22 Postoperative Pain in Children

22 Postoperative Pain in Children
The Massachusetts General Hospital Handbook of Pain Management

Postoperative Pain in Children

William T. Denman and Jane Ballantyne

Charm ache with air and agony with words.
—William Shakespeare (1564–1616)

I. Planning for postoperative analgesia
II. Assessing acute pain in infants and children
III. Treatment choices

1. Acetaminophen and the nonsteroidal anti-inflammatory drugs

2. Opioids

3. Regional anesthesia and analgesia

4. Nonpharmacologic techniques
IV. Conclusion
Selected Reading

It has been only over the last two decades that pain relief in children has become an area of major concern. As an example of this, in a paper published in 1976, the anesthesia technique for ligation of patent ductus arteriosus was oxygen and muscle relaxants. Major strides have been made over the last 10 years in assessment, monitoring, and therapy. Pain services have been developed to deal with the special issues surrounding postoperative analgesia in infants and children. Why has pain relief been denied to children for so long? The reasons are multifactorial: neonates and young infants were presumed to be insensitive to pain, children heal quickly, caregivers have had a fear of prescribing opioid analgesia to children for a variety of reasons.
Recent research shows clearly that neonates and infants are in fact sensitive to pain and mount physiologic, sometimes deleterious, responses in much the same way as adults. Moreover, it shows that traumatic pain experiences can scar young children and make them fearful for a long time because they are not mature enough to be able to rationalize their experience.
There are many differences between adults and children that make pain treatment in children a particular challenge. It is not as easy to assess pain in children. Children, particularly neonates and infants, do not handle drugs as well as adults. Children hate needles. Epidurals are technically more difficult to place and more difficult to maintain. And the sight of a child in pain is particularly distressing, especially to the parents.
The intraoperative and postoperative courses and the postoperative analgesia plan cannot be viewed separately. Planning for postoperative analgesia should begin prior to surgery and involves choosing an anesthetic that provides postoperative as well as intraoperative analgesia, and preparing the child and parents for the surgical experience.
Children should be told honestly what to expect, and they should be reassured that they will be cared for and everything will be done to alleviate any pain or discomfort. This reassurance is also of great importance to parents.
It is often helpful to ask how the child copes with pain and distress, and how he or she communicates pain. For example, what words are used to describe pain (e.g., “boo-boo,” “hurt,” “sore”), and does the child rely on special blankets or toys? If the child has had surgery before, the parents and child should be questioned about the previous experience:

What medications were used in the past and did they work well?

What was the past pain experience of the child?

Were nonpharmacologic techniques used?

What has worked well in the past?

What coping techniques were beneficial?
Choosing an assessment tool and preoperatively teaching the child how to use it will ensure the best results from the assessment process. If patient-controlled analgesia (PCA) is to be used, it is helpful to teach children and their parents the principles of PCA. Similarly, explain regional anesthetic techniques if these are chosen.
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 the parents, and so that the process is as objective as possible and comparisons can be made between nursing shifts. The parent and child should be intimately involved in the evaluation, management, and decision making whenever possible.
The assessment of pain in children is challenging because they may be nonverbal (very young) or they may communicate pain in ways we do not always understand (e.g., by withdrawing, or by telling us they do not have pain in case we inflict more). In neonates and infants, clinical judgment alone is used, whereas simple assessment tools are useful in older children. Appropriate methods of pain assessment in children differ at different ages. Broadly, there are three stages of a child’s development when different means of pain assessment are suitable.
1. Infants, neonates, and very young children (0 to 4 years)
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 give a self-report of pain intensity before about 3 years of age. At 3, they can give a gross indication, such as “no pain,” “a little pain,” and “a lot of pain,” but this is not always reliable. The mother’s or father’s impression is often the best indicator in these very young patients. Nurses and doctors need to listen to the parents in addition to using objective measures of pain. Behavioral and physiologic responses can be used as a measure of pain in young children, particularly in noncommunicating ones. These signs, which may not be specific to pain, include the following:

