Over the past fifteen years, there has been considerable progress in studies of neonatal and pediatric analgesia. Until recently, it was widely held that infants did not have the cortical maturation to experience pain. It is now quite clear that the development of the physiologic mechanism and pathways for pain perception take place during late fetal and neonatal life.

The following examples can be used to demonstrate the pain response of neonates.

• Premature infants show metabolic stress responses post operatively that can be blocked by intravenous opioids.
• The increasing crying and behavioral changes occur for days after circumcision can be blocked with the use of regional anesthesia.

Pain Measurement in Pediatric Patients

Most clinicians agree that in caring pediatric pain patients the most difficult task is to obtaining an objective, quantitative, and accurate measurement of pain in children. Currently, most methods available are not applicable to all pediatric age groups and none has been accepted universally.

Methods for measuring pain in children can be divided into three categories:

1. Self reported measures of pain. This include routine questions, verbal scales, numeric scales and pictorial scales.
2. Behavioral measures of pain. This include motor responses, facial expressions, crying and complex behavioral responses such as the sleep-wake patterns.
3. Physiologic measures of pain. This include changes of pulse rate and blood pressure as well as measurement of palmar sweating.

Pharmacological Considerations

In order for clinicians to master pharmacological management of pain in children, the initial step is to understand the general principles of pediatric, especially newborn, physiology and its effects on the pharmacology of medications.

Some important points are summarized below:

• Neonates have delayed maturation of liver enzyme systems which involved in drug metabolism.
• Children have a higher percentage of body weight as water and less as fat. Dosages of water soluble drugs vs. fat soluble drugs should be adjusted.
• Children have reduced plasma albumin. This results in a greater availability of active drugs and increased risk for toxicity.
• Neonates have immature blood brain barriers. This means that there is increased medication passages into the brain.
• Neonates have diminished ventilatory responses to decreased oxygen contents in the blood.

Pharmacological Management

Non Opioid Analgesics

The usage of acetaminophen, salicylates and the nonsteriodal anti-inflammatory agents in children, except in neonates, are not much different than in adults. Among these, IV Ketorolac has shown good results in relieving pain for children who undergone orthopedic surgery.

Opioid Analgesics

Opioids are used for treatment of pain in patients of all ages. If dosing correctly, for the vast majority of children, opioids produce excellent analgesia. Opioids can be administered by different routes, including orally, intravenously, rectally, transdermally or transmucosally. It is important to avoid intramuscular or subcutaneous injections for pediatric patients. Most opioids are available in elixir form, and can be easily administered to children who are not able to swallow pills. Recently, fentanyl patch and "fentanyl lollipop" have gained their popularity in children for treatment of cancer pain.

Antidepressants

Beside opioids, antidepressants have been used as an adjuvant treatment of chronic pain syndromes, especially in treating headaches and neuropathic pain. The mechanism of actions is thought to be related to their effects on serotonin and norepinephrine, critical pain neurotransmitters. For children who are not able to ingest pills, nortriptyline (a tricyclic antidepressant) in a solution form can be prescribed. The antidepressant is usually prescribed as a once a day at bed time medication.

Patient-Controlled Analgesia

PCA in now a widely used method of providing postoperative pain relief. Children as young as seven years of age can independently use the PCA pump to provide pain relief. Children between age of four and six, may able to use PCA with parental or nursing assistance. This means that nurses or parents communicate with the child and jointly decide whether the pain is severe enough to push the button. Parents and nurses should not press the button for the child. The important factor for successful PCA treatments is the child's ability to understand the concept of patient controlled pain relief.

Epidural Analgesia

For patients whose pain is not able to be controlled or experiencing side effects by the conventional methods, epidural analgesia may provide excellent pain relief. It is important to remember that before performing a regional block in a child, attention must be paid to the psychological preparation of the child and the parents. Most children will be much more cooperative if they know exactly how the block is performed and what to expect after the procedure.

Psychiatric and Psychological Evaluation and Treatment

Lastly, it is important to remember that depression and other affective disorders may occur in children of all ages with chronic pain. Depression in children is often underdiagnosed. Psychiatric or psychological consultation and family therapy should be readily available as part of the multidisciplinary pain treatment program for children and adolescents.