Neuraxial Blockade in Pediatrics Made-Easy

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Neuraxial Blockade in Pediatrics Made-Easy
Hany El-Zahaby, MD
Ain Shams University
2012
Neuraxial Blockade in Pediatrics

Why ?

What are the anatomical, physiological, and pharmacological
features of clinical importance?

What is the common international practice?

What is available for me to use to improve my practice?
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Anatomical Features
Anatomical features
Implications
Lower termination of dural sac
Wet tap with caudal epidural
Lower termination of spinal cord
L4-5, L5-S1 for spinal in neonates
Delayed myelination
Faster onset
Nerve sheath loosely attached
Leakage of LA
No growth of sacral hiatus
Small sacral hiatus after 8 Yrs
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Anatomical Features
Anatomical features
Implications
Poorly calcified vertebral laminae
Midline approach is preferred
Deep sacral dimple
Spina bifida occulta contraindicating
caudal block
The ligamentum flavum is
much thinner and less dense
Wet tap is more common
Tuffier’s line at L5-S1
Inter-vertebral leveling
Compact &globular fat
Less epidural vascular component
Epidural catheter threaded caudally can
reach thoracic level (<6Yrs)
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Distance from Skin to Subarachnoid Space
Distance from Skin to Epidural Space is 0.1 cm/kg
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Physiological Features
Physiological Characters
Implications
Delayed acquisition & conceptualization
GA or heavy sedation is needed??
Enzymatic immaturity
↑ half life of LAs, ↓ area of EMLA cream
↑ECF
↓ Cmax, accumulation with infusion
t1/2 = (0.693 • VDss)/Cl
↓ α1-Acid glycoprotein in neonates
↑ systemic toxicity, ↓ dose of epidural LA
by 30% when < 6 Months
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Physiological Features
Physiological Characters
Implications
Sympathetic immaturity
Less vaso-active drugs with spinal
↑↑↑ CSF volume/kg
↑ LA doses for spinal
Leakage around spinal nerves
↑ LA doses for spinal
↑↑ CSF turn-over rates
Shorter duration of spinal
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CSF Volume
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Spinal Anesthesia
 With
the recognition of the risk of postoperative apnea, the
use of spinal anesthesia has increased.
 Concomitant
use of ketamine with spinal anesthesia resulted
in more apnea than with general anesthesia.
 Good
candidates are former premature infants (<60 W
post-conceptual age) undergoing lower abdominal or lower
extremity surgeries of short duration.
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24G IV cannula
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Spinal Anesthesia
 Bupivacaine
0.5% (Heavy)
 Doses:
0.1ml/kg for B.W. < 5kg
0.08 ml/kg for B.W. > 5-15kg
0.06 ml/kg for B.W. >15kg
 Traces of Epinephrine 1:10,000 can be left in the tuberculin
syringe as with heparinized syringes used for ABG analyses,
to prolong the duration from 35 min to around 90 min for
mid to upper thoracic regions.
 Other additives??
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When solid subarachnoid block is
achieved, most neonates fall
asleep due to "de-afferenation"
of the sensory input to RAS as
evidenced by BIS & SEF. It can
be helped by dipping pacifier
in Dextrose solution.
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Spinal Anesthesia
 Subarachnoid
block is not common outside the neonatal
period as in childhood light general anesthesia is usually
combined with caudal epidural block.
 Complications:
Total spinal anesthesia (apnea without cardiovascular compromise)
PDPH (very uncommon because of the low CSF pressure and the high
rate of its formation
Backache
Neurologic sequelae
Lumbar epidermoid tumors when non-styletted needles are used
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Indications:
 “65 W
postconceptual age ex-premi male baby who has
been on chronic ventilatory support-sepsis-PDA-IVH-NECmultiple medications-BPD - extubated with great difficulty
in NICU & planed to have inguinal hernial repair”.
 Past or current apnea of prematurity requiring aminophyline
therapy
 Chronic lung disease requiring oxygen therapy
 High-risk infants with CHD & airway anomalies
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Contraindications of Spinal Anesthesia
 Anatomic
abnormalities of spine
 Degenerative neuromuscular disease
 Parental refusal
 Coagulopathy
 Local infection
 High intracranial pressure
 Presence of VP shunt
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Caudal Epidural
Catheter through18G IV cannula
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anterior sacral wall
pelvis
lateral foramen,
Misplacement
subperiosteum
false “decoy” hiatus
posterior sacral ligaments
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 Aim
is to place catheter
tip at mid-point of
surgical incision
 Failure rate between
2.7-11%
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Accurate location of the epidural catheter tip
 Epidurography
(risk of radiation and anaphylaxis)
 U/S (dural displacement with test bolus injection
of 0.3ml/kg saline).
 Electric nerve stimulation through an indwelling
styletted epidural catheter and observation of
myotomal contractions before injecting LA or
muscle relaxant.
 Epidural electrocardiography for thoracic epidural
catheter by matching the evolving ECG recorded
from the tip of epidural catheter to the surface