Crying, screaming, moaning, whimpering

Facial expression, grimacing, furrowed brow

Posture, tone, guarding, thrashing, touching painful area

Palmar sweating

Sleep pattern

Respiratory rate and pattern

Heart rate and blood pressure
Hospitals may choose to use one of several systematic and validated measurement tools [e.g., CRIES (Krecehel and Bildner)] that utilize various combinations of these physiological and behavioral indicators of pain, although their use is not often warranted in the acute pain setting. The principles of pain assessment in very young children, and issues of nervous system and cognitive development are described in Chapter 33.
2. Young children (4 to 7 or 8 years)
Assuming developmental normality, older children (from 4 years to 7 or 8 years old) can provide reliable self-reports of pain by using assessment tools designed for young children, such as the faces scale (see Chapter 6, Fig. 1), by communicating via their parents, and often by direct communication with their doctors and nurses. Simple numeric scales using childish language may be helpful at the upper end of this age range. For example, “If 0 means no hurt and 10 means the biggest pain you’ve ever had, what is your pain now?”
3. Older children (>7 or 8 years)
Older children who understand the concept of numeric order can use verbal or visual numeric scales such as those used in adults (see Chapter 6).
Treatment of both procedural and postoperative pain has improved greatly over the last 20 years. This has come about with the development of pain centers, protocols, and a realization that pain treatment and prevention is important. Children now are benefiting from improved analgesia in the form of topical analgesics, opioids, patient controlled analgesia (PCA), and regional anesthesia and analgesia. There has also been an increase in the provision of sedation and general anesthesia for children undergoing painful procedures.
When children are being prescribed for, the following guidelines should be kept in mind:

Liver conjugation is the predominate method of metabolism for most analgesics.

Neonates, having an immature cytochrome P450 system, conjugate drugs slowly.

Renal function in the first few weeks of life is decreased compared to adults. Usually, clearance of drugs and metabolites is adequate within 2 weeks of birth. Prior to this, the half-life of many drugs may be increased, necessitating an increase in dosing intervals.

Because of the increase in total body water in neonates, drugs that are water soluble have a larger volume of distribution.

Neonates have less plasma protein binding, resulting in increased free drug.
In general, these pharmacokinetic factors mean that lower doses per kilogram are needed in neonates and infants, sometimes at increased dosing intervals. However, the effects of immaturity are complex, and some drugs may actually be needed in greater 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 the nonsteroidal anti-inflammatory drugs
Acetaminophen and the nonsteroidal anti-inflammatory drugs (NSAIDs) are cyclooxygenase/prostaglandin inhibitors. They are effective for mild to moderate pain, or as adjuncts to opioid and regional analgesia. They have the great advantage in children of not being associated with respiratory depression. However, although acetaminophen is relatively free of side effects, the NSAIDs have several potentially dangerous side effects that limit their use. These drugs (including acetaminophen) are described in Chapter 8. Pediatric dosing for the more commonly used of these drugs is presented in Table 1.

