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I.
Introduction
Traditionally, pain in children is a topic that has received
only minimal attention.
Much
of our understanding of pain in children has been extrapolated
from adult studies.
As
recently as 20 years ago clinicians felt that it was unnecessary
to prevent or treat pain in children because the prevailing
opinion was that:
1)
the peripheral nerves of neonates and infants were poorly
myelinized and
2)
they don't have the cortical maturation to experience
pain
The
classic example of this way of thinking is demonstrated
by the Liverpool technique for neonatal anesthesia which
utilized nitrous oxide plus muscle relaxant w/o supplemental
volatile agent or narcotic.
In 1983 Mather & Marker conducted a landmark study of
post-op pain in children:
1) The study involved 2 hospitals in Australia; a children's
hospital and a University hospital.
2) In 16% of the patients analgesics were not ordered
post-op.
3)
Narcotics that were ordered prn were not given @ all 39%
of the time.
4)
Only 25% of patients were pain free on the day of surgery.
5) 40% had moderate to severe pain.
The
authors concluded that there was marked variability in
the prescribing habits of the medical staff, that doses
were too small and infrequent, and the medical and nursing
staff did not take full advantage of the drugs available.
We
now realize that the mechanisms & pathways for pain perception
are intact during late fetal and neonatal life. In fact
as early as the 7th week of gestation cutaneous sensory
perception appears in the perioral area. In the newborn
infant pain perception can be traced from sensory receptors
in the skin to the cerebral cortex.
An
"Established Pain Response" has been described to occur
in neonates who have undergone procedures such as circumcision
& heel lancing without anesthesia or analgesia.
Note:
1) I.V. opiates can block the post-op metabolic stress
response in preemies.
2) Regional anesthesia can decrease the crying that occurs
after circumcision.
3) Repeated heel lances can sensitize the patient and
cause a hyperalgesic response.
Fortunately
over the past decade considerable progress has been made
in the field of neonatal & pediatric pharmacology. Multi-disciplinary
pain teams are being developed. Modalities such as PCA,
epidural blockade, & regional blockade are being applied.
The
concept of pre-emtive analgesia may be very important
in diminishing post- operative pain in children.
Following
a painful injury (eg. surgical incision) peripheral nociceptors
are sensitized (primary hyperalgesia). This can result
in central sensitization of dorsal horn cells. Altered
central processing of nociceptive input can prolong post-operative
pain. Blocking the noxious input prior to surgery as opposed
to after their surgery prevents central sensitization.
Thus the rationale for pre- emptive analgesia. This concept
is well supported in the literature.
II
Pain Assessment in children:
"Pain is a unique, highly subjective multidimensional
experience encompassing many sensory & affective components".
Its objective measurement can be very difficult. In adults
behavioral signs can be colored by cultural background,
emotional status & psychological status. In children,
particularly those under 6 years of age, pain assessment
is particularly difficult.
A) The Visual Analogue Scale(VAS) is useful in
children older than 6-7 years of age
| No
pain |
Worst
possible pain |
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The patient is presented with a 10 cm line, labeled as
above, and asked to mark an `X' on the line indicating
the intensity of their pain. The result is then measured
with a metric ruler and scored between 0 - 10.
B)
The Numerical Rating Score (NRS) is similar to the
VAS with the addition of the numbers 0 through 10 spaced
along the line. This can be used with children who understand
the concept of numbers. (Approximately ages 5-6)
C)
The Oucher Scale (AKA Faces Rating Scale or Smiley Analogue
Scale) depicts a range of numbered faces that the
child can relate to. This scale can be used in all verbal
children. As young as ages 3-5.
D)
The Poker Chip Scale quantitates the child's pain
by the number of chips (0-4) he/she/ selects, "pieces
of hurt".
E)
Analogue Chromatic Continuous Scale(ACCS) This system
potentially is useful for children as young as 3 years
old. Children tend to associate red & black with increased
pain sensation. (The back is ruled for easy scoring)
F)
Body Outlines is a useful tool that allows children
to color the area that hurts. Coloring is a favorite pastime
for children. They tend to associate blue with cold and
red with hot. What color is pain?
IN
CHILDREN WHO ARE UNABLE TO VERBALLY REPORT THEIR PAIN
INTENSITY BEHAVIORAL SCALES HAVE BEEN DEVISED.
