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SPECIAL ARTICLE |
a Pain Relief Program, Connecticut Children's Medical Center, Hartford, Connecticut
b Department of Pediatrics, University of Connecticut School of Medicine, Farmington, Connecticut
c Department of Pediatrics, St Francis Hospital and Medical Center, Hartford, Connecticut
d Department of Psychology, Georgia State University, Atlanta, Georgia
e Centre for Research in Pediatric Pain, IWK Health Centre, Halifax, Nova Scotia, Canada
f Department of Psychology, Dalhousie University, Halifax, Nova Scotia, Canada
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ABSTRACT |
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 TOP ABSTRACT BEFORE THE INJECTIONDURING THE INJECTIONCONCLUSIONSREFERENCES |
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Key Words: immunizations • injection • clinical practice • pain control
Abbreviations: DPT—diphtheria-pertussis-tetanus • EMLA—eutectic mixture of local anesthetics • MMR—measles-mumps-rubella
The development and administration of immunizations are among the greatest public health achievements of the 20th century, and their positive impact on disease prevention and reduction of human suffering is almost incalculable. Hundreds of millions of cases of illness and millions of deaths have been prevented by these agents. To provide this protection, the current Centers for Disease Control and Prevention schedule recommends immunizations against 14 diseases, which translates into 14 to 20 separate injections before the age of 2 years, depending on the number of combination vaccines available.1 Therefore, immunizations are the most frequently occurring painful procedures performed in pediatric settings. The number of immunizations now recommended necessitates that multiple injections be administered at the same visit (eg, 3 separate injections at the 2-month visit and 3 at the 4-month visit).
Despite the proven benefit of these procedures, the pain associated with these injections is a source of great anxiety and distress for many. In fact, recent research suggests that not only the children themselves but also their families and health care providers have concerns about the pain associated with multiple frequent injections.
For children, concerns about injections are often evident at the beginning of any clinical encounter. Although modern pediatric practice has broadened in scope to include health supervision and counseling, many children are so preoccupied with the possibility of an injection that this worry dominates the entire visit and limits the opportunity for other interventions. Every nurse or physician who works with children has entered an examining room to find a cowering child whose first question is, "Am I going to get a shot?" The needle is a powerful negative symbol for many children,2,3 is a phobia for some,4 and unfortunately has become iconic of medical care. All children, even at young ages, seem to have a pain memory,5 to anticipate painful procedures,6,7 and to react more intensely if they have had previous painful procedures with inadequate analgesia.8 There are enormous differences among children in their responses to injections, however, and it is clear that a host of variables, both inherent and environmental,9–11 may amplify or dampen their responses to injections.
Family members also are often quite concerned about immunization pain. Meyerhoff et al,12 in an attempt to quantify parental concern regarding multiple immunizations, developed a "willingness-to-pay" method for estimating that distress. According to their survey of 294 families drawn from a random sample of 26 centers around the United States, parents reported they would be willing to pay an average of $57 to avoid a 2-injection visit and nearly $80 to avoid a 3- or 4-injection visit. Regardless of the specific numerical sum parents reported and the veracity of their actual willingness to pay it, the data of Meyerhoff et al12 indicate significant parental concern about the pain associated with immunizations. That conclusion is supported by other research that suggests that parental concern about injections affects their compliance with medical care.13
Similar unease exists among providers. Woodin et al14 reported that, depending on the child's age, 56% to 65% of practicing physicians had strong concerns about 3 injections at a single visit. Eighty percent had strong concerns about administering 4 injections at a single visit, irrespective of the child's age. In fact, practicing physicians were statistically more likely to have concerns about multiple injections at a single visit than were parents. Similarly, Reis15 reported that doctors and nurses were 6 times less likely to give all of the immunizations at a given visit if a child was scheduled for 
3 injections than if he or she was scheduled for 
2.
Despite the frequency with which immunizations are administered and the distress they provoke in children, their parents, and the providers who must administer the immunizations, there is a paucity of evidence-based data available on many aspects of good immunization practice. The literature in this area is often anecdotal, based on experience rather than research, and scattered through journals of the various disciplines that are involved in immunization administration. As a result, there is presently no available evidence-based algorithm that addresses all of the strategies that have evolved to reduce the pain of immunizations in children of all ages.
Because members of the Pain Relief Program at Connecticut Children's Medical Center have had long-standing interest in this topic,9,16 we applied for and received a grant from the Mayday Fund to host a consensus conference to more formally review the existing literature and to generate from it recommendations regarding best practices for reduction of injection pain. Initially, we separated the immunization process into multiple components (eg, preparation, technique, location, needle length, and local anesthetic use). We then identified experts (defined as individuals who had published research in these areas) and invited those who were available to participate in the conference. This panel was supplemented by research methodologists and experienced local clinicians who were actively involved in immunizations in their practices. Relevant literature was distributed to all participants before the meeting. At the meeting, each expert presented a review of his or her assigned area, offered recommendations, and detailed the evidence base supporting those recommendations. When there were randomized, clinical trials or meta-analyses with clear results, the task was straightforward. When the evidence was limited, the group discussed the available information until a consensus was reached. This approach allowed for recommendations that were supported by the literature and bolstered by informed opinion. The results of those deliberations are summarized here, and a clinical algorithm of best practices for immunization pain reduction is offered.