Table 1. Pediatric dosing of commonly used NSAIDs and acetaminophen

(i) Acetaminophen
Acetaminophen is the most widely used analgesic and antipyretic, both in the home and in hospitals. It has only minimal antiinflammatory effects since its effects are mainly central. This accounts for its lack of adverse effects on the renal and gastrointestinal (GI) systems and on platelet function. It is probably the most useful adjunct and analgesic for mild pain in the management of pediatric pain. Acetaminophen is available in many formulations, including tablets, capsules, syrups, suspensions, and suppositories. It is also included in many commercially available combination analgesics. Doses of 10 to 15 mg/kg every 4 hours up to a daily maximum of 100 mg/kg are useful for the treatment of mild to moderate pain, and a single dose of 30 to 40 mg/kg may be given either orally or rectally to aid in the management of acute postoperative pain. The rectal route is useful in children and used frequently for acetaminophen. Usually, children do not mind rectal drug administration, preferring it to injection by needle. Rapid absorption occurs because there is no first-pass liver metabolism from the distal rectum. Occasionally, drugs are rapidly expelled from the rectum (before absorption can take place), which precludes the use of this route.
(ii) Nonsteroidal anti-inflammatory drugs
Because currently used NSAIDs do not cross the blood–brain barrier in appreciable amounts, their effects are mainly peripheral. This contributes to their value as adjunctive analgesics, as their mechanism of action is completely different from that of centrally acting analgesics such as the opioids. NSAID use is associated with well-recognized side effects, including gastritis, possible GI bleeding, and platelet and renal dysfunction. These side effects limit the use of NSAIDs after major surgery and in certain patients (e.g., those with renal disease or coagulopathies). However, when used with care, these are useful analgesics for children undergoing surgery, as they are free of the respiratory depressant and mood altering effects of opioids.
Aspirin (acetylsalicylic acid), the most utilized NSAID for over 100 years, currently has very limited use in pediatrics because of its recently recognized association with Reye’s syndrome. The most widely used NSAID is ibuprofen, available in a number of formulations including an oral suspension and chewable tablets appropriate for pediatric use. Doses of 5 to 10 mg/kg every 4 hours, up to a daily maximum of 40 mg/kg, may be used either as needed, or preferably around the clock for 48 to 72 hours. With refractory pain, ibuprofen and acetaminophen doses can be alternated every 3 hours, allowing the maintenance of a steady-state inhibition of prostaglandin synthesis while minimizing side effects and staying below maximum dosage guidelines.
Other NSAIDs used in the treatment of children include naproxen, tolmetin, diclofenac, and ketorolac. Of these, only ketorolac, at doses up to 0.5 mg/kg, is approved for parenteral as well as oral administration for the treatment of pain. Ketorolac can be very useful for treating postoperative pain when the oral route cannot be used, when opioids are poorly tolerated, or when additional analgesia is needed. Intravenous (IV) indomethacin is used to treat patent ductus arteriosus, but it has virtually no application in the treatment of pain. Indomethacin suppositories may be useful occasionally.
The newer selective COX-2 inhibitors (rofecoxib and celecoxib) are less likely to cause side effects because they selectively inhibit the inducible cyclooxygenase (COX-2), sparing the constitutive enzyme (COX-I), particularly in the GI tract. They may be useful as an alternative to standard NSAIDs when there is a concern about the GI effects of the latter, although studies of the use of these drugs in the pediatric population have not yet been completed.
2. Opioids
Opioids (see Chapter 9) are the most commonly prescribed analgesics in the treatment of moderate to severe pain; they are the only analgesics that do not have a ceiling effect and the only analgesics that are effective for severe pain. Opioids can be used safely in children with appropriate monitoring, dosing regimens, and techniques of administration. Traditionally, opioids have been underused in children for a variety of reasons, including misconceptions about children’s ability to feel pain, a lack of familiarity with dosing, and fear of side effects.
(i) Pharmacokinetics
Children handle opioids differently at different ages, and it is necessary to understand these differences to prescribe opioids safely to pediatric patients. In newborns and infants, the pharmacokinetic factors described earlier mean that lower per kilogram doses are needed than in older children, although opioids’ larger volume of distribution 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 are not even analgesic. Infants are also at an increased risk for the development of apnea following a rapid bolus dose because of the rapidity at which the circulation delivers the peak dose to the brain. The half-life of morphine in neonates is 6 to 8 hours and about 10 hours in the premature (compared to 2 hours in adults), necessitating markedly lower infusion rates than in older individuals. However, higher plasma levels of morphine are needed for equal analgesia, possibly because the production of morphine-6-glucuronide (an active metabolite of morphine) is greatly reduced. As children grow, morphine clearance rapidly approaches adult levels, and in adolescence it is actually greater than in adults. Young children appear to be less likely to vomit after opioids. Recommended opioid dosages for children are presented in Table 2.

