Central Neuraxial Blocks in Pediatrics
Dr. Helena Oechsner
Chief Resident
Dr. Melissa Ehlers
Director of Pediatric Anesthesia
Department of Anesthesiology
Albany Medical Center
I. Introduction
In the last two decades, regional anesthesia and analgesia has become a fully integrated
part of perioperative and postoperative care in pediatrics. Key to this integration has been an
increased understanding of children’s perception and responses to pain,1 as well as improved
comprehension of the pharmacology of local anesthetics and the specific differences of local
anesthetics in pediatrics.
Regional anesthesia has been used in children since the beginning of the 20th Century.
The first reported case occurred in 1901 and involved 12 spinal anesthetics in high-risk infants
unsuitable for general anesthesia.2 The use of neuraxial blocks with insufficient understanding of
physiology and pharmacology led to a high incidence of complications. As general anesthesia
became safer, regional anesthesia in pediatrics was largely abandoned from the 1950's through
the 1980's. However, improved knowledge and success of regional techniques in adults
eventually led to increased interest in reintegrating regional blocks into pediatric anesthesia.
Today, regional blocks in pediatric anesthesia are primarily employed in conjunction with
general anesthesia to reduce opioid requirements, opioid related side effects and inhalation agent
requirements, as well as to accelerate recovery3 and improve postoperative pain management.
II. Neurodevelopmental Differences
Small children differ from adults not only in their size, but also in important anatomical,
physiological and pharmacological respects. Myelinization does not become complete until the
12th year of life,while ossification and fusion of vertebral arches posteriorly finishes around the
3rd-5th year of life. Infants also have a larger volume of CSF (>4ml/kg versus <2ml/kg in adults).
When performing neuraxial blocks, positional changes of the spinal cord during
development are crucial to keep in mind. During the embryological period, the spinal cord fills
the entire spinal canal. At the 6th month of prenatal life, however, terminal level of conus
medullaris (TLCM) moves up to the level of S1 vertebra. A full-term neonate has the TLCM at
L1-L3 and the dural sac at S3-S5 versus an adult’s TLCM at T12-L2 and dural sac at S2.4
III. Safety of Placement of Neuraxial Blocks Under General Anesthesia
It is important to weight the risks and benefits of placing a neuraxial block in a child who
is awake versus a child under general anesthesia. Often the child is preverbal or uncooperative
and will not be able to hold still for the procedure. Accordingly, it appears safer and more
practical to perform the block under anesthesia or heavy sedation. Multiple studies have
confirmed the safety of regional blocks under anesthesia or heavy sedation. The largest
prospective study, conducted by ADARPEF (The French-Language Society of Pediatric
Anesthesiologists) and reported in 1996, included 24,409 children. This study found a low
complication rate with no serious or long-term sequelae.5
However, a similarly sized earlier retrospective study, also done also by ADARPEF in
1991, reported five serious incidents. These incidents had important common points: all five
were healthy young infants (6 -11 weeks of age) without coexisting medical conditions or
associated malformations, 4 out of 5 were African America, they had a mean weight 5200g, and
they all presented for common surgical procedures. Experienced pediatric anesthesiologists
performed the neuraxial blocks after induction and intubation and full ASA standard monitoring
was in place. The accidents affected the spinal cord at all levels in four of the patients, and one
child had cerebral cortical and subcortical lesions. These complications caused death in three of
the children; of the two who survived one was tetraplegic, the other paraplegic. On
neuroradiological examination signs of ischaemia were constantly observed. Because no signs of
compression were noted, the lesions were almost certainly vascular in origin. The lumbar
epidural space was localized using the loss of resistance (LOR) technique with air in four of the
five cases; a possible venous air embolism could not be excluded. An air bubble in the epidural
vein could cause local thrombosis and explain the spinal pathology seen on MRI/CT. The other
possibility is local vasoconstriction in a case of intravascular injection of local anesthetic
containing epinephrine 1: 200, 000. In addition, local neurotoxicity should be considered in case
of unmyelinated fibers exposed to local anesthetics. The fact that four of the five infants were
African-American warn us to take special precautions secondary to possible racial differences in
spinal cord vascularization and lower position of dural sac in that population.
6
Other safety precautions are suggested based upon this study. It appears safer to use the
LOR technique employing normal saline instead of air in the case of neonates and infants.
Consider avoiding epinephrine in the usual concentration (1:200, 000), instead use a diluted
amount (1:400, 000). This concentration should be sufficient for a“test dose”. Also reconsider
the indications for lumbar epidural in infants with incomplete myelination (about 18 month of
age), especially in African-American babies.
