6.2 Paediatrics Flashcards
Regional anaesthesia
Regional anaesthesia in children
is usually done under
general anaesthesia or sedation.
In neonates
Metabolism and effect
In neonates,
the liver enzymes
and metabolic processes are immature,
hence there is less metabolism of local anaesthetics and greater chances of toxicity as compared to adults.
A1 acid glyco levels
effects
In neonates,
α1 acid glycoprotein levels
are 20%–40% of adult levels,
hence higher plasma levels
of unbound free drug
contributes to toxicity as well
When does conjugation of LA reach adult level
Around 3 months of age,
the conjugation of
local anaesthetics reaches
adult value,
When does clearance reach adult level
whereas full maturation
and clearance equivalent to adults
occur by around 8 months.
is there diff in plasma concentrations when LA injected
In children, there may be
higher vascular absorption of
local anaesthetics and
higher plasma concentration.
Is the paediatric nerve equally sensitive to LA
As myelination is incomplete up to
the age of 12 years,
local anaesthetic can penetrate
better in the nerves.
Is the mg/kg dose the same vs adults
Because of
greater sensitivity and
potential for toxicity,
the dose of local anaesthetic in
children (mg/kg) is less than adults.
Because of loose fascial layers,
volume of LA is a key factor
for spread than dose.
Ester local anaesthetics metabolism
vs amide
why diff
Ester local anaesthetics
do not depend on liver
for their metabolism
and have more rapid clearance
than amide local anaesthetics in neonates.
Ester LA and neonates dose
why
However, because of
low levels of plasma
cholinesterases in neonates,
ester local anaesthetics
should be used with caution.
Local anaesthetics with their recommended doses
Lignocaine
Lignocaine 7 mg/kg (with adrenaline)
5 mg/kg (without adrenaline
Bupivacaine/ropivacaine/levo-bupivacaine dose
Bupivacaine/ropivacaine/ 2–4 mg/kg
Procaine
Procaine 10 mg/kg
2-Chloroprocaine dose
2-Chloroprocaine 20 mg/kg
Bupivicaine and neonates
There is
greater risk of toxicity
with bupivacaine in neonates
than adults because of:
1
Liver enzymes being immature –
less metabolism of bupivacaine.
2
Low levels of alpha-1 glycoprotein –
higher free fraction of
bupivacaine.
Early signs of LAST in paeds
Regional blocks are usually done
under sedation in paediatric patients.
Therefore, the central nervous system signs of local anaesthetic toxicity are usually masked and the first sign usually detected is cardiorespiratory arrest.
Some anatomical facts in neonates and children
Spinal cord terminates
reaches adult level
Spinal cord terminates at L3
and reaches adult level of
L1 by 1 year of age.
Dural sac
neonates ends @
reaches adult level by
Dural sac ends at S4 in neonates
and reaches adult level S2 by 1 year of age.
sacrum formed by
Sacrum is formed by fusion of sacral vertebrae by 8 years of age.
Tuffier’s line neonates
what level @1
Tuffier’s line passes through L5/S1
junction in neonates
and lies at L4/L5 by 1 year.
Epidural space found how estmiation
Epidural space may be found at 1 mm/kg body weight.
Are epidural contents the same
There is easy passage of catheter in
epidural space, as epidural fat is
less densely packed than adults.
what does spread of LA correlate well with
Spread of local anaesthetic correlates
better with body weight than
age in paediatric patients.
Optimum doses for caudal block in children are
Optimum doses for caudal block in children are:
0.2% ropivacine 1 mL/kg
or
0.125%–0.175% bupivacaine 1 mL/kg
Epidural opiods in DOSA
Epidural opioids are avoided in day-case surgery because of side
effects like nausea, vomiting, respiratory depression and urinary
retention.
