Is this infant in pain? Caveats from the clinical setting

Commentary

Is This Infant in Pain? Caveats From the Clinical Setting Ronald G. Barr

ne of the more striking asymmetries in the context of pediatric are of pain experience is the difference between a parent’s and a physician’s opinion about whether an infant is experiencing pain in response to a procedure. Few parents watching an infant receive an immunization or undergoing a heel stick would hesitate to confirm that their infant is in pain. In sharp contrast, however, Schechter and Allen” ascertained that, for many physicians, pain experience “similar to adults” does not occur in infants. All physicians surveyed believed that the pain was similar only after children reached age 12. Only 50% felt that pain in infants under 1 month of age was similar. Of the three groups of physicians surveyed (family practitioners, pediatricians, and pediatric surgeons), surgeons were the least convinced, with only 30% believing that infants under 1 month felt pain similar to adults. In his focus article describing recent work on the facial expression of pain, Dr. Craig articulately describes another important asymmetry, namely, the difference between the emphasis placed on verbal self-report and the relative neglect of facial activity as both a sign and a measure of pain experience. While the significance of his argument is not limited to the assessment of pain in infants, it will no doubt strike a particularly salient chord in pediatric clinicians for whom assessing pain in the absence of verbal self-report is a daily occurrence. Dr. Craig confirms a number of important points, including that facial expression in infants can be coded objectively, that such coding has been used successfully in a variety of studies involving noxious stimuli, and that facial expression is an important (maybe the most

0

From McGill University-Montreal Institute, Montreal, Quebec, Reprint requests: 2300 rue Tupper,

Ronald Montreal,

Children’s

Hospital

Research

G. Barr, Montreal Children’s QC, Canada H3H-1 P3.

Hospital,

Canada.

APS Journal l(3): 187-190, 1992

important) component of an adult’s judgment of the severity of the noxious stimulus. Perhaps most interesting is the argument that “a facial expression relatively specific to pain” has been described in infants. This is potentially of great importance because the ability to tell that an infant is or is not in pain would undeniably represent a significant advance. Indeed, one might ask whether a redressing of the asymmetric emphasis on self-report might contribute to a redressing of the asymmetry between physicians and parents as to whether infants are experiencing pain (and therefore deserve analgesia). Of course, beliefs about pain experience in infants and practices concerning analgesic use have multiple determinants, and no one measure, verbal or nonverbal, is likely to be solely responsible for a change in beliefs or practice. However, if the promise of being able to measure pain in infants is fulfilled, and especially if it specifically measures pain in individual infants, an important hurdle to the clinical treatment of pain in infants will have been overcome. After reading the evidence reviewed by Craig, my impression is that attention to facial (or nonverbal) expressions will contribute to clarifying, but not resolving, the problem of deciding whether an infant is in pain. In trying to illustrate why, I will limit myself to examples with infants. These comments take nothing away from the impressive recent advances in the systematic study of nonverbal responses Craig describes (and to which he himself has contributed significantly); they are rather in the nature of a caveat concerning their possible significance in clinical problem solving. Some reasons for the predominance of attention to verbal self-report measures that Craig suggests are that they are believed to provide direct access to subjective pain experience, can convey the complexity of the experience, have the advantage of providing retrospective accounts, are a fundamental informa187

188

COMMENTARY/Barr

tion source, and logistically, are easier to obtain. On the other hand, they are recognizably subject to reporting bias and are not, as he points out, “equivalent” to the subjective experience. With the exception of the provision of retrospective accounts, systematic study of the “language” of facial expression could, at least in principle, provide similar information, albeit with a little more effort. The predominance of self-report measures for these reasons would seem to be simply a function of lack of study, logistic feasibility, or investigator bias, rather than any logical or conceptual limitation. However, when one asks whether an infant is in pain, another potential reason for the predominance of self-report becomes apparent by highlighting a dilemma determined by the rules of our language. In ordinary discourse, the term pain refers to a quintessentially subjective phenomenon, and there is no objective marker by which one can say that pain is or is not experienced by another individual, even in adults. In the Wittgensteinian sense, the rules of the language game for the term pain do not include there being a marker independent of the solipsistic world of the experiencer. However, it is at least meaningful to ask an adult whether they experience, for example, pain or pressure when they undergo a lumbar puncture, and it is meaningful for them to say “I most certainly do feel pain, not just pressure.” Despite the possibility of deception and subject to some cultural differences, we have some access to the subjective world of pain in adults, even though we do not have independent “objective” measures. With preverbal infants, this access to pain experience is denied us. However, it is not denied because infants are more biased reporters; rather, it is denied a priori. In the primary sense in which we use the word pain in our language, the question-as applied to infants-is unanswerable. Infants cannot, so to speak, answer “I most certainly do feel pain” to our question. This conceptual limitation does not (and should not, of course) keep us from studying pain in infants. However, the study of pain in infants is the study of responses to noxious stimuli, which we “know,” on the basis of verbal report, to be painful in adults. And, indeed, significant advances have been made in recent years. For example, Anand and colleagues’~2 have articulately summarized the evidence to show that those components of the nervous system known to be necessary for the sensation of pain in adults are present and functional in newborns and even premature infants. Consequently, it is decreasingly plausible to argue that infants do not feel pain because of “neurological immaturity.” On the other hand, knowing that they can does not mean that they do,