IV. General Principles
There are several areas to consider when placing a neuraxial block in children.
1. Patient monitoring
Monitors should be applied and functioning before performing the block with special
attention to the EKG. The P wave, QRS complex and an upright T wave should be seen.
Baseline heart rate and blood pressure should be noted.
2. Sympathetic tone
Clinically significant hypotention is very rare in children less than 8 years of age. A preblock volume load, which is common practice in adults, is not necessary in pediatrics.7
3. Skin preparation
Colonization of epidural and caudal catheters is common in the pediatric population
occurring in up to 35% of caudal catheters, to lesser amount in lumbar epidural catheters 4-6%.8
9 10
Most common pathogens are gram-positive (Staphylococcus. epidermidis) but gramnegative (Klebsiella pneumonia) may also occur, mostly in caudal catheters in very young
children. Despite the significant percent of colonization, the risk of clinical epidural infection is
very low. Because epidural abscess, meningitis, paralysis or death are a potential complications
however, effective cutaneous antisepsis and aseptic surgical technique is mandatory. 0.5%
Chlorhexidine appears more effective than 10% Povidone Iodine11 in reducing catheter
colonization. The superior performance of chlorhexidine is explained by its more potent
bactericidal activity, its high permeability into the hair follicles and more prolonged activity
against coagulase-negative staphylococci.12
4. Test dose
Test dose together with careful aspiration is strongly recommended to avoid intravascular
or inadvertent subarachnoid injection. It is not, however, 100% reliable, so slow incremental
injections with careful monitoring of vital signs even after negative test dose are recommended.
The recommended test dose is 0.1mL/kg of local anesthetic with 5mcg/mL of epinephrine to
maximum volume of 3mL (or 2.5 mcg/mL in the child less than 18 month old – see section III.)
A positive “test dose” is defined as an increased heart rate 10 beats per minute above
baseline within 1 minute of injection or increase of systolic blood pressure of 15 mmHg within 2
minutes of injection and/or 25% change (increase or decrease) in T-wave amplitude.13 14 15
Changes in T-wave amplitude provide excellent evidence of intravascular injection in children
under general anesthesia using sevoflurane with 100% sensitivity, specificity, and positive and
negative predictive value compared to the use of halothane where the sensitivity was only 90%.
Their results suggest that sevoflurane may be safer than halothane in combined general
anesthetic and regional techniques in children because the use of sevoflurane preserves the
potential for vasoconstriction and a positive inotropic response from epinephrine better than
halothane
5. Pharmacology of local anesthetic
The pharmacology of local anesthetics in infants and children has been increasingly
studied in recent years. Dose response assessment is somewhat difficult in pediatrics since most
blocks are done under general anesthesia and sensory block postoperatively is difficult to
estimate in infants or preverbal children. Because of this, dosing is largely based on safe doses in
adults. In neonates, decreased concentration of albumin, alpha1-acid glycoprotein and decreased
protein binding results in a greater unbound fraction of local anesthetic and increased potential
for toxicity. This is offset however by a larger volume of distribution secondary to the neonates
greater total body water content. A larger amount of CSF and less fat content in the epidural
space also allows local anesthetics to spread more easily. In addition infants and young children
have increased permeability of endoneurium and uncompleted myelination so both latency and
duration of nerve blockade is decreased.
6. Indication for regional block
Most regional blocks are used in combination with light general anesthesia or sedation; there are
relatively few indications for regional block as a sole anesthetic in the pediatric patient. Some
potential exceptions would be a hypotonic infant, child with history of malignant hyperthermia,
premature infants with histories of apnea or severe BPD that required prolong ventilation,
patients with cystic fibrosis or even the older child or adolescent with fear of unconsciousness or
loss of self-control.
7. Contraindications
One clear absolute contraindication is lack of parental consent or infection at site of
injection. Relative contraindications would include:
 Coagulopathy
 Poorly controlled seizure
 Difficult airway
 Anatomic abnormalities
 Neurological disease (MS)
 VP shunt (Safety of VP shunt and neuraxial block was not studied)
 Sepsis
V. “Single-Shot” Caudal Block
Single-shot caudal is the most commonly used block for children in combination with
general anesthesia to provide analgesia for surgical procedure in T10-S5 dermatomes. It is
technically simple, fast and a reliable procedure with a failure rate less than 4% in children less
than seven years of age. It is safe with a complications rate 1: 1000; most of which were failed
blocks due to misplacement of a needle without serious sequelae.
Caudal block is best performed in the lateral decubitus position after induction, peripheral
IV placement, and intubation with ASA standard monitoring in place.
