Neuraxial Blockade in Pediatrics Made-EasyHany El-Zahaby, MDAin Shams University

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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

Implications Anatomical features

Wet tap with caudal epidural Lower termination of dural sac

L4-5, L5-S1 for spinal in neonates

Lower termination of spinal cord

Faster onset Delayed myelination

Leakage of LA Nerve sheath loosely attached

Small sacral hiatus after 8 Yrs No growth of sacral hiatus

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Implications Anatomical features

Midline approach is preferred Poorly calcified vertebral laminae

Spina bifida occulta contraindicating caudal block

Deep sacral dimple

Wet tap is more common The ligamentum flavum ismuch thinner and less dense

Inter-vertebral leveling Tuffier’s line at L5-S1

Epidural catheter threaded caudally can reach thoracic level (<6Yrs)

Compact &globular fatLess epidural vascular component

Anatomical Features

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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

Implications Physiological Characters

GA or heavy sedation is needed??

Delayed acquisition & conceptualization

↑ half life of LAs, ↓ area of EMLA cream

Enzymatic immaturity

↓ Cmax, accumulation with infusion t1/2 = (0.693 • VDss)/Cl

↑ECF

↑ systemic toxicity, ↓ dose of epidural LA by 30% when < 6 Months

↓ α1-Acid glycoprotein in neonates

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Physiological Features

Implications Physiological Characters

Less vaso-active drugs with spinal

Sympathetic immaturity

↑ LA doses for spinal ↑↑↑ CSF volume/kg

↑ LA doses for spinal Leakage around spinal nerves

Shorter duration of spinal ↑↑ CSF turn-over rates

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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. > 5-15kg0.06 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 BackacheNeurologic sequelaeLumbar 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-NEC-multiple 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

Caudal Epidural

Catheter through18G IV cannula

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Misplacement

subperiosteum

posterior sacral ligaments

false “decoy” hiatus

anterior sacral wall

pelvis

lateral foramen,

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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 tipEpidurography (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.

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

shivering slurred speech muscle twitching generalized seizures

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peripheral VD myocardial

depression bradycardia V-tach Ischemic changes

in S-T

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Unintentional intravascular injection of bupivacaine with epinephrine in children

Toxicity of local anesthetics in neonatesBecause 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 LAhas 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

Thank You

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