Spinal anesthesia in infants

Techniques in Regional Anesthesia and Pain Management (2007) 11, 255-259

Spinal anesthesia in infants Alexander Paloma, MD, Tetsu Uejima, MD, Santhanam Suresh, MD, FAAP From the Department of Pediatric Anesthesiology, Children’s Memorial Hospital, Northwestern University, Feinberg School of Medicine, Chicago, Illinois. KEYWORDS: Spinal anesthesia; Premature infant; Children

Spinal anesthesia, although uncommonly performed in infants and children, may have a role in the premature infant predisposed to postoperative apnea and bradycardia. The duration of surgical anesthesia is often limited, which leads to the necessity of adjuvant anesthetics. This article will describe the anatomy and physiology of the subarachnoid space of infants and children as well as discuss the technique of performing a subarachnoid block in this population. Judicious dosing and use of local anesthetics and potential adverse effects of this technique are discussed. © 2007 Elsevier Inc. All rights reserved.

Spinal anesthesia is one of the oldest modalities for providing pain relief in patients undergoing surgery. J.L. Corning is credited with administering the first spinal anesthetic published in a peer reviewed medical journal.1 This technique was seldom used in the pediatric practice until Melman,2 and later, Abajian and coworkers reported in 1984 a series of high-risk infants undergoing surgery with spinal anesthesia.3 In the early 1980s, multiple reports of apnea following general anesthesia in preterm infants appeared in the pediatric literature.4-8 Abajian’s series offered practitioners an alternative technique with reportedly fewer complications. Since then, a number of series in all age groups for a variety of surgical procedures have attested to the safety and efficacy of spinal anesthesia.9-11 The use of spinal anesthesia in children is usually restricted to infants, particularly premature infants, who would otherwise have received a general anesthetic (Table 1).

Anatomy To safely and proficiently administer a spinal anesthetic in children, it is crucial to understand the anatomic differences Address reprint requests and correspondence: Santhanam Suresh, MD, FAAP, Children’s Memorial Hospital, Department of Pediatric Anesthesiology, 2300 Children’s Plaza, Chicago, IL 60614. E-mail address: [email protected].

1084-208X/$ -see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1053/j.trap.2007.09.006

between adults and infants regarding termination of spinal cord and dural sac, surface anatomy, and volume of CSF (Table 2). The spinal cord and dural sac terminate at a more caudad level in neonates and in infants with the conus medullaris ending at approximately the L2 or L3 level in neonates and infants versus the L1 level in adults. Therefore, to avoid potential injury to the spinal cord, dural puncture should be performed below the level termination of the spinal cord; below L2–L3 in neonates and infants. In adults, spinal anesthesia is often administered at the interspace that is nearest an imaginary line stretching across the top of the iliac crests; the intercristal or Truffier’s line, which is most commonly the L3–L4 interspace. Since neonates and infants have a proportionately smaller pelvis and the sacrum is located more cephalad relative to the iliac crests, the intercristal line crosses the midline of the vertebral column at the L4 –L5 or L5–S1 interspace. Therefore, the intercristal line is a landmark applicable in all pediatric patients.12-14 The dural sac of neonates and infants also terminates more caudad at a level of S3 compared with adults at a level of S1. This location may lead to accidental dural puncture during performance of a single-shot caudal block if the caudal needle advances too far into the caudal epidural space.13 Infants and neonates have a larger cerebrospinal fluid (CSF) volume (4 mL/kg) compared with adults (2 mL/kg).15

256 Table 1

Techniques in Regional Anesthesia and Pain Management, Vol 11, No 4, October 2007 Indications for spinal anesthesia Hernia repair Circumcision Exploratory laparotomy Meningomyelocele repair Muscle biopsy Cardiac surgery

This fact may account for the higher local anesthetic dose requirement and shorter duration of action of spinal anesthesia in infants.

