Update in Central Neuraxial Blockade in Pediatrics

Update in Central Neuraxial blockade in

Pediatrics

by

Hytham Khaled Abou El-FotouhAssistant lecturer of Anesthesia & Intensive care

Faculty of Medicine - Zagazig University

Contents- Introduction.

- The important anatomical differences between pediatrics

and adults vertebral column with their central neuraxial block

implications.

- The Important physiological differences between pediatrics

and adults with their central neuraxial block implications.

- Indications of CNAB.

- Contraindications of CNAB.

- Preoperative management.

- Measures for patient safety during establishment of CNAB.

- Technical procedures.

- Advantages.

- Disadvantages.

- Complications.

- Conclusion.

Introduction:- Neuraxial blockade entails interruption of neuronal

transmission at the level of the neuraxis (i.e. the spinal cord)

by means of local anesthetic drugs.

- They provides adequate intra and postoperative analgesia

When combined with general anaesthesia, it reduces the

requirement of anaesthetic and analgesic agents.

- It is a simple technique, but it has some rare potential life

threatening complications as Local anaesthetic toxicity.

- To perform these blockades safely in pediatrics, it is

mandatory to know the anatomical and the physiological

differences between pediatrics (especially neonates and

infants) and adults with their central neuroaxial block

implications.

The important anatomical differences between pediatrics and

adults vertebral column with their central neuroaxial block

implications:

a- The spinal cord reaches:

- L3-4 in the neonates and below 1 y old

infants.

- lower border of L1 (the adult level) at 1y old.

So,lumbar puncture for subarachnoid block in neonates

and infants should be performed at the L4-L5 or L5-S1

interspace to avoid needle injury to the spinal cord.

b- Thoracic spinous processes in neonates

and infants are more horizontal in position

but with older ages they become more

oblique, so

- In less than 1 year of age, the needle insertion

is perpendicular to the spinous process line.

- In older ages the needle insertion acquires

cephalic orientation (up to a 45-degree angle to

the skin).

Fig. (1): Shows the end of

both spinal cord and

dural sac beside the

shape of sacrum, in

pediatrics and adults.

b- Sacrum:- Shape and fusion:- In comparison with adult, the sacrum in infant and

young children is flat not fused and consists of five

distinct vertebrae (fig.1).

- This allows an easy sacral inter-vertebral approach.

- The dural sac reaches:- S3-4 in the neonates and below 1 year old infants.

- S1-3 (The adult level) at 1 year old.

so, there is great liability to accidental intrathecal injection

Fig. (1): Shows the end of both

spinal cord and dural sac beside

the shape of sacrum, in pediatrics

and adults.

with caudal extradural blockade in below one years old patient than adults.

- The sacral hiatus is situated :- Near the natal cleft in adults.

- Much higher in infants.

- At the middle of sacrum in neonates.

- Epidural fat: - Less fibrous in pediatrics (up to 6-7 years of age) so, spread of LA and

catheter insertion is easy.

The important anatomical differences between pediatrics and adults vertebral column with their central

neuroaxial block implications (Cont.):

c- Tuffier's line level ( the line that joins both anterior superior iliac

spinous processes):

- Due to delayed ossification and growth of iliac crests:

- It crosses the spine at L5-S1 inter-space in infants.

- It crosses the spine at L4-L5 inter-space in adults.

d- Ligamentum flavum:

- It is much thinner and less dense in infants and children than in

adults.

- This makes the engagement of the epidural needle more

difficult to detect and unintended dural puncture during

epidural catheter placement a greater risk for the infrequent

operator.

The important anatomical differences between pediatrics and adults vertebral column with their central

neuroaxial block implications (Cont.):

The Important physiological differences between pediatrics

and adults with their central neuroaxial block implications:

- Neonates, infants and children are uncooperative, so heavy

sedation or general anesthesia is required before

establishment of regional blockade.

- Nerve fibers in neonates and young children are

- Thinner.

- Have less myelin

This makes neonates, infants and children more sensitive to the effects of local anaesthetics with subsequent rapid onset.So, diluted local anesthetic is as effective as more concentrated

anesthetic in adults

- Cerebrospinal fluid (CSF)

volume as a percentage of

body weight is greater in

infants and young children.

