NYSORA - The New York School of Regional Anesthesia: Spinal Anesthesia in Children Spinal Anesthesia in Children ================================================================================ Solme Kim on 2009-03-14 15:53:00 TABLE OF CONTENTS (click here to expand) *Introduction *Anatomy *Technique of Spinal Anesthesia in Children *Preparation *Patient position *Technique *Assessing the block *Local Anesthesic Choices and Doses *Relative Contraindications *Clinical Uses *Apnea and Former Preterm Infants *Spinal Anesthesia for Procedures other than Herniorrhaphy *Spinal Anesthesia for Cardiac Surgery 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 Hernia repair Circumcision Exploratory laparotomy Meningomyelocele repair Muscle biopsy Cardiac surgery 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 Figure 4. Equipment for spinal anesthesia in the neonate. Shown are the disinfectant, hypodermic needle for local infiltration and the spinal needle. 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 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