It is important to note that there are a number of factors that cannot be modified that affect the pain associated with immunizations. Age, gender, temperament, previous painful experiences, and cultural background all contribute to the child's pain experience; obviously these factors cannot be altered, but they can be recognized as moderators of the experience of pain. Some of these factors have been examined in relation to immunization pain,9,17,18 whereas others have not. A comprehensive discussion of these variables is significantly beyond the scope of this review but is available elsewhere.19–21
For purposes of discussion, the injection process has been divided into 2 time periods, that is, before the injection and during the injection. Aspects of the immunization before the injection that are reviewed include preparing the child and family, site selection for the injection, selection of needle length and gauge, and specific properties of the injectate. Elements during the injection itself that are reviewed include parental demeanor, use of sucrose, use of topical anesthetic agents, nonpharmacologic and physical strategies, and specific aspects of administration technique.
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BEFORE THE INJECTION |
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TOPABSTRACTBEFORE THE INJECTIONDURING THE INJECTIONCONCLUSIONSREFERENCES |
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In a survey study, Megel et al30 examined how parents prepared their children before preschool immunizations. Five types of preprocedural preparation/discussion were postulated: information sharing (what will happen), sensory information (how it will feel), justifying the procedure (explaining why the procedure is necessary), teaching relaxation strategies, and role playing. The results suggested that parents used a mixture of various types of preparation. Seventy-five percent of children received informational preparation from their parents, typically involving a description of the events that would occur. Of the 25% of children who received no information, 9 children were <3 years of age. Forty-two percent of parents also used some sensory information in their description. Forty percent of parents offered a rationale for receiving the injection. Relatively few parents (10%) offered the children any strategies for how to cope with the procedure (eg, relaxation, breathing, or distraction). Unfortunately, the relationship between the type of preparation and the child's subsequent distress was not reported by the researchers.
Although there are few studies of preparation for pediatric immunizations, the rich literature on preparation for other painful procedures and hospitalizations allows some recommendations to be made. For parents, information about the immunization should include the reason for the vaccination, with emphasis on its benefits, and realistic information about how much pain is associated with the immunization procedure. In addition, parents should be provided with techniques (breathing techniques, reading or telling a story, or involving the child in a fantasy) they can use to "coach" their children through the procedure, to promote coping.
For children, the extensiveness and style of preparation should be guided by each child's age and developmental level. In general, specific discussion about the immunization itself has more relevance for children >2 years of age. Research suggests that preparation should have at least 3 components, namely, what will happen (where, how long it will last, and what will be done), how it will feel (pressure, temperature, and level of discomfort to be expected), and strategies to cope with the stressor.31–33 Children should be asked what strategies they think will help them to cope and, if possible, those strategies should be incorporated into the immunization administration. In addition, given the strong data supporting distraction, that technique should be used during the immunization procedure.
In terms of the timing of preparation, literature findings are mixed. Studies have found that providing information too far in advance34 or too close to the event35 can heighten anxiety. Although some research revealed optimal timing for particular age ranges,36,37 those studies were not examining preparation for immunizations. Extrapolating from the literature on the development of children's sense of time, it seems that toddlers and preschool-aged children should be informed of the injection as close to the actual administration as possible, to prevent escalating anxiety. For older children, much depends on their individual coping styles. In summary, findings from the broader preparation literature suggest that preparation for pediatric immunization is important and there are some indications regarding how it might be performed, but clear detailed guidelines are not yet available, because of the limitations of research on preparation specifically for pediatric immunizations.
Injection Site Selection
Despite limited supporting evidence, there seems to be agreement among most major professional and educational organizations in this field regarding the sites of intramuscular injections. At this time, most endorse the use of the anterolateral thigh (vastus lateralis) for infants and the upper arm (deltoid) for children >18 months of age.1,38–41
The anterolateral thigh was selected for young infants because of its relatively large muscle mass and lack of vital structures. The shift from thigh to arm should occur when the upper arm has adequate muscle mass to allow injection. This shift is driven by research that suggests that injection in the thigh is more painful and causes more incapacitation than injection in the arm. Ipp et al42 found that, at 18 months, severe pain occurred in 30.5% of patients injected in the thigh but only 8.1% of those injected in the arm. Those authors stated that 50% of patients injected in the thigh had decreased movement of the extremity, compared with 35% of those injected in the arm. Two thirds limped for 24 to 48 hours after the immunization. Ipp et al42 also noted, however, that redness and swelling occurred significantly more frequently in the deltoid group. They suggested, on the basis of their data, that the shift to the arm should occur at 18 months. Others, such as the County of Los Angeles Department of Public Health40 and the Colorado Immunization Project,43 suggested that 36 months is a more-appropriate changeover time. The Red Book of the American Academy of Pediatrics1 is nonspecific on this issue. It suggests that parents and toddlers prefer the arm at 18 months, whereas some health care professionals prefer the thigh through toddlerhood.