Table 2. Recommended starting doses for opioids in children weighing under 50 kg

(ii) Choice of opioid
For IV use, morphine is the drug of choice in the pediatric population because it is well tolerated, caregivers are familiar with its use, and it has been widely used in children. Because of its associated histamine release, morphine may be contraindicated in asthmatics, but most asthmatics actually tolerate morphine infusions well. Hydromorphone or fentanyl may be used instead. Codeine, oxycodone, and morphine are the opioids most commonly chosen for oral administration in children.
(iii) Routes of administration
Opioids can be given parenterally, orally, rectally, or neuraxially. In the immediate postoperative period, since the oral route may not be available, the IV route (via an indwelling catheter) is most commonly chosen for ease of titration and avoidance of needles. If there is no IV in place, the rectal route may be useful. Pain after minor surgery can often be satisfactorily treated with nonopioid analgesics, so that oral opioids usually follow an IV regimen only in the case of major surgery. Neuraxial opioids may be given by the spinal and epidural routes.
a) Parenteral
Intramuscular and subcutaneous injections are avoided because they are distressing (especially to young children), and unnecessary and unpredictable in their effects. An indwelling subcutaneous needle is occasionally used when there is difficulty with IV access. The IV route is the parenteral route of choice. Drugs can be given either intermittently or by continuous infusion. Continuous infusions are the standard at MGH for small children who cannot use PCA. Intermittent boluses are used as a backup if pain gets out of control. PCA is used as soon as children are old enough to use this technique.
To provide effective and safe analgesia using IV opioids in children, it is necessary to understand a very basic principle of opioid dosing in young patients. As already stated, when children are too young to communicate their pain, judgments about pain are derived from signs such as screaming and crying, but these signs are not at all specific to pain. Thus, it is quite possible to assume pain exists when a child is simply fed up and exhausted.
The correct response is for an experienced physician or nurse to stay with the child and give monitored intermittent bolus injections (morphine at 0.025 to 0.1 mg/kg) every 5 minutes, while the child is soothed, until the child settles. If a continuous infusion of opioid is being used, the rate may be increased slightly in response to uncontrolled pain but it should not be repeatedly and rapidly increased. When the child finally settles, the increased infusion rate can result in overdose and respiratory depression—often well after medical personnel have left the room. This inappropriate reaction to a child’s distress is such a common error, and a regular cause of potentially dangerous respiratory depression, that it is worth emphasizing.
Continuous IV infusion
In young children (<5 to 7 years) with moderate to severe pain, continuous IV infusions are used to maintain steady plasma drug levels and stable analgesia. Prior to starting the infusion, a loading dose is given to achieve a steady state, after which the infusion maintains effective analgesia. Careful monitoring, using regular vital sign assessments and sometimes special monitors, is necessary to prevent excessive sedation and respiratory depression. This is particularly important in neonates and all spontaneously breathing children.
Morphine is the most commonly used opioid for continuous infusions. It has been extensively studied in all age groups. Analgesic levels are usually obtained after a loading dose of 25 to 100 µg/kg of morphine and then starting an infusion at 2 to 5 µg/kg/hr. Recommended infusion rates vary according to age and pain severity (Table 3). In some circumstances, it may be desirable to use an alternative opioid (see Chapter 9). However, as a general principle, it is wise to use and become familiar with a single opioid in pediatric practice because correct dosing is so critical. The MGH standard orders for continuous opioids infusions are shown in Figure 1.

Table 3. Guidelines for continuous intravenous infusion of morphine

Figure 1. Continuous IV morphine order sheet.

Patient controlled analgesia
PCA is used in older children (>5 to 7 years) at MGH as soon as they understand how to use it. Unfortunately, PCA is not available in all hospitals, and if it is not, continuous IV infusions should be substituted, with bolus injections for breakthrough pain. For children, it is sometimes appropriate to allow parents or nurses to control PCA, but caution should be exercised. Before allowing parents to participate, the prescribing physician should be absolutely certain that the parents understand the principles of PCA (see Chapter 21), and in particular that they should not press the button unless the child is awake and requesting analgesia, or obviously in pain. Standard MGH PCA orders are shown in Figure 1 of Chapter 21. Table 4 presents dosage guidelines for morphine and hydromorphone.

