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Dr. Steven Richeimer

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

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.

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Dr. Steven Richeimer is the Director of the University of Southern California Pain Center. He has triple board certifications in Psychiatry, Anesthesiology, and Pain Management.

See Dr. Steven Richeimer's Listing on Experts.com.

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