It should be noted, however, that there is an alternative view to the one presented above. For the past 20 years, the nursing literature has suggested that an alternative location, the ventrogluteal site, is preferred for both younger and older children.44–47 The ventrogluteal site, colloquially known as the "hip site," is identified by "placing the palm of your hand over the greater trochanter, index finger over the anterosuperior iliac tubercle, and middle finger along the posterior iliac crest. The needle should be injected perpendicularly into the center of the V formed by the separated fingers."48 Cook and Murtagh44,45 reported on 2 studies in which children 2 to 18 months of age receiving either whole-cell pertussis vaccine or acellular pertussis vaccine were assigned randomly to receive their injection in either the anterolateral thigh or the ventrogluteal site. The ventrogluteal site had lower rates of systemic reactions (irritability and persistent crying) and local reactions (bruising and erythema). Parental acceptability for the ventrogluteal site was greater in both studies. For reasons that are unclear, despite nursing enthusiasm, this site is not endorsed by any of the major medical organizations, although it is mentioned as an option in the recent edition of the Red Book.1
Use of the buttocks (gluteus maximus), which had been common in the past, is no longer supported, for a variety of reasons. Sciatic nerve injuries were reported in the past when the buttocks were used for intramuscular injections, although Thompson49 argued that those injuries did not occur with modern medications. In fact, MacDonald and Marcuse50 solicited, from the practicing community, case reports of children who had sciatic nerve injury secondary to vaccine injection in the buttocks, and only 1 case was reported to them. In addition, the buttocks lack adequate phagocytic cells, which are necessary for antigenicity; therefore, there may be a delay in the development of the immune response51 if they are used. Because of these concerns, the buttocks are no longer used for intramuscular injections except when large volumes of injectate are necessary, such as for immunoglobulin.52
Although the evidence is limited and somewhat controversial, it is generally agreed by influential stakeholders in the area, such as the American Academy of Pediatrics, that the anterior thigh (vastus lateralis) should be used for intramuscular immunization injections until at least 18 to 36 months. After that, the deltoid muscle is suggested. In rare situations in which a very large volume of injectate is necessary, the buttocks may be considered. The ventrogluteal site typically is not included in recommendations that originate from medical authorities. Clearly, however, additional research comparing the various sites with respect to pain, local reaction, antigenicity, and parental acceptability is necessary. Only then can recommendations that are supported by adequate evidence be generated.
Needle Length
The length of the needle selected for intramuscular injections has been examined in a number of studies. Although it would seem intuitive that the shortest needle with the thinnest gauge would produce the least trauma and pain, this does not seem to be the case. A number of studies support the contention that longer needles, which are more likely to penetrate muscle than are shorter ones, cause less pain and fewer adverse effects.
Diggle and Deeks53 examined 4-month-old infants scheduled to receive their diphtheria-pertussis-tetanus (DPT)/Haemophilus influenzae type b vaccine in the anterolateral thigh. The patients were assigned randomly to receive the immunization with either a 16-mm (-inch), 25-gauge needle or a 25-mm (-inch), 23-gauge needle. The nurses used the World Health Organization injection technique, in which the skin is stretched taut and the needle is inserted at a 90° angle. Parents used a diary to report on the redness, swelling, and tenderness at the site for 3 days after the injection. More than one half of the infants vaccinated with the 16-mm needle developed redness and swelling initially, whereas only one third of the group vaccinated with the longer needle did. This difference between the groups persisted and in fact increased over the 3 days of observation. Differences in the reported rates of tenderness were not significant. An unfortunate flaw in the study was the fact that needle length was not the only independent variable, because the gauge of the needle also was changed. A meta-analytic review of this subject by Davenport,54 however, supported the conclusions drawn by Diggle and Deeks.53 The previously mentioned study by Ipp et al42 of 18-month-old children receiving DPT and polio vaccines also examined needle length. Those authors identified greater redness and swelling when immunizations were administered into the thigh with a smaller (16-mm) needle than with a longer (25-mm) one.
Two other studies call these conclusions into question, however. Studies by Cook and Murtagh55 and Groswasser et al56 both used ultrasonographic techniques to measure the subcutaneous tissue and muscle layer thickness of 2-, 4-, 6-, and 18-month-old children. Both studies identified the fact that, if the World Health Organization technique of immunization (skin taut, 90° angle) was used, then the shorter needle was adequate; however, if the skin was bunched, then the 16-mm needle deposited drug in the subcutaneous tissue and not the muscle. Diggle,57 responding to the article by Goldwasser et al,56 identified the fact that most children in that study were smaller than the normal population (most were between the 10th and 50th percentiles), which casts doubt on the generalizability of the finding that the smaller needle was adequate. In addition, the ultrasound studies were only indirect measures of potential pain and irritation and not direct measures. Complexity is added with the suggestion by Zuckerman51 that wider-gauge needles are associated with less localized erythema because they dissipate the injectate over a wider area.
The available data, therefore, are somewhat confusing. The Royal College of Pediatrics and Child Health,38 in response to the lack of clarity, thought that there was insufficient evidence to recommend any change in practice. It can be said, however, that, for larger infants or with skin-bunching techniques, a shorter needle would probably be inadequate to reach muscle and might result in increased local reactivity and likely pain and tenderness. Zuckerman51 therefore suggested the need for individualization of needle length on the basis of patient size and injection technique. The Red Book1 suggests a needle length of inch for newborns to 2 months of age and 1 inch for infants. For toddlers and older children, it suggests to 1 inch if the deltoid is used and 1 to 1 inch if the anterolateral thigh is used. For adolescents and adults, for whom the deltoid is clearly recommended, the needle length should be 1 to 2 inches. These recommendations are generally in line with the majority of literature reports, and we endorse them.