and even knowing in general that they do is not the same as knowing that any particular infant is in pain at any point in time. It is this latter situation that represents the crux of the clinical problem of assessment of pain in infants. It is here that the evidence for the “relative specificity” of facial activity could potentially be important, especially in infants. However, the very same evidence that demonstrates its relative specificity also demonstrates its likely limitations, at least for solving our clinical problem. As Craig notes, the facial expression thought to be specific has been derived from studies of immediate responses to invasive procedures, such as heel lance, finger sticks, intramuscular injection, and venipuncture. As nonpain stimuli, Craig and colleagues (and others) have used conditions such as prelance handling, alcohol swabbing on the opposite thigh, and application of triple dye to the umbilical stump.*-‘o In general, two findings emerge: (1) total facial activity and a cluster of facial actions (brow bulge, eye squeeze, nasolabial furrow depth, and open mouth) are significantly associated with the “pain” condition,1° and (2) facial activity is used by adults to distinguish pain from non-pain stimuli and to assess the severity of pain response.6,7 Furthermore, relative to the measured acoustic parameters of the infant’s cry, facial features seem to predominate as determinants of adult judgments. This clearly does provide evidence for some specificity, which, in addition, is detectable and used by adult observers. From the point of view of research strategy, this is a relevant paradigm and does support the usefulness of facial activity in such studies. Nevertheless, with regard to its usefulness for deciding whether a particular infant is in pain in the clinical setting, the data are not very promising. First, these facial actions were associated more frequently, but not uniquely, with the pain condition. Second, the variability indicated considerable overlap, both for the presence of facial actions and for the parent ratings based on them. Thus, for example, the means and 1 SD of total facial activity were 23.2 2 6.4 during injection and 14.5 + 7.6 during the relatively innocuous thigh swab procedure. lo Despite the fact that this represents a sizeable mean difference for groups of infants, many individual subjects will show facial activity in the injection range when having a thigh swab and vice versa. Mean differences in discomfort ratings between these two conditions were approximately 10 points, with standard deviations of 8-12 points, when adult observers had access to face, cry, or both on which to make their judgments.’ Third, if there is this much overlap for procedures presumed

189

COMMENIARY/Barr

to have clearly different “pain” potential and using only the initial most extreme facial and vocal reaction, how will one decide whether an infant is in pain when undergoing procedures with more moderate pain potential, or subtler degrees of difference between pain and non-pain? Fourth, as Craig points out, we know little or nothing about what the “pain” response looks like or how specific it is after the immediate reaction, in response to repetitive stimulation, under conditions of chronic procedural pain, or in the absence of an extrinsic stimulus. Both the potential and the limitations of facial activity as a sign of pain were demonstrated in our use of facial activity during crying before and after meals in infants with colic.5 The entity of colic is a particularly good prototype to illustrate the extent of our ignorance about pain experience in infants. In contrast to virtually all of the work to date on both crying and facial response to noxious stimuli, the crying (both vocalizations and facies) of infants with colic is recurrent rather than acute, lasts for minutes (to hours) rather than seconds, is unpredictable rather than predictable, and occurs in the absence rather than in the presence of any apparent noxious stimulus. I have argued elsewhere4 that there could be no better illustration of how little is known about the nature of pain in infants than to try to demonstrate the assumption that colic is a pain syndrome. Nevertheless, most parents, about 25% of authors on the subject3 and apparently Dr. Craig himself perceive that the syndrome represents “recurrent pain” in the infant. In our study, we used Grunau and Craig’s9 facial coding system to determine whether there were any differences in the “crying facies” of three groups of infants: those whose mothers complained of their crying and did or did not meet “Wessel’s criteria” for colic (Wessel’s colic and non-Wessel’s colic, respectively) and control infants. The results for the measure total facial activity are shown in Fig. 1, which illustrates that before feeding Wessel’s colic infants showed more facial activity when crying than the control infants, but also more than non-Wessel’s colic infants. To our knowledge, this is the first demonstration of an objective difference between infants with colic and control infants that is not subject to reporting bias and which, furthermore, suggests there may be two subgroups of infants with colic. For this alone, the facial coding system has been extremely useful. However, as is apparent from attending to the within-group variability (indicated by the standard deviation bars), there is much overlap between groups. When we looked at the rate of presence of a “pain concatenation” (simultaneous pres-

