Pain can be defined as an unpleasant sensory and emotional experience arising from actual or potential tissue damage (1,2). Managing pain is a large part of emergency care, both diagnostic and therapeutic, and an assessment of pain is now considered by many as the “fifth vital sign.” Most injuries are associated with pain, and it is often a marker for serious illness.

Pain is multifactorial and subjective (3). In the emergency setting, several factors affect the nature and degree of pain a child experiences. These factors are related to the child, the provider, and the procedure. Child-related factors include any underlying medical conditions, previous painful events, the culture and environment in which the child is reared, and his or her developmental, cognitive, and emotional level. Provider factors include the attitude, experience, and competence of the physician. In addition, the type of procedure, the part of the body involved, the duration of manipulation, the degree of immobility required, and the type of medication used will affect the child’s perception of pain.

It is important to understand the terminology used in describing pain control. Anesthesia is the medically induced loss of all sensation. When sensory loss is restricted to one anatomic area, it is termed local anesthesia, whereas general anesthesia refers to a state in which the patient is completely insensate. Analgesia is the reduction or elimination of pain sensation (4). Lidocaine is an excellent local anesthetic because infiltration eliminates the ability to perceive pain in the area involved. Acetaminophen and ibuprofen are appropriate analgesics because they reduce the general feeling of pain. Sedation is the act of calming that can be achieved by pharmacologic or psychological interventions, such as distraction, cognitive behavior therapy, and hypnosis (4). Sedation can help a child cope with a painful procedure but does not by itself alleviate pain. Procedural sedation and analgesia refers to the technique of administering sedatives or dissociative agents with or without analgesics to induce a state that allows the patient to tolerate unpleasant procedures while maintaining independent cardiorespiratory function (5).

As shown in Table 33.1, the American Society of Anesthesiologists (ASA) has described the different levels of sedation and analgesia by taking into account the patient’s response to commands as well as airway, ventilation, and cardiovascular functions (6). Light (or minimal) sedation is a pharmacologically induced state in which the patient can respond to verbal stimulation, albeit more slowly than normal, and should be able to follow commands. Lightly sedated patients maintain airway protective reflexes and generally experience minimal, if any, effects on the cardiovascular system. The moderately sedated
patient responds to verbal stimulation or light tactile stimulation but may not be able to follow commands. Airway protective reflexes are intact, and spontaneous ventilation is usually adequate. Cardiovascular function is generally not affected. Finally, the deeply sedated patient may experience ventilatory compromise, and airway protective reflexes are suppressed and may be lost. The patient generally requires more vigorous stimulation to elicit a response and is unlikely to be able to follow verbal commands, although cardiovascular function is typically normal. By contrast, with true general anesthesia, the normal protective airway reflexes (most importantly, closure of the epiglottis over the glottic opening with vomiting or regurgitation of stomach contents) are absent, putting the patient at risk for aspiration pneumonitis. Self-maintenance of airway patency is also much less likely (1). Sedation producing this state should only be induced in an operating room by an anesthesiologist or during rapid sequence intubation in the emergency department (ED).

Although the specific terminology just presented is now preferred over the more generic term conscious sedation used previously, it is important that the physician and support staff understand that these definitions are merely (somewhat arbitrary) points along a continuum that begins with full alertness and ends with general anesthesia. Any patient can be more or less sedated than was originally intended and can move in either direction along this spectrum as a result of changes in the degree of stimulation, the passage of time, or the administration of additional medication.

The physician caring for young children is faced with the challenging additional task of separating pain from anxiety and discerning which is the predominant contributor to the child’s state. In the ED, there is often a need for both pain reduction and alleviation of anxiety. Some drug classes, such as benzodiazepines, do not provide analgesia but offer a significant sedative effect; other agents, like nonsteroidal anti-inflammatory drugs (NSAIDs), can relieve pain but not anxiety; while still other agents, most notably the opioids, have both effects, although their analgesic effect is predominant. It is the important responsibility of the physician to strike a balance between safety and symptom relief by choosing appropriate agents and ensuring adequate monitoring. In many cases, it is prudent to administer an anxiolytic initially, because the operator can perform a more accurate examination and thus better assess the need for analgesia once the child is calm. Furthermore, the psychological development, pain threshold, and anxiety level of the individual must be considered on a case-by-case basis (Table 33.2). A younger child may require sedation for a painless procedure like a computed tomography (CT) scan, while an older child may need nothing more than a local anesthetic for repair of a large wound.

