8. pediatric neuraxial anesthesia-mueller.pdf
TRANSCRIPT
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Pediatric Neuraxial Anesthesia from Caudals, to Thoracic Epidurals, to Awake Spinals
Martin Müller, MDAssistant Professor
Division of Pediatric Anesthesia
Iowa Symposium XIII
May 4, 2013
Disclosure
• No financial ties, compensation from or obligation to manufacturers of biomedical products or drugs
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Overview
• Caudal single shot
• Thoracic epidural catheter
• Awake spinal block
Introduction
• Most common block in children
• Easy to learn1
• Minimal equipment
• Favorable risk/benefit ratio
• ↓ Surgical stress response2
1 Schuepfer G; et al.: Reg Anesth Pain Med 2000; 25: 385–8 2 Erol A; et al.: Pediatr Int. 2007;49:928-32
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Indications
• Augmentation for GA and post‐operative analgesia
• Pediatric surgeries involving lower body
• Ureteral reimplantation, orchiopexy1, complex hypospadias repair, inguinal herniorrhaphy, clubfoot repair, etc.
1 Rice LJ; et al: Canadian Journal of Anesthesia 1990; 37:429-31
Contraindications
• Refusal, no parental consent
• Skin infection
• Sepsis
• Immunodeficiency
• Coagulopathy/thrombocytopenia
• Post‐operative testing of motor/sensory function
• Anatomical – sacral dimple indicative of myelodysplasia
• Ultrasound to confirm anatomy1
1 Schwartz D; et al: Pediatric Anesthesia 2011; 21:1073–1088
S1 S2
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Anatomy
Anatomy: Pediatric
• Sacrum narrow, flat – direct route to dural sac
• Conus medullaris @ L3
• Dural sac @ S3
• Incomplete ossification
• Thin ligamentum flavum
• ↑ Compliance & ↑ size of epidural space
• ↑ Intervertebral foramina –LA escape
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Physiology
• Relative CSF volume↑1
• CSF turnover↑
• Hemodynamic stability in children < 6 years with neuraxial block2
– Small venous capacitance of lower extremities
– Lack of resting sympathetic peripheral vascular tone
1 Cutler RWP; et al.: Brain 1968;91:707-20
2 Dohi S; et al.: Anesthesiology 1979; 50: 319–23
Dohi S; et al.: Anesthesiology 1979; 50: 319–23
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Technique
• Monitoring: standard ASA monitors (ECG)
• Patient position: lateral decubitus, hips and knees flexed
• Operator: standing or sitting posteriorly vs. anteriorly bending over
• Good lighting
Technique: Landmarks
• Equilateral triangle posterior superior iliac spines and sacral hiatus
• Hiatus rostral of gluteal crease
• Effect of gravity on skin
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Technique: Needle
• Short bevel 22G straight needle
(↓ intravascular injection)
• 22G Jelco IV catheter
– Soft tip: ↓ perforation
– Kinking
Short Bevel Regular Bevel
Technique: Pop and Drop
• Palpation of hiatus
• Needle insertion 45⁰
• Characteristic “give” through sacrococcygeal ligament
• Drop angle
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Technique: Verification
• Needle hub open to air
• Aspiration (clear fluid, blood)
• Test dose
– Lidocaine with 1:200 000 epinephrine
– Controversial
– Sensitivity questioned in children1
1 Fisher QA; et al.: Can J Anesth. 1997;44: 592-8
Technique: Injection
• Slow, incremental
• 10 cc syringe (comparable resistance)
• Subcutaneous palpation
• ECG monitoring (ST segment, T‐wave)
Normal
LA toxicity
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Caudal Video
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Bupivacaine
• 0.175% ideal for outpatient surgery (max. sensory block w/ minimal motor block)
• Max. dose: 2.5 mg/kg
• CNS toxicity: seizures
• Cardiac toxicity: therapy‐resistant arrhythmias, cardiac arrest
• 20% Intralipid, 1.5 ml/kg bolus, then infusion 0.25 ml/kg/h
Ropivacaine