Injectate Properties
Properties Studied
A number of investigators have attempted to examine the impact of properties of the injectate itself on the pain associated with intramuscular injection. Three areas have been examined, namely, (1) changing the temperature of the injectate, (2) changing the diluent used to dilute it, and (3) changing the chemical properties of the injectate. Although all of these factors may have a role in reducing injection pain in general, few have been studied with respect to immunization pain specifically.
Temperature Changes
It has been theorized that some of the pain of immunization administration stems from the fact that many vaccines are refrigerated just before injection. Because it is generally assumed that injection of a cold substance is more painful than injection of a warm substance, it has been postulated that warming the injectate before administration may reduce pain. Studies on warming of other agents (such as lidocaine) before administration have substantiated this hypothesis.58 In a study comparing the pain associated with injection of a cold substrate with that of injection of a substrate at room temperature or body temperature, the latter was identified as least painful. With immunizations, however, there is the added complexity of the impact of temperature changes on biological availability and reactogenicity. In fact, in the one study that addressed the issue of injectate temperature and pain in immunizations, the authors found essentially no relationship. Maiden et al59 randomly assigned patients >16 years of age who required adult diphtheria-tetanus vaccine when they arrived at an emergency department to receive "cold" vaccine, "rubbed" vaccine (rubbed between the palms for 1 minute), or "warmed" vaccine (warmed in a 37°C incubator to body temperature). Although the cold vaccine had a significantly lower temperature when it was administered than did the vaccine in the other groups, there was no difference in time-averaged or peak pain scores. Although this area requires more research, changing the temperature of the immunization cannot be endorsed.
Type of Diluent
The choice of diluent may reduce both the short-term and long-term discomfort of an injection. Schichor et al60 randomly assigned adolescents scheduled to receive a ceftriaxone injection to 2 groups, one in which the diluent was sterile water and the other in which the diluent was lidocaine. There were dramatic differences between the groups, both initially and at 4 and 24 hours after injection. Amir et al61 reported similar results using lidocaine as a diluent for benzathine penicillin G, compared with sterile water. Because a number of vaccines are not premixed (eg, measles-mumps-rubella [MMR], varicella, and Haemophilus influenzae type b) and require dilution, the use of lidocaine instead of sterile water as diluent may be of benefit. Unfortunately, the impact of lidocaine on the biological activity of current vaccines has not been studied; therefore, this practice cannot be supported at this time.
Injectate Formulation
Two studies have compared the associated pain of various formulations of MMR vaccine. In the first study, by Lyons and Howell,62 the MMR II vaccine (Merck and Co, Whitham Station, NJ) was compared with the Pluserix MMR vaccine (GlaxoSmithKline, Middlesex, England) in children whose average age was 44 months. Those given the MMR II vaccine were at least 2 times more likely to cry, compared with those given the Pluserix vaccine. In the more-recent study by Ipp et al,63 12-month-old infants were assigned randomly to receive the MMR II vaccine or the Priorix vaccine (GlaxoSmithKline), a vaccine similar to the Pluserix vaccine. Sophisticated pain-assessment measures were used to evaluate the different responses of the infants, including behavior pain ratings based on a review of videotapes of the infants receiving their injections. Visual analog scale scores reported by the parents and the pediatrician were also obtained. There were dramatic differences in pain scores on all measures, with the Priorix group experiencing significantly less pain. Ipp et al63 suggested that the pain reduction might be associated with the slightly higher pH of the Priorix vaccine (7.2–7.6 vs 6.2–6.6). The Pluserix vaccine also was less acidic than the MMR II vaccine. This work is in keeping with previous work on the impact of buffering, lidocaine, and subsequent reduction of pain on injection.64 If available, these vaccines should be used.
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DURING THE INJECTION |
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TOPABSTRACTBEFORE THE INJECTIONDURING THE INJECTIONCONCLUSIONSREFERENCES |
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Unfortunately, one of the adult distress-promoting behaviors, reassurance, has also been found to be the most common adult vocalization during immunizations.68 Although the positive relationship between parental reassurance and child distress is counterintuitive, it has been supported by both correlational66 and experimental69 studies. However, not all children may be affected negatively by reassurance. For example, Broome and Endsley70 showed that some children reacted in a very negative manner (increased distress) to very positive parental behavior (including reassurance), whereas others responded positively.
Although the previously cited work focused primarily on older children, parental impact on the responses to pain in infants also is evident. Sweet et al71 found that, at 6 months, maternal behavior accounted for 26% of infant pain behavior, with an additional 17% accounted for by infant difficultness. Furthermore, infant vagal tone interacted with maternal behavior. The pain behavior of infants with high vagal tone was not affected by maternal behavior, whereas maternal behavior did affect the pain behavior of infants with lower vagal tone. Cohen et al72 examined discrete parental behaviors during infant immunizations and found that adult distraction was related to infants engaging in distraction and adult reassurance was related to infant distress.