Table 4. Guidelines for patient-controlled analgesia (PCA) dosing

b) Oral
The oral route is used when pain is subsiding and when it is mild to moderate. Clearly, this route cannot be used if the child is nil per os (NPO) or vomiting. Either pure opioid or opioid combinations can be chosen. Codeine, oxycodone, morphine elixir, Tylenol #3 (acetaminophen with codeine), and Percocet (oxycodone with acetaminophen) are all useful in children. Recommended doses can be found in Table 2. Tylenol #3 and Percocet are reserved for children over 20 kg; one to two tablets are used every 4 hours, according to weight and pain severity.
c) Rectal
Morphine and hydromorphone are available as suppositories and may be useful when the oral and IV routes are not available. Rectal doses are the same as oral doses (see Table 2).
d) Neuraxial
Opioids given intrathecally or epidurally provide selective spinal analgesia that is both effective and relatively free of side effects because much smaller doses are used. Hydromorphone and fentanyl are used at MGH. Differences between opioids when administered neuraxially are described in Chapter 21 (IV, 4, iv). As a general principle, epidural doses are one-tenth IV doses, whereas intrathecal (spinal) doses are one–one hundredth IV doses.
3. Regional anesthesia and analgesia
Regional and local anesthetic techniques, which are often used in children, have the great advantages of providing prolonged analgesia that extends into the postoperative period, reducing distress, and reducing the need for opioids. Infants and young children appear to be relatively resistant to the hemodynamic and respiratory effects of epidural or spinal blockade, so the techniques are generally safe. Catheters may be utilized to prolong the effects of regional anesthesia even further, and to provide analgesia. The most common catheter therapy used in children is epidural therapy. For epidural analgesia, low-dose local anesthetics are used (blocking C-fibers specifically, and sparing sensory and motor nerves so that patients can move normally) with or without opioids. Opioids have a selective spinal effect because of their preferential absorption onto spinal cord receptors from the proximal site of administration.
(i) Epidural analgesia
Many of the principles of epidural analgesia use in adults (see Chapter 21) apply also to children and are not repeated here. In small children, epidural catheters are technically more difficult to place (although with experience this difference disappears), and once placed, it is more difficult to keep them in, to protect them from the diaper area, and to maintain their patency because of their smaller size. As in adults, epidural catheter maintenance is time consuming, labor intensive, and not without complications, so catheters should be reserved for cases where the benefit outweighs these considerations (e.g., major abdominal and thoracic surgery). Many hospitals choose not to offer epidural catheter treatments to their pediatric patients on regular floors because of the difficulty of providing appropriate staffing to manage these catheters.
Single-shot epidural injections, including caudal injections, are very useful in children and provide excellent analgesia during the early postoperative phase. For a single-shot caudal injection, we give 1 mL/kg of 0.125% to 0.25% bupivacaine, sometimes with the addition of 2 to 4 µg/kg clonidine, which provides additional analgesia with minimal risk of hypotension (see Appendix VIII).
a) Indications
At MGH, postoperative epidural catheter treatments in children are reserved for thoracic, abdominal, and lower limb procedures that are expected to produce severe pain. Single-shot techniques are much simpler and provide useful analgesia after many surgical procedures of the torso, pelvis, and lower limb, including hernia repair, circumcision, tendon lengthening, and club foot release. The caudal route is most commonly selected for single-shot epidural injections.
b) Contraindications
Contraindications to epidural placement are the following:

Patient or parent refusal



Local infection at epidural insertion site

Spine pathology, neurologic deficit, raised intracranial pressure (relative contraindications)
c) Benefits
The benefits of epidural analgesia that apply particularly to children are superior analgesia, opioid sparing with clear sensorium and decreased risk of respiratory depression, increase in bowel mobility, and decrease in bladder spasms after urologic surgery.
d) Disadvantages and risks

Risk of local anesthetic toxicity

Respiratory depression if central neuraxial opioids are used

Urinary retention (common)

Pruritus (in up to 30% of patients)

Nausea (rare in this population)

Catheter migration, resulting in intrathecal, intravascular, or extradural placement (indicators: sudden increase in block density, blood in catheter, or failure to provide analgesia)