120 r

Fc2.w

= 5.10;

P < .Ol

110 05 ‘;

100 90

2 g

00

x

70

8 ii

60

:: v-

50

E

40

t

30

2

2 20

10 2

:

(29)

(20)

(10)

NON-WESSEL

CONTROL

WESSEL

,

COLIC

Figure 1. Facial activity rates. The rates of occurrences per 120 seconds when crying before feeding for total facial activity are represented for infants with Wessel’s colic (closed bar), non-Wessel’s colic (hatched bar), and controls (open bar). The F-statistic for the one-way ANOVA comparing the groups is in the upper section of the panel. Starred brackets indicate significant between group comparisons (** = /Jcr .Ol). From Barr et al. Pediatrics (in press) 1992 (with permission)

ence of eye squeeze, deepened nasolabial furrow, open mouth, and brow bulge-the “typical” reaction to acute invasive procedureslO), a similar pattern and variability among groups was found. This may help explain why infants with Wessel’s colic are thought to be in pain, but does not demonstrate that they were in “more pain” than their peers. Craig’s arguments that the value of nonverbal, and particularly facial, expression has been underestimated and underused relative to verbal reports are convincing. This may have been due to biased beliefs about, or a logistically easier ascertainment of, verbal reports but may also relate to a conceptual primacy for verbal reports determined by the rules of our language. While the presence of a “typical” facies in response to noxious stimuli and its salience for adult judges is promising, the evidence for its “specificity” is based on immediate responses to relatively differentiated, known, acute stimuli in groups of infants. Even under these circumstances, the overlap among responses in individual infants and between condi-

190

COMMENTARY/Barr

tions is considerable. ceptual and empirical

Consequently,

for

both

con-

reasons, determining whether a particular infant is in pain at any particular time may prove refractory, even if we understand facial expression better. This should not discourage investigation and use of facial expression, but promissory notes that it will solve our clinical problems might best be issued with caution.

References 1. Anand KJS, Carr DB: The neuroanatomy, neurophysiology, and neurochemistry of pain, stress, and analgesia in newborns and children. Pediatr Clin North Amer 36:795-822, 1989 2. Anand KJS, Hickey PR: Pain and its effects in the human neonate and fetus. N Engl J Med 317:1321-1329, 1987 3. Barr RG: Colic and gas. p. 55. In Walker WA, Durie PR, Hamilton JR et al (eds): Pediatric gastrointestinal disease: pathophysiology, diagnosis and management BC Decker, Burlington, VT, 1991 4. Barr RG, Geertsma MA: Colic: the pain perplex. In

5.

6.

7.

8.

9. 10.

11.

Schechter NL, Berde C, Yaster M (eds): Pain management in children and adolescents. Williams & Wilkins, Baltimore (in press) Barr RG, Rotman A, Yaremko J et al: The crying of infants with colic: a controlled empirical description. Pediatrics (in press) Craig KD, Grunau RVE, Aquan-assee J: Judgment of pain in newborns: facial action and cry as determinants Can J Behav Sci 20:442-451, 1988 Craig KD, Grunau RVE, Johnston C, Hadjistravropoulow H: Facial and cry determinants of adult judgments of pain in newborns. (submitted) Craig KD, McMahon RS, Morison JD, Zaskow C: Developmental changes in infant pain expression during immunisation injections. Sot Sci Med 19:1331-1337, 1984 Grunau RVE, Craig KD: Pain expression in neonates: facial action and cry. Pain 28:395-410, 1987 Grunau RVE, Johnston C, Craig KD: Neonatal facial and cry responses to invasive and non-invasive procedures. Pain 42:295-305, 1990 Schechter NL, Allen DA: Physicians’ attitudes toward pain in children. J Dev Behav Pediatr 7:350-354, 1986