Upload
dulcie-stanley
View
224
Download
0
Tags:
Embed Size (px)
Citation preview
Neuraxial Blockade in Pediatrics Made-EasyHany El-Zahaby, MDAin 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?
2012
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
2012
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
2012
Distance from Skin to Subarachnoid Space
Distance from Skin to Epidural Space is 0.1 cm/kg
2012
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
2012
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
2012
CSF Volume
2012
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.
2012
2012
24G IV cannula
2012
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??
2012
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.
2012
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
2012
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
2012
2012
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
2012
Misplacement
subperiosteum
posterior sacral ligaments
false “decoy” hiatus
anterior sacral wall
pelvis
lateral foramen,
2012
Aim is to place catheter tip at mid-point of surgical incision
Failure rate between 2.7-11%
2012
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.
2012
Epidurography
2012
2012
2012
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).
2012
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%.
2012
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.
2012
2012
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.
2012
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.
2012
Toxicity of Local Anesthetics
circumoral parethesia lightheadedness and
dizziness visual and auditory
disturbances difficulty in focusing tinnitus
shivering slurred speech muscle twitching generalized seizures
2012
peripheral VD myocardial
depression bradycardia V-tach Ischemic changes
in S-T
2012
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
2012
2012
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
2012
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.
2012
2012
2012
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
2012
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
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012
2012