So, comparatively larger doses of local anesthetics

required for surgical

anesthesia with sub-

arachnoid block in infants

and young children.Figure (2): Approximate volume of

cerebrospinal fluid (CSF) relative to

weight and age

- The CSF turnover rate is greater in infants and children with

subsequent much briefer duration of subarachnoid block with any

given agent.

The Important physiological differences between pediatrics and adults with their central neuroaxial

block implications (Cont.):

The Important physiological differences between pediatrics and adults with their central neuroaxial block

implications (Cont.):

- Attachment of spinal nerve sheaths in neonates and young

children is loose and this leads to leakage of LA along spinal nerve

roots during epidural blockade with subsequent the need to large

volume of local anesthetic to compensate for this leak along spinal

nerve roots.

- The incidence of LA toxicity in neonates and infants is

higher especially with repeated LA administration due to:

: due to large volume of distribution and Prolonged elimination ½ life-

impaired renal function.

: larger amount of free drug.Lower albumin concentrations-

: due immature hepatic metabolic Diminished metabolic clearance-

pathway and renal function (reach adult levels by 3-5 months of age).

that leads to Increased regional Increased cardiac output and heart rate-

blood flow with subsequent increased systemic absorption of local anesthetic.

- The incidence of apnea in neonates are at greatest following

opioids caudal extradural administration because of:

- Morphine clearance in neonates is one quarter that of adults.

- Immature respiratory centre.

Indications of CNAB:a- For providing anesthesia and analgesia in Lower

abdominal and Lower extremity surgery (hip, leg and foot

surgical procedures).

b- For providing post operative analgesia:

- It is established at the end of operation and before

recovery from GA to provide post-operative analgesia

(continuous infusion method).

c- As an adjuvant to GA:

- For surgical procedures below the umbilicus.

d- For pre-emptive analgesia:

- It is established before start of surgical procedures

under GA to avoid post operative pain.

Contraindications of CNAB:

A- Absolute:- Parents refusal.

- Coagulopathy.

- Therapeutic anticoagulation.

- Skin infection at injection site.

- Raised intracranial pressure Accidental dural puncture in a patient with

raised ICP may lead to brainstem herniation (coning).

- Hypovolaemia to avoid profound circulatory collapse.

- History of allergy to LA.

B- Relative:- Pre-existing neurological disorders: such as multiple sclerosis, may be a

contraindication, because any new neurological symptoms may be

ascribed to the epidural.

- Fixed cardiac output states.

- Myasthenic patient.

- Anatomical abnormalities of vertebral column such as spina bifida,

meningomyelocele or scoliosis.

- Prophylactic low dose heparin.

Preoperative management:- Pre-operative visit to:- A formal pre-anaesthetic assessment as prior general anesthesia should

be carried out with special considerations to:

- The patient's cardiovascular status, especially valvular lesions or other conditions that might impair the ability to increase

cardiac output in response to the vasodilatation that inevitably follows

sympathetic blockade.

- The back should be examined and any lesions or

abnormalities noted.

- Laboratory assessment of the patient's coagulation status.

INR (or prothrombin time), APTT and absolute platelet count should be

within the normal range.

- Prior to performing the block, all equipment should be

checked.

Measures for patient safety during establishment of

CNAB:

- The procedure should be conducted in the anesthesia

room or theatre .

- Stabilizing venous access (to allows administration of intravenous

fluids preloading or coloading).

- Sedative agents (if required)

- Patient monitoring (ECG, BP and SpO2 if sedation is planned).

- Drugs and equipments for resuscitation and airway

management should be available and ready.

Techniques for establishment of CNAB:- CNAB are classified according the following:

According to the position of needle or catheter insertion it is classified into:

- Sacral (Caudal) epidural block.

- Lumbar spinal or epidural block.

- Thoracic epidural block.

- Cervical epidural block.

According to the approach:

- Median.

- Lateral.

According to the method of administration of LA:

- Single-shot technique

- Intermittent bolus.

- Continuous infusion technique.

According to the combination with spinal or general anaesthesia:

- Sole CNAB (cannot applied in pediatrics because they are uncooperative).

