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| INTRODUCTION |
Advances
in the neonatal care have resulted in the survival of a greater number
of preterm infants.These infants are also often of a young post conceptual
age. Anaesthesia for elective and emergency procedure in these infants
presents a challenge with an increased risk of life threatening apnoeas
after surgery.
Children are different : They have an inherent fear of needles
like most adults. Central or peripheral blocks are done under GA or
sedation to ensure an immobile patient and safe execution of the block.
Many published series reveal low complication rates. However, assessment
of these blocks and detection of signs of toxicity is difficult under
sedation or GA |
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| ANATOMY1 |
| Line
joining superior iliac crest |
-
Crosses the L3/4 interspace in adults
- Crosses the L5/S1 interspace in neonates
- Crosses the L5 vertebra in children |
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| Dural
sac |
-
Level S4 at birth
- Reaches S2 at the end of the first year |
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| Spinal
cord |
-
Terminates at L3 at birth
- Reaches L1 at the end of the first year |
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| Sacrum |
-
In infancy, incomplete fusion of the sacrum makes it easy to enter via
the posterior approach at all levels (S1 - S4) and the sacral hiatus
is relatively larger and higher in neonates.
- After age 7, the dimensions are reduced and caudals become less easy
to perform |
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| Curvature |
-
At birth the vertebral column presents only an anterior concave curvature
and the relationship between spinous processes to each other is similar
and hence spinal and epidural techniques can be performed with the same
orientation at any level.
- The cervical lordosis appears in the first 3 months of life with the
ability to hold the head upright.
- From 6-9 months, the lumbar lordosis appears as the child learns to
walk. This curvature makes spinal/epidural technique similar to adults.
Distance from skin to epidural space2 - increases with age (Fig. 1).
|
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| Positioning
of patient |
In
preterm infants, it is recommended that in the lateral position, there
should be partial neck extension or if done in the sitting position, the
head should be supported, to reduce hypoventilation.
Gleason4 and colleagues measured transcutaneous pO2 and pCO2 in three
positions.
| 1 |
Lateral
position with neck flexion |
| 2 |
Lateral
position with partial neck extension |
| 3 |
Sitting
position with head support |
|
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| Results |
Mean
transcutaneous pO2 decreased in all three with the largest drop in the
flexed position and transcutaneous pCO2 increased only in the flexed
position and remained elevated for 5 minutes after discontinuing the
position.are awake, cooperative usually over the age of - over 7 years
old. - increases the ease of epidural puncture. - But increases the
risk of dural puncture because the spinal cord moves. Dorsally in this
position and the pressure on the CSF is increased.
Lateral position - common position under GA. - If the size
of pillow is correct, the line of spinous process is parallel to the
operating table. - The pelvis does not play as important a role in children
and adolescents as in adults
Prone position - Rarely used except for specific reasons e.g.
Patients with large plaster cast or with spinal deformities. - May accentuate
the lumbar lordosis thus making epidural access difficult (Use towels
on each iliac spine or using a frame such as one used for scoliosis
surgery) |
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| Volume
of injection5 |
Epidurals
- Schulte - Stenberg formula6 ® volume required to block one spinal
segment = 1/10 age in years (up to puberty).
In practice 0.5 - 1.0 ml/kg up to a maximum of 20 mls is used.
Caudal : One milliliter per kilogram of bupivacaine 0.125%
with epinephrine 1:200,000 reliably produces 4 to 6 hours of analgesia.
Higher concentrations have been used, but motor blockade is significantly
increased without improving the quality or duration of pain control.
The addition of opioids may increase the potency of the neuraxial block.
Fentanyl 1 to 2 µg/kg may also prolong the block, but pruritus
and nausea or vomiting are increased. Morphine (30 µg/kg) has
also been used by this route, but side effects (nausea or vomiting and
pruritus) often occur and the increased risk of respiratory depression
precludes its use in out patients.
