Regional anaesthesia in pediatrics

REGIONAL ANAESTHESIA IN CHILDREN

Dr Tarun Yadav

Jawarlal Nehru Medical College , Sawangi(M) , Wardha

Regional anaesthesia in children Differences in anatomy and

physiology

Selection of techniques, agents and equipments

Central neuraxial blockade in children including caudal block

Introduction

Regional anaesthesia in children first studied by August Bier in 1899

In 1900, Bainbridge reported a case of strangulated hernia repair under spinal anaesthesia in an infant of three months

Tyrell Gray, a British surgeon published a series of 200 cases of lower abdominal surgeries in infants and children under spinal anaesthesia in 1909-1910

Introduction(contd.)

Advantages over GA:

Safe, reliable technique in infants at risk of apnoea, bradycardia and desaturation after GA

Good alternative for day care surgeries

Minimal risk of postoperative respiratory depression

Limited stress response to surgery

Cost effective

Difference in Perception of pain from adults

Immature connections b/w dorsal horn neurons and C fibres till 2wks of life

Heightened response to nociceptive stimulation till 2 wks of life in response to large amounts of substance P

Immaturity of inhibitory control pathways till 2wks of life

Spinal cord anatomy

Relevant Differences between Children and AdultsAnatomic factors Anaesthetic implications

Lower termination of spinal cord (L3-4)

•Increased risk of direct trauma to the spinal cord•Avoid epidural approaches above L3

Lower projection of dural sac (S3-4)

•Increased risk of inadvertent penetration of the dura mater

Delayed myelinization of nerve fibers

•Easier intraneural penetration of local anesthetics•Onset time shortened•Diluted local anesthetic as effective as more concentrated anesthetic

Anatomic factors Anaesthetic complications

Cartilaginous structure of bones and vertebrae

•Danger of direct trauma and bacterial contamination of ossification nuclei•Use short and short beveled needles

Lack of fusion of sacral vertebrae

•Persistence of sacral intervertebral spaces

Delayed development of curvatures of the spine

•Same orientation of epidural needles at all level before 6 months of age

Changing axis of coccyx and absence of growth of sacral hiatus

•Identification of sacral hiatus difficult above 6-8 years •Increased failure rate of caudal anesthesia

Delayed ossification and growth of iliac crests

•Tuffier’s line passes over L5-S1 interspace

Anatomic factors Anaesthetic implications

Increased fluidity of epidural fat

•Increased diffusion of local anesthetic up to 6-7 years of age with excellent caudal blockade

Loose attachment of sheaths and aponeuroses to underlying structures

•Larger volume of LA for epidural blocks due to leakage along spinal nerve roots•Increased spread along nerve paths with danger of penetrating remote anatomic spaces and blocking distant nerves

Sympathetic immaturity, diminished autonomic adaptability of the heart, smaller vascular bed in lower extremities

•Hemodynamic stability during neuraxial blocks•Fluid preloading and use of vasoactive agents unnecessary

Pharmacologic factors Anaesthetic implications

Low plasma protein content (HSA and AAG)

•Increased unbound free fraction of all local anesthetic: greater danger of systemic toxicity

Increased cardiac output and heart rate

•Increased regional blood flow resulting in increased systemic absorption of LA: shorter duration of action

Enzymatic immaturity •Slower metabolism of LA with risk of accumulation

Increased extracellular fluids

•Increased distribution volume and mean body residency time of LA with increased risk of accumulation after continous infusion

Pharmacologic factors

Anaesthetic implications

Red cell storage •In neonates: high hematocrit values and enlargement of erythrocytes result in consistent “entrapment” of LA•In infants: physiologic anemia reduces red cell storage; protective effect against systemic toxicity of LA

Pulmonary extraction

•Children with right-to-left shunts undergo considerable increase in arterial plasma concentration of LA due to pulmonary bypass

Absorption from epidural space

•The time (Tmax) to reach peak plasma concentration (Cmax) remains basically unchanged•Ropivacaine and Levobupivacaine Tmax is prolonged up to 2 hours in infants and Cmax is increased •Reduced continous infusion rates/repeat injections dosage

Pharmacologic factors Anaesthetic implications

Metabolism •Low plasma cholinesterase activity•Decreased cytochrome P450 activity•Phase 2 reactions immature upto 3yrs of age

Elimination half life •>1yr: same as adults•< 1yr: increased thus favoring accumulation with repeated injections

Systemic toxicity •Thresholds of toxicity of the unbound form of LA:0.3 μg/ml for bupivacaine0.6 μg/ml for ropivacaine

Hepatic extraction and clearance of aminoamides

•High hepatic extraction ratio•GFR 30% of adult values

Pharmacologic factors

Anaesthetic implications

Opioids : morphine •Elimination half-life of neuraxial opioids increase in neonates and infants•CSF concentrations very high after epidural injection; takes 12 to 24 hours before their decrease below minimal effective concentrations (near 10 ng/mL)

Fentanyl, sufentanil •Acute respiratory depression (sudden apnoea)

Additives: Clonidine •Clearance in neonates is approximately one third that in adults owing to immature elimination pathways;

•Several instances of respiratory depression in neonates and small infants•Should be avoided during the first 6 month of life.

