muscle contraction, and rigidity. C fibers are fully functional from early fetal life onward. Connections between C fibers and dorsal horn neurons are not mature before the second week of postnatal life. However, nociceptive stimulations transmitted to the dorsal horn by C fibers elicit long-lasting responses, probably as a result of extensive depolarization of surrounding neurons in response to the production of large amounts of substance P. As the number of dorsal horn receptors to substance P decreases during the first 2 weeks of life, this exaggerated response of neonates to nociceptive stimulation progressively disappears. The inhibitory control pathways, which are immature at birth, develop concomitantly.
Painful procedures during the neonatal period modify subsequent pain responses in infancy and childhood, depending on the developmental stage of the infant (full-term vs. preterm) and the infant’s cumulative experience with pain. Noxious procedures in full-term neonates react with heightened behavioral responsiveness, whereas preterm neonates react with a dampened response. When analgesic drugs (local anesthetics or opioids) are administered before painful procedures, infants demonstrate less evidence of procedural pain and a reduction in the magnitude of long-term changes in pain behaviors.
A major difficulty in assessment, and, at times, even identification of pain in children pertains to the inability of young patients to communicate with their caregiver and precisely express their distress and discomfort. During the past 2 decades, pediatric pain has received considerable attention, and reliable age-related pain scales have been developed to evaluate both the severity of pain and the efficacy of its treatment.
Pharmacology of Local Anesthetics and Additives
Two main factors influence pharmacologic properties of medications in children: (1) immaturity of some enzyme pathways and their replacement by other biochemical pathways and (2) progressive increase in body surface area concomitantly with the growth process. Drug prescriptions made according to body surface area are the same as (or in simple ratio with) adult dosing. However, body surface area is not easily obtained and, in practice, doses are calculated according to body weight and require constant adaptation as the child grows up; dosage errors are not infrequent.
Local Anesthetics
Chemical properties and mechanisms of action of local anesthetics are detailed elsewhere in this book (see also Chapter 29); they are basically the same during the pediatric period and only pharmacokinetic properties may notably differ, especially in neonates and infants.
Local Fixation
Schematically, local anesthetic fixation is reduced and spread is increased in infants in contrast to the occurrence in adults, especially within the epidural space, because the epidural fat is more fluid and less densely packed. The main consequences are (1) shorter onset time of action, (2) more extended longitudinal and circumferential spread of local anesthetics, and (3) shorter duration of action because of reduced secondary release from local binding sites.
Regional Spread Toward the Target
The target of local anesthetic action is voltage-dependent sodium channels located within nerve fibers. Nonionized molecules can achieve penetration of only biologic membranes, and the speed of the process depends on the number and thickness (increasing with age) of sheaths.
Systemic Absorption and Distribution
Plasma Protein Binding
Nonionized local anesthetics easily traverse the capillary wall close to the injection site. Because cardiac output and local blood flow are two to three times greater in infants than in adults, systemic local anesthetic absorption is increased accordingly and vasoactive agents such as epinephrine are very effective in slowing systemic uptake.
Once they have penetrated within the vascular bed, local anesthetics undergo plasma protein binding mainly to human serum albumin (HSA) and α 1 -acid glycoprotein (AGP), or orosomucoid. HSA has a low affinity for local anesthetics, and many pharmacologic agents can compete at available binding sites. Furthermore, plasma levels of HSA are low during the first months of life, especially in premature and fasted infants; thus the protection offered by HSA against systemic toxicity of local anesthetics is low and decreases postoperatively. The affinity of AGP for local anesthetics is 5000 to 10,000 times greater than that of HSA, which makes AGP very effective to protect the patient from systemic toxicity (which depends on the unbound free form of local anesthetics). However, plasma concentration of AGP is very low at birth (0.2-0.3 g/L) and does not reach adult levels (0.7-1.0 g/L) before 1 year of age.
Because plasma concentration of the two proteins able to bind local anesthetics are low at birth, the free fraction of all local anesthetics is increased in infants; therefore the maximum doses of all aminoamides must be significantly reduced in this age group even though the plasma concentration of AGP increases postoperatively, except in case of liver insufficiency. On the other hand, with the stress of surgery, particularly in infants with infection or in an emergency surgery, plasma levels of AGP may increase. The increase in plasma AGP concentration can change the proportion of free fraction of ropivacaine, increasing the plasma concentration of the bound fraction of this molecule and thus protecting from systemic toxicity of local anesthetic. These phenomena can largely reduce the potential risk of local anesthetics after a single injection by retaining their plasma concentration within the safety margins.
Red Cell Storage
Once in the bloodstream, local anesthetics distribute to red blood cells, which retain 20% to 30% of the total dose, depending on the anesthetic and the hematocrit. Red cell storage usually has a minor impact on the pharmacokinetics of local anesthetics except in the following situations:
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In neonates: High hematocrit values (which may exceed 70%) and enlargement of erythrocytes (physiologic macrocytosis) result in consistent “entrapment” of local anesthetics, thus lowering peak plasma concentration (C max ) values after a single injection but increasing secondary release, thus increasing the half-life of all local anesthetics.
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In infants: Physiologic anemia reduces red cell storage and its protective effect against systemic toxicity of local anesthetics (after a single-shot injection only) when the plasma protein binding sites are saturated—that is, close to toxic blood concentrations.
Absorption from the Epidural Space
Absorption of local anesthetics has been well studied in the epidural space. In children and infants, the same kinetics of absorption is reported, but the younger the patient, the less accentuated is the biphasic shape of the plasma concentration curve. The peak plasma concentration and the slope of the decreasing concentration curve are increased, whereas the time (T max ) to reach C max remains basically unchanged; for example, the T max of bupivacaine is approximately 30 minutes regardless of the patient’s age.
