Introduction

Spinal anesthesia is perhaps one of the oldest and well tested modalities for providing pain relief in patients undergoing surgery. J. Leonard Corning is credited with discovering and administering the first spinal anesthetic in 1885 which was published in a medical journal.1. Although the use of spinal or intrathecal anesthesia administration in children was described in the early 20th century,2-4 this technique was seldom used in the pediatric population until Melman4, later followed by Abajian et al. reported in 1984 a series of high-risk infants who underwent successful surgery under spinal anesthesia.5 Reports of apnea following general anesthesia in preterm infants appeared in the literature in the early 1980’s6-10 and Abajian’s series offered practitioners an impetus to offer an alternative technique with reportedly fewer complications. A number of series have since been reported in all age groups for a variety of surgical procedures attesting to the safety and efficacy of spinal anesthesia. 11;12;12;13 The use of spinal anesthesia in children is most commonly used in premature infants who would otherwise require a general anesthetic. (Table 1)

 

 Table 1: Indications for spinal anesthesia

 Nerves to subclavius

 C4-C6

 Subclacious muscle

 Dorsal scapular nerve

 C5

 Rhomboid muscles and levator scapulae muscle

Anatomy

Understanding of the anatomic differences between adults and infants are crucial in order to safely, and in a technically proficient fashion administer spinal anesthesia in children. (Table 2)

 

 Table 2: Anatomic differences in Spinal canal

 Conus medullaris ends at L2-L3 compared to L1 in adults

 Small pelvis with sacrum that starts more cephalad

 Dural sac ends more caudad

The spinal cord terminates at a much more caudad level in neonates and in infants compared to adults, Figure 1. The conus medullaris ends at approximately L1 in adults and at the L2 or L3 level in neonates and infants. In order to avoid potential injury to the spinal cord, dural puncture should be performed below the level of the spinal cord, i.e. below L2-L3 in neonates and infants. In adults, spinal anesthesia is often administered at the interspace that is nearest an imaginary line that stretches across the top of both iliac crests, the intercristal or Truffier’s line; corresponding to the L3-4 interspace. However, neonates and infants have a proportionately smaller pelvis than adults and the sacrum is located more cephalad relative to the iliac crests. Therefore, Truffier’s line crosses the midline of the vertebral column at the L4-5 or L5-S1 interspace, well below the termination of the spinal cord making this landmark applicable in all pediatric patients14-16 The dural sac in neonates and infants also terminates in a more caudad location compared to adults, usually at about the level of S3 compared to the adult level of S1. The more caudad termination of the dural sac makes it more likely to have an inadvertent dural puncture during performance of a single-shot caudal block if the caudal needle is advanced too far into the caudal epidural space.15

Figure 1. The spinal cord terminates at a much more caudad level in neonates and in infants compared to adults. The conus medullaris ends at approximately L1 in adults and at the L2 or L3 level in neonates and infants.

 Clinical Pearls

 In infants Truffier’s line crosses the midline of the vertebral column at the L4-5 or L5-S1 interspace, well below the     termination of the spinal cord making this landmark applicable in all pediatric patients

 The dural sac in neonates and infants also terminates in a more caudad location compared to adults, usually at about the     level of S3 compared to the adult level of S1.

 The more caudad termination of the dural sac makes it more likely to have an inadvertent dural puncture during     performance of a single-shot caudal block if the caudal needle is advanced too far into the caudal epidural space.

Cerebrospinal fluid (CSF) volume is larger on a mL/kg basis in infants and neonates (4mL/kg) compared to their adult counterparts (2mL/kg). This may, in part, account for the higher local anesthetic dose requirements and shorter duration of action of spinal anesthesia in this population.

Technique of Spinal Anesthesia in Children

Preparation

EMLA (eutectic mixture of local anesthetic cream) or LMX (4% lidocaine cream) may be applied to the puncture site prior to surgery. The operating room should be warmed prior bringing the patient into the room. Warm blankets and radiant heating lamps will help to diminish heat loss in infants. With older children, the room should be quiet and if possible, surgical instruments should be covered so as to minimize patient anxiety. Newer operating rooms may be equipped with stereo or video equipment which may be used to distract older children if the block is performed while the child is awake or sedated. Standard monitoring devices (blood pressure cuff, pulse oxymeter, electrocardiogram leads) should be applied prior to performing the block.