Mothers and fathers may hold differing opinions about reassurance and related constructs. In a study by Schechter et al,9 fathers were more likely than mothers to agree strongly with the idea that "comforting encourages more crying." In addition, it may be that parental views of reassurance are changed by personal experience of its negative effect. For example, although parents trained to reassure their children during immunizations were more confident in their ability to help before the procedure than were parents trained to distract, those who reassured were significantly more upset after the procedure.69
Although parents can be trained to interact with their children in a manner conducive to less distress and increased child coping,73,74 training nurses may affect parental behavior. For example, Cohen et al74,75 found that a distraction coaching intervention was equally effective in increasing child coping and decreasing distress when only the nurses or the parents, children, and nurses were trained. Unfortunately, it is difficult to select parents who need targeted training in effective techniques because parents are not able to give accurate self-reports of their behavior during their children's immunizations. Cohen et al68 identified no significant relationship between what parents report they do and what they actually do during an immunization procedure. There was also no significant relationship between what parents say they do and child distress or coping during the procedure.
Nurse and parental behavior may have differing effects on children during immunizations. More specifically, several studies with both infants and older children have demonstrated that nurse behavior is associated with child coping, whereas parental behavior is related to child distress.65,73,74,76 Sweet and McGrath73 found that mothers of infants made more coping and distress-promoting verbalizations than did medical staff members across all phases (baseline, injection, and recovery). The impact of adult behavior on infant pain, measured as facial action, varied across phases, with no impact found during baseline. Maternal distress promotion and staff coping promotion accounted for 33% of variability in child pain during the injection phase, whereas maternal distress promotion accounted for 10% in the recovery phase.
Beyond the specific parental behaviors exhibited during pediatric immunizations, research has examined other parental qualities that may affect child behavior, such as parenting style, attachment relationship, and anxiety. Parenting style has also been shown to influence the amount of distress a child demonstrates. Broome and Endsley77 found that children of authoritative mothers (defined as high in warmth and high in control) were significantly less distressed during an immunization than were children of authoritarian (low in warmth and high in control), permissive (high in warmth and low in control), or unresponsive (low in warmth and low in control) mothers.
In summary, parental behavior during immunization clearly affects the child's distress during the procedure and the ability to cope. Although it seems counterintuitive, excessive parental reassurance, empathy, and apologies might increase distress, whereas humor and distraction tend to decrease distress. As discussed below, teaching parents techniques that they can use to promote coping should benefit parents by giving them roles that reduce their sense of helplessness and should benefit the child by reducing distress and increasing mastery. Nurse behavior may ameliorate some of the distress-promoting parental behaviors. Although it has not been studied, physician behavior is likely to follow the same pattern.
Securing the Child
There is limited literature on how children should be restrained during the injection. For young children, the goal is to have the thigh exposed and relaxed. Often this involves having the parent hold the child in his or her lap. Older children either can sit in their parent's lap, facing the parent with their legs wrapped around the parent (the so-called "big hug"), or can sit facing forward. The deltoid should be exposed and relaxed if at all possible. Some parents are unable or unwilling to be involved in restraining their child. This preference should be respected if there are adequate office staff members, but the parents should remain present during the procedure, distracting the child during needle insertion and soothing the child after the procedure.
Distraction
In the arsenal of nonpharmacologic, pediatric immunization, pain management techniques, distraction is recognized as one of the key interventions.78,79 There are a number of possible explanations for the function of distraction. The gate-control theory,80,81 one of the early scientific models to explain pain transmission, suggests that the central nervous system modulates the pain experience and thus cognitive attention might affect the processing and perception of pain. Neurophysiologic data support this explanation. For example, the areas of the brain known to process pain stimuli have been shown to be less active during distraction tasks.82–84 Consistent with the gate-control theory, the limited-attentional capacity theory suggests that, if some attention is allocated to a distracting task, then there are necessarily fewer resources available to attend to pain.85 Behaviorally, distraction can be described as introducing a stimulus with previous positive associations (eg, favorite toy), evoking behaviors that are incompatible with pain behaviors (eg, laughing at a movie), and reinforcing nonpain reactions.29
A number of distraction stimuli have been evaluated for pediatric acute pain. For example, researchers have examined movies,86 party blowers,69 nonprocedural talk,87 interactive robots,88 virtual reality goggles,89 kaleidoscopes,90 bubble-blowing,91 short stories,92 and music.93 In a meta-analysis of 19 pediatric pain management studies using distraction, results suggested a moderate effect size in decreasing distress behavior but minimal impact on self-reported pain.94 Results also indicated that distraction was most effective for children <7 years of age; there were no gender or ethnic differences in the efficacy of distraction.
Although a variety of distraction stimuli have been examined, few studies have compared them to determine whether one might be better than another. Mason et al92 compared cartoon movies versus a storybook that required button pressing in an attempt to distinguish passive and interactive distraction with 7 preschool-aged children undergoing Port-a-cath (Smiths Medical, Kent, England) and Hickman line access procedures. Results suggested that the interactive distraction decreased children's pain more effectively; movies did not differ from control treatment. The small sample size and the apparent low distraction quality of the selected movies limit the findings. Recently, MacLaren and Cohen95 found that movies were superior to an interactive robot for venipuncture pain in 88 children. Until more comparison studies are performed, it remains unclear whether some distraction stimuli might be optimal.