Ropivacaine is a remarkable exception. After caudal or lumbar epidural injection, T max is prolonged up to 2 hours in infants and C max is increased. This atypical pharmacokinetic profile may be explained by factors such as enzyme immaturity, slower systemic uptake, and decrease in distribution volume. Intrinsic vasoconstrictive properties of ropivacaine also may play a role in the same way as the addition of epinephrine. This significant increase in both C max and T max values must be kept in mind because surgeries in infants are brief and the young patient may have left not only the operating room but also the postanesthesia care unit (PACU) less than 2 hours after the caudal or epidural procedure was performed, usually before peak plasma concentration is reached.
Importantly, levobupivacaine displays a similar pharmacokinetic profile. After caudal injection of levobupivacaine 2 mg/kg in infants younger than 2 years of age, the C max range is 0.41 to 2.42 μg/mL (0.91 ± 0.40 μg/mL), which is higher than the C max reported after caudal injection of the same dose of racemic bupivacaine. T max values also are delayed (50 vs. 30 minutes) in infants younger than 3 months of age as a result of reduced plasma clearance.
When repeat injections are considered, the epidural dose must be reduced to keep C max values in the same range as that resulting from the first injection. For the second injection, the following recommendations can be made:
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Reduce the dose to one third of the initial dose and do not inject it less than 30 minutes (lidocaine, mepivacaine, prilocaine) or 45 minutes (bupivacaine, levobupivacaine, ropivacaine) after the first injection;
or
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Inject half of the initial dose, but 60 minutes (lidocaine, mepivacaine, prilocaine, chloroprocaine) or 90 minutes (bupivacaine, levobupivacaine, ropivacaine) after the first injection.
If repeated injections are necessary, dosing should be further reduced to half of the second dose (i.e., one sixth of the initial dose) while respecting the same delay as for the second injection.
Continuous infusions aim to produce a steady-state concentration at the 24th hour postoperatively. This goal is easily achieved in adolescents with infusion rates of approximately 0.3 mg/kg/h of bupivacaine and levobupivacaine or 0.4 mg/kg/h of ropivacaine.
In infants, infusion rates must be reduced, not exceeding 0.2 mg/kg/h with bupivacaine (or equipotent doses of other local anesthetics) in infants younger than 4 months and 0.25 mg/kg/h in older infants. Infants younger than 4 months (occasionally up to 9 months) may develop systemic toxicity even at these “safe” infusion rates with racemic bupivacaine because no steady-state plasma concentration is reached, even at 48 hours. In this age group, levobupivacaine or ropivacaine instead of racemic bupivacaine is preferred because stable plateau concentrations are obtained from the twenty-fourth hour onward.
Absorption from Other Injection Sites
Absorption of local anesthetics deposited along mucous membranes is increased in infants. Mucosal topical anesthesia has long been considered contraindicated in this age group. However, the technique can be safely used with certain precautions—selection of specific transmucosal patches or sprays with diluted lidocaine and recognition that topical lidocaine exaggerates laryngomalacia.
After cutaneous application of EMLA (lidocaine and prilocaine) cream, peak plasma concentrations occur 4 hours later and remain low —less than 200 ng/mL for lidocaine and less than 131 ng/mL for prilocaine, even in infants younger than 6 months of age.
Absorption of local anesthetics from compartment blocks (e.g., fascia iliaca, umbilical, ilioinguinal, pudendal blocks) follows the same biphasic curve as for the epidural space. Because of the extended surface of absorption, injection of highly concentrated solutions of local anesthetics often leads to high, occasionally potentially toxic peak plasma concentrations, especially with 0.5% ropivacaine, whereas use of more diluted solutions results in rather low plasma concentrations.
Absorption from peripheral nerve conduction blocks also follows a similar biphasic curve with different C max and T max values depending on the local anesthetic, the addition of epinephrine, and the site of injection; the more distal the injection, the slower is the absorption process (as in adults).
Pulmonary Extraction
After they have reached the venous bloodstream and undergone plasma protein linkage and erythrocyte storage, aminoamides reach the right cardiac cavities and then the pulmonary circulation, from which they are extracted by the lung. Their plasma concentration in pulmonary veins and then in systemic arterial circulation (especially coronary and cerebral arteries) is consistently decreased. Thus pulmonary extraction represents a temporary protection against systemic toxicity. However, certain medical conditions suppress this protective effect. Some medications such as propranolol decrease pulmonary extraction in a clinically relevant way. Also, children with right-to-left shunts undergo considerable increase in arterial plasma concentration of local anesthetics because of pulmonary circulation bypass; even with small doses of local anesthetics they can develop systemic toxicity.
Distribution Volume
After intravenous injection, volume distribution at the steady state (Vd ss ) is 1 to 2 L/kg for all aminoamides ( Table 76.2 ). After administration at other sites, calculated distribution is increased, often considerably, because of the “flip-flop” effect, especially for long-lasting local anesthetics. In infants and neonates, owing to higher extracellular fluid content ( Table 76.3 ), the distribution volume of all local anesthetics is greater than in adults, the consequences of which are (1) significant decrease in peak plasma concentration of all local anesthetics, thus decreasing the danger of systemic toxicity after a single dose; and (2) accumulation with reinjections, which increases drug plasma concentration and elimination half-life while concomitantly decreasing clearance.
