NYSORA - The New York School of Regional Anesthesia: Spinal Anesthesia in Children

Spinal Anesthesia in Children
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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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