Epidural hematomas and abscesses (rare)
e) Epidural placement in children
ANATOMIC DIFFERENCES. In infants, the level of the spinal cord and dural sac are continuously changing up to 1 year of age. In the full-term neonate, the dural sac extends to S3-4, with the spinal cord ending at L4. By 6 months, the dural sac ends at S2 and the spinal cord at about L2-3. At 1 year, the dural sac terminates at about S1, with the cord reaching L1 (adult levels). The line drawn between the iliac crest changes relative to the spine: the line crosses L5-S1 in the neonate, L5 in the older child, and L4-5 in adults.
It is useful to have an idea about the depth of the epidural space in children, especially because the ligaments are less dense and provide a feel that is different from that of the adult ligaments. A useful formula to approximate depth (in millimeters) of the epidural space in children is as follows:
Infant: depth (mm) = 1.5 × weight (kg)
Child: depth (mm) = 1 × weight (kg)
TECHNIQUES. The epidural space is located outside the dural sac. A needle or catheter may be placed in this space at the appropriate dermatomal level to inject or infuse local anesthetics, opioids, or other medications. Epidural catheters may be placed via several routes. It is possible to position the catheter either by inserting it at the appropriate dermatomal level without threading or, in small children, by threading the catheter up the epidural space to the desired location.
For caudal epidural injections, the needle is inserted between the sacral cornua at the base of the sacrum, and if a catheter is used, this is threaded into the caudal canal. The caudal epidural space is contiguous with the lumbar epidural space, and catheters can usually be threaded upward in the epidural space. In infants and young children, catheters can usually be threaded to any level desired. In older children, it still may be possible to thread epidural catheter several vertebral levels above the insertion site. In fact, it is common practice to place all epidurals in young children at the caudal or lumbar (not the thoracic) level, threading upward if necessary. This is because epidural catheters are usually placed under general anesthesia (or deep sedation) in young children and asleep thoracic epidural placement is considered unsafe because of the proximity of the spinal cord to the epidural space at this level.
f) Managing epidural infusions
CHOICE OF MEDICATION. The selection of dosage and drug used in epidural infusions depends on the surgery, the site of the surgery, the age of the child, and comorbidity, although standard infusions work well in most cases. Epidural opioids are avoided or used with caution in infants and children at risk (e.g., those with pulmonary dysfunction or developmental delay).
The infusion is normally started at a standard rate (0.2 to 0.3 mL/kg if the catheter tip is below T10; 0.1 to 0.2 mL/kg if the catheter tip is above T10), and titrated upward as needed. The standard infusion for use in infants and young children (3 months to 5 years) at MGH consists of 0.1% bupivacaine with 2 µg/mL fentanyl. We use plain 0.1% bupivacaine in neonates (<3 months) and 0.1% bupivacaine with 20 µg/mL hydromorphone in older children (>5 years). Figure 3 in Chapter 21 shows the standard epidural order sheet used at MGH. Occasionally, if analgesia is inadequate, the concentration and/or volume of infusate may need to be adjusted.
If a child leaves the operating room with inadequate analgesia, a bolus injection will be needed before beginning the infusion. The bolus can be a local anesthetic or a standard epidural mix. If this initial bolus is needed, it is acceptable to give either lidocaine or bupivacaine at 0.05 mL/kg per spinal segment. It is important not to exceed a dose of 5 mg/kg of lidocaine or 2.5 mg/kg of bupivacaine. If the analgesia is expected to cover a large range of dermatomes, a more dilute solution may be needed to ensure that the local anesthetic fills the epidural space without toxicity.
GENERAL CARE. The standard of care when providing epidural analgesia for children is similar to that given to adults:

24-hour anesthesia coverage for patients receiving epidural analgesia

Ventilatory status monitored and recorded hourly

Vital signs monitored and recorded every 4 hours

Pain service evaluation daily, including check of neurologic status

Daily examination of the catheter site for signs of inflammation or infection

Low threshold for more intensive monitoring in children less than 6 months old (considered at risk of ventilatory depression)

Heels padded to prevent pressure sores

No systemic opioids given while receiving epidural opioids
g) Treatment of side effects and complications
Local anesthetic toxicity is rare in the postoperative setting. If it occurs, it should be treated as described in Chapter 37. Sensory or motor changes are common after injection of local anesthetics but are not expected when low-dose (0.1%) bupivacaine is used. The abnormal neurologic examination may indicate residual block from surgery, migration of the catheter to one side or one nerve root, catheter irritation, or, more sinisterly, impending epidural hematoma or abscess. In most cases, recovery occurs when the dose of infusate is reduced, the catheter is pulled back, or the treatment is stopped.
The cardinal signs of epidural hematoma or abscess are back pain and sensory or motor weakness. These symptoms and signs should always prompt withdrawal of treatment, close monitoring, and possible investigation with magnetic resonance imaging. Surgical decompression is the only way to prevent permanent neurologic damage.
Epidural opioid side effects include pruritus, nausea and vomiting, urinary retention, and respiratory depression. Treatment is summarized in Table 5. Respiratory depression is the most serious of these complications. Lipophilic agents such as fentanyl are less likely to cause respiratory depression than the more hydrophilic opioids (especially morphine), but vigilance is still required (see Chapter 21).