Table 76.2
Age-Related Differences in Pharmacokinetic Parameters of Aminoamides
| Local Anesthetic | Protein Binding (%) | Distribution Volume at Steady State (Vd ss ) | Clearance (mL/kg/min) | Elimination Half-Life (h) |
|---|---|---|---|---|
| Lidocaine | ||||
| Neonate | 25 | 1.4-4.9 | 5-19 | 2.9-3.3 |
| Adult | 55-65 | 0.2-1.0 | 11-15 | 1.0-2.2 |
| Mepivacaine | ||||
| Neonate | 36 | 1.2-2.8 | 1.6-3 | 5.3-11.3 |
| Adult | 75-80 | 0.6-1.5 | 10-13 | 1.7-6.9 |
| Bupivacaine | ||||
| Neonate | 50-70 | 3.9 (±2.01) | 7.1 (±3.2) | 6.0-22.0 |
| Adult | 95 | 0.8-1.6 | 7-9 | 1.2-2.9 |
| Levobupivacaine | ||||
| Infant | 50-70 | 2.7 | 13.8 | 4 |
| Adult | 95 | 0.7-1.4 | 28-39 | 1.27 ± 0.37 |
| Ropivacaine | ||||
| Infant | 94 | 2.4 | 6.5 | 3.9 |
| Adult | 94 | 1.1 ± 0.25 | 4-6 | 1.15 ± 0.41 |
Table 76.3
Variation of Body Fluid Distribution by Age Group
| Distribution of Body Fluids | Preterm Neonates (%) | Full-Term Neonates (%) | Infants (%) | Children (%) | Adults (%) |
|---|---|---|---|---|---|
| Total body fluids | 80-85 | 70-75 | 65 | 55-60 | 50-55 |
| Intracellular | 20-25 | 30-35 | 35 | 35-40 | 40-45 |
| Extracellular | 55-60 | 45 | 30 | 20-25 | 20 |
Hepatic Extraction and Clearance of Aminoamides
Short-acting local anesthetics undergo high hepatic extraction (0.65-0.75 ratio for lidocaine), which depends mainly on hepatic blood flow and not much on their plasma concentration. Only limited pediatric data are available for levobupivacaine. After a single injection, the clearance of levobupivacaine increases during the first months of life, but during continuous infusion (even with 0.0625% levobupivacaine), it tends to decrease almost to the same extent as that for racemic bupivacaine, and plasma concentrations do not reach a plateau.
Placental Transfer
In pregnant women, placental extraction may consistently affect tissue distribution of local anesthetics. Protein binding influences placental transfer. The concentration ratio between umbilical venous blood and maternal arterial blood is approximately 0.73 for lidocaine, 0.85 for prilocaine, but only 0.32 for bupivacaine. Chirality may play a role, too, at least for bupivacaine, because placental transfer of D-bupivacaine exceeds that of L-bupivacaine but only with solutions containing epinephrine. Most aminoesters undergo such a rapid plasma hydrolysis that placental transfer is not an issue. Tetracaine and cocaine, the hydrolysis of which is slow, are used only for topical applications or (tetracaine only) spinal anesthesia; systemic uptake is slow and plasma concentrations remain extremely low and thus are not issues again for placental transfer.
Metabolism
Aminoesters are rapidly hydrolyzed by plasma cholinesterases. This enzymatic activity is low at birth (but no adverse clinical consequences are to be feared) and gradually reaches adult levels by 1 year of age. Chloroprocaine is eliminated at the fastest rate (4.7 mol/mL/h), procaine at a slower rate (1.1 mol/mL/h), and cocaine at only 0.3 mol/mL/h. Procaine and chloroprocaine are also metabolized, in part, by hepatic cholinesterases.
Aminoamides are metabolized within the liver, where they are subjected to two types of enzymatic reactions. Phase I reactions occur first, during which oxidation of the amide link is achieved within hepatic microsomes by the cytochrome P (CYP)450 enzyme superfamily, then phase II reactions, during which glucuronic acid or amino acid residues are appended to phase I metabolites, produce atoxic and water-soluble compounds, which are thus easily eliminated from the body.
CYP450 enzymatic activities are reduced during the first months of life. Bupivacaine is mainly metabolized by CYP3A4 in adults, but this enzyme is defective in infants. However, fetal CYP3A7 remains very active in infants, thus allowing metabolism of bupivacaine to be almost as effective as with CYP3A4. Ropivacaine and levobupivacaine are metabolized by CYP1A2, which is not fully functional before the third year, and, to a minor extent, by CYP3A4. This enzyme immaturity is clinically relevant but with limited consequences (lower clearance, delayed T max and, for ropivacaine only, increased C max but within clinically acceptable levels): it does not preclude administering these local anesthetics in neonates and infants.
Phase II reactions, especially glucuro-Vd ss conjugation, are immature at birth and remain so until the third year of life. However, other conjugation pathways such as sulfoconjugation are active and quite effective during the first months of life.
Elimination Half-Life
Elimination half-life (t ½ β) depends on both distribution and metabolism. It can be calculated using the formula below ( Cp is the plasma clearance and Vd ss the distribution volume at the steady state):
Basically, t ½ β is the same in children older than 1 year of age and adults, mainly because the increase in Vd ss is compensated by concomitant increase in Cp (related in part to higher hepatic blood flow in children, whose liver accounts for 4% of body weight, vs. only 2% in adults). Before the age of 1 year, Cp is low and elimination half-life of all local anesthetics is prolonged (see Table 76.2 ), thus favoring accumulation with repeat injections. Nevertheless, Bricker and colleagues measured no consistent differences in pharmacokinetic parameters between infants and adults.
systemic toxicity
Clinical signs of neurologic toxicity have been reported with plasma concentration ranging from 7 to 10 μg/mL for lidocaine or mepivacaine and 1.5 to 2 μg/mL (intraoperatively) to 2 to 2.5 μg/mL (postoperatively) with bupivacaine. However, plasma concentrations of bupivacaine higher than 4 μg/mL have been reported without evidence of clinical toxicity. From studies in adult volunteers, the following thresholds of toxicity of the unbound form of local anesthetics have been defined:
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0.3 μg/mL for unbound bupivacaine
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0.6 μg/mL for unbound levobupivacaine or ropivacaine
Because plasma protein binding is lower in infants, hazards of systemic toxicity might be increased, the more so as cardiac toxicity is usually concomitant with, not preceded by, central nervous system toxicity.