Technique for performing spinal anesthesia A local anesthetic cream such as EMLA (eutectic mixture of local anesthetic cream) or LMX (4% lidocaine cream) may be applied to the puncture site before performing the subarachnoid block. The operating room should be warmed and warm blankets and/or radiant heating lamps used to help diminish heat loss in infants. With older children, ambient noise should be limited and surgical instruments should be covered to minimize patient anxiety. Audiovisual equipment helps to distract older children if the block is performed while the child is awake or sedated. Before performing the block, standard monitoring devices (blood pressure cuff, pulse oximeter, electrocardiogram leads) should be applied. We recommend providing a venous access before performing spinal anesthesia in neonates or infants. The use of concomitant intravenous sedation or general anesthesia should be dictated by the medical condition, patient age, and the comfort level of the anesthesia provider as well as the nature and anticipated length of the surgical procedure. In former preterm infants, it is common practice to perform spinal anesthesia without adjuvant sedation or general anesthesia when lower abdominal procedures under 90 minutes are planned. The concomitant use of ketamine may increase the incidence of apnea and bradycardia in infants receiving spinal anesthesia.16 Older children may require sedation or light general anesthesia before performing the anesthetic.

Position In children, spinal anesthesia is customarily administered in the lateral or sitting position. When the sitting position is used in infants, special attention must be paid to ensure the neck is not flexed, which may result in airway obstruction. Spinal anesthetics performed in the flexed position carry the greatest risk of potential morbidity, and it is recommended that this position be modified with neck extension or in the upright position.17 In infants, the area corresponding to the L4 –L5 or L5–S1 interspace should be identified, prepped, and draped in a

sterile fashion. In older children, the L3–L4 interspace may be used. The desired dose of local anesthetic should be calculated and be prepared in a syringe before dural puncture, ensuring the accuracy of the dose administered. A short 22- or 25-gauge spinal needle is often used in a midline approach. In children, the ligamentum flavum is very soft and a distinctive “pop” may not be appreciated when the dura is punctured. The drug(s) should be administered slowly once clear CSF is seen exiting the needle. The barbotage method is not recommended since it may result in unacceptable high levels of motor blockade and potential for a total spinal anesthesia. Once the subarachnoid block is performed, the caudal end of the patient should not be elevated. This also can result in a total spinal from spread of the local anesthetic solution to a higher spinal level. Assessing the level of blockade may be difficult in infants and young children as well as in those who have received sedation or general anesthesia. In infants, response to pin prick or cold stimuli (eg, an alcohol swab) can be used. The gold standard, a Bromage score,18 can usually be accomplished in children older than 2 years of age. If a rapidly rising level of blockade is noted, the patient may be placed in reverse Trendelenburg.

Adverse effects The adverse effects from spinal anesthesia commonly seen in adults, such as hypotension, bradycardia, postdural puncture headache, and transient radicular symptoms, are less common in children. Despite high levels of blockade and the absence of routine fluid loading, hypotension and bradycardia are very rare occurrences after performing spinal anesthesia in children.19 A report of 1132 consecutive spinal anesthetics performed with sedation showed a mild drop in blood pressure in 9 of 942 patients who were less than 10 years of age.20 Temperature change in the lower extremities occurring in infants after subarachnoid block may be evidence of sympatholysis, but blood pressure seems to remain within normal ranges.21 Postdural puncture headache (PDPH) is seen less frequently in children compared with adults. A large series reported a low incidence of PDPH after frequent lumbar punctures for spinal tap in children.22 A study using different types of needles for spinal tap showed no difference in the incidence of postdural puncture headaches.23 Treatment of PDPH consists of bed rest and caffeine followed by blood patch if the headaches do not resolve with noninvasive

Table 2

Anatomic differences in spinal canal

Conus medullaris ends at L2–L3 compared with L1 in adults. Small pelvis with sacrum that starts more cephalad. Dural sac ends more caudad.