Related to the quality of the distraction, MacLaren and Cohen95 found that, the more children are engaged in distraction, regardless of the type of distraction stimuli, the lower the pain. This inverse relationship between attending to distraction and decreased distress was also found by Cassidy et al96 in an evaluation of cartoon movies for preschool-aged children's immunizations. Therefore, the particular distraction stimuli might be less relevant than whether or not they engage the patient's attention.
The distraction literature is complicated by the fact that many distraction interventions incorporate other psychosocial components, such as role-playing,97 coping skills training,98 and positive reinforcement of cooperative behavior.99 Similarly, the manner in which the distraction is conducted varies across studies. For instance, the clinician performing the procedure has performed the distraction,86 parents have served as coaches,76 and the researchers have been the mode of distraction.95 One of the only studies to compare methods of distraction suggested that using the nurses to coach might be as effective but more practical than training the parents to coach.76 However, this would likely vary depending on the complexity of the distraction stimulus.
Although distraction for immunization pain has been examined, much of the data on distraction have been obtained with children undergoing other procedures, such as venipuncture99 or lumbar punctures and bone marrow aspirations.98 In the immunization pain literature, the majority of work has focused on preschool-aged children, because they exhibit high distress and require immunizations before entering school. In fact, only a few studies have examined distraction for immunization distress in infants,29,100,101 and one study was performed for immunizations in preadolescents.102 These studies provide moderate support for adult-led distraction for non-preschool-aged children, but it is clear that more research on distraction for immunization pain in non-preschool-aged children is warranted.
When selecting a distraction stimulus, health care professionals should consider a number of factors. For example, the age and cognitive maturity of the patient is a critical consideration; age-appropriate and engaging stimuli (eg, toys or movies) should be selected. Other factors to consider are the cost, time, and space required for the stimulus. Clinicians might also consider children's natural coping tendencies76 and temperament,9 patient preferences, and other individual characteristics when selecting an intervention. Research suggests that emotional valence and novelty of the distraction stimulus might be important factors, but these variables have not been examined sufficiently to allow direct recommendations.103 Given the ease of use, the growing body of empirical support, and the lack of apparent negative consequences, clinicians should routinely use distraction for pediatric immunizations. As researchers continue to examine the mediators and moderators of distraction for pain management, clear recommendations might be available to indicate how, when, where, what type of, and for whom distraction is optimal.
Use of Sucrose
Sucrose water (12%–50%; typically 1 packet of sugar in 10 mL of water) or other sweet solutions, when administered just before the procedure, have been shown to decrease the pain associated with procedures in neonates.104,105 It has been suggested that sucrose interacts with opioid pathways to accomplish this phenomenon; however, recent studies call this model into question.106,107 Sucrose can be administered with a pacifier or directly instilled into the mouth with a small syringe. It seems to work best in the neonatal period and loses its efficacy by 4 to 6 months of age.105 Nonnutritive sucking (sucking on a pacifier) also seems to have analgesic properties in neonates and may be synergistic with the use of sucrose.108–110 The combination of direct parental contact and sucrose seems to have an additive effect on the reduction of pain.111 Breastfeeding has also been shown to provide analgesia when allowed to continue during heel lancing.112
Sucrose has been studied for pain reduction associated with immunization. Lewindon et al104 showed reductions in both crying time and nurse Oucher ratings for infants at 2, 4, and 6 months who received 2 mL of a 75% sucrose solution before immunization, compared with those who received sterile water. Barr et al105 showed mild reduction of postinjection crying in 2- and 4-month-old infants who received a 50% sucrose solution. Allen et al113 found 12% sucrose to be no more effective than sterile water but more effective than no intervention in reducing crying times for 2-week-old, 9-month-old, and 18-month-old children receiving a single injection. Neither sucrose nor sterile water provided any benefit, compared with no treatment, for 2-, 6-, and 15-month-old children receiving >1 injection. Crying time was the only outcome studied. Ramenghi et al114 found that 50% sucrose resulted in shorter crying times, compared with 25% sucrose, glucose, or sterile water, for 4-month-old children. There was a trend toward shorter crying times for 2- and 3-month-old children receiving 50% sucrose in that study, but it did not reach statistical significance. Some studies evaluated sucrose in combination with other techniques. Reis et al111 found that sucrose in combination with oral stimulation and parental holding decreased crying duration but not heart rate changes in 2-month-old children. Lindh et al115 showed less crying and less change in modified behavioral pain scores, as well as lower parent and nurse visual analog scale scores, for 3-month-old children who received eutectic mixture of local anesthetics (EMLA) cream plus glucose, compared with placebo cream plus sterile water, before the DPT immunization.
Although sucrose use has been studied and clearly has efficacy for young infants, a systematic research approach to this issue is indicated. This would include testing a variety of sucrose concentrations for 2-, 4-, and 6-month-old children, with and without other modalities such as nonnutritive sucking and parental contact, by using a variety of standard pain measures, including crying time, behavioral pain scores, heart rate variability, and salivary cortisol measurements. At this time, however, there seem to be sufficient data to recommend sucrose use as a routine part of immunization administration for infants 6 months of age.
