Download ANATOMIC AND PHYSIOLOGIC DIFFERENCES

Mansour Choubsaz MD
Kums.ac.ir
Barriers to Pediatric Pain Control
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Belief that children, especially infants, do not feel
pain the way adults do
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Lack of routine pain assessment
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Lack of knowledge in pain treatment
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Fear of adverse effects of analgesics, especially
respiratory depression and addiction
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Belief that preventing pain in children takes too
much time and effort
Background
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Historically children and infants received less postoperative analgesia than adults
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children are often undertreated for pain Specifically in
neonates:
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neonates can experience pain by 26 weeks of
gestation
•
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Mature afferent pain transmission
Untreated pain in neonates lead to increased
distress and altered pain response in the future
5 General Principles of
Pain Management
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Anticipate & prevent pain
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Adequately assess pain
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Use multi-modal approach
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Involve parents
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Use non-noxious routes
Assessment in Neonates &
Infants
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Challenging
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Combines physiologic and behavioral parameters
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Many scales available
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NIPS (Neonatal Infant Pain Scale)
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FLACC scale (Face, Legs, Activity, Cry
Consolability)
ANATOMIC AND PHYSIOLOGIC
DIFFERENCES
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Total body water represents about 80% of body
weight in full-term newborns. This drops to 60%
of body weight by 2 years of age,
The larger extracellular and total
body water in infancy lead to a:
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greater volume of distribution for water-soluble
drugs.
Cardiac output is relatively higher in infants and
children than adults
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is preferentially distributed to vessel rich tissues
such as the brain
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allowing for rapid equilibration of drug
concentrations.
Immaturity of the blood–brain
barrier in early infancy
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increased passage of
more water-soluble
medications such as
morphine
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This combination of increased blood flow to the brain
and increased drug passage through the blood–brain
barrier can lead to:
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higher central nervous system drug concentrations
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more side effects at a lower plasma
concentration.
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Both the quantity and binding ability of serum
albumin and a-1 acid glycoprotein (AAG) are
decreased in newborns relative to adults.
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This may result in higher levels of unbound drug,
with greater drug effect and toxicity at lower overall
serum levels.
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This has led to lower local anesthetic dosing
recommendations in neonates and young infants,
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although neonates have shown the ability to
acutely increase AAG levels while on
continuous local anesthetic infusions.
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The difference in serum protein quantity and
binding ability disappears by approximately 6
months of age.
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Neurotransmitters and peripheral and central
pathways necessary for pain transmission are
intact and functional by late gestation
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opiate receptors may function differently in the
newborn than in adults
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Cardiorespiratory, hormonal, and metabolic
responses to pain in adults have also been well
documented to occur in neonates
The spinal cord and Dura mater in the newborn
and infant
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extend to approximately the third lumbar (L3)
and third sacral (S3) vertebral level
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reach the adult levels of approximately L1 and
S1 to S2 by about 1 year of age.
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The lower-lying spinal cord in young infants is
thus theoretically more vulnerable to injury
during needle insertion at mid- to upper-lumbar
levels. .
ANATOMIC AND PHYSIOLOGIC
DIFFERENCES
•
The intercristal line connecting the posterior
superior iliac crests, used as a surface landmark
during needle insertion, crosses the spinal
column at the S1 level in neonates versus the
L4 or L5 level in adults.
There is less and more loosely connected fat in
the epidural space in infants versus adults
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explaining in part the relative ease with which
epidural catheters inserted at the base of the
sacrum can be threaded to lumbar or thoracic
levels in infants and small children.
pediatric patient may be unable or unwilling to
verbalize or quantify pain
a number of developmentally appropriate pain
assessment scales have been designed for use in
both infants and children
. They are based on :
self-report
behavioral and/or physiologic measures
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Children over approximately 8 to 10 years of
age may be able to use the standard adult
numeric rating or visual analog scale to selfreport their pain.
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Specialized self-reporting scales can be used in
patients as young as 3 years of age
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Behavioral or physiologic measures are
available for younger ages and for
developmentally disabled
Children between 3-8 years
• Usually have a word for pain
• Can articulate more detail about the
presence and location of pain; less able
to comment on quality or intensity
• Examples:
– Color scales
– Faces scales
NONOPIOID ANALGESICS
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Acetaminophen (paracetamol) is very commonly used in
pediatric patients, alone or in combination with other
analgesics.
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It is often administered rectally in the perioperative
period in infants or children for whom oral intake is not
an option.
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higher dosing, at least initially, is needed if given rectally
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Suppository insertion prior to surgical incision does not
appear to significantly alter acetaminophen kinetics and
may result in more timely analgesia in the early
postoperative period.
Higher-dose rectal acetaminophen
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has been shown to be equianalgesic to
intravenous ketorolac following tonsillectomy
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to have a significant opioid-sparing effect in
children undergoing outpatient surgery.
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An intravenous form of acetaminophen is also
available
Acetaminophen dosing in premature and
term neonates is less well defined
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overall elimination in small studies is similar
between neonates, children and adults.
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Dose-dependent hepatotoxicity is the most
serious acute side effect of acetaminophen
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Acute hepatotoxicity appears to be less
common and less likely to be fatal in children
than adults.