A plan should be made regarding the concomitant use of intravenous sedation or general anesthesia. The approach should be dictated by the medical condition and age of the patient, the comfort level of the anesthesia provider and the nature and anticipated length of the surgical procedure. In former preterm infants undergoing lower abdominal procedures of less than 90 minutes duration, it is common practice to perform spinal anesthesia without adjuvant sedation and to conduct the anesthetic without supplemental intravenous or general anesthesia. In fact it has been shown that the use of concomitant sedation may predispose these infants to apnea and bradycardia.17 Older children may require supplemental sedation or light general anesthesia prior to performing the block. In some cases, spinal anesthesia may be combined with caudal or epidural anesthesia.

Patient position

Spinal anesthesia is customarily administered in the lateral (Figure 2) or sitting position in children, Figure 3. Hypobaric solutions are not commonly utilized in infants. If the sitting position is preferred, special attention must be paid in infants to insure that the neck is not flexed which may result in airway obstruction Figure 3. Neck flexion is not necessary as it does not facilitate performance of the block.18 (Fig-1) In older children, an assistant should be present to maintain good positioning and to reassure and distract the child while the block is being performed. It is essential to monitor the oxygen saturation of the infant while performing the spinal to ensure the adequacy and patency of the airway.

Figure 2. Spinal anesthesia in the neonate; shown is the lateral position.

Figure 3. Spinal anesthesia in the neonate in the sitting position; head flexion must be avoided to prevent respiratory obstruction.

Technique

In infants, the L4-5 or L5-S1 interspace should be identified; the L3-4 interspace may be used in older children. The area should be cleared and draped in a sterile fashion. If EMLA or LMX were not applied preoperatively, local anesthesia should be administered prior to the block in awake or sedated children, Figure 4. The desired dose of local anesthetic should be calculated and be prepared in a syringe prior to dural puncture to insure that the correct dose is administered. A short 22- or 25-gauge spinal needle is often used. A midline approach is usually recommended over a paramedian approach. The ligamentum flavum is very soft in children and a distinctive “pop” may not be perceived when the dura is penetrated. Once clear CSF is seen exiting the needle, drug(s) should be injected slowly. The barbotage method is not recommended as this may result in unacceptable high levels of motor blockade and potential for a total spinal blockade. The caudal end of the patient should not be elevated for placement of the electro-cautery return electrode as a total spinal can result from spread of local anesthetic solution to a higher spinal level. One of the techniques we have resorted to in our teaching institution to prolong the duration of surgical analgesia is the use of spinal anesthesia using 0.8 mg/kg of bupivacaine followed immediately by a caudal block using 0.1% bupivacaine. We turn the patient to the side that has the largest hernia at the time of performance of the block. This prolongs the duration of anesthesia and analgesia. Alternatively, hypobaric solution of local anesthetic can be injected in the lateral position with the operative side up, Figure 5 and Figure 6.

Figure 4. Equipment for spinal anesthesia in the neonate. Shown are the disinfectant, hypodermic needle for local infiltration and the spinal needle.

Figure 5. Spinal anesthesia in the neonate; needle insertion.

Figure 6. Spinal anesthesia in the neonate; injection of the local anesthetic.

Assessing the block

Assessing the level of blockade may prove difficult in infants and young children, particularly if the patients have received sedation or those in whom the block is being performed under general anesthesia. In infants, pin prick or their response to cold stimuli (e.g., an alcohol swab) may be used as well as observation of their rate and pattern of ventilation. In children older than 2 years we use the Bromage scale. Care should be taken to avoid placing the patient in the Trendelenburg position following the block as this will result in an extremely high or total spinal, as may occur when placing a electrocautery grounding pad on an infant’s back by lifting the lower extremities. In the event of a rapidly rising level of blockade, the patient may be placed in reverse Trendelenburg.

 Clinical Pearls

 Evaluation of spinal anesthesia: Bromage scale

 No block (0%) Full flexion of knees and feet possible

 Partial block (33%) Just able to flex knees, still full flexion of knees possible.