G)
The Children's Hospital of Eastern Ontario Pain Scale
(CHEOPS): is based on observation of child behavior
by physicians or nurse. The scale assigns a point score
to 6 categories of behavior and the total score is supposed
to correlate with pain. Its not too reliable. Note: crying
can be caused by pain, hunger, frustration, restraints
or anxiety.
H)
The objective pain scale combines physiologic and
behavioral parameters . The ability to calm the child
is important when using this scale.
III. Management of Acute Pain in Children
A) Behavioral Considerations:
-
Guided Imagery
-
Distraction
-
Being held or rocked.
B)
Pharmacological management:
Remember:
1)
In neonates and preemies (especially) the enzyme systems
involved in drug metabolism are immature.
2)
GFR is decreased in first week of life.
3)
Neonates have a larger % of their body wt as water.
4) Neonates have decreased plasma concentration of albumin
and alpha - glycoprotein.
5)
Brain and viscera account for disproportionate amount
of body mass in neonates.
6) Neonates (particularly preemies) have decreased ventilatory
responses to hypoxia & hypercarbia).
1) Non -opiod Analgesics
A) APAP(acetaminophen) is probably the most popular. Immaturity
of the newborn hepatic enzymes serves to be protective.
B)
Acetylsalicylic Acid (ASA) continues to be useful in children
with mild to moderate pain of inflammatory origin (e.g.
JRA). Concerns:
Reyes Syndrome GI side effects, platelet dysfunction.
C)
Ibuprofen is available in liquid form. (Pediaprofen. 100
mg/5ml) useful for treatment of JRA. Concerns: Renal compromise,
& bleeding diathesis are contraindications.
D)
Indomethacin - I.V. use to promote closure of PDA
E) Choline Mg Trisalicylate (Trilisate) is a long acting
non-acetylated salisylate with less GI upset and platelet
dysfunction.
F)
Ketololac is available p.o. IM I.V. Side effects include
nausea, GI bleed platelets dysfunction, and interstial
nephritis.
2)
Opiod Analgesics:
An
understanding of opiate pharmakinetics in the neonate
is important. Because hepatic enzymes take time to mature
(3-6months) theT½ of morphine is twice as long in the
neonate as in the adult. Morphine is metabolized into
morphine -3-glucuronide (inactive) and morphine-6-glucuronide
(active) Infants with:
1)
Gastroschisis have even further decrease
2)
Omphalocele in opiod clearing secondary to decreased
3)
Intestinal malrotation . hepatic blood flow
Children
with myelomeningocele may present post-op after urologic
or lower extremity orthopedic procedure. The dermatomal
level of the procedure can be near their sensory level.
If they have Type I Arnold Chiari Malformation this makes
them particularly sensitive to the respiratory depression
effects of narcotics. In this situation a continuous infusion
of narcotics is inappropriate (_ risk of respiratory depression).
Use
of a PCA is OK if the child is older than 7 years of age.
A)
Intermittent boluses of narcotic on demand is probably
the best course to take. This should be administered IV
and not I.M. Chldren in pain may prefer pain to the "shot"
( and they'll under report their pain).
Intravenous morphine @ 30-100 mcg/kg q 1-2h is an appropriate
but labor intensive approach to this situation. A useful
alternative would be to use IV methadone since its longer
elimination T½ allows less frequent dosing. Start with
a L.D. of 50mcg/kg q 10 minutes in the recovery room then
use a "reverse prn" sliding scale to maintain comfort.
B)
Continuous opiod infusions: via the IV route can be
useful in the ventilated patient, the very young, or in
patients with cognitive or physical handicaps that preclude
use of a PCA. This approach is pharmacologically elegant
in that it maintains steady state blood levels of drug.
Morphine:
Bolus or Loading dose: 50-100 mcg/kg (25-50mcg/kg
q 10 min.)