Additive Recommended doses

Maximum doses

Morphine•Epidural•Intrathecal

30 µg/kg10 µg/kg

50 µg/kg20 µg/kg

Fentanyl (epidural)

1-1.5 µg/kg 2.5 µg/kg

Sufentanil (epidural)

0.25-0.5 µg/kg 0.75 µg/kg

Clonidine (epidural)

1-1.5 µg/kg 2 µg/kg

Ketamine (epidural)

0.5 mg/kg 1 mg/kg

Commonly used additives in pediatric RA

Psychological factors Anaesthetic implications

Delayed acquisition of body scheme and conceptualization, anxiety

•Inability of patients to locate precise body areas

•Concept of paresthesia not understandable

•Difficult cooperation

•Heavy sedation or general anesthesia is required in most patients

Indications of regional anaesthesia Infraumbilical extraperitoneal surgeries like inguinal

hernia, circumcision, hypospadias, orchidopexy, cystoscopy, colostomy for imperforate anus, rectal biopsy and other perineal surgeries

Lower extremity orthopaedic and reconstructive surgeries

Preterm and former preterm infants less than 60 weeks post-conceptual age/less than 3 Kg/hematocrit <30% and with other co-morbidities who are prone to post-operative apnoea, bradycardia and desaturation after GA

Indications(contd.)

Neonates with respiratory diseases like bronchopulmonary dysplasias, hyaline membrane disease

Children with h/o or high risk for malignant hyperthermia

Children with acute respiratory conditions, chronic disease of the airways like asthma or cystic fibrosis

Indications(contd.)

Management of nonsurgical paina. Herpes zoster, AIDS, mucocutaneous leisons-regional

blocks

b. Vaso-occlusive crisis of sickle cell disease

Non analgesic indicationsa. Sympathetic blockade for severe trauma

b. Vascular insufficiency in Kawasaki disease

c. Severe frostbite

d. Accidental intra arterial injection of LA

Contraindications to regional anaesthesia Absolute contraindications to neuraxial

blocks: Severe coagulation disorders- constitutional or

acquired Severe infection such as septicemia or meningitis Hydrocephaly and intracranial tumoral process True allergy to local anesthetics Chemotherapies (such as with cisplatin) Uncorrected hypovolemia Cutaneous or subcutaneous lesions at the

contemplated site of puncture Parental refusal

Contraindications( contd.) Absolute contraindication to PNB

procedures: True allergy to the local anaesthetic agent

Relative contraindications: Patients at risk of compartment syndrome Sickle cell ds a/w hypoxemia and hemodynamic

disorder Extended malformations of vertebrae, spinal

fusion, myelomeningoceles, open spina bifida, and major spondylolisthesis

Pre-existing neurologic disorder

Complications of regional anaesthesia Local complications: Inappropriate needle insertion damaging the

nerve and surrounding anatomic structures Tissue coring and introduction of epithelial

cells into tissues where they do not belong Injection of neurotoxic solutions Leakage around the puncture site which

may cause partial block failure and favor bacterial contamination

Systemic complications: Accidental iv injection of LA Excessive dosing

Selection of materials, techniques and agents Considerations for selection of

suitable procedure: Adequate sensory blockade Minimal potential morbidity Postoperative analgesia

Various approaches: Single-shot technique with either a short-

acting or a long-acting local anaesthetic Single-shot technique with local anaesthetic

and adjuvants Catheter technique with repeat/continuous

injections of local anaesthetic

Selection of equipments….(contd.) Identification of anatomic space: Surface mapping or percutaneous guidance Ultrasound techniques (Jockey probes) Acoustic devices Electrostimulation Loss of resistance with air or saline Whoosh test is now obsolete

Selection of equipments….(contd.) Selection of anaesthetic agent

depends on: Site/ extent of surgery Expected duration of intense postoperative pain Hospital stay vs early dischargeLocal

anaestheticUsual conc.