- Combined with spinal blockade: Combined spinal-epidural.

- Combined with general anesthesia: Adjuvant to general anaesthesia.

Techniques for establishment of CNAB (Cont.):

Equipment:- The tray is prepared with the following:- Sterile towels and 4"x4" gauze packs.

- Pediatric size spinal or epidural needlesNeedles should have a clear plastic hub and a

small dead space.

- 1or 2 syringes (the selected size depends on the

calculated LA volume which will be used

for blockade).

- Marker in case of caudal blockade.

- The selected Local anesthetic type and

concentration.

- Sterile gloves.

- Antiseptic solutions.

- Plaster.

Pediatric epidural Needle sizePediatric spinal needle sizes

Techniques for establishment of CNAB (Cont.):

Identification of epidural space:

a- loss of resistance technique.

b- Hanging drop technique.

Techniques for establishment of CNAB (Cont.):

Identifications of Sacral Hiatus (SH) for

caudal blockade:

Methods of identifications of SH:i- Draw an equilateral triangle, the base of which is

the distance between posterior superior iliac

spines.

- The apex of this triangle will point inferiorly over

sacral hiatus.

ii- The sacral hiatus can be located by: first

palpating the coccyx, and then sliding the

palpating finger in a cephalad direction (towards

the head) until a depression in the skin is felt.

iii- Fluoroscopy to locate the sacral hiatus and

determination of the optimal angle of needle

insertion during caudal block.

iv- Ultrasound Guidance to locate the sacral hiatus

and determination of the optimal angle of needle

insertion during caudal block.

Techniques for establishment of CNAB (Cont.):

Confirmation of Proper Epidural Needle/Catheter Placement:

1- Aspiration.

2- Test dose.

3- Radiographic methods:

- X-ray imaging in conjunction with a contrasting agent

precisely identifies the tip of the catheter at a specific spinal

level.

- Fluoroscopy permits the real-time monitoring and

adjustment of advancing catheters.

4- Ultrasound-guided techniques:

- It allows the real-time visualization of epidural needle tip

and catheter placement.

5- Epidural electric stimulation

test (Recently used):

PrincipleStimulation of the spinal nerve roots with

electrical current conducted through normal

saline in the epidural space via an

electrically conducting catheter.

Sign of correct placement of epidural

catheter tip:-Correct placement of the epidural catheter

tip (1-2 cm from the nerve roots) is indicated

by a motor response elicited with a current

between 1-10 mA.

Limitations of the use of Epidural stimulation

test:

- It cannot be performed if any significant

neuromuscular blockade is present or local

anesthetics have been administered in the

epidural space.

Figure 1. Epidural electric stimulation

test Equipment: The stimulating

catheter set-up requires the cathode

lead (black for block) of the nerve

stimulator to be connected to the

epidural catheter via an electrode

adapter while the anode lead is

connected to an electrode on patient’s

skin as the grounding site

Techniques for establishment of CNAB (Cont.):

Confirmation of Proper Epidural Needle/Catheter Placement (Cont.):

6- Epidural ECG technique:

- Using epidural ECG, the

anatomical position of the

epidural catheter is determined

by comparing the ECG signal

from the tip of the catheter to a

signal from a surface electrode

positioned at the “target”

segmental level.

Techniques for establishment of CNAB (Cont.):

Confirmation of Proper Epidural Needle/Catheter Placement (Cont.):

LA dose for various CNAB in pediatrics:a- LA dose for spinal blockade in pediatrics:

Local Anesthetic Dose (mg/kg) Volume (mL/kg)

Tetracaine 1% 0.4-1.0 0.04-0.1

Tetracaine 1% with

epinephrine0.4-1.0 0.04-0.1

Bupivacaine 0.5% isobaric

or hyperbaric0.5-1.0 0.1-0.2

Levobupivacaine 0.5% 1.0 0.2

Ropivacaine 0.5% 1.08 0.22

- Usual Doses of Local Anesthetics for Spinal Anesthesia in Neonates (up

to a Weight of 5 kg) are presented in the following table:

Local Anesthetic Usual Dose(s)