After sterile preparation the sacral cornua are palpated and the sacrococcygeal membrane is
perforated with a small needle, (we use a 20G or 22G intravenous catheter at our institution) and
a specific “give” or “pop” is detected. After negative aspiration and test dose, the local anesthetic
is slowly given in increments. For surgeries lasting more than three hours, we commonly repeat
the block with 0.75 mL/kg of 0.125% bupivacaine with epinephrine 1:200,000.
Alternatively, the block may be placed at the conclusion of surgery. One potential
disadvantage is the increased risk of respiratory depression postoperatively if the patient received
any opiods intra and postoperatively prior to the onset of the block.
1. Dosing
Height of the block is affected by volume, while intensity is determined by concentration.
There are a number of formulas calculating the amount of local anesthetic. The most commonly
used is 1ml/kg of 0.25% bupivacaine with epinephrine 5mcg/mL, up to a maximum of 20 mL,
which produces about 4-6 hours of analgesia. Some studies have shown that using lower
concentrations of 0.125%- 0.2% is possible without significant differences in the quality and the
length of analgesia.16 Higher concentrations have a faster onset with better pain scores17 on
arrival to PACU if block is placed postoperatively.
In the search for prolonged analgesia there is a number of studies evaluating the use of
different additives to local anesthetics. The one most commonly used is epinephrine in 1:200,000
concentrations, which speeds up the onset and prolongs analgesia.
Adding opiods, fentanyl 1-2 mcg/ kg 18or morphine 50 mcg/kg increases respiratory
depression, requires obligatory respiratory monitoring 24 hours postoperatively and possibly
causes urinary retention. Clonidine 1-2mck/kg19 increases rate of PONV and sedation, ketamine
0.5mg/kg causes behavioral changes, neostigmine 2mck/kg20 and tramadol increases PONV, and
midazolam increases sedation. All additives (if used) must be preservative free.
2.Complication
Complications are not very common and usually minor or easily treatable in the OR setting.
Misplacement of needle usually results in block failure. In young children ossification is not
fully complete so the sacral bone may be easily penetrable by a sharp needle. Thus we can have
subcutaneous, subperiosteal or intraosseous placement of the needle. Subcutaneous wheel on
injection or difficulty of injection should make us to suspect incorrect positioning of the needle.
Intrathecal puncture may result in high spinal anesthesia. Intravascular or intraosseous injection
may lead to systemic toxicity.
3. Confirmation of placement
Besides earlier mentioned technique like detecting “pop” or negative aspiration and easy
injection. Tsui 21 had been evaluating use of nerve stimulator and assessing. The needle
placement was classified as correct or incorrect depending upon the presence or absence of anal
sphincter contraction (S2-S4) to electrical stimulation (1-10 mA) with 100% success rate in their
study.
VI. Continuous Caudal Catheter
There are several types and sizes of caudal catheters available on the market. At our institution
we are using a Kimberly-Clark styletted 24G caudal catheter, which is placed through a standard
20G intravenous catheter. Proper depth of insertion can be crudely predetermined by measuring
along the spinous processes of the child from desired dermatome down to the insertion site.
Successful caudal insertion of catheters as high as the thoracic dermatomes is frequently
reported, especially in neonates. This is most likely due to very loose epidural fat at this age (and
possibly absence of septae which may form in the epidural space as we age) that allows for
relatively free cephaled passage of the catheter. Some authors suggest radiological22confirmation
of proper catheter placement before use, while others rely on easy removal of the stylet, negative
aspiration and test dose, and easy injection as sufficient. Studies suggesting use of a nerve
stimulator23or EKG24as confirmation of catheter placement have also been published recently.
Special caution must be taken to prevent fecal contamination of the insertion site. It is
recommended to discontinue the catheter after 72 hours (48 hours in neonates) or if the dressing
becomes soiled.
VIII. Epidural Block
In children, line drawn between the two iliac crests passes over the fifth lumbar vertebra,
although in neonate it may pass lower over the L5-S1 interspace25 versus L3-L4 in adult patient.
Thus, developmental changes in the position of the spinal cord and dural sac are important
consideration. The distance between the skin and the epidural spaces increases with age.26In a
10kg child for example, the distance skin-lumbar epidural space would be only 1.5-2 cm.
During placement, the anesthetized or sedated patient is placed usually in the lateral
decubitus position; the spine is arched to open the interspinous space and enlarge the
interlaminar space. Midline approach and loss of resistance technique (LOR) is used.