NONSTEROIDAL ANTI-INFLAMMATORY
DRUGS
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widely administered to children.
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reduced postoperative pain scores
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decreased supplemental analgesic requirements
Intravenous ketorolac is used widely in
children, with a generally good safety record.
The clinical significance of NSAID effects
on bleeding remains controversial
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avoidance by some in procedures such as
tonsillectomy.
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Bleeding, renal damage, and gastritis are more likely
to occur with :
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prolonged administration
in the presence of coexisting disease.
•
•
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Acetaminophen and NSAIDs are often given in
combination
they work by different mechanisms
their toxicity does not appear to be additive.
Aspirin is not used for postoperative
pain management in infants and children
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highly significant association with Reye
syndrome.
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Reye syndrome is an acute, fulminant, and
potentially fatal hepatoencephalopathy
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occurs in children with influenza-like illness or
varicella who ingest aspirin-containing
medications.
OPIOID ANALGESIA
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Oral, parenteral, and epidural opioids are widely
employed in infants and children
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Codeine is given orally in a dose of 0.5 to 1
mg/kg and often in combination with
acetaminophen
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More potent oral opioids commonly administered
to adults are also used
PATIENT-CONTROLLED
ANALGESIA
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used in children as young as 5 to 6 years of age
with morphine the most commonly used
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hydromorphone and fentanyl more commonly used
alternatives
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Compared to PRN intramuscular opioids, PCA has
been shown to be safe in children and provide
more effective analgesia
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A low-dose continuous or “background” infusion
is sometimes added for patients following major
surgery to optimize analgesia.
PARENT/NURSE-ASSISTED ANALGESIA
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The concept of PCA has been expanded to
allow parent- or nurse-assisted analgesia in
select cases in which the patient is unwilling or
unable, because of age, developmental delay, or
physical disability, to operate the PCA button.
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used with caution as it does away with one of
the safety features of PCA, in that the patient
is theoretically less likely to self-overdose.
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More recently the concept of parent- or nurseassisted epidural analgesia has been introduced
to optimize dosing flexibility and pain relief given
via the epidural route
Compared to adults given morphine, neonates
and premature infants have a :
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longer elimination half-life
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lower plasma clearance
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marked interindividual variability in plasma
morphine concentration.
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achieve a higher plasma concentration for a
longer duration
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By approximately 6 to 12 months of age, the
kinetics of morphine and fentanyl approach
adult values
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children soon thereafter demonstrate increased
plasma clearance and a shorter elimination halflife
“SINGLE-SHOT” CAUDALS
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One of the most widely used pediatric regional
techniques
palpable landmarks
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ease of caudal block insertion in infants and children
versus adults.
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SSC is used in infants and children up to approximately
10 to 12 years of age having surgery from lumbosacral
to midthoracic
“SINGLE-SHOT” CAUDALS
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Bupivacaine in concentrations of 0.125% to
0.25% is the most commonly used
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volumes of 0.5 to 1.5 ml/kg will provide upperlumbar to low-thoracic levels, respectively
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An upper volume limit of 20 ml is generally
used.
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The maximum recommended bupivacaine dose is 2.5
to 3.0 mg/kg, with an upper limit of 1.25 mg/kg
recommended in early infancy It is unclear whether
block placement at the beginning versus the end of
the procedure prolongs postoperative analgesia.
test dose
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0.1 ml/kg (maximum 3 ml) of local anesthetic with
1:200,000 epinephrine (5 mg/kg) is used to ensure
correct needle or catheter position.
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A 25% increase in T-wave amplitude
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10-beat/min increase in heart rate
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10% increase in systolic blood pressure within 60 s
of administration
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considered a positive test dose
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It is unclear whether block placement at the
beginning versus the end of the procedure prolongs
postoperative analgesia
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procedure prolongs postoperative analgesia.
Although usually used alone, bupivacaine can
be combined epidurally with fentanyl, morphine,
the a-2-adrenergic agonist clonidine, or other
additives to prolong the duration and/ or density
of analgesia.
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Delayed respiratory depression up to 22 hr can
occur with epidural morphine.
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Greater risk is seen in children less than 1
year of age and when parenteral opioids have
also been given.
CONTINUOUS EPIDURAL INFUSIONS
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Epidural local anesthetic infusions with or without
opioids or a-2-agonists have been used in
infants and children for postoperative analgesia
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. Lower infusion rates are generally
recommended in neonates and infants less than
3 to 6 months old
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As a rule, optimal analgesia is obtained with the
catheter tip positioned at or near the
dermatomes to be blocked.
CONTINUOUS EPIDURAL INFUSIONS
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It is possible in infants and smaller children to
thread caudally inserted catheters to lumbar or
thoracic levels.
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Catheter insertion may take place following
induction of general anesthesia in infants and
children
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Patient-controlled epidural analgesia has been
successively used in children as young as 5
years of age.
Peripheral and truncal nerve blocks
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play an increasing role in pediatric postoperative pain relief
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These are typically performed under general anesthesia and
increasingly with the use of ultrasound guidance.
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Ilioinguinal / iliohypogastric, rectus sheath, transverse
abdominus plane, head and neck, and upper and lower
extremity blocks are being done more frequently to provide
analgesia in suitable candidates