Factors associated with infant pain response following an immunization injection

Abstract

Objectives

Specific potential determinants of infant pain response were assessed in the context of a 4- or 6-month immunization injection. The distal influences of gender, gestational and current age, temperament, and early nociceptive stimuli were considered, as well as the proximal influences of parental and nurse coping-promoting statements within the treatment room.

Study design

An observational study design was used. Pain responses in 93 infants receiving an immunization injection were videoed and coded using the Neonatal Facial Coding System (NFCS) and duration of crying was recorded. Parent and nurse vocalizations were coded using the Child–Adult Medical Procedure Interaction Scale-Revised.

Results

A multiple regression analysis evaluated the influence of the 5 distal and 2 proximal factors on NFCS scores, and found parental coping-promoting statements in the 30 s period before the injection to have the strongest effect on facial pain response (p < 0.01). Parents made significantly more coping-promoting statements (p < 0.05), and generally talked more (p < 0.05), to female infants than male infants.

Conclusions

The findings suggest that parental behavior in the treatment room has a key role in influencing how infants respond to painful procedures.

Introduction

There is considerable variation in the way that infants respond to painful stimuli. Whereas some infants react vigorously, others show little response to seemingly comparable nociceptive events [1], [2]. A better understanding of the factors which influence how infants respond to painful stimuli has important implications for devising improved pain management plans for infants.

In considering the broad array of factors that may influence infant pain responses, a distinction will be drawn between variables that are temporally and functionally distal and those that are temporally and functionally proximal to the immunization context [3], [4]. Distal factors are defined here as any factor present before the infant came into the treatment room for the current procedure, including gender, gestational age, infant temperament, and early painful experiences. Proximal factors are defined here as factors that occur within the treatment room immediately prior to or during a medical procedure, for example, parental and nurse verbal behaviors. The current study sought to investigate the relative influences of a number of distal factors, namely gender, gestational age, temperament and experience of early nociceptive stimuli, as well as two proximal factors, namely parent and nurse coping behavior in the treatment room, on infant pain response following an immunization injection.

Early painful experiences may produce alterations to nociceptive circuitry [5], [6]. A number of studies have found that exposure to acute pain during the neonatal period may result in a decreased pain threshold [7], [8] or heightened distress responses for subsequent procedures [9], [10]. Infants born more prematurely have been found to have a dampened behavioral response to painful stimuli [5], [11], although they may have heightened physiological pain and stress responses [5].

Although a number of studies have found temperament [2] and gender [12] to be associated with infant pain responses, these relationships have not been consistently documented in the literature [1], [13], [14], [15].

In considering proximal factors that may impact on pain outcomes of infants and children, the behavior of parents and nurses within the treatment room is likely to be of key importance [16], [17], [18]. Adult behaviors that may facilitate adaptive infant coping during an acute pain experience include humor, non-procedural talk, and distraction [19], [20], [21]. In contrast, adult reassurance and apologizing have been found to be associated with increased child distress [22], [23]. There has been little research to investigate the relative roles of parents versus nurses within the context of infant medical procedures. One exception was a study by Sweet and McGrath (1998), which evaluated the role of parent and staff behavior within the infant immunization context [18]. They found that mothers' distress-promoting behavior, as defined using the Child Adult Medical Interaction Scale-Revised, predicted greater infant pain behavior. In contrast, staff coping-promoting behavior (e.g., distraction) predicted lower infant pain responses.

The aim of the current study was to examine the relative influence of a number of distal factors (infant gender, temperament, gestational age at birth, and early invasive medical procedures) and two proximal factors (parental and nurse coping statements in the treatment room) on infant pain responses. The primary hypothesis was that when controlling for the influence of the distal factors on infant pain outcomes, the proportion of coping-promoting statements made by parents and nurses in the treatment room just prior to the immunization injection would account for significant additional variance in terms of infant pain response.