Opioids
Elimination half-life of neuraxial opioids is considerably increased in neonates and infants. After epidural injection, morphine reaches its peak concentration in plasma within 10 minutes, but this concentration is very low and unable to provide clinically relevant analgesia. Elimination half-life from cerebrospinal fluid (CSF) is similar to that from plasma, but CSF concentrations are very high after epidural injection; therefore it takes 12 to 24 hours before they decrease below minimal effective concentrations (near 10 ng/mL). Usual doses of neuraxial narcotics are listed in Table 76.4 . Short-acting lipid-soluble opioids (fentanyl, sufentanil) can be used, but, as in adults, they do not significantly prolong postoperative pain relief unless repeat injections are given or a continuous infusion is established. Their analgesic effect is mainly a systemic effect, and the patient may experience acute respiratory depression (sudden apnea); this condition is very different from the progressive and delayed respiratory depression, preceded by generalized pruritus, sedation, and bradypnea, reported after excessive doses of epidural and intrathecal morphine.
Table 76.4
Commonly Used Additives and Recommended Doses in Pediatric Regional Anesthesia
| Additive | Recommended Doses | Maximum Doses |
|---|---|---|
| Morphine | ||
| Epidural | 30 μg/kg | 50 μg/kg |
| Intrathecal | 10 μg/kg | 20 μg/kg |
| Fentanyl (epidural) | 1-1.5 μg/kg | 2.5 μg/kg |
| Sufentanil (epidural) | 0.25-0.5 μg/kg | 0.75 μg/kg |
| Clonidine (epidural or along peripheral nerves) | 1-1.5 μg/kg | 2 μg/kg |
| Ketamine ∗ (epidural or occasionally along peripheral nerves) | 0.5 mg/kg | 1 mg/kg |
∗ Preservative-free ketamine (preferably preservative-free S -ketamine).
Other Additives
Epinephrine 5 mg/L or 1/200,000 concentration is frequently coadministered with local anesthetics to decrease plasma peak concentration and prolong the duration of blockade, especially in children younger than 4 years of age. Another benefit expected from epinephrine is early detection of accidental intravenous injection (test dose) because young children are very sensitive to arrhythmogenic properties of epinephrine. Neuraxial epinephrine has long been suspected to potentially elicit spinal ischemia: even though this fear proved to be unfounded, many anesthesiologists recommend using lower concentrations of epinephrine (2.5 mg/L or 1/400,000) in local anesthetic solutions administered to neonates and infants; at such concentrations, the absorption rate of caudal bupivacaine is decreased by 25%.
Clonidine, like epinephrine, is an α 2 -adrenergic agonist that offers several benefits in children when added to local anesthetics either neuraxially or peripherally (see Table 76.4 ) ; it increases (by a factor of ∼2) the duration of nerve blockade without eliciting hemodynamic disorders, decreases plasma peak concentration of the local anesthetics, and produces a slight sedation for 1 to 3 hours postoperatively (which does not preclude hospital discharge). Addition of clonidine often eliminates the need for placement of a catheter to prolong postoperative pain relief, thus reducing morbidity and costs. However, its clearance in neonates is approximately one third of that in adults owing to immature elimination pathways and several instances of respiratory depression in neonates and small infants have been reported ; this additive should be avoided during the first 6 months of life.
Ketamine, especially S-ketamine, is an interesting adjuvant because of its blocking effects on N- methyl- d -aspartate receptors and interaction with sodium channels in a local anesthetic–like fashion (it shares a binding site with local anesthetics). Coadministered at a dose of 0.25 to 0.5 mg/kg, ketamine prolongs the duration of analgesia for many hours with no significant adverse effects. This is not approved for use in the United States for this indication.
Many other agents have been occasionally used as adjuvants to local anesthetics. Even though some of them proved to have analgesic properties (corticosteroids, buprenorphine, neostigmine, tramadol, and midazolam), they all produce significant adverse effects that preclude their use in most patients. Furthermore, their administration to pediatric patients raises ethical questions, and they are not approved for pediatric use in the United States.
Physiologic Factors
Surgery generates a neuroendocrine stress response in neonates, infants, and children, resulting in undesirable alterations of the metabolic state and immune function. Epidural anesthesia diminishes or even suppresses this stress response. Central blocks do not affect left ventricular function and are virtually free of measurable hemodynamic effects, at least up to the age of 8 years. Epidural anesthesia does not result in systemic or pulmonary hemodynamic changes as measured by mean blood pressure, end-diastolic diameter of the left ventricle, ejection fraction of the left ventricle, and mean velocity circumferential fiber shortening. However, pulmonary Doppler flow velocity is decreased during epidural anesthesia, probably owing to an increase in the pulmonary arterial resistance. Preloading with saline is not recommended in children, and, even in adolescents, fluid therapy or injection of vasoactive agents is rarely required.
Psychological Factors
Children are frightened by new environmental conditions in the operating room, and most of them cannot cope with their anxiety. They feel abandoned by their parents and exposed to strangers who are threatening them with needles. Furthermore, children younger than 10 years of age have not acquired their complete body image and cannot clearly make a distinction between adjacent parts of their body such as forearm and arm. Young patients cannot understand the concepts of paresthesia and differential blockade (“touch” is not “pain”). Thus localization of nerve trunks and anatomic spaces requires using physical methods independent of the patient’s cooperation (loss of resistance [LOR] seeking, nerve stimulation, ultrasound techniques). Infants and most children cannot cope with their anxiety and fear of needles; therefore sedation or light general anesthesia may be needed before attempting a block procedure to avoid panic attacks and unwanted movements. Prospective regional anesthesia registries have demonstrated that awake versus asleep placement of regional blocks in children do not have any deleterious effects in outcomes.
Regional anesthesia has a significant psychological impact. A pain-free postoperative course improves the morale of the patient, the family, and the nurses. Surgeons are happy to examine quiet, alert, and manageable patients. Occasionally, negative psychological effects can be observed—persistent motor (even sensory) blocks postoperatively may be frightening to some children (3-5 years of age especially) and their parents even though precise explanations had been given preoperatively as to the expected course of events during the postoperative period. Offering friendly environmental conditions, empathy, and additional explanations on local anesthetic pharmacology can reduce this postoperative anxiety.