Epidural : In children older than 10 years of age, a simple
formula calculates the volume (V) necessary to block one spinal segment:
V (in mL) = 1/10 x (age in years)
In younger children, the weight of the patient should be considered;
0.04 mL/kg/segment provides an initial bolus-dose estimate. |
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| Assessment
of blocks |
Adults
- loss of cold discrimination, loss of pain sensation, loss of light
touch commonly used methods may not be applicable to neonates, infants
and small children.
Differential sensory perception is also age dependent and limited by
the cognitive and linguistic capability of the child.
1.5-2 year olds begin to use words to describe pain. 2-3 year olds begin
to attribute pain to an external cause. 4-5 year old child only starts
to discriminate between all or none and probably able to quantify the
degree of pain.
The term paraesthesia is difficult to explain to a child and may not
be comprehensible in children under 6 years old.
Assessment is mostly based on a physiological response (pulse rate,
BP, respiratory rate or withdrawal reflex) to a noxious stimuli.
Other methods include loss of sensation to skin pinch, to finger nails
and pin prick, the sensory level of blockade being regarded as the point
at which a withdrawal response, facial grimace or cry occurs. (It has
been suggested that a skin pinch is a more intense stimulus and may
give a different estimate of sensory loss). |
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| The
test dose7,8 |
How
reliable is it?
A test dose should be 0.1 mL/kg of a local anaesthetic solution with
5 µg/mL of epinephrine to a maximum volume of 3 mL. An increase
in heart rate of 10 beats per minute above baseline occurring within
1 minute of injection is a reasonable predictor of intravascular injection
for children anaesthetized with sevoflurane.9,10 This sign is less reliable
in children anaesthetized with halothane.11 Pretreatment with atropine
may improve the accuracy of heart rate changes in detecting intravascular
injection for both inhalation agents.
Calculate max.dose, administer slowly or in small boluses and be vigilant. |
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| Contraindications |
Contraindications
are few and similar to those in adults. These include coagulopathy,
infection at the insertion site, true local anaesthetic allergy, and
abnormal superficial landmarks or lumbo-sacral myelomeningocoele because
of the risk of malposition of the cord or dural sac. Progressive neurologic
disease is a relative contraindication primarily because of medico-legal
concerns. |
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| COMPLICATIONS12 |
| 1.
Complications of puncture |
Subcutaneous
and intramuscular injection - a feeling of a give similar to a loss
of resistance can be felt especially in neonates because of the high
degree of hydration and low density tissue.
Injection into paravertebral space - the loss of resistance felt is
similar to that of the epidural space. The increase in the resistance
of the ligamentum flavum is probably not felt. This may result in unilateral
single spinal nerve block or a patchy block because the epidural space
communicates freely with the paravertebral space.
Injury to discs, ligaments, blood vessels.
Dural puncture - incidence is about 2.5% or less in adults, 2% or less
in children. Consequences of dural puncture in children are negligible.
Postural puncture headache is exceptional before the age of 10 years
and unusual before puberty.
Damage to spinal cord and nerve roots : Direct trauma to nerve roots,
conus medullaris can occur. Sensory deficits may persists while the
motor deficits may resolve over a few days. Usually other factors are
involved e.g. vascular injury, hypotension or compression by an epidural
haematoma of the spinal artery entering into the spinal cord or nerve
root. Intraneural injection of LA can cause permanent damage to nerve
fibres. In an awake patient this is manifested by paraesthesia when
the needle penetrates the neural sheath and intense pain when the injection
is made where a high resistance to injection is usually felt. Risks
increases with the patient under GA |
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| 2.
Complications of epidural catheter13 |
| • |
Puncturing
the dura giving rise to spinal anaesthesia and postdural puncture
headache.. |
| • |
Subdural
placement causing an extensive block |
| • |
Migration into vessel causing systemic symptoms |
| • |
Migration into vessel causing systemic symptoms |
Fracture
- can occur if pulled out through the needle, if the catheter has been
left in for a long time resulting in adhesions, due to formation of
loops or knots when a longer length of catheter is introduced or when
multiple catheters are used at different levels.