Topical Anesthetics
Topical anesthetics have been shown to reduce the pain of both subcutaneous and intramuscular injections, despite their limited skin penetration. This finding has spurred attempts to develop better topical anesthetics for use in office settings. Such agents should be safe and inexpensive, should have rapid onset (10 minutes), and should have no effect on vaccine immunogenicity.
The topical anesthetic most studied for use with immunization is EMLA cream.116–119 Despite the limited depth of penetration of EMLA, some studies suggest that it is effective in reducing the pain of both subcutaneous and intramuscular immunizations. The success of EMLA in reducing injection pain is likely attributable to a decrease in pain as the needle penetrates the skin, as well as a reduction in the underlying muscle spasm associated with this pain. EMLA is safe, even for premature infants, and does not alter the immunogenicity of the MMR or DPT/inactivated polio/Haemophilus influenzae vaccines.116,120,121 Unfortunately, EMLA's onset of action (
1 hour) limits its applicability for immunization in the office setting.
Amethocaine (4% tetracaine gel; Smith-Nephew, London, England) also seems efficacious for subcutaneous immunization.122 In comparative trials with EMLA, it might provide superior anesthesia for a range of procedures, and it has a time to onset of anesthesia of 30 minutes.123 Amethocaine is not presently available in the United States.
Vapocoolant sprays provide anesthesia in 30 seconds and are inexpensive (50 cents per application). Although one study found vapocoolants to have efficacy equivalent to that of EMLA for immunization pain in 4- to 6-year-old children, other studies have not shown them to be better than placebo.124–126 Reis and Tarbell127 studied vapocoolant spray as an adjunct to sucrose and comfort measures for 6-month-old children and found no additional benefit.
Liposomal lidocaine (LMX4; Ferndale Labs, Detroit, MI) is effective for venipuncture but has not been studied for immunization pain.128,129 This anesthetic preparation, like EMLA, is handicapped by its delayed onset of action (>30 minutes) and thus is less likely to be useful in the office setting. Lidocaine iontophoresis is also effective for venipuncture and reduces injection pain but has not been studied specifically for immunizations.130–132 It is rapidly effective (in 10 minutes) and penetrates more deeply than EMLA; however, some available systems are cumbersome and can be uncomfortable for some children.131 Newer technologies that work more rapidly (5 minutes) may overcome problems related to the use of topical anesthetics in busy outpatient settings. These technologies include laser ablation of the stratum corneum, powder injection technology, and the use of ultrasonography to enhance the permeability of the stratum corneum.133–137 These technologies have not yet been evaluated for safety and efficacy for pediatric immunization but may have a role in the future.
Given the lack of availability of a rapidly acting topical anesthetic with proven efficacy and the potential expense associated with application, universal use of local anesthetics cannot be endorsed at this time. For selected children who are needle phobic or in offices where logistic and financial factors permit such an approach, topical anesthetics certainly should be considered. Vapocoolant sprays might be used more routinely because they are inexpensive, but their efficacy remains uncertain.
Technical Variables
General Considerations
A number of technical factors associated with the injection itself have been examined, to determine their impact on injection pain. As with other aspects of the injection experience, there are very few studies that help guide practice, despite the frequency with which injections are administered. The studies that exist often have methodologic flaws that limit their usefulness. However, enough evidence exists to allow tentative recommendations for providers.
Injection Technique
There seems to be general agreement regarding the technique of needle insertion. For intramuscular injection, whether in the anterolateral thigh, deltoid, or ventrogluteal area, the general suggestion is that the skin should be held taut around the injection site and the needle darted into the skin at an 90° angle.39 Traditionally, the plunger is then slightly withdrawn to certify that the needle did not enter a vein. Recently, however, researchers examined the value of this practice and found it to be unnecessary.1 The vaccine is then injected under steady pressure, and the needle is withdrawn at the same angle at which it was inserted. If the vaccine is to be administered subcutaneously (inactivated polio, MMR, or varicella vaccine), then the skin around the site is typically pinched or bunched and the needle is inserted at a 45° angle. The rest of the process is identical to that for intramuscular injection.38–40
An alternative technique that was suggested in the nursing literature 20 years ago is the Z-track technique. In this technique, the injector's hand is placed on edge across the injection site. The skin is then displaced from the underlying subcutaneous tissue, and the injection is administered. When the injection is completed, the skin is released and returns to its normal position, trapping the injectate in the muscle and eliminating any seepage back into the subcutaneous tissue. In a study by Keen138 of adults receiving medications other than immunizations, less pain was reported in the Z-track group, compared with the standard-technique group. There are no available data on the frequency with which this technique is now or was ever used.
Site Pressure
It was suggested that pressure at the injection site would reduce the pain associated with immunization. This work is based on the gate-control theory of pain, which posits that flooding an area with a stimulus that is nonnoxious reduces the intensity of a painful stimulus in the same general area.80,81 The example traditionally offered is rubbing your knee when you bump it on a table.
Barnhill et al139 randomly assigned 93 adults who were scheduled for intramuscular injection of immunoglobulin to 2 groups; one group received 10 seconds of direct pressure to the injection site, and the other group received the standard injection technique. Those authors found that the pressure group reported a slight but statistically significant reduction in the immediate pain of the injection (13.6 vs 21.5 mm on a 100-mm visual analog scale; P = .03).