Indications, Contraindications, and Complications
Indications
Indications for regional anesthesia in children are not identical to those in adults, not only because surgical pathologic processes are quite different but also because regional block procedures are used as techniques of analgesia in anesthetized children rather than in conscious or lightly sedated adult patients. There are data to demonstrate that performing regional anesthesia in children can be done with them asleep safely.
Anesthetic Indications
Some children and adolescents are occasionally willing to undergo their surgery under regional anesthesia while remaining conscious. If a regional block can provide adequate analgesia, there is no reason to refuse such management, especially for short-duration surgery. Occasionally, such a management approach can be considered in children at risk for severe complications during general anesthesia from certain problems, such as the following :
- ▪
Testicular torsion or incarcerated hernia at immediate risk for rupture in children who have nothing by mouth (NPO) guideline violation
- ▪
Inguinal hernia repair in former preterm infants younger than 60 weeks of postconceptual age who are at risk for developing severe postoperative apnea
- ▪
Severe acute or chronic respiratory insufficiency
- ▪
Emergency conditions in children with severe metabolic or endocrine disorders
- ▪
Neuromuscular disorders, myasthenia gravis, or some types of porphyria
- ▪
Some congenital syndromes and skeletal deformities
Cervical instability (making tracheal intubation a risk for tetraplegia) is seen in children with Chiari malformation, achondroplasia, and Down syndrome. Patients with facial deformities, microstomia, metabolic disorders like Hurler and Hunter syndromes and mandibular hypoplasia can be difficult to intubate, thus making general anesthesia less safe. Also, infants with epidermolysis bullosa are extremely difficult to manage under general anesthesia; occasionally, regional block procedures may represent an alternative with lower morbidity. Trauma patients with extremity lesions may greatly benefit from peripheral nerve block for alleviating pain without impeding monitoring and evaluation of head trauma or hemodynamic disorders and allowing wound dressing as well as temporary stabilization of fractures, provided that appropriate precautions are taken to avoid masking development of compartment syndromes (see later).
Intraoperative and Postoperative Analgesia and Procedural Pain
Analgesia is currently the main indication for regional blocks in children because they offer the best risk-benefit ratio for many outpatient and inpatient surgeries: orthopedic (including scoliosis surgery), thoracic, urologic, and upper and lower abdominal surgeries. Cardiac surgery is a more controversial indication, and many anesthesiologists are reluctant to perform neuraxial blocks in children scheduled to receive anticoagulants although this is changing with more recent guidelines from the American Society of Regional Anesthesia and Pain Medicine (ASRA) regarding heparinization after 60 minutes of placing the block.
Procedural pain can easily be anticipated and thus prevented mostly by topical anesthesia or infiltration techniques. The indications for perineural catheters depend on the expected duration of postoperative pain. Also, surgery associated with intense postoperative pain (major orthopedic surgery, hand or foot amputation) and postoperative pain management or painful physical therapy necessary for several days (knee arthroscopy and repair) are excellent indications for catheters.
A comparative evaluation of suitability, and risk-benefit ratio for most regional techniques is provided in Table 76.5 .
Table 76.5
Evaluation of the Suitability and Benefit-to-Risk Ratio and Feasibility With Ultrasound Guidance of Most Techniques of Regional Anesthesia in Children
| Technique | Ease of Performance | Benefit-to-Risk Ratio | Feasibility With Ultrasound | Catheter Placement |
|---|---|---|---|---|
| Central blocks Spinal block Caudal block Lumbar epidural anesthesia Thoracic epidural anesthesia Sacral epidural anesthesia Cervical epidural anesthesia |
+ to ++ +++ +++ +++ ++ Avoid |
+++ ++++ +++ +++ ++ Very low |
Mild Easy Difficult Difficult Difficult Avoid |
No Occasionally Yes Yes Yes Avoid |
| Limb plexus and peripheral nerve conduction blocks Interscalene block Parascalene block Subclavicular block Axillary block Psoas compartment block Femoral block Proximal sciatic blocks Subgluteal sciatic block Popliteal sciatic block Distal block |
++ +++ +++ ++++ +++ +++ ++ to +++ +++ +++ ++ to +++ |
++ ++++ +++ ++++ ++ ++++ +++ ++++ ++++ +++ |
Mild Mild Mild Easy Difficult Easy Mild Easy Easy No |
Occasionally Yes Yes Occasionally Occasionally Yes Yes Yes Yes No (except tibial nerve at ankle) |
| Truncal compartment blocks Intercostal block Intrapleural block Thoracic paravertebral block Rectus sheath block Ilioinguinal-iliohypogastric nerve block Transabdominis plane block Penile block Pudendal nerve block |
++ ++++ ++ ++++ ++++ ++++ ++++ +++ |
+ 0 to + + +++ +++ +++ ++++ +++ |
No No Difficult Easy Easy Easy Mild Difficult |
Occasionally Yes Yes No Occasionally Occasionally No No |
| Facial blocks Trigeminal superficial block Suprazygomatic maxillary nerve block Mandibular nerve block |
++++ +++ +++ |
++++ +++ +++ |
Mild Mild Difficult |
No Occasionally No |
| Other techniques Bier block Wound infiltration Topical anesthesia |
++ to +++ ++++ ++++ |
+ +++ ++++ (skin) |
No No No |
No Yes No |
Management of Nonsurgical Pain
Relief of pain associated with some medical conditions such as herpes zoster, acquired immunodeficiency syndrome (AIDS), mucosal and cutaneous lesions, and cancer can be achieved using regional block techniques. Children with sickle cell disease may greatly benefit from epidural analgesia during vasoocclusive crisis or thoracic syndromes with intractable pain by other means, provided that pain is localized to limited areas and concomitant fever is not due to bacteremia.