The pathway by which pain is transmitted from the skin or other organs to the brain is multifaceted and can be modulated in several ways. A peripheral stimulus for pain is detected by specialized sets of peripheral nerve endings in the skin. One set of these pain receptors, or nociceptors, is composed of thinly myelinated Aδ fibers, which conduct impulses rapidly and are responsible for the initial feeling of sharp or pricking pain. The other set of nociceptors contains unmyelinated C fibers, which conduct impulses more slowly and are responsible for longer-lasting burning or dull pain sensations (16). Because the fibers of these nociceptors are unmyelinated, they are more amenable to the effects of local anesthesia (17). Aδ fibers are located in the skin and mucous membranes; C fibers are widely distributed in deep tissues and the skin. In addition to nociceptors, thermoreceptors and mechanoreceptors are composed of Aα or Aβ fibers, which are responsible for the perception of touch and light pressure. All these receptors convert a stimulus to electrical activity, which is then transmitted through various routes in the spinal cord to the brain. The initial cortical response is probably reflexive, but the subsequent response may be altered by cortical activity, including inputs from the frontal lobes and the limbic system (18).

Several theories have been offered to explain why other cutaneous stimuli and emotional stress can alter the quality and intensity of pain. For example, the gate control theory, hypothesized by Melzack and Wall (19), suggests that input from the Aβ touch fibers and input from the Aδ and C fibers have antagonistic effects on so-called “gate cells” in the substantia gelatinosa in the spinal cord (16). This would explain why a person who suffers a blow to the arm instinctively rubs the affected area—that is, to stimulate the touch fibers that antagonize the pain receptors—or why a cream that causes a mild burning sensation in the skin alleviates underlying muscle pain. This principle can be applied when attempting venipuncture by rubbing or slapping the skin before inserting the needle.

A variety of developmental and psychological factors, combined with responses conditioned by the environment, interact to influence a child’s perception of and response to pain (20). Appreciation for the child’s cognitive developmental level is mandatory for appropriate pain management. The explanation of a procedure must be age appropriate and address the fears of the patient. A developmental sequence of understanding pain is shown in Table 33.2 (21).

An understanding of some general pharmacologic principles and metabolic differences in the pediatric age group will help determine the most appropriate type of drug, the proper dosage, and the route of administration. As always with pediatric patients, one of the most challenging issues is the major age-related variations that exist from infancy through adolescence, the most obvious being body size. Although body surface area represents a highly reliable reference measurement for medication dosing in children, the child’s weight in kilograms is a reasonable and more accessible alternative for clinical management. Drug dosage is determined on a per-kilogram basis throughout the early pediatric years. However, the calculated dose should serve only as a starting point. In many cases, it will be necessary to administer additional medication in a titrated fashion to achieve the desired effect. No single agent or dosage is appropriate for all children. Therefore, the medication used and the dosing regimen should be determined by the nature of the procedure and the child’s psychological and physiologic makeup.

The speed of onset, peak effect, and duration of action of a given drug are determined largely by its rate of absorption and clearance. The rate of absorption is influenced by drug solubility, rate of dissolution, concentration, absorbing surface, circulation to the site of absorption, and route of administration (22). Six common routes of administration of sedative and analgesic medications used in the ED are oral, intramuscular, intravenous, subcutaneous, intranasal, and rectal. Each route has characteristic absorption patterns that may provide specific advantages depending on the clinical setting. For example, when careful titration of medication is necessary, the intravenous route is preferred.

The clinician must be aware of drug metabolism when choosing a route of administration. Alkaline drugs, such as opiates and benzodiazepines, cross cell membranes more easily than acidic drugs, because the intracellular pH is more acidic than the extracellular pH. Acidic drugs, such as barbiturates, do not enter cells as readily. The elimination half-life of alkaline drugs is usually longer, because the drugs are more widely distributed (23). Both the medication chosen and the route of administration will determine the level of sedation. Wide variation in the clinical effects of medications given in similar doses by the same route is the rule, not the exception. An understanding of physiology and pharmacokinetics does not replace careful dosing and meticulous monitoring.