• Onset 7‐14 min
• Duration 4‐6 h
• Good sensory/weak motor block
• 0.2 % ideal for caudal
• More expensive
• Less CNS and cardiac toxicity1
1 Scott DB; et al.: Anesth Analg 1989;69:563-9
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2,3‐Chloroprocaine
• Denser block
• Ester hydrolysis
• Less risk of toxic accumulation in neonates
• Continuous infusion1
• Cheap
• Neurotoxic with subdural administration
1 Tobias JD; et al.: Can J Anesth 1996; 43: 69-72
Adjuvants
• Clonidine– Optimal dose 1‐2 mcg/kg– Sedation– Bradycardia, hypotension, apnea in neonates
• Ketamine– Preservative‐free ketamine not available in US
• Neostigmine– PONV ↑ 30%
• Opioids– Delayed respiratory depression
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Caudal:Complications
• Intravascular/intraosseous injection
• Epidural hematoma
• Neural injury
• Subarachnoid injection
• Epidural abscess
• Urinary retention (opioids)
Thoracic Epidural Catheter:Indication/Goals
• Abdominal/thoracic surgery
• Post operative analgesia
• Older children
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Thoracic Epidural: Technique
• Under general anesthesia
• Lateral decubitus position
• Midline vs. paramedian approach
• LOR with NS (avoid air embolism)
• Ligamentum flavum not as prominent
• Depth of epidural space: ca. 1 cm/10 kg
Thoracic Epidural Complications
• Drugs– CNS/cardio toxicity– Intravascular/subarachnoid injection
• Catheter placement– Trauma to epidural structures (nerves, spinal cord, vessels)
– Catheter migration‐spinal block1
– Infection
1 Taenzer AH: Anesthesiology 2003; 98:1014-15
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Awake Spinal Anesthesia
Indications
• Preferable to avoid general anesthesia
–Muscular hypotonia (post‐op ventilation)
– Post op apnea
– ?Neurotoxicity
– Difficult AW (Pierre Robin)
• Inguinal hernia repair, muscle biopsy
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Spinal: Technique
• PIV (timing variable)
• ASA monitors
• Sitting position
– Needs a good “babysitter”: restrain all 4 extremities, lumbar lordosis, avoid neck flexion (AW obstruction)
– pacifier
Spinal: Technique
• 22g 1‐½ inch spinal needle
• TB syringe (slip tip)
• Sterile prep iodine/alcohol
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Spinal: Technique• Barbotage
• Supine positioning
• Soft restraints
• Immediate start of surgery
L3-4
Spinal: Drugs
Drug Concentration %
Dose mg/kg
Durationmin
Lidocaine 5 3 56
Bupivacaine 0.5 1 70
Tetracaine 1 0.5 80
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Spinal: Complications1
• Desaturation
• “High” spinal
• Bradycardia (<100 bpm)
• Apnea
• Rarely: infection, bleeding, nerve damage, spinal cord injury
• CSF leak
1 Williams RK; et al.:Anesth Analg. 2006; 102:67-71
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Common Problems
• Incomplete block (failed spinal)
– Rare (5‐20%)
– Repeat SAB, do caudal block, i.v. supplementation, cancel surgery
• Agitation
– From heat, covers, physical restraints
– Solution: sweetened pacifier, padding, ventilation, i.v. sedation (benzodiazepines, propofol)
Common Problems
• Time running out:
– Avoid delays during prep and intraop
– Have good communication with surgeon
– Addition of epinephrine
– Combination with caudal block:
• Total dose 2.5 mg/kg bupivacaine divided into– SAB: 1 mg/kg (0.2 cc/kg of 0.5% bupivacaine)
– Caudal: 1.5 mg/kg (0.6 cc/kg of 0.25% bupivacaine)
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Summary
• Caudal: most common block, easy to learn
• Intralipid needs to be immediately available
• Thoracic epidural: potential for serious complications, LOR with NS, asleep vs. awake
• Awake spinal: wonderful alternative to GA, potential to avoid suspected neurotoxic effects of GA, time limitations
Questions?
[email protected] www.anesth.uiowa.edu