In a more-recent article, Chung140 reported on 74 adults who each received 2 injections, 1 with 10 seconds of pressure before the injection and 1 with no previous pressure. Their findings were similar to those of Barnhill et al,139 although slightly more robust (1.77 vs 2.86 on a 10-point visual analog scale; P = .0001).
An extension of this work has been the development of a device known as the ShotBlocker (Bionix, Toledo, OH). The ShotBlocker is a horseshoe-shaped plastic sheet that is tufted on one side. The device is placed around the injection site, and the needle is placed in the middle of the horseshoe. The theory is that the multiple tufts, which are pressed gently against the skin, diffuse the pain sensation. The company that developed this device reported only 2 studies in children with the ShotBlocker, neither of which was published. One study by Guevarra (A. D. Guevarra, MD, unpublished data, 2003) reported the use of the ShotBlocker for 59 kindergarten students receiving an immunization and compared those children with 60 control subjects. Pain was assessed by using the Wong-Baker scales and reportedly 93% of the ShotBlocker group reported no pain, compared with 51% of the non-ShotBlocker group. Similar findings were reported in an unpublished study by Gundrum et al (T. Gundrum, PharmD, C. Sherman, MD, S. Ruhlman, BA, unpublished data, 2001). Both of those studies were methodologically flawed and presented only limited data supporting their conclusions. In contrast, Foster et al141 reported that the ShotBlocker, in a randomized, controlled trial at an immunization fair, was ineffective in reducing immunization pain. That study was compromised by its broad age range (3 months to 17 years) and the fact that children received 1 to 7 immunizations during the intervention. Although these studies are inconclusive and more rigorous research is necessary, a wealth of anecdotal data support the value of pressure at the injection site as both effective and without adverse effects.
Simultaneous Versus Sequential Administration
Finally, in this era of multiple injections at each visit, the possible advantage of simultaneous injections (multiple staff members injecting at different sites at the same time), as opposed to sequential ones (one after the other), has been suggested. To date, 2 studies have examined this question, 1 in infants and 1 in older children.142,143 Those studies yielded essentially the same conclusion; although there was no detectable decrease in discomfort in the child when the immunizations were given simultaneously, compared with sequentially, parents preferred simultaneous administration if possible.
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CONCLUSIONS |
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TOPABSTRACTBEFORE THE INJECTIONDURING THE INJECTIONCONCLUSIONSREFERENCES |
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When the situation is actually examined, however, there is a price to pay for intramuscular immunizations. As mentioned above, although immunizations are an inconvenience for most children, they are truly dreaded by some. In general, anticipation of an injection fosters an air of persistent tension that hangs over the clinical encounter, especially in this era of multiple injections. This tension is experienced not only by the child but also by his or her parents and the clinician. It behooves us, therefore, to minimize this pain if that can be reasonably accomplished.
This review attempted to collate the relevant literature and to draw some conclusions about the appropriateness and efficacy of currently available interventions. Before any review, it should be noted that, even in areas in which there is general agreement among experts, controversy persists. In addition, the complexities of child development necessitate modifications based on age and understanding.
Before the injection, preparation seems to be beneficial for children >2 years of age. For young children (<4 years of age), preparation should be done in close chronological proximity to the injection itself. For infants and toddlers up to 18 months of age, the current standard site for intramuscular injection is the anterior thigh (vastus lateralis), with a - to 1-inch needle for children >2 months of age. The ventrogluteal site may be an alternative. At >36 months of age, the deltoid should be used instead of the thigh, but the ventrogluteal site may still be an alternative. Between 18 and 36 months of age, there is controversy regarding the most-appropriate site.
During the injection, there is strong evidence to suggest that parental demeanor has an impact on child behavior. Although it seems counterintuitive, children often are more distressed when parents are more rather than less involved. Therefore, a matter-of-fact, supportive, nonapologetic approach is endorsed. Parents should be instructed to use distraction techniques that are in concert with their personal style and their child's age and temperament. These techniques may include storytelling, reading to the child, deep breathing, and blowing. Given the expense and time, universal local anesthetic administration is not necessarily appropriate, but use should be considered for children who will require multiple procedures in the future or who are phobic or particularly anxious about the pending injection. Sucrose, which is relatively inexpensive, should be used for children <6 months of age. Pressure at the site, applied either manually or with the aid of a mechanical device, has some support in the literature, is noninvasive and without adverse effects, and is inexpensive. Finally, it is clear that properties of the injectate itself can affect pain, but this area has had almost no sophisticated research and is an open area for investigators to explore. In Table 1, the specific techniques discussed and the levels of support for their efficacy are summarized.144
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ACKNOWLEDGMENTS |
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We appreciate the invaluable contributions of other members of the consensus group, including Leonard Banco, MD, Bruce Bernstein, PhD, Frederick Bogin, MD, Kathleen McKay, PhD, Lee Pachter, DO, and Harry Weinerman, MD.
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FOOTNOTES |
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Address correspondence to Neil L. Schechter, MD, Pain Relief Program, Connecticut Children's Medical Center, 282 Washington St, Hartford, CT 06106. E-mail: nschech{at}ccmckids.org
Financial Disclosure: Dr Zempsky is a consultant to Anesiva Pharmaceuticals.
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