Chronic Pain Relief and Palliative Care
Chronic pain is less unusual in children than commonly believed, and regional techniques such as epidural anesthesia, stellate ganglion blockade, or continuous peripheral nerve blocks may help treat this condition, especially in case of phantom limb pain and complex regional pain syndrome (CRPS), leading to pain reduction (minimal pain scores), facilitating physiotherapy, and functional rehabilitation. Treatment of intractable refractory pain from a chronic dislocated hip with long-time perineural catheter has been described. Erythromelalgia, a rare but extremely painful condition, can be successfully relieved by continuous epidural analgesia. Cancer pain resulting from either primary tumor or metastases also can be controlled by regional techniques when other medications fail or produce too many adverse effects. Virtually all techniques of regional anesthesia have been reported in this ultimate management of pain in children, from epidural analgesia to intrathecal infusions to celiac or brachial plexus block.
Nonanalgesic Indications
For certain medical conditions, analgesia is not the only benefit expected from regional blockade. Sympathetic blockade is essential to protect and improve blood supply to an upper or lower extremity in a context of severe trauma. Also, continuous epidural blockade proved to be effective in treating vascular insufficiency resulting from Kawasaki disease, accidental intra-arterial injection of an anesthetic drug, penile block with a local anesthetic containing epinephrine, and severe frostbite. Axillary and stellate ganglion blocks have also successfully treated acute vascular insufficiency of the upper limb.
Contraindications and Limitations
Absolute Contraindications to Neuraxial Blocks
Medical conditions that contraindicate neuraxial blocks in children are (1) severe coagulation disorders, which may be constitutional (hemophilia), acquired (disseminated intravascular coagulation), or therapeutic; (2) severe infection such as septicemia or meningitis; (3) intracranial tumor with increased intracranial pressure; (4) true allergy to local anesthetics (a very rare condition even with aminoesters); (5) certain chemotherapies (such as with cisplatin) prone to induce subclinical neurologic lesions that can be acutely aggravated by a block procedure; (6) uncorrected hypovolemia; and (7) cutaneous or subcutaneous lesions, whatever their nature (infection, angioma, dystrophic, tattoo) at the contemplated site of puncture. Parental refusal is a nonmedical absolute contraindication.
Depending on the clinical condition of the patient and the possibility to cure (at least temporarily) the impeding disorder, a regional block may be considered in spite of the existence of a contraindication. After correction of hypovolemia, injection of factor VIII to a hemophilic child, or effective antibiotic treatment of a septicemic patient, a central block may be performed, provided that the expected benefits consistently outweigh the risks by comparison with other techniques of analgesia. Also, some authors consider it acceptable to perform a caudal block in children with shunt devices under protection of antibioprophylaxis. In a single-center study, it was demonstrated that caudal blocks in children with VP shunts can be safely performed.
Absolute Contraindications to Peripheral Nerve Block Procedure
True allergy to local anesthetics is the only absolute medical contraindication to peripheral nerve blocks. Coagulation disorders are less hazardous than during neuraxial blocks, but it is prudent to avoid techniques with a danger of arterial trauma, especially in an area where compression is difficult or impossible (infraclavicular brachial plexus block, psoas compartment block). Septicemia does not necessarily contraindicate peripheral nerve blockade if expected benefits are significant. Local skin infection at the puncture site should be considered before performing a peripheral nerve block, especially if a catheter is implanted. Hypovolemia should preferably be corrected but does not preclude peripheral blocks because hemodynamic consequences are minimal.
Patients at Risk for Compartment Syndrome
Because pain is one of the cardinal symptoms of a compartment syndrome, any pain treatment, including regional anesthesia, is often claimed to be contraindicated because it can suppress this manifesting symptom, thus delaying the rescuing surgery. Such a refusal of pain management is not acceptable either medically and ethically. Fractures are very frequent in the pediatric population, whereas compartment syndromes are very rare; whether or not a compartment syndrome is in progress, intense pain is a constant feature. Adequate pain management, including continuous epidural analgesia, does not preclude early diagnosis, and this fact was confirmed by the National Pediatric Epidural Audit in Great Britain.
The European Society of Regional Anaesthesia and ASRA collaboration recently published guidelines for the use of regional anesthesia and compartment syndrome.
Excruciating pain is not a “manifesting” symptom but a late symptom of compartment syndrome. Patients at risk should be monitored adequately, which is not done most of the time even in university hospitals, and precautions must be taken including avoidance of closed plaster casts; elbow immobilization with an angle greater than 90 degrees ; closed reduction of supracondylar fractures of the humerus; repeat clinical evaluation of the distal perfusion and tissue oxygenation of the limb; and noninvasive monitoring of the intracompartmental pressure, even though this monitoring is not 100% reliable. If the risk is considered high (e.g., displaced humeral fractures, intramedullary nail fixation of tibia or radius, obtunded patients), intracompartmental pressure close to the fracture site should be invasively monitored. The procedure is easy and almost inexpensive, requiring only a venous cannula, an intravenous line, and a pressure gauge (as for central venous pressure measurement).
Hemoglobinopathies
Children with sickle cell disease are prone to develop hemolysis in case of desaturation and undergo repeat episodes of extreme pain as a result of extended microthromboses when local blood flow slows down (e.g., hemoconcentration, shock, surgical tourniquet). In the case of a danger of hypoxemia (respiratory disease) or hemodynamic disorders (surgery known to produce significant blood loss, tourniquet placement), regional (especially neuraxial) blocks should be avoided. Regional anesthesia has been shown to improve symptoms in children with sickle cell disease and decrease their pain.
Bone and Joint Deformities
Minor or localized malformations of the spine (hemivertebra, spina bifida occulta, Scheuermann disease) do not preclude neuraxial blocks, whereas extended malformations of vertebrae, spinal fusion, myelomeningoceles, open spina bifida, and major spondylolisthesis are relative contraindications. Tethered cord syndrome is not unusual and is often misdiagnosed. The diagnosis must be suspected if a clump of hairs or a dystrophic lesion of the skin is present at the lower extremity of the spinous process line or in the case of minor neurologic disorders involving pelvic nerves (minimal sphincter disorders, perineal dysesthesia). This can be diagnosed using ultrasound guidance. Although some authors consider that this condition is not a contraindication, it is preferable to select another technique of analgesia than epidural blockade. Many pediatric syndromes, cerebral palsy, and kyphoscoliosis are associated with bone and joint deformities that represent more of a technical difficulty than a contraindication to performing a regional block.