Bacterial contamination, adhesion formation and nflammatory reactions
increase with the amount of time left in the space.
|
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| Complication
relating to the injected solution |
Wrong
solution - label, place in different tray
Intravascular injection14 : Damage to vascular plexus by needle
or catheter. - Aspiration of blood is usually but not always seen. -
Detection of toxicity may be difficult under GA. - Convulsions are unlikely
to be seen under GA. Most episodes of convulsants are reported postoperatively
during top ups or when continuous infusion is used. - Arrhythmias usually
seen before CNS toxicity becomes manifest.
Subarachnoid injection15 : May lead to a total spinal which
is rapid in onset. - Cardiorespiratory support if occurs but in children
< 8 years old, hypotension is usually not seen. - Keep patient asleep.
Subdural injection16 : May present as a high sensory block.
- Delay onset about 20 minutes after a presumed epidural injection.
- Motor and sympathetic block usually minimal but may require support
in some cases.
Complications due to opioids17 : Increases the quality and
duration of analgesia but associated with side effects in 50% of cases.
- Commonly pruritus nausea, vomiting, urinary retention. - Respiratory
depression; the first signs usually appear after 3-24 hrs after injection
and severe depression appears 2-3 hours after the initial signs. - Signs
of respiratory depression usually but not always preceded by severe
generalised pruritus and increasing somnolence. Treatment is supportive
(ABC), stopping the opioid and consider giving naloxone 10 mcg/kg followed
by an infusion of 10 mcg/kg/hr for 24 hours with close monitoring.
Cardiovascular effects18 : Cardiovascular changes related to spinal
anaesthesia are less frequent in children. Minimal changes in heart
rate and blood pressure have been noted following high thoracic spinal
anaesthesia in neonates and infants. Above 5 years - Bradycardia and
hypotension is seen more frequently.
Respiratory changes : Respiratory effects of spinal anaesthesia
have generally occurred with high sensory and motor level above T1.
Many of these problems were not due to excessive dosing but to factors
such as leg lifting after spinal injection.
Post Dural Puncture headache19,20 : PDPH occurs in older children.
Partial or complete failure of block : Repeat procedure, repeat
dose of LA or use alternative analgesia
Other complications : Infection and chemical meningitis
Dermoid cyst - due to the introduction of epidermal cells in the spinal
canal and can cause spinal cord compression.
Poor psychological tolerance in children of a motor block
Flaring up of latent infections e.g. herpes
Allergy to LA : Shivering - thought to be due to the temperature
of the injected solution < 37°C stimulating the temperature receptors
in the epidural canal. |
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| CONCLUSION |
Paediatric
regional anaesthesia is considered a safe and reliable technique providing
a painfree state but even in skilled hands is not free of complications
and requires strict attention to technical detail and precise, gentle
manipulations.
The use of regional anaesthesia alone or in combination with other therapies
is cost effective and also improve postoperative outcome. |
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| ACKNOWLEDGEMENT |
| I
would like to thank the Rameshwardas Birla Smarak Kosh Scholarship which
enabled me to go for my fellowship to the KK Women’s and Childrens
Hospital for Paediatric Anaesthesia and learn speciality work there. |
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|
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MONTELUKAST
PLUS FLUTICASONE IS EQUIVALENT TO SALMETEROL AND FLUTICASONE
Adding montelukast to the treatment regimen of asthma
patients whose symptoms remain uncontrolled by fluticasone provides
equivalent control to adding salmeterol. In a double blind randomised
controlled trial, Bjermer and colleagues randomised 1500 patients
with uncontrolled asthma symptoms taking fluticasone to receive
either montelukast or salmeterol as well. At one year, 20% of
patients in each group had had an exacerbation of asthma. The
authors say that the b agonist salmeterol and the anti-leukotriene
montelukast are known to reduce the risk of exacerbation when
combined with a corticosteroid, but the two had not been compared
directly in a long term study with exacerbation of asthma as the
primary end point.
BMJ 2003; 327 : 891 |
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