0.5% Isobaric or hyperbaric bupivacaine5 to 15 kg: 0.4 mg/kg (0.08 mL/kg)

>15 kg: 0.3 mg/kg (0.06 mL/kg)

0.5% Isobaric or hyperbaric tetracaine5 to 15 kg: 0.4 mg/kg (0.08 mL/kg)

>15 kg: 0.3 mg/kg (0.06 mL/kg)

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

- Usual Doses of Local Anesthetics for Spinal Anesthesia in Children and

Adolescents are presented in the following table:

Techniques for establishment of CNAB (Cont.):

Techniques for establishment of CNAB (Cont.):

LA dose for various CNAB in pediatrics (Cont.):

b- LA dose for epidural blockade in pediatrics:

- Up to 10 Kg: 0.2ml/kg increments (0.8ml/kg total).

- Above 10 to 25Kg: 0.15ml/kg increments (0.6ml/kg total).

- Above 25 to 40Kg: 0.1ml/kg increments (0.4ml/kg total).

- Above 40Kg: 0.075ml/kg increments (0. 3ml/kg total to a

maximum of 20 ml).

Techniques for establishment of CNAB (Cont.):

LA dose for various CNAB in pediatrics (Cont.):

c- Calculation of the appropriate dose of bupivacaine in single shot'

technique to provide caudal block for the various surgical levels:

1- According to Armitage:- Armitage recommended the following bupivacaine volume for the various

surgical levels:- 0.5 ml/kg for a lumbo-sacral block.

- 1 ml/kg for a thoraco-lumber block.

- 1.25 ml/kg for a mid- thoracic block.

- Also he recommended the following bupivacaine concentration:- For volume up to 20 ml. 0.25% bupivacaine is recommended.

- For volume above 20 ml 0.19% bupivacaine is recommended (a part of 0.9%

NaCl + three parts of 0.25% bupivacaine = 0.19% mixture).

2- According to Scott :Scott calculates the dose of bupivacaine for various block levels according to

child's age or weight.

Techniques for establishment of CNAB (Cont.):

Testing the spread of CNAB :a- Pinprick or touch sensation and cold stimulus with ice.

Disadvantages:- These are subjective methods for testing.

- Disturbing for the child.

b- Transcutaneous electrical stimulation:

- It is a precise, reproducible, feasible and inexpensive method

for both clinical and research use.

Advantages of CNAB in comparison with GA:1- Reduced risk of airway obstruction or the aspiration of

gastric contents.

2- Less risk on patients with respiratory disease.

3- Relatively minimal cost.

4- Less risk on diabetic patients.

5- Excellent muscle relaxation.

7- Increase splanchnic blood flow and this may reduce the

incidence of anastomotic dehiscence.

8- Rapid return of normal gut function following surgery.

9- less post-operative deep vein thrombosis and pulmonary

emboli.

Disadvantages of CNAB:- Difficult to find the sub-arachnoid or epidural space in some

cases.

- Associated with some failures.

- Liability to unilateral, patchy and too low block level.

- Liability to hypotension especially with higher blocks.

- Liability to visceral injury.

- Not accepted by some parents or surgeons

- Single shot CNAB is not suitable for surgery lasting longer

than approximately 2 hours.

- Relatively it needs long time to perform.

- Risk of introducing infection into the extradural or sub-

arachnoid space.

- Liability to neurologic injury.

- Liability to postdural puncture headache.

Complications of CNAB :

Early Complications:

- LA toxicity.

- Total spinal block

- Hypotension.

- Bradycardia.

- Cardiac arrest .

Late Complications:

- Neurologic injury.

- Visceral injury.

- Postdural puncture headache.

- Backache.

- Infection.

- Urinary retention.

Conclusion:- Central neuraxial blockade in pediatric is relatively a simple

technique but it has some rare potential life threatening

complications as:

- Local anaesthetic toxicity.

- High spinal blockade.

-- To perform this block safely in pediatrics, it is mandatory to

know : - The anatomical and physiological differences between

pediatrics and adults with their central neuroaxial block implications.

- The correct technical procedures.

- The safety measures before LA injections

- Beside close monitoring of ventilation, oxygenation, and

circulation during and after blockade.