ECG placed at the target vertebral level.
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Epidurography
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Dosages for Single Injection Caudal epidural
Block
 The
volume of LA is calculated by Takasaki:
Volume (ml) = 0.05ml/kg/dermatome to be blocked.
Example: 10kg child in whom we wish to produce T10
dermatome level, (0.05ml x 10kg x 12 dermatomes =
6ml
 A more simple way is to give 1ml/kg of 0.125-0.2%
bupivacaine (up to 20ml) with 1:200,000 epinephrine to
produce good sensory block with minimal motor block up to
T4-6 level.
 The maximum bupivacaine dose is 1ml/kg of 0.25% solution
(2.5mg/kg).
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Continuous Epidural Block
 It
obviates the need for repetetive test dose injection and
ensures a constant block assuming appropriate doses are
used.
 A maximum of 0.4mg/kg/hr of bupivacaine after the initial
block is established, with 30% reduction of dose for infants
younger than 6 months.
 Common Bupivacaine concetration used is 0.125%.
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Inter-Vertebral Epidural Technique
 Advantages
include catheter being away of diaper area and
less doses of LAs.
 Only experienced pediatric anesthesiologist should perform
this block.
 Midline approach.
 Only saline is used for loss of resistance which is less
apparent than in adults.
 The distance from skin to the epidural space is
approximately 0.1mm/kg.
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Epidural Opioids
 It
can be used to augment intraoperative analgesia as well
as to provide postoperative analgesia. If combined with
systemic opioids, tracheal extubation is usually delayed.
 Morphine (hydrophilic) in a dose of 30 µ /kg helps to cover
wider range of dermatomes when combined with
bupivacaine if the surgical site is remote from catheter tip.
However, unfortunately, it increases the possibility of
respiratory depression as a result of rostral spread in CSF to
brainstem centers.
 We limit its use for patient admitted to ICU for
postoperative care.
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Epidural Opioids
 Fentanyl
1 µ/ml combined with bupivacaine 0.1% at rates of
0.1-0.3ml/kg/hr via caudal catheters advanced to lumbar
position without locating its tip provides adequate analgesia
for most lower abdominal and lower extremity surgeries.
 Complications include respiratory depression, pruritis, nausea
and vomiting as well as urine retention are treated with
naloxone 1 µ/kg IV followed by IVI of 0.25 µ /kg/hr with
ventilatory support when needed.
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Complications of Neuraxial Blockade
 Complications
include intravascular or intraosseous injection,
epidural hematoma, neural injury and infection. Injury of
bowl or pelvic organ may follow perforation of the sacrum.
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Toxicity of Local Anesthetics
 circumoral
parethesia
 lightheadedness and dizziness
 visual and auditory disturbances
 difficulty in focusing
 tinnitus
 peripheral
VD
 myocardial depression
 bradycardia
 V-tach
 Ischemic changes in S-T
 shivering
 slurred
speech
 muscle twitching
 generalized seizures
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Unintentional intravascular injection of bupivacaine with
epinephrine in children
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Toxicity of local anesthetics in neonates
Because
of the lower threshold for cardiac
toxicity with bupivacaine, cardiac and CNS
toxicity may occur virtually simultaneously in
infants and children
the risk of cardiac toxicity may be increased
by the concomitant use of volatile anesthetics
and the CNS effects of the general anesthetic
may obscure the signs of CNS toxicity until
devastating cardiovascular effects are
apparent
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 Toxicity
depends on:
 Total dose (lean body weight)
 Site of administration (ICE Block)
 Rate of uptake (+ epinephrine)
 Toxic threshold (midazolam)
 Technique of administration (passive blood flow, ↓sensitivity
to test dose with halothane)
 Rate of degradation, metabolism, and excretion
 Acid-base status
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 Treatment:
 Airway
& ventilation
 Midzolam or thiopentone/propofol
 20% lipid emulsion 1ml/kg over 1 min, followed by 0.25
ml/kg/min
 for CV collapse: increments of IV boluses of 10 ml/kg
crystalloid, phenylehrine/epinephrine.
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A 6-month-old, 6kg child, ASA 1, presented for
ureteric re-implantation
 Continuous
epidural infusion through caudally inserted
catheter without localization.
 Drug: Bupivacaine 0.1% + Fentanyl 1µ/ml
 Bolus: 10 dermatomes X 0.05ml X 6kg = 3 ml
 Infusion: 0.2ml/kg/hr = 0.2 X 6 = 1.2 ml/hr
 Apnea monitoring, continuous pulse oximetry, and frequent
observation
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Take-home messages:
 Spinal
anesthesia is valuable for neonates,
requires higher doses of LA
has fast onset and short duration (prolonged by epinephrine)
does not require GA or sedation
 Epidural
analgesia is frequently combined with GA for older
infants and children.
Doses of LAs are reduced by 30% under 6 Month-old.
Bolus dose is 0.05ml/dermatome.
Continuous infusion is 0.02ml/kg/hr 0.1% bupivacaine with
fentanyl 1µ/ml.
Apnea monitor, oximetry and close observation is
recommended
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Thank You
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