Paloma and Suresh Table 3

Spinal Anesthesia in Infants

Dosage for spinal anesthesia

Local anesthetic solution Tetracaine: 0.5–1 mg/kg Bupivacaine: 0.5–1 mg/kg Additives Epinephrine wash Clonidine 1–2 mcg/kg Morphine 10 mcg/kg (only for cardiac surgical patients who will be ventilated postoperatively)

thearpy.24 When conservative therapy fails, postdural puncture headaches have been treated by performing an epidural blood patch (0.3 mL/kg of blood) with good results.25 Transient radicular symptoms with no long-term adverse effects have been reported in children following spinal anesthesia.26

Agents and doses Many agents and doses have been described in the literature, including tetracaine, bupivacaine,20 lidocaine, amethecaine, levobupivacaine, and ropivacaine27 (Table 3). We use a dose of 0.5 mg/kg to 1 mg/kg of tetracaine or bupivacaine for spinal anesthesia. An epinephrine wash of the syringe is preferred to a standard dose of epinephrine. Hyperbaric solution with glucose or eubaric solution does not seem to alter the duration of the spinal block in children and provided the same result.28 Higher doses are preferred, and the risk of a total spinal is rare as long as the procedure is performed diligently. An adjuvant to spinal solution, clonidine in a dose of 1 ␮g/kg, added to bupivacaine (1 mg/kg) has been used in spinal anesthesia in newborns and provided almost twice the duration of spinal anesthesia.29 We have noted a transient drop in blood pressures with the use of 2 ␮g/kg of clonidine and a propensity to greater sedation in the postoperative period. The use of intravenous caffeine (10 mg/kg) to prevent any potential apnea in the postoperative period may be indicated, especially if clonidine is used in the spinal anesthetic solution.

Clinical use Spinal anesthesia can be used to anesthetize infants and children for multiple proposed surgical procedures. The intraoperative position, anticipated length of surgical procedure, surgical site, comorbidities, and the anticipated degree of postoperative pain must be considered. Although a patient with a known difficult airway may provide impetus to provide an anesthetic without manipulation of the airway, special consideration should always be given to these patients before performing a spinal anesthetic. The presence of an airway abnormality should not deter the practitioner from

257 using a neuraxial technique, but a plan to secure the airway must be made should the need arise. Infants and children have limited reserve of oxygen predisposing to catastrophe and untoward events if mishaps occur. If available, the medical record should be consulted for previous anesthetic care and successful techniques. Caution should be employed when considering sedation during administration of spinal anesthesia. Relative contraindications to the use of spinal anesthesia in children are similar to those in adults (Table 4). They include anatomic deformities, infection at the puncture site, presence of an underlying coagulopathy, hemodynamic instability, presence of a ventriculo-peritoneal (or other ventricular) shunt, systemic generalized sepsis, neuromuscular disease, increased intracranial pressure, difficult airway, and poorly controlled seizures. Patients with neuromuscular disorders with concurrent pulmonary disease may benefit from a subarachnoid block, but the risk of exacerbating the neuromuscular symptoms must be weighed against the potential benefit. Outside of the former preterm infant, most pediatric patients will receive a general as well as a spinal anesthetic, which potentially increases the overall risk of anesthetic complications.

Apnea and former preterm infants A common indication for spinal anesthesia in pediatric patients is the former preterm infant scheduled for hernia repair due to their increased incidence of apnea in the postoperative period.7 Although a number of small studies have confirmed this finding, there is considerable disagreement regarding the postconceptual age at which a former preterm infant can safely undergo general anesthesia on an outpatient basis. The lack of uniformity in study design, small patient population sizes, and variations in methodology probably account for these differences. Meta-analysis of 8 studies investigating postoperative apnea in former preterm infants following general anesthesia comprising a total of 255 patients showed that the risk of apnea was independently related to both gestational age and conceptual age.7 Additional risk factors for postoperative apnea were anemia (hematocrit ⬍30%) and the presence of apneic episodes at home. The study stratified infants into two risk groups; risk of apnea did not fall below 5% until

Table 4

Relative contraindications to spinal anesthesia Anatomic abnormalities of the spine Degenerative neuromuscular disease Patient and family dissent Coagulopathy Bacterial infection Increased intracranial pressure Patients with ventriculo-peritoneal shunts

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patients reached a postconceptual age of 48 weeks with a gestational age of 35 weeks (95% statistical confidence) and did not fall below 1% until reaching 54 weeks postconceptual age with a gestational age of 35 weeks or postconceptual age of 56 weeks with a gestational age of 32 weeks (95% statistical confidence).7 The use of regional anesthesia alone, compared with general anesthesia, may decrease the incidence of postoperative apnea. Unfortunately, very little information is available regarding the potential benefits of spinal anesthesia in former preterm infants over the use of general anesthesia. A small randomized study of former preterm infants who received spinal anesthesia showed a decrease in the incidence of postoperative desaturation and bradycardia compared with patients who received general anesthesia for inguinal herniorrhaphy.30 However, they observed no significant difference in the incidence of postoperative apnea between the two groups. In the Cochrane Database of Systematic Reviews, Craven and coworkers found that there was no reliable evidence concerning the effect of spinal as compared with general anesthesia on the incidence of postoperative apnea, bradycardia, or oxygen desaturation in former preterm infants undergoing herniorrhaphy.31 However, if the former preterm infants having preoperative sedation are excluded, the meta-analysis demonstrated a reduction in postoperative apnea in patients receiving spinal anesthesia. Overall, only borderline statistical advantage of a spinal anesthetic over a general anesthetic was found.

Spinal anesthesia for procedures other than herniorrhaphy Spinal anesthesia has been successfully used in children for a variety of surgical procedures.10,11 Reports in the literature involve patients undergoing not only herniorrhaphy but also a variety of general, urologic, lower abdominal, lower extremity, and orthopedic procedures as well as repair of meningomylocele.9,26,32,33 Interestingly, the study populations included infants with medical conditions the authors felt increased the risk of general anesthesia, including laryngomalacia, macroglossia, micrognathia, congenital heart disease, Down’s syndrome, adrenogenital syndrome, failure to thrive, arthrogryposis, and Gordon’s syndrome. The use of spinal anesthesia for cardiac surgery may provide potential benefit as there have been multiple studies regarding combining anesthetic techniques to facilitate early extubation.34 A large prospective randomized analysis of the use of spinal anesthesia for children undergoing elective cardiac surgery with early extubation in the operating room required less opioids in the postoperative period compared with the control group.35 They also demonstrated that there was no associated adverse hemodynamic, respiratory, or other adverse effects compared with controls.

Conclusion Spinal anesthesia, although not commonly used in children, has a distinct role in pediatric anesthesia. The use of ultrasonography to recognize depth of the subarachnoid space along with innovative newer needles may facilitate a resurgence of the use of spinal anesthesia in children.

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23. Kokki H, Salonvaara M, Herrgard E, et al: Postdural puncture headache is not an age-related symptom in children: a prospective, openrandomized, parallel group study comparing a 22-gauge Quincke with a 22-gauge Whitacre needle. Paediatr Anaesth 9:429-434, 1999 24. Yucel A, Ozyalcin S, Talu GK, et al: Intravenous administration of caffeine sodium benzoate for postdural puncture headache. Reg Anesth Pain Med 24:51-54, 1999 25. Ylonen P, Kokki H: Management of postdural puncture headache with epidural blood patch in children. Paediatr Anaesth 12:526-529, 2002 26. Salmela L, Aromaa U: Transient radicular irritation after spinal anesthesia induced with hyperbaric solutions of cerebrospinal fluid-diluted lidocaine 50 mg/ml or mepivacaine 40 mg/ml or bupivacaine 5 mg/ml. Acta Anaesthesiol Scand 42:765-769, 1998 27. Kokki H, Ylonen P, Laisalmi M, et al: Isobaric ropivacaine 5 mg/ml for spinal anesthesia in children. Anesth Analg 100:66-70, 2005 28. Kokki H, Hendolin H: Hyperbaric bupivacaine for spinal anaesthesia in 7-18 yr old children: comparison of bupivacaine 5 mg ml-1 in 0.9% and 8% glucose solutions. Br J Anaesth 84:59-62, 2000 29. Rochette A, Raux O, Troncin R, et al: Clonidine prolongs spinal anesthesia in newborns: a prospective dose-ranging study. Anesth Analg 98:56-59, 2004

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