Local anaesthetic adjuvants for epidural in children
most common
most common adjuvant used is epinephrine
Epidural opioids
dosa?
s/e
Avoided in day-case surgeries
Side effects like nausea, vomiting, respiratory depression and urinary retention
adjuvants for epidural
Clonidine
dose
s/e
Clonidine
1–5 mcg/kg
Side effects:
hypotension and sedation
Ventilatory response to
increasing levels of carbon dioxide is blunted
adjuvants for epidural
Ketamine
dose
solution
safety?
s/e
Ketamine
0.25–0.5 mg/kg
Preservative-free solution must be used
Its safety for epidural use is not established
There are few animal studies suggesting neurotoxicity
Side effects: psychomimetic effects
adjuvants for epidural
Midazolam
dose
solution
safety
Midazolam
0.05 mg/kg
Preservative-free solution must be used
Its safety for epidural use is not established
adjuvants for epidural
Neostigmine
dose
solution
safety
s/e
Neostigmine
2 mcg/kg
Preservative-free solution must be used
Its safety for epidural use is not established
Side effects: nausea and vomiting
complication of epidural block
predominant organism colonising epidural catheter
predominant organism colonising epidural catheter is
Staphylococcus epidermidis.
The treatment of post-dural puncture headache in children involves
The treatment of post-dural puncture headache
in children involves
1
bed rest, sedation and
2
analgesics like non-steroidal antiinflammatory
drugs.
3
Blood patch may be used if medications fail.
EBP in paeds dose
The optimum dose of blood for
blood patch is 0.3 mL/kg.
cardiac instability and epidural
Unlike adults,
use of epidural in children is cardiostable
and presence of hypotension may
indicate intrathecal location
of catheter or
local anaesthetic toxicity.
How are test doses monitored in paeds epidurals
Test dose must always be
used for epidural catheter,
with continuous
ECG monitoring
for T-wave changes.
Confirmation of epidural catheter position can be done with
1
Ultrasonography:
2
Epidural ECG:
3
Electrical stimulation test (Tsui test)
Ultrasonography
aids in identifying relevant anatomic structures and
placement of epidural catheter. It is reliable only in children aged
< 6 months, as calcification of vertebral bodies prevents visualisation
after this age.
Epidural ECG
what changes
Epidural ECG:
T-wave changes help in
identifying intravascular
location of catheter.
It may not identify intrathecal placement.
Epidural ECG
Electrode connected to catheter
The right-arm electrode is connected to the epidural catheter, and epidural ECG is compared with standard reference ECG.
QRS amplitude
Epidural ECG
The amplitude of QRS complex in
ECG obtained from epidural catheter
increases as the tip reaches thoracic region,
where it is comparable to the reference ECG.
Epidural ECG
can it be used to confirm placement
It can be used to confirm placement of epidural catheter after neuromuscular blockers have been given or local anaesthesia given in epidural space.
Electrical stimulation test (Tsui test)
cathode to anode to
Electrical stimulation test (Tsui test):
cathode attached to epidural
catheter while the anode
is attached to skin.
Electrical stimulation test (Tsui test)
Change after LA if correct
Within the epidural space,
after correct placement of
local anaesthetic,
there would be increase in the current threshold current required to produce the motor response.
Electrical stimulation test (Tsui test)
No change after dose
not useful when
No change in threshold current
indicates intravascular placement of
catheter.
It is not useful if neuromuscular blockers have been
administered or
local anaesthetics given in epidural space.
Nerve stimulators for epidural stim
what current
same as peripheral?
Nerve stimulators used for
epidural stimulation test must be able to
deliver a current up to 10 mA.
As the nerve stimulators used for
peripheral nerve blocks usually deliver a current up to 5 mA, they are unsuitable.
What element can be added to stim catheter to help
Nerve stimulators used for epidural stimulation
Epidural-stimulating catheter containing
metal element helps in
proper electrical conduction
and decreases the resistance to flow of the
current.
Stylet epidural catheter use?
Nerve stimulators used for epidural stimulation
The epidural catheter with stylet
protects the tip and
helps in easy threading of the catheter
Stylet ends how far from tip
what shape does that produce
Nerve stimulators used for epidural stimulation
The stylet ends 10 mm proximal to tip,
forming a J shape during insertion.
Where is ground electrode placed
Nerve stimulators used for epidural stimulation
why
The ground electrode must be
placed on
upper limb and
lower limb for
lumbar and thoracic epidural catheter,
respectively, to avoid any error
from direct muscular stimulation
by the electrical current
Caudal block
needles with stylet
Caudal block can be done with
needles with stylet, as they provide good tactile sensation and prevent contamination of epidural space with skin tags
Caudal block
IV cannulae
Intravenous cannula can be used,
as they aid to detect placement in
the blood vessel or bone.
Caudal block position
Caudal block can be performed
in prone (adults) or
lateral decubitus position (children)
How to identify sacral hiatus
margins
Proper identification of
sacral hiatus is done by
drawing a line between the
two posterior superior iliac spines.