Max dose of plain soln mg/kg

Max dose with epinephrine mg/kg

Lidocaine 0.25-0.2 5 10

Bupivacaine 0.125-0.5

2 3

Levobupivacaine

0.125-0.5

3 4

Ropivacaine 0.1-10 3 Not recommended

Selection of equipments….(contd.) Selection of block needles and

catheters:Block procedure

Recommended device

Spinal anaesthesia

Spinal needle (24-25 gauge; 30, 50 or 100 mm long, Quincke bevel, stylet)

Caudal anaesthesia

Short (25-30 mm) and short beveled (45-degree) needle with stylet

Epidural anaesthesia

Tuohy needle (22, 20, and 19/18 gauge); LOR syringe and medium epidural catheter

PNB Insulated 21-23 gauge short beveled needles

Safety precautions

Acceptable environment for performing regional blocks:

Minimal mandatory monitoring Anaesthetic and emergency drugs Resuscitation equipments Trained anaesthesiologist Trained staff iv line in situ

Discharge criteria- Modified Aldrete score

Parameters Scores

Level of consciousness•Fully awake•Arousable on calling•No response

210

Oxygen saturation•>90% on room air•>90% on oxygen•<90% on oxygen

210

Circulation/ BP•SBP within 20mm Hg of pre sedation values•SBP within 20-50 mm Hg of pre sedation values•SBP >50 mm Hg of pre sedation values

210

Movement /activities•Moves all extremities on command•Moves 2 extremities•Does not move

210

Respiration•able to breathe and cough freely•Dyspnea is with shallow breathing•Apneic

210

Spinal anaesthesia Anatomy and physiology: The spinal cord and dural sac of infants younger than 1

year of age end at a lower level Volume of CSFa. 10 mL/kg in neonatesb. 4 mL/kg in infants weighing less than 15 kgc. 3 mL/kg in childrend. 1.5 to 2.0 mL/kg in adolescents and adults

e. 50% CSF volume is located within the spinal subarachnoid space versus 25% in adults

f. Lower CSF hydrostatic pressure g. Children older than 5yr behave like adults after spinal

anaesthesia, whereas younger patients remain hemodynamically stable, without significant hypotension or bradycardia

Spinal anaesthesia(contd.)

Indications: Inguinal hernia repair in former preterm infants

<60 weeks of postconceptual age Elective lower abdominal or lower extremity

surgery

Cardiac surgery or cardiac catheterization (controversial)

Spinal anaesthesia(contd.) Technique of spinal anaesthesia: Position:a. Lateral position with head extended to avoid airway

compromiseb. Sitting position Firm grasp of the awake infant by an assistant Neonates and infants: 1.5” 25-27G spinal needle

with stylet at L4-5 level >2yr: longer needle, smaller guage Pop felt as needle enters the ligamentum flavum Free flow of CSF Inject the LA slowly Child to remain supine and legs should not be

raised for any reason

Spinal anaesthesia(contd.)Local anaesthetic (neonates)

Dose mg/kg Volume ml/kg

0.5% bupivacaine isobaric/hyperbaric

o.5-1 0.1-0.2

0.5% levobupivacaine 1 0.2

0.5% ropivacaine 1.08 0.22

Local anaesthetic (children)

Usual dose

0.5% bupivacaine isobaric/hyperbaric

5 to 15 kg: 0.4 mg/kg (0.08 mL/kg)>15 kg: 0.3 mg/kg (0.06 mL/kg)

0.5% levobupivacaine

5 to 15 kg: 0.4 mg/kg (0.08 mL/kg)15-40 kg: 0.3 mg/kg (0.06 mL/kg)>40 kg: 0.25 mg/kg (0.05 mL/kg)

0.5% ropivacaine 0.5 mg/kg (max 20 mg)

Caudal anaesthesia

Anatomy of sacral hiatus

Caudal anaesthesia(contd.) Anatomy of sacral hiatus: V-shaped aperture formed d/t lack of dorsal fusion

of the 5th and 6th sacral vertebral arches Limited laterally by sacral cornua Covered by sacrococcygeal membrane Mean distance from skin to anterior sacral wall: 21

mm (2 mo to 7 yr) Less suitable after 6-7yrs asa. Change in axis of sacrum

b. Difficulty to identify sacral hiatus

c. Densely packed epidural fat

Caudal anaesthesia(contd.)

