Neuraxial Blockade in Pediatrics Made-Easy

1. Neuraxial Blockade in Pediatrics Made-Easy Hany El-Zahaby, MD Ain Shams University 2012

2. 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

3. Anatomical Features 2012

4. Anatomical Features 2012

5. Distance from Skin to Subarachnoid Space Distance from Skin to Epidural Space is 0.1 cm/kg 2012

6. Physiological Features 2012

7. Physiological Features 2012

8. CSF Volume 2012

9. 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

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11. 24G IV cannula 2012

12. 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?? 2012

13. 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

14. 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 2012

15. 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

16. Contraindications of Spinal Anesthesia • Anatomic abnormalities of spine • Degenerative neuromuscular disease • Parental refusal • Coagulopathy • Local infection • High intracranial pressure • Presence of VP shunt 2012

17. Caudal Epidural Catheter through18G IV cannula 2012

18. Misplacement anterior sacral wall pelvis lateral foramen, subperiosteum false “decoy” hiatus posterior sacral ligaments 2012

19. Aim is to place catheter tip at mid-point of surgical incision • Failure rate between 2.7-11% 2012

20. 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. 2012

21. Epidurography 2012

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24. 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

25. 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 Bupivacaineconcetration used is 0.125%. 2012

26. 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

27. 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. 2012

28. 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

29. 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

30. Toxicity of Local Anesthetics • circumoralparethesia • lightheadedness and dizziness • visual and auditory disturbances • difficulty in focusing • tinnitus • shivering • slurred speech • muscle twitching • generalized seizures • peripheral VD • myocardial depression • bradycardia • V-tach • Ischemic changes in S-T 2012

31. Unintentional intravascular injection of bupivacaine with epinephrine in children 2012

32. 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 2012

33. 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

34. 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

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37. 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

38. 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 2012

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