Table 5. Adjuncts in pediatric acute pain management

Treatment is the administration of oxygen, ventilatory support if necessary, stopping of the epidural infusion, and naloxone (2 µg/ kg IV). It is also possible that catheter migration could have occurred, resulting in an intrathecal infusion. Pruritus is treated with diphenhydramine (Benadryl), 0.5 mg/kg, or low-dose naloxone (Narcan), 0.5 to 1 µg/kg. Nausea is treated with ondansetron, 0.1 mg/kg, or droperidol, 0.01 to 0.025 mg/kg 6 hourly.
(ii) Spinals
Spinal anesthesia is capable of providing good postoperative analgesia for several hours after surgery. This can be prolonged by injecting a bolus dose of opioid with the local anesthetic. Spinal anesthesia and analgesia are most commonly used in neonates, in whom the risk of apnea and bradycardia after general anesthesia is highest. The space chosen is L4-5, since there is a risk of injuring the spinal cord if a higher space is used. In the neonate, the doses of local anesthetic are higher than they would be for an older child or adult, and the duration of action is shorter than in the older patient.
Hyperbaric bupivacaine and tetracaine are the most commonly used agents. A single injection of an opioid (most commonly preservative-free morphine, Duramorph) into the spinal fluid prolongs the analgesia (12 to 24 hours or more) despite the small dose (2 to 10 µg/kg), but this is reserved for older children (>5 years). There is little or negligible systemic absorption, but respiratory depression is liable to occur because of the passage of morphine to higher centers in the cerebrospinal fluid.
(iii) Other techniques
Peripheral nerve blocks provide anesthesia and analgesia in the early postoperative period and are often chosen for this reason. Useful blocks in children include ilioinguinal, femoral, penile, brachial plexus, and lumbar plexus blocks. Occasionally, catheters are inserted so that the block can be prolonged further. EMLA cream (a eutectic mixture of local anesthetic, lidocaine, and prilocaine) has proved very useful in children to numb the skin before needling, and even to provide postoperative pain relief (e.g., after circumcision). Other topical local anesthetic preparations are occasionally useful (e.g., lidocaine gel for mucus membranes).
4. Nonpharmacologic techniques
Nonpharmacologic techniques are adjuncts to analgesic medications that can be used to help ease a child’s discomfort or anxiety level associated with pain or painful procedures. They work best when the patient and family are introduced to the particular technique and are offered the opportunity to actively participate.
Cognitive approaches
Education has been shown to be effective in children, especially when preoperative teaching has been conducted. Children are also excellent at developing pain-controlling strategies that involve imagination.
Distraction may be useful in all age groups but needs to be age specific. Attention is focused on stimuli other than the pain sensation. Distraction can be very effective with children for brief episodic pain such as that associated with drain removal. To be effective, the distraction must be interesting to the patient and consistent with the developmental level, energy level, and capability of the child, and it must stimulate major sensory modalities (hearing, vision, touch, movements). Some examples for specific ages are as follows:

Toddler/preschooler: blowing bubbles, singing, music cassettes, pop-up books, “I Spy” books

School age/adolescent: music or story via headset, singing or tapping rhythm, conversation
Cutaneous stimulation
Massage or rubbing the skin may be very soothing but is generally not recommended for premature or full-term neonates. The application of heat or cold is often useful for localized pain. Transcutaneous electric nerve stimulation (TENS) can also be used (see Chapter 16).
Guided imagery
This uses the patient’s own imagination to develop sensory images to decrease the pain, make it more acceptable, or change it into a different sensation that is less intense—for example, throwing pain away like a snowball, blowing pain away, or imagining the medication traveling through the body to relieve the pain.
For example, tell a story in which the child can be actively involved. Utilize the child’s favorite place or fictional character and include the child as part of the story. Ask questions to keep the child engaged.
These techniques are used to decrease anxiety and skeletal muscle tension, potentially relieving some of the mental and physical effects of pain. Techniques include breathing exercises, progressive relaxation, remembering past peaceful experiences, and, in infant and toddlers, the use of pacifiers and stroking.
The increase in concern and improvement in pain therapies for children is a welcome and much-needed improvement in the medical care of children. Further advances in education, research, and knowledge will allow us to apply the lessons learned in adults to the benefit of our pediatric patients. It is incumbent on all anesthesiologists and other caregivers to consider pain and analgesia at every juncture in the process of caring for children.
The authors gratefully acknowledge the help of Dr. Michael Girshin and Dr. David B. Kaplan, Fellows in pediatric anesthesia at New England Medical Center.

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Zwass M, Polaner D, Berde C. Postoperative pain management. In: Cote CJ, Todres ID, Ryan JF, Goudsouzian NG, eds. A practice of anesthesia for infants and children. Philadelphia: WB Saunders, 2001:675–697.

5 comments on “22 Postoperative Pain in Children

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