Maintenance
infusion: 10-15 mcg/kg/hr < 3-6 months If > 6 months
of age: 25-30mcg/kg/hr
Fentanyl:
Bolus or Loading dose: 0.5-1 mcg/kg
Maintenance infusion: 0.5-1 mcg/kg/hr
C)
Patient Controlled Analgesia (PCA)
Following appropriate pre-operative teaching children
as young as seven years of age can learn to use a PCA
pump. Occasionally there is a particularly bright 5 or
6 year old that also makes a good candidate.Parent
Controlled analgesia should be discouraged since it circumvents
the internal safeguard of PCA. Some centers, however,
encourage a parent controlled analgesia in children with
chronic pain from Cancer or Acquired Immunodeficiency
Syndrome.
Parent
Assisted Analgesia is a compromise where by both parent
and child decides on appropriatness of using the PCA Device.
Typical
MSO4 Dosing regimen: Increment 20-30 mcg/kg
Lockout
7 min
basal.
15 mcg/kg/hr.
_________________
4hr limit 300 mcg/kg
Use
of a background infusion is controversial. It might provide
better analgesic during sleep but this is not supported
by the literature. It may also _ risk the of respiratory
depression. Addition of a NSAID (e.g.Ketorolac) can preclude
use of a basal infusion. Many oncology patients, with
prior opioid use, appear to benefit from a basal rate.
Side
Effects
Nausea, vomiting and urinary retention appear to be no
more frequent with PCA than with IM narcotics. Respiratory
depression is rare except when combined with other sedating
drugs.
D).
Epidural Analgesia
". . . the pediatric anatomy seems to have been designed
with regional techniques in mind. For example what other
purpose has anyone found for the sacral hiatus except
for easy access to the pediatric epidural space by anesthesiologists."
The
epidural space can be approached at any level but the
caudal and lumbar approach are the most popular in children.
It
is possible in infants (not preemies) to successfully
thread a lumbar a caudal catheter rostrally to a thoracic
level.
Note
- in spite of concerns about soilage of caudal catheters
this has not been a problem. They do, however, require
meticulous care & should be dressed with occlusive dressings.
When
placing a catheter using LOR technique use saline. Use
of air runs the risk of a paradoxical air embolism in
infants with patient foramen ovale.
Epidural
Dosing:
Morphine 30-50 mcg/kg q 6-12 h Hydomorphone is approximately
5 times as potent (pruritis appears to be less of a problem
with hydomorphone)
Recommended
Dosing for Post-op Epidural Infusion:
Bupivacaine 0.1%, with fentanyl 2 mcg/ml. Run at 0.3 ml/kg/hr
Bupivacaine Dosing (upper limit): Bolus: 2-2.5 mg/kg
Infusion:
0.4mg/kg/hr Infants <2 months of age: .25 - .3 mg/kg/hr.
Side
Effects (rare):
1)
seizure
2) cardiac arrest 1:40,000 from local anesthetic
3) pruritis
4) nausea
5) Respiratory Depression _liklihood with
A)
additional systemic narcotics
B)
high catheters
C)
age less than 6 months
D) preemies < 60weeks gestational age
e)
Single injection Regional techniques:
Caudal block
Penile block
Ilioinguinal Iliohypogastric block:
Fascia iliaca block:
f) Other approaches:
1) SQ administration of opioids
2) Transderm fentanyl
3) EMLA Cream
4) Nasal, p.r., p.o. IV
Concluding
Comments
Multiple
opportunities exist along the pain pathways to modulate
and attenuate the pain response intra-op & post-op.
Morphine
can exert its affects, peripherally, spinally & supraspinally.
NSAID's, antihistamines, and serotonin antagonists can
be important in attenuating hyperalgesia.
Regional anesthesia with local anesthetic can ameliorate
the surgical stress response. Epidural analgesia may decrease
the incidence of postsurgicial morbidity and mortality.
Thoracic level epidural anesthesia/analgesia may be the
ideal way to effectively treat post-thoracotomy & post
abdominal surgery pain.
Epidural
opioids probably provide superior analgesia and therefore
probably decreased post-op pulmonary and cardiac complications,
but further studies are needed to confirm this. Epidural
analgesia with local anesthetics can improve post-op GI
function and decrease paralytic ileus time. Epidural opioids,
however decrease GI propulsion motility and can cause
nausea, and vomiting. The secret is to use combined therapy
in a pre-emptive way to decrease post-op pain and prevent
the occurrence of chronic pain.
Copyright
© 2000, Steven Richeimer, MD.
You may reach The Richeimer Pain Institute at www.helpforpain.com
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