Indications of caudal anaesthesia: Surgical procedures below the umbilicus As an adjuvant to GA Sole anaesthetic technique in fully awake ex-premature

infants younger than 60 wk of post conceptual age

Contraindications to caudal anaesthesia:

Major malformations of sacrum (myelomeningocele, open spina bifida)

Meningitis Intracranial hypertension

Caudal anaesthesia

Caudal anaesthesia(contd.) Technique of caudal anaesthesia: Positioning the patienta. Sim’s positionb. Semipronec. Prone- esp. in non anaesthetized (frog position) Palpate for sacral cornua along the spinal processes at

the level of sacrococcygeal joint The sacral hiatus along with both PSIS forms an

equilateral ∆ Introduce needle in midline at 45⁰ or less Resistance felt on piercing the sacrococcygeal

ligament Acute the angle of needle by 10-15 degree. Inject the LA with frequent aspirations Finger should palpate the skin cephalad t the injection

to ensure drug is not s/c

Caudal anaesthesia(contd.) The armitage regime: O.5 ml/kg- all sacral dermatomes blocked 1 ml/kg- sacral and lumbar dermatomes blocked 1.25 ml/kg- upto midthoracic levels blocked

Bupivacaine in

Concentration

Dose Possible additives

Single dose caudal

0.175%- 0.5%

0.75- 1.25 ml/kg (max. 3 ml/kg)

Epinephrine 2.5- 5 µg/kgClonidine 1- 2 µg/kgMorphine 30- 70 µg/kg

Continous caudal

0.1%- 0.25%

0.4 ml/kg Fentanyl 2- 5 µg/kg

Caudal anaesthesia(contd.)

Complications with caudal blocks: Risks during performance of the blocka. Intravascular placement

b. Needle into subarachnoid space

c. Needle into sacral marrow

Risks from injection of LA Side effects of other agents used Block failure (3%- 5%)

Epidural anaesthesia

Anatomy and physiology of epidural space: The epidural space surrounds the spinal cord and the

meninges from the foramen magnum to the sacral hiatus

Limited posteriorly by the vertebral laminae and the ligamenta flava

Communicates quite freely with the paravertebral spaces

Near the spinal ganglia, connected with the subarachnoid space owing to protrusion of arachnoid granulations

Contains blood vessels and lymphatics Filled with loose fat in infants and in children up to 6 to 8

years of age

Epidural anaesthesia(contd.) Indications of epidural anaesthesia: Major abdominal surgeries Retroperitoneal, pelvic and thoracic surgeries Pectus excavatum repair Scoliosis corrective surgeries Controversial in cardiac surgeries

Contraindications to epidural anaesthesia:

Severe malformations of spine and spinal cord Intraspinal leisons and tumors Tethered cord syndrome Hydrocephalus, unstable epilepsy Previous spine surgery

Epidural anaesthesia(contd.) Technique (for lumbar epidural

anaesthesia): Midline approach below L2-L3 interspace, which

represents the lower limit of the conus medullaris Paramedian approach in spinous process anomaly or

spine deformity Semiprone position with the side to be operated

lowermost and the spine bent to enlarge the interspinous spaces

LOR with air in infants and saline in older children Distance from skin to epidural space 1 mm/kg b/w

6mo- 10yr Disconnect the LOR syringe No reflux of biological fluid at hub Catheter is inserted to not more than 3 cm in order to

avoid buckling, knotting, and lateralization of blockade or erratic migration

Epidural anaesthesia(contd.)

Agent Initial dose Continous infusion (max dose)

Bupivacaine, levobupivacaine

Solution: 0.25% with 5 µg/mL (1/200,000) epinephrineDose:<20 kg: 0.75 mL/kg20-40 kg: 8-10 mL>40 kg: same as for adults

<4 mo: 0.15 mL/kg/hr of 0.125% or 0.3 mL/kg/hr of 0.0625% (0.2mg/kg/hr)4-18 mo: 0.2 mL/kg/hr of 0.125% or 0.4 mL/kg/hr of 0.0625% (0.25mg/kg/hr)>18 mo: 0.3 mL/kg/hr of 0.125% or 0.6 mL/kg/hr of 0.0625% (0.3mg/kg/hr)

Ropivacaine Solution: 0.2%Dose: same regimen in mL/kg as for bupivacaine

Same age-related infusion rates in mg/kg/hr as for bupivacaine (0.1%, 0.15%, or 0.2%)Do not infuse for more than 36 hr in infants < 3 mo

References

Bernard DJ. Regional anesthesia in children. In: Miller RD, editor. Miller’s Anaesthesia. 7th ed. Philadelphia: Churchill Livingstone; 2010.

Pawar D. Regional anaesthesia in pediatric patients. Indian J. Anaesth.2004;48(5).

Davis PJ, Cladis FP et al. Smith’s anaesthesia for infants and children. 8th ed. 2012.

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