Oral administration of medications is convenient and economical, but absorption may be variable and incomplete. Factors that limit or delay absorption by the oral route include a full stomach, decreased gastric emptying, and reduced small bowel surface area. Many oral medications undergo a “first pass effect” by the liver whereby they are metabolized before reaching the systemic circulation. Furthermore, many pediatric patients cannot or will not take medication orally. Nevertheless, for management of postprocedural pain, especially on an outpatient basis, the oral route is preferred.

When it is impossible or inappropriate to give oral medication, acceptable alternatives include intranasal and rectal administration. The intranasal route has been shown to be effective for certain medications such as midazolam. Midazolam is rapidly absorbed from the nasal mucosa. However, it is difficult to deliver large volumes, especially in small children, by the intranasal route, and this might make it difficult to provide an adequate dose of medication. Some medications, particularly those that are lipophilic, are well absorbed through the rectal mucosa. However, absorption can be delayed by stool in the rectum, and introduction of the medication might stimulate the urge to defecate, causing some medication to be expelled. Oral, intranasal, and rectal agents are useful for less painful procedures such as routine laceration repair, for which a local anesthetic will also be given. Additionally, these routes are often preferred when sedating a child for nonpainful diagnostic studies such as magnetic resonance imaging (MRI) or CT scans. However, as noted previously, the onset, depth, and duration of sedation are less predictable than with parenterally administered drugs.

Nitrous oxide, an inhalational agent, is appropriate for adolescents and cooperative children who are able to follow directions (see Chapter 34). When administered with a local anesthetic, it is useful for brief procedures involving mild to moderate pain. It may also be used for procedures that are merely anxiety provoking.

In most cases, subcutaneous and intramuscular administration can provide prompt and sustained absorption of the drug resulting in a smoother induction of analgesia. However, drugs given in this manner cannot be titrated. In addition, when circulation to the site of injection is poor (e.g., impaired perfusion of an extremity, large burns), absorption may be erratic. In these cases, intramuscular and subcutaneous routes may be ineffective for the prompt delivery of pain medications. While these routes are generally associated with fewer complications at a given dose, the pain of injection to some degree defeats the purpose of the sedation and analgesia, and a child may refrain from requesting pain medications for fear of the injection.

For the management of acute pain in the ED, the intravenous route allows the most rapid and reliable delivery of medication. Intravenous analgesia usually provides immediate pain relief. Intravenous sedation should be considered for any child undergoing a very painful procedure, such as closed reduction of a fracture or incision and drainage of a large abscess. In general, the intravenous route allows the operator to safely induce a deeper and more controlled level of sedation, which not only maximizes patient comfort but also facilitates procedures requiring meticulous care by ensuring that the patient remains motionless. Precise titration of sedation and/or analgesia using incremental doses of intravenous medication prevents “overshooting” to a level of sedation that is deeper than intended. A final advantage of the intravenous route is the ability to rapidly administer reversal agents such as naloxone or flumazenil if needed. Yet the physician must also be aware of the drawbacks of intravenous administration. For example, drugs given by this route escape the first pass effect in the liver, which increases the risk of complications, because high concentrations of the drugs are achieved rapidly and overdosing may occur. Intravenous medications should therefore be administered slowly at the T connector site by an experienced provider, with constant monitoring of the patient (Fig. 33.1).

The equipment required for administration of pain medications depends on the agent administered or the technique used.
Nonpharmacologic techniques and common oral analgesics (acetaminophen, ibuprofen, concentrated sucrose solution for infants) can generally be administered without risk of serious side effects and require no special monitoring equipment. The more potent analgesics and sedatives, including narcotics and benzodiazepines, should be given by a physician who has experience using these medications and is familiar with the management of potential associated complications. Both a physician and a nurse must assume responsibility for monitoring the child when these medications are used. Nonpharmacologic means of sedation and local anesthetics have no risk for respiratory depression or cardiovascular compromise and therefore require little, if any, monitoring, although the clinician must be alert to the risk of allergic reaction when using local anesthetics. However, administration of agents with potentially untoward physiologic effects requires continuous electronic monitoring of cardiac rate and rhythm, respiratory rate, and pulse oximetry as well as visual and/or auscultatory assessment of respiratory effort and an assessment of mental status and response to stimulation.

Patient monitoring should be recorded on a sedation or pain-control flow sheet in the medical record. Vital signs, pulse oximeter reading, level of consciousness, response to stimulation, and color should be noted at premedication and at regular intervals (5 to 15 minutes) thereafter. The following equipment and medications should be available at the bedside: