Managing Pediatric Pain
During the past two decades, pain treatment in children has received a considerable amount of attention. Numerous books and papers have been published on the management of pediatric pain. Guardiola and Barios, in a published review, revealed that there has been an increased published interest in pediatric pain issues.1 Nevertheless, there exists a culture that allows the under-treatment of pain in children to exist. Outdated methods of restraint, such as strapping a child down in a papoose fashion, without the benefit of sedation, are still being used for procedures such as circumcisions. Documentation of this inadequate care persists.2,3,4 Children who have pain that is not adequately treated have less satisfactory medical outcomes.5-6 The recent evidence that pre-emptive, perioperative pain management in infant males undergoing circumcision has an impact on their future physiological and behavioral pain responses to vaccination, may guide practitioners to new and better ways of thinking about pain in children and treating pain in children.7-8
Pain Assessment in Children
The International Association for the Study of Pain (IASP) defines pain as, “an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.”9-10 The definition has been criticized because of its lack of utility when being applied to the neonate or non-verbal patient. The definition speaks more specifically to adult patients because it assumes an ability to verbalize which is not present in a large, very vulnerable segment of the pediatric population. Even though some aspects of pain in the neonate and young infants (and some adults) may be subcortical or reflexive (not cortically processed or associated with emotions), we have assumed that children have pain and are subjected to the beneficial protective aspects of pain.11 It is also assumed, in those cases where the child cannot verbalize, they can suffer the untoward sequelae of unrelieved pain. There are compelling reasons why a more expansive conceptualization of pain with respect to infants is necessary. Our current knowledge base for objectively and efficiently measuring pain in infants is very limited. Therefore, for at least humanitarian reasons, we should assume the presence of the pain experience in the neonate and infant, just as we do in the laboratory animal.
Assessment of pain in children is challenging and with regard to the neonate presents an especially formidable task to the uninitiated. The problematic nature of defining pain in children makes the assessment of pain in this age group even more enigmatic. Some older children may have difficulty describing their pain because of inexperience and a limited vocabulary. The developmental psychology issues in the pediatric population also serve to confound pain assessment. Perrin and Gerrity found that young children tend to blame themselves for illness, thus associating punishment with painful medical procedures.12 Adolescents are able to think in the abstract, so a more complex understanding of illness is usually reached during this period of development. Whether old or young, the assessment of pain is needed to determine the presence of pain. It is also important for the determination of the magnitude of pain present, the impact of pain on homeostasis, and very importantly, the effectiveness of therapy.
Pain assessment measures may be classified as behavioral, physiological, or self-report, depending on the nature of the response that is measured. Pain may be assessed by displays of distress (e.g. grimaces, cries, and protective guarding gestures). It may also be assessed by measuring a child’s physiological state (e.g. heart rate, sweating, blood pressure, and cortisol level), or even by obtaining a child’s direct self-report (e.g. words, numerical ratings, and drawings). To be useful, pain measures must have: (1) validity; (2) reliability; and (3) minimal bias. To be valid, pain measure must unequivocally measure a specific aspect of a child’s pain (e.g. intensity) so that changes in a child’s pain rating represent a meaningful and proportional change in the child’s pain experience. The measure must be reliable in that it provides trustworthy and consistent pain ratings that do not change over time. The measure must be free from response bias, in that children use it similarly regardless of how they may wish to please the questioner or how adults administer the tool. In addition, the pain measure should be practical for assessing different types of pain, (acute, recurrent, and persistent) for many different children (according to age, cognitive level, and cultural background), and versatile for use in a variety of settings (clinic, postoperative recovery room, emergency room, and home). A thorough review of pain assessment in children can be found in, Pain in Children: Nature, Assessment, and Treatment, by Patricia McGrath.13
An increased understanding of analgesic and anesthetic pharmacology, and familiarity with new drug delivery technologies, means that a profound impact on a patient’s level of pain, as well as his or her potential to develop chronic pain can be made. A new therapy and an old therapy implemented in a new way to attack the problem of pediatric pain are discussed.
EMLA and Other Topical Analgesics
One of the most terrifying childhood experiences is receiving a shot, a needle stick, or a venipuncture. The pain and anxiety provoked by these early childhood experiences crosses cultural and ethnic boundaries and can have an impact in later life. For several decades, researchers have tried to find methods to eliminate the pain caused by this mechanical stimulation to the skin and underlying structures. Localized skin pressure, cold, ischemia, and topical agents have been utilized to lessen the discomfort associated with many medical procedures. EMLA, a eutectic (a combination of drugs with a lower melting point than the individual agent property is termed, eutectic) mixture of local anesthetics, and more recently Amethocaine, an aqueous gel, have gained acceptance as a means of providing topical pain relief.
To attain the requisite high concentration of local anesthetic in the skin, to block the transmission of pain signals, a topical drug has to not only penetrate the surface of the skin, it most then transit through to the dermis and block the A-delta and C fibers. Local anesthetics, generally, are weak bases. They are marketed as water-soluble hydrochloride salts because the free bases are insoluble or are poorly soluble and unstable in water. The hydrochloride salts are usually acidic leading to a higher proportion of the drug existing in the cation form. The concentrations of the hydrophilic, cation (charged) form and the lipophilic, uncharged species are dependent upon the pKa of the drug. The pKa of most local anesthetics ranges from 7.5-9.0. It is the cation form of the local anesthetic that blocks the transmission of pain sensation, however, it is the uncharged lipophilic base that diffuses through the skin, across a concentration gradient, to the site of action.