 Almost complete block (66%) Unable to flex knees. Flexion of feet still possible.

 Complete block (100%) Unable to move legs or feet.

Adverse effects from Spinal Anesthesia

Adverse effects from spinal anesthesia commonly seen in adults are less common in children. These include hypotension, bradycardia, postdural puncture and transient radicular symptoms.

Hypotension

Hypotension and bradycardia are very rare occurrences when performing spinal anesthesia in children, in spite of high levels of blockade and the absence of routine fluid loading prior to blockade (10 mL/kg).19 We however do recommend that a venous access be obtained prior to performing spinal anesthesia in neonates or in infants. Puncah et al recently reported their experience with 1132 consecutive spinal anesthetics. Only 27/1132 received supplemental analgesia. All spinal blocks were performed with sedation. Hypotension was rarely reported. Mild decrease in blood pressure was reported in 9/942 patients who were

Postdural puncture headache

The incidence of PDPH is less in children compared to adults. Large series have been reported after frequent lumbar punctures for spinal tap in children with lower incidence of postdural puncture headaches.20 An incidence of 8% was noted in this subgroup of oncology patients with dural puncture. The use of different types of needles for spinal tap has been studied. They were divided into two groups either using a Quincke needle or a pencil point Whitacre needle. There was no difference in the incidence of headaches between to two needle groups (15% Quincke; 9% Whitacre; p=0.43)21 Moreover, the incidence of headaches was not different in different age groups with 8/11 PDPH occurring in children under 10 years of age with the youngest reported in a 23 month old baby. Transient radicular symptoms have been reported in children following spinal anesthesia with no long term adverse effects.22 Postdural puncture headaches have been treated with epidural blood patch (0.3mL/kg of blood) with very good results. 23 Bed rest and caffeine are initiated followed by blood patch if the headaches do not resolve.24 In our own practice we tend to place a prophylactic blood patch if a suspicion of PDPH is entertained.

Local Anesthesic Choices and Doses

A variety of agents and doses have been described in the literature including tetracaine, bupivacaine25, lidocaine, amethecaine, levobupivacaine and ropivacaine.26 (Table -3) A dose of 0.5mg/kg to 1 mg/kg of tetracaine or bupivacaine is generally what we have been using for spinal anesthesia. An epinephrine-wash rather than a standard dose of epinephrine for the syringe is preferred in our practice. Hyperbaric solution with glucose or eubaric solution result in the similar quality and duration of the spinal block in children.27 Although a higher dose is preferred, the risk of a total spinal anesthesia is rare as long as the procedure is carried out diligently. Adjuvants to spinal solution have recently been reported. Clonidine in a dose of 1mcg/kg added to bupivacaine (1mg/kg) used in spinal anesthesia in newborn infants has shown to prolong the duration of the block to almost twice the duration of spinal anesthesia without clonidine.28 We have seen transient decrease in blood pressures with the use of 2mcg/kg of clonidine and a propensity to greater sedation in the postoperative period. It may be advisable to use a dose of caffeine (10mg/kg) intravenously to prevent any potential apnea in the postoperative period especially if clonidine is used in the spinal anesthetic solution.

Relative Contraindications

Contraindications to the use of spinal anesthesia in children are similar to those in the adult population. The use of spinal anesthesia in children with neuromuscular diseases particularly central core disease or congenital neuromuscular disease is controversial. Other contradications to spinal anesthesia may include anatomic deformities, infection at the puncture site, presence of an underlying coagulopathy, hemodynamic instability, presence of a ventriculo-peritoneal (or other ventricular) shunt and poorly controlled seizures. We avoid spinal anesthesia in neonates and children who may have increased intracranial pressures.

Special consideration should be given to the child with a known difficult airway when considering a spinal anesthetic. While spinal anesthesia may be a reasonable choice in these patients, the first consideration should be the ability of the practitioner to manage the airway. Obviously the nature of the surgical procedure will dictate the use of regional techniques. Spinal anesthesia has been used for myelomeningocele repair, exploratory laparotomy and other invasive abdominal procedures in infants. The surgical site, anticipated length of the procedure and the surgical position (supine, lateral, prone) are important factors. A third consideration is the age of the child. Spinal anesthesia can be administered in infants while awake but preschool and school-age children may require intravenous sedation which poses its own set of risks in pediatric patients with a difficult airway.

Clinical Uses

Apnea and former preterm infants

The most common indication for spinal anesthesia in pediatric patients is its use in former preterm infants undergoing bilateral inguinal hernia repairs. Apnea can occur in former preterm patients following a general anesthetic.5;9 A number of small studies have confirmed this finding however, there is considerable disagreement regarding the incidence of apnea and the conceptual age at which a former preterm infant may safely undergo general anesthesia on an outpatient basis. Lack of uniformity in study design, small patient population sizes and variations in methodology probably account for the differences.

Cote et al.9 performed a meta-analysis of eight studies investigating postoperative apnea in former preterm infants following general anesthesia comprising 255 patients. Overall, the risk of apnea was independently related to both gestational age and conceptual age. Additional risk factors for postoperative apnea were a hematocrit

The use of regional anesthesia may decrease but not eliminate the incidence of postoperative apnea. The concomitant use of ketamine may increase the incidence of postoperative apnea above that reported in control patients17;29 Unfortunately, very little information is available regarding the potential benefits of spinal anesthesia over general anesthesia in this particular population. 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 those who received general anesthesia for inguinal herniorraphy.30 They observed no significant difference in the incidence of postoperative apnea between the two groups. An observational study of over 250 former preterm infants found a 4.9% incidence of postoperative apnea after spinal anesthesia for inguinal herniorraphy.11 A prospective study from France reported no incidence of postoperative apnea in a subset of 30 former preterm infants who received spinal anesthesia. Craven et al. reviewed several randomized controlled studies and found only borderline statistical advantage of a spinal anesthetic over a general anesthetic31

Spinal anesthesia for procedures other than herniorrhaphy

Spinal anesthesia has been successfully used for a variety of surgical procedures in children.12;13 Most of the reported series in the literature involve infants. The early report by Abajian et al.11 not only included infants undergoing herniorrhaphy but also those undergoing a variety of general, urologic and orthopedic procedures. Interestingly, the study population included infants with medical conditions the authors felt increased the risk of general anesthesia. These conditions included laryngomalacia, macroglossia, micrognathia, congenital heart disease, Down’s syndrome, adrenogenital syndrome, failure to thrive, arthrogryposis and Gordon’s syndrome.

Blaise et al. reported 30 patients aged 7 weeks to 13 years who underwent spinal anesthesia for a variety of surgical procedures.12 Kokki et al. reported satisfactory anesthesia in 92 of 93 children aged 1-17 yrs undergoing ropivacaine spinal anesthesia for lower abdominal or lower extremity procedures.26;32 Spinal anesthesia has been used in infants for various other procedures including meningomyelocele repair.33, and major abdominal surgery.

Spinal Anesthesia for cardiac surgery

Regional techniques have been used in cardiac surgery to facilitate early extubation.34 The largest series of use of spinal anesthesia for cardiac surgery comes from a prospective randomized analysis from Stanford University.35 The group that received spinal anesthesia for postoperative pain relief had less opioid requirement in the postoperative period in children undergoing elective cardiac surgery with early extubation in the operating room.

 Clinical Pearls

 Special considerations for infants and children undergoing spinal anesthesia.

 Choose of patients who are not likely to have a significant decrease in systemic vascular resistance after spinal     anesthesia.

 Ability to perform atraumatic spinal anesthesia especially since these patients will be heparanized in the postoperative     period

 Use of hydrophilic opioid so that a rostral spread can ensure longer duration of analgesia

 Surgeon’s motivation

In summary, spinal anesthesia in pediatrics is most commonly used in the preterm infant undergoing anesthesia for hernia repair. Spinal anesthesia can also be used effectively in children for postoperative pain relief especially if opioids are used. Finally, in some clinical settings, spinal anesthesia may be may be the only anesthetic option available.

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21.

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22.

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28.

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32.

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33.

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36.

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