Postoperative Pain in Children
Lucy L. Chen
Jane C. Ballantyne
Charm ache with air, and agony with words.
—William Shakespeare, 1564–1616
It has only been over the last two decades that pain relief in children has become an area of major concern. Recent research clearly shows that neonates and infants are in fact sensitive to pain and that pain elicits physiologic, sometimes deleterious responses in them in much the same way as adults. Moreover, such research shows that traumatic pain experiences can psychologically scar young children and make them fearful for a long time because they are not mature enough to be able to rationalize their experiences.
There are many differences between adults and children that make pain treatment in children a particular challenge: (a) it is not as easy to assess pain in children as it is in adults; (b) children, particularly neonates and infants, do not metabolize drugs as well as adults; (c) children hate needles; (d) epidural catheters are technically more difficult to place and more difficult to maintain in children; and (e) the sight of a child in pain is particularly distressing, especially to the parents. This chapter discusses general issues about postoperative pain management in children.
I. PLANNING FOR POSTOPERATIVE ANALGESIA
The intraoperative and postoperative anesthesia and analgesia plan should be made before the surgery. Children and their parents should be told honestly what to expect and be reassured that everything will be done to alleviate any pain or discomfort. It is often helpful to find out how the child copes with pain and distress, how he or she communicates pain (e.g., “boo–boo,” “hurt,” “sore”), and whether the child relies on special blankets, toys, or other means for comfort and reassurance. If the child has had surgery before, then the following questions apply:
What was the past pain experience of the child?
What medications were used in the past, and did they work well?
Were nonpharmacologic techniques used and did they work well?
What coping techniques were beneficial?
If patient-controlled analgesia (PCA) is used, it is helpful to teach the child and the parents the principles of PCA or to explain regional anesthetic techniques if they are chosen. The parents and child should be intimately involved in the evaluation, management, and decision making whenever possible.
II. ASSESSING ACUTE PAIN IN INFANTS AND CHILDREN
Pain assessment is the key to effective pain management. Consistent assessment must occur regularly and the same scale and format must be used for each assessment so as not to confuse the child or parents. In neonates and infants, clinical judgment alone is often used, whereas simple assessment tools are useful in older children. Broadly, there are three stages of a child’s development, each of which requires a different means of pain assessment.
1. Infants, Neonates, and Children Aged 4 Years and Younger
Infants and neonates clearly cannot report their pain. However, children as young as 18 months can indicate their pain and give a location, although they cannot specify pain intensity before about 3 years of age. At the age of 3 years, they can give a gross indication, such as “no pain,” “a little pain,” or “a lot of pain,” but their reports are not always reliable. The parents’ impression is often the best indicator in these very young patients. Nurses and doctors need to listen to the parents, as well as use objective measures of pain. The following behavioral and physiologic responses can be used as a measure of pain in young children, particularly those who are noncommunicating, although the signs may not be specific to pain:
Crying, screaming, moaning, whimpering
Facial expression (e.g., grimacing, furrowed brow)
Posture, tone, guarding, thrashing, touching painful area
Palmar sweating
Sleep pattern
Respiratory rate and pattern
Heart rate and blood pressure
Several systematic and validated measurement tools could be used, such as CRIES (developed by Krechel and Bildner in 1995), that utilize various combinations of physiologic and behavioral indicators of pain, although their use is not often warranted in cases of acute pain. The principles of pain assessment in very young children and issues of the nervous system and cognitive development are described in Chapter 33.
2. Children Aged 4 to 8 Years
Assuming that the young children (from 4 years to 8 years) have normal development, they can provide reliable self-reports of pain using assessment tools designed for young children, such as the FACES pain-rating scale (see Chapter 6, Fig. 1), by communicating through their parents, or through direct communication with doctors and nurses. Simple numeric scales using age-appropriate language may be helpful at the upper end of this age range.
3. Children Older Than 7 Years
Children older than 7 years who understand the concept of numeric order can use verbal numeric scales or visual analog scales such as those used in adults (see Chapter 6).
III. TREATMENT CHOICES
When choosing treatment options for both procedural and postoperative pain for children, the following considerations should be kept in mind:
Drug conjugation in the liver is the predominant method of metabolism for most analgesics. Neonates, having an immature cytochrome P450 system, will conjugate drugs slowly.
Renal clearance of drugs and their metabolites is usually adequate at 2 weeks after birth. Before this, the clearance of many drugs may be delayed, necessitating an increase in dosing intervals.
Because of the increase in total body water concentration in neonates, water-soluble drugs have a larger volume of distribution.
Neonates have less plasma protein binding, resulting in increased free drug concentration.