Preexisting Neurologic Disorders or Diseases
Controlled epilepsy is not a contraindication to regional anesthesia, including neuraxial blockade. Preexisting central nervous system disorders and degenerative axonal diseases have long been considered to be contraindications, at least relative, even though no data support the hypothesis that a regional block could worsen their course.
Complications
Complications of regional anesthesia are essentially the same as those in adults. The complication rate found recently in a large epidemiologic study was 0.12%, with two major risk factors—age and the central blocks. They can be classified as local, regional, and general (or systemic).
Local Complications
The four main types of local complications are as follows:
- 1.
Inappropriate needle insertion damaging the nerve and surrounding anatomic structures
- 2.
Tissue coring and introduction of epithelial cells into tissues where they do not belong and where they can develop as compressive tumors (especially in the spinal canal)
- 3.
Injection of neurotoxic solutions (syringe mismatch, epinephrine close to a terminal artery)
- 4.
Leakage around the puncture site, especially when a catheter has been introduced, which may cause partial block failure and favor bacterial contamination (very rare)
These local complications are easily avoidable by using adequate devices and applying standard precautions (appropriate dressing and bacterial precautions). Tunneling the catheter and applying a slightly compressive dressing can reduce leakage around the catheter.
Local anesthetics are locally toxic. Myelin, effective protection of nerve roots, is less abundant or absent in children, potentially making the nerves more sensitive to local anesthetics. In animals, it has been clearly demonstrated that the sensitivity of nerve fibers to local anesthetics is inversely correlated with age. However, in most cases, perineural injection is around muscle. The myotoxicity of local anesthetics has been previously demonstrated in humans and animals, primarily through mitochondrial damage. This also has been demonstrated in young animals. By comparing continuous bupivacaine perineural administration in adult rats and young rats, the authors showed that muscle, mitochondrial, and ultrastructural toxicity was significantly greater in the juvenile group, thus emphasizing the need to use lower dosages in younger patients.
Systemic Complications
Systemic complications usually result from accidental intravenous injection of local anesthetics or, less frequently, excessive dosing. Systemic toxicity is essentially of two types: neurologic and cardiac resulting from heart failure by blocking sodium and potassium channels. Early signs of neurologic toxicity (tinnitus, malaise, metallic taste in the mouth) are unfortunately masked by general anesthesia. The main complications are heart conduction disorders, cardiac arrhythmias (bradycardia or tachycardia), and atrioventricular block. QRS widening, bradycardia, and torsade de pointes are followed by ventricular fibrillation, asystole, or both. Nevertheless, signs of cardiac and neurologic toxicity occur at lower plasma concentrations of bupivacaine than ropivacaine. This toxicity may be aggravated by a decrease in plasma binding protein, mainly AGP, resulting in a greater proportion of the unbound form of local anesthetic. The plasma concentration of this protein is low at birth, and tends to increase with the age of the child to reach values equivalent to those of adults at the age of 10 months. However, special care must be taken during continuous injections; the dosage of local anesthetic should be systematically reduced in very young children or after prolonged administration (>48 hours).
Systemic complications can be life threatening and should be managed in the same way as in adults. The major difference between adults and children is that cardiovascular complications are not preceded by neurologic signs but are concomitant with cerebral toxicity. In addition to pharmacokinetic factors, the rapid heart rate of children may increase the risk for cardiac toxicity induced by local anesthetic toxicity. Even if toxic events occur with ropivacaine, small doses of epinephrine should produce rapid recovery. Impaired ventricular conduction is the primary manifestation of local anesthetic toxicity. Treatment includes oxygenation, cardiac massage, and epinephrine, which is given in small incremental boluses beginning with 1 to 2 μg/kg. If ventricular fibrillation persists, defibrillation (2-4 J/kg) is performed. Although resuscitation measures must be initiated immediately, the specific treatment of local anesthetic toxicity is rapid administration of Intralipid. The recommended dose of 20% Intralipid for pediatric patients is 2 to 5 mL/kg by intravenous bolus. If cardiac function does not return, this dose (up to 10 mL/kg ) is repeated.
Epidemiology
Available pediatric information is limited. The first report of the American Society of Anesthesiologists (ASA) closed claims analysis contained 238 pediatric cases (10% of claims), but only 7 involved children who received regional anesthesia ; however, at that time regional anesthesia was not commonly used in children, making this apparently low rate of complications meaningless. In 1996, the 1-year prospective study of the French-Language Society of Pediatric Anesthesiologists evaluated 85,412 pediatric anesthetic procedures, including 24,409 involving regional anesthesia. Twenty-three complications (no sequelae, no death, and no legal consequences) were found, all following neuraxial blocks. In 2000, the Australian Incident Monitoring Study included 2000 claims involving 160 pediatric cases with a regional block procedure (83 epidurals, 42 spinals, 14 brachial plexus, 4 Bier blocks, 3 ophthalmic blocks, and 14 local infiltrations). The largest single cause of complications was circulatory problems; 24 drug errors (including 10 “wrong drugs” and 14 “inappropriate use”) were found. In 2007, the British National Pediatric Epidural Audit reported 96 incidents in 10,633 epidural blocks performed, as follows:
- ▪
Fifty-six (0.53%) were associated with the insertion or maintenance of epidural anesthesia, and most were of low severity; only one child had residual effects from cauda equina syndrome (after a programming error of the infusion pump).
- ▪
Forty (0.38%), mainly pressure sores, were believed to be associated with the epidural infusion technique.
A significantly higher rate of incidents occurred in the neonatal age group, mainly because of drug errors (13 cases) and local anesthetic toxicity (1 case); these incidents were not related to catheter insertion. Twenty-eight infection-related incidents occurred, of which 85% were relatively minor skin infections; caudal catheters did not result in increased incidence of infections. Six children older than 8 years of age had mild postdural puncture headache. Four patients developed a compartment syndrome, but the condition was not masked by the epidural infusion.
From November 2005 to October 2006, a large epidemiologic study recorded the characteristics and developments of regional anesthesia in children in 47 French hospitals. As previously demonstrated by Rochette and colleagues, the authors reported a radical change in regional practice among French anesthesiologists with a transition from using predominantly neuraxial blocks to peripheral nerve blocks, including catheter techniques. A recent 1-year prospective survey of regional anesthesia evaluated complications and side effects in 31,132 cases of regional anesthesia. Complications (41, involving 40 patients) were rare and usually minor and did not result in sequelae. The study recorded a very low overall rate of complications of 0.12%, significantly six times lower for peripheral blocks than for neuraxial blocks. Age was also a risk factor, because the incidence of complications was higher before 6 months of life than after (0.4% vs. 0.1% after 6 months of life). Fifteen cases of cardiotoxicity were observed, of which 87% occurred with a central block. The occurrence of complications does not seem to increase with the use of catheters.
A large North American Regional anesthesia registry (Pediatric Regional Anesthesia Network- PRAN) has just published prospective data on 100,000 blocks in over 20 centers. The incidence of systemic toxicity was 0.76:10,000 cases with the majority occurring in infants. No permanent neurologic deficits were reported; however the risk of transient neurologic deficit was 2.4:10,000 and was not different between peripheral and neuraxial blocks.
In conclusion, regional block procedures—mainly neuraxial blocks—are associated with the occurrence of adverse incidents (∼0.5%) that are mostly minor but occasionally severe. The majority of these complications result from insufficient precautions at the time of the block procedure (drug errors) and postoperatively (pressure sores). Also, of major importance is the fact that compartment syndrome is not hidden by regional anesthesia provided that adequate monitoring is guaranteed.
Selection of Materials and Anesthetic Solution
Selection of Block Procedure
Careful selection of block procedures is based first on anatomic considerations. Sensory blockade must cover all areas from which noxious stimuli can originate (e.g., operative field, sites for skin or bone graft tissue, placement of tourniquet or drains). Then, the potential morbidity of the technique, from the medical condition of the patient, the requested positioning, or the “intrinsic” morbidity of the technique itself, must be evaluated. The anticipated duration of postoperative pain is the third most important factor to take into account because the regional technique should provide adequate analgesia until minor analgesics are sufficient. The anesthesiologist will select one of the following approaches:
- ▪
A single-shot technique with either a short-acting or a long-acting local anesthetic
- ▪
A single-shot technique with local anesthetic and adjuvants
- ▪
A catheter technique with repeat or continual injections of local anesthetic
Selection of Equipment
Epidural anesthesia (sacral, lumbar, or thoracic) is performed using Tuohy needles ranging in size from 17 to 21 gauge and in length from 50 to 90 cm; shorter Tuohy needles (25 cm) would be more appropriate in neonates and infants but are not easily available. Caudal anesthesia has been performed in the past with almost all types of needles. This is no longer acceptable, and only short beveled needles (Crawford needles) with a guide sealing their lumen or intravenous cannulas with an introducer needle should be used. Ultrasound guidance has not been introduced for placement of epidural catheters in neonates and infants with greater precision and less complications.
Spinal anesthesia in premature infants can be performed using either a neonatal lumbar puncture needle (22 gauge) or, preferably, a thinner spinal needle (shorter than 50 mm). The distal end of the needle does not have the same importance as in adults because the incidence of postdural puncture headache remains low in children and may not be influenced by the design of the tip of the needle. What matters most is the distance separating the tip of the needle from its distal orifice; this distance must be as short as possible to avoid extradural leakage if the needle has not been introduced far enough through the dura mater. Pencil-point needles have no advantage in infants and young children; they do not improve the results and are even suspected to decrease the success rate by favoring subdural spread of the local anesthetic. A summary of recommended needles for most regional block procedures in pediatric patients is provided in Table 76.6 .
Table 76.6
Recommended Devices for Most Regional Block Procedures in Children
| Block Procedure | Recommended Device | Alternate Device |
|---|---|---|
| Intradermal wheals and metacarpal blocks | Intradermal needles (25 gauge) | None |
| Subcutaneous infiltrations and field blocks | Standard intramuscular needles (21-23 gauge) | Intradermal needles (25 gauge) |
| Compartment blocks (thoracic paravertebral, rectus sheath, ilioinguinal-iliohypogastric, pudendal, penile) | Short (25-50 mm) and short beveled (45-55 degrees) needles | Epidural needles (intercostal block) Neonatal spinal needle |
| Peripheral mixed nerve blocks and plexus blocks | Insulated 21-23 gauge short beveled needles of appropriate length connected to a nerve stimulator (0.5-1 mA) Specific catheter (for continuous techniques) |
Sheathed pencil-point needles Unsheathed needles only when ultrasound guidance is used Epidural catheter (for continuous techniques) |
| Spinal anesthesia | Spinal needle (24-25 gauge; 30, 50 or 100 mm long, Quincke bevel, stylet) | Neonatal lumbar puncture needle (22 gauge, 30-50 mm long) Whitacre spinal needle |
| Caudal anesthesia | Short (25-30 mm) and short beveled (45-degrees) needle with stylet | Intravenous cannula (22-18 gauge), especially for epidural catheter insertion Pediatric epidural (occasionally spinal) needle |
| Epidural anesthesia | Tuohy needle (22, 20, and 19/18 gauge); LOR syringe and medium epidural catheter | Crawford, Whitacre, or Sprotte epidural needles appropriately sized; LOR syringe and medium epidural catheter |
LOR, Loss of resistance.
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