This line forms the base of an
equilateral triangle whose apex is
formed by the sacral hiatus
The needle angle for the skin puncture
change after what is punctured
Caudal block
The needle for the
skin puncture must be
angulated at an
angle of 70°– 80° and
the angle must be decreased to
20°–30° once the
sacrococcygeal ligament
is punctured.
Cannula over needle technique
aids
how
For caudal block,
the cannula-over-needle technique
aids in proper identification
of the caudal space.
The cannula slides off easily
in the caudal space if the needle
is in the right location.
Cannula over needle technique
helps also ID what
decreases risk of
It also helps in identifying needle
placement in the bone or blood vessel.
It decreases the risk of intrathecal
placement.
epidural block in paediatric
skin to epidural space distance in children vs adults
skin to epidural space distance in children
is less than in adults
skin to epidural space distance in neonates
mean
mean distance in neonates is around 1 cm.
Puncturing lig flavum vs adults
There is less tactile sensation on puncturing the ligamentum flavum
as compared to adults
is hypotension common in epdural block
Sympathetic blockade is
well tolerated in the paediatric population,
and presence of hypotension
must prompt suspicion of
intravascular or
intrathecal placement.
distance of the epidural space from skin may be dependen
distance of the epidural space from skin
may be dependent on age
and body weight of the child.
Tip of epidural catheter location
tip of the catheter must be
at the surgical site,
as the distance in
children between adjacent
vertebrae is very small
Threading the catheter into a
thoracic location from a lumbar insertion site
Because of formation of lumbar curvatur
as the child grows,
threading the catheter into a
thoracic location from a lumbar insertion site
becomes difficult
Approach for thoracic epidurals
Thoracic epidural block is done via
median approach in children,
compared with paramedian approach in adults.
CSF volume infants v adults
Cerebrospinal fluid volume in
infants is 4 mL/kg,
whereas in adults it
is 2 mL/kg.
in neonates in mL/kg is larger than
adults
Duration of spinal in paeds vs adults
dose
block duration increases with
duration of spinal anaesthesia is
shorter than for adults and
they require higher dose of local anaesthetic.
Duration of block increases with age.
Spinal positioning in paeds vs adults
why
For proper positioning in sitting position,
neck flexion,
required in adults,
must be avoided in infants.
Neck flexion may compromise the
airway in infants and is
not very helpful for spinal anesthesia.
Hypobaric soln and infants
Hypobaric solutions are not routinely used in infants
What scale can be used to assess block <2yo
Bromage scale can be used to
assess spinal block in
children under 2 years of age
Modified Bromage score
1 Complete block (unable to move feet or knees)
2 Almost complete block (able to move feet only)
3 Partial block (just able to move knees)
4 Detectable weakness of hip flexion while supine (full flexion of knees)
5 No detectable weakness of hip flexion while supine
6 Able to perform partial knee bend
PDPH kids v adults
In children,
the incidence of PDPH is less than for adults.
Sympathetic block
HD changes
Sympathetic blockade is better
tolerated in infants,
and changes in
heart rate and blood pressure are rare.
Preloading in infants
Preloading is rarely required in infants prior to spinal blockade
Is spinal in prem a relative C/I
Spinal anaesthesia is
preferred in preterm infants,
as it reduces but
does not eliminate the risk of post-operative apnea
Spinal anaesthesia and post op apnoea in prem eliminated
reduces but
does not eliminate the risk of post-operative apnea
Relative contraindications to spinal anaesthesia in paeds
Relative contraindications to spinal anaesthesia include
coagulation abnormalities,
local infection,
raised intracranial pressure,
degenerative neurological disease,
refusal by parents and
presence of ventriculoperitoneal shunts.
Scalene approach in paeds
Parascalene approach is preferred
over interscalene in children to
reduce risk of complications
In parascalene approach
whats blocked
In parascalene approach,
roots and trunks of brachial plexus are blocked.
Needle approach
In parascalene approach
The needle is inserted at the
junction of upper two thirds
and lower one third of an imaginary
line drawn from C6 to the midpoint of
clavicle.
Commonest BP block approach in paeds
Axillary block is the most common approach to brachial plexus
block in the paediatric population
change in complication in paeds given performed under GA
Despite performance of blocks under general anaesthetic, the incidence
of complications is not increased