In general, these pharmacokinetic factors mean that lower per-kilogram doses are needed in neonates and infants, but sometimes at increased dosing intervals. However, the effects of immaturity are complex and some drugs may actually be needed in larger doses because of differences in drug sensitivity and distribution. There is no substitute for using pediatric drug tables when prescribing drugs for young children.
1. Acetaminophen and Nonsteroidal Antiinflammatory Drugs
Acetaminophen and nonsteroidal antiinflammatory drugs (NSAIDs) are effective for mild to moderate pain or as adjuncts to opioid and regional analgesia. Such drugs offer the advantages of not being associated with respiratory depression and being relatively free of side effects. Pediatric dosing for these drugs is presented in Table 1.
(i) Acetaminophen
Acetaminophen has only minimal antiinflammatory effects because its effects are mainly central. In patients who have a history of asthma or an increased risk of gastrointestinal (GI) mucosal insult or renal insufficiency, acetaminophen is favored over NSAIDs. Acetaminophen is available in many formulations, including tablets, capsules, syrups, suspensions, and suppositories. It is also included in many compound analgesics (Tylenol no. 3, Percocet, Vicodin, Ultracet, etc.). The intravenous (IV) form of acetaminophen (Paracetamol) is available in Europe but not in the United States. Rapid absorption without first-pass liver metabolism makes the rectal route useful in children.
(ii) Nonsteroidal Antiinflammatory Drugs
Currently used NSAIDs do not cross the blood–brain barrier in appreciable amounts; therefore their effects are mainly peripheral.
The use of NSAIDs is associated with well-recognized side effects including gastritis, possible GI bleeding, platelet dysfunction, and renal dysfunction. These side effects limit their use after major surgery and in certain patients (e.g., those with renal disease or coagulopathies).
The use of NSAIDs is associated with well-recognized side effects including gastritis, possible GI bleeding, platelet dysfunction, and renal dysfunction. These side effects limit their use after major surgery and in certain patients (e.g., those with renal disease or coagulopathies).
Table 1. Pediatric dosing of commonly used nonsteroidal antiinflammatory drugs (NSAIDs) and acetaminophen | |||||||||||||||||||||
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Aspirin (acetylsalicylic acid) currently has very limited use in children and in infants because of its recognized association with Reye syndrome. The most widely used NSAID is ibuprofen, available in a number of formulations including an oral suspension and chewable tablets appropriate for use in children and infants. Dosages of 5 to 10 mg per kg every 4 hours up to a daily maximum of 40 mg per kg may be used either as needed or preferably around the clock for 48 to 72 hours. Other NSAIDs used in the treatment of children include naproxen, indomethacin, tolmetin, diclofenac, ketoprofen, and ketorolac. Of these, only ketorolac, at doses up to 0.5 mg per kg, is approved in the United States for parenteral and oral administration for the treatment of pain. Ketorolac can be useful for treating postoperative pain when the oral route cannot be used, when opioids are poorly tolerated, or when additional analgesia is needed. IV indomethacin is used to
treat patent ductus arteriosus but has virtually no application in the treatment of pain. Indomethacin suppositories may be useful occasionally.
treat patent ductus arteriosus but has virtually no application in the treatment of pain. Indomethacin suppositories may be useful occasionally.
The newer selective cyclooxygenase (COX-2) inhibitors are less likely to cause GI side effects because they selectively inhibit the inducible COX-2, sparing the constitutive enzyme (COX-1), particularly in the GI tract. They may be useful as an alternative to standard NSAIDs when there is concern about the GI effects from NSAIDs, although studies regarding the use of these drugs in children and infants have not yet been completed.
2. Opioids
Opioids are the most commonly prescribed analgesics and are potent and effective in the treatment of moderate to severe pain. These drugs are fully described in Chapter 9. Opioids can be used safely in children with appropriate monitoring, dosing regimens, and techniques of administration.
(i) Pharmacokinetics
Opioids are metabolized differently in children at different ages. In newborns and infants, the pharmacokinetic factors described in the preceding text indicate that lower per-kilogram doses are needed than in older children, although the larger volume of distribution of these drugs may mean that a relatively large loading dose (given under controlled conditions) may be needed. Neonates and premature infants are extremely sensitive to the respiratory depressant effects of opioids, and respiratory depression may occur at doses that do not even produce analgesia. Infants are also at an increased risk of apnea following a rapid bolus dose because of the rapid peak dose to the brain. The half-life of morphine in neonates is 6 to 8 hours and about 10 hours in premature infants (compared to 2 hours in adults), necessitating markedly lower infusion rates than in older individuals. As children grow, morphine clearance rapidly approaches the adult level, and in adolescents it is actually greater than that in adults. Recommended opioid doses for children are presented in Table 2.
Table 2. Recommended starting doses for opioids in children weighing <50 kg | |||||||||||||||||||||||||||
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