Whether air or saline should be used has been debated.27 Air has been available, reliable
and simple to use. But severe complications have been reported, including paraplegia28, air
embolism in children29, possible death7. This led to recommendation by some to replace air-LOR
technique with the saline-LOR technique. Saline, however, is not as reliable, may cause dilution
of local anesthetic and difficulty to distinguish CSF from saline. In general the risk-benefit ratio
seems to favor the use of saline, especially in small children.
1.Dosing (for all epidural catheters)
The volume of local anesthetic necessary for analgesia/anesthesia depends on location of
surgery and epidural catheter. In young children the estimated volume would be: 0.04
mL/kg/segment30. In children older than 10 years of age simple formula can be used: V (in mL)
= 1/10 x (age in years)31. A common dose (and what we use at our institution) for continues
infusions are 0.1-0.3 mL/kg/hr of 0.07% bupivacaine and 0.2-0.4 mL/kg/hr of 0.1% bupivacaine
in older children. Infants younger than 1 month are prone to accumulation of local anesthetic
metabolites (witch may also be active) so infusion should be discontinued after 48 hours to avoid
toxicity. Fentanyl 2mcg/mL of hydromorphone 3 mcg/mL are frequently added to the local
anesthetic to provide additional analgesia.
2.Complications
Some possible complications of epidural catheter placement include intrathecal and
intravascular injection, epidural hematoma formation (appears to be even rarer in children than in
adults), spinal headache, possible cord/nerve root trauma, infection, bleeding, or block failure,
usually from misplacement of the needle or the catheter. Unilateral block can result from catheter
migration into the spinal foramina; migration into the epidural vein can cause loss of analgesia
and increased sedation if opioids are used, and potentially systemic toxicity from local
anesthetics. All opioids can cause nausea, pruritus and urinary retention. Possibility of air
embolism, spinal cord injuries are extremely rare and were discussed previously.
IX. Spinal Anesthesia
Spinal anesthesia is mainly used for a very select population undergoing short procedures
on extraperitoneal sites below T10 dermatomes. These patients are mostly neonates who were
premature and have a history of prolonged ventilation with difficulty weaning from the
ventilator. Main reason is to reduce the risk of postoperative apnea, bradycardia and desaturation
32 33
. Infants born at less than 37 weeks gestational age and less than 60 weeks posconceptual age
at the time of surgery, term infants less than 44 weeks of postconceptual age, infants on
continuing apnea monitor at home, infants with anemia34 and past medical history of NEC or
BPD are at risk for postoperative apnea. Concomitant use of sedation may even increased risk of
postoperative apnea.35
1.Positioning
Spinal anesthesia can be performed in lateral position or more commonly in the sitting
positioning the former preterm infants. The assistant holds the infant so that both arms and legs
are bent and elbows and knees are brought together, and the back is arched toward the anesthesia
practitioner. Care must be taken to support the head to avoid airway obstruction.
2.Technique and local anesthetic
We using midline approach at L4-L5 interspace, some practitioners use local anesthetic
for the skin. It is recommended to gently aspirate and reinject after subarachnoideal injection of
local anesthetic to assure proper position and complete dose administration.
The patient should be immediately returned to supine position without elevating legs.
Elevating legs shortly after injection may cause a high spinal.36
Generally, in the younger infant a larger dose of local anesthetic is required and shorter
duration of block is expected. Dosing recommendations for spinal anesthesia vary. Longer acting
local anesthetics are preferred, and high concentrations of lidocaine are not recommended
because of a possible link to transient neurologic syndrome (TNS) and also have too short
duration in preterm infants. Hyperbaric tetracaine 0.5% with epinephrine 0.3mg-1mg/kg or
hyperbaric tetracaine 1% with epinephrine 0.5 - 1mg/kg, hyperbaric bupivacaine 0.75% 0.3-0.6
mg/kg is the most common choices.
3.Comlications
In the ADARPEF’s prospective study was only one complication reported (intravascular
injection) out of 506 spinal anesthetics.6 Other studies report post-dural puncture
headaches,37High spinal, nausea, shivering, hypotention, bradycardia, post-operative apnea,
infection, and aseptic meningitis38 as possible complication. Overall, cardiovascular stability is
good with this block. Unlike adults, neonates usually tolerate high thoracic spinal anesthesia with
minimal change in heart rate and arterial blood pressure.39
X. Conclusion
Although rarely used as the sole anesthetic, neuraxial blocks are commonly used as
adjuncts for pain control in the pediatric population. Complication rates appear to be quite low
with proper selection of the patients and regional technique. Pain control with these blocks is
typically excellent and they are relatively easy to perform.40
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27
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