The Toddler-Preschooler postoperative pain scale: an observational scale measuring postoperative pain in children aged 1–5. Preliminary report

Pah), 50 (1992) 273-280 ((.7) 1992 Elsevier Science Publishers B.V. All rights reserved 0304-3959/92/$05.00

273

PAIN 02094

The Toddler-Preschooler Postoperative Pain'Scale- an observational scale for measuring postoperative pain in children aged 1-5. Preliminary report Sally E. Tarbell, I. Thomas C o h e n and Julie L. Marsh Department of Surgery, Unit,ersity of Massachusetts Medical Center, Worcester, MA 01655 (USA) (Received 2 August 1991, revision received 24 February 1992, accepted 2 March 1992~

Summary This study evaluates the reliability and validity of the Toddler-?~eschooler Postoperative Pain Scale (TPPPS), an observational scale developed to be a clinically useful measure of postoperative pain in children aged 1-5 years. The TPPPS consists of 7 items divided among 3 pain behavior categories: (1) Vocal pain expression; (2) Facial pain expression; and (3) Bodily pain expression. These items were derived from preliminary studies by the authors and from other observational studies of children's pain behavior. Seventy-four children between the ages of 12 and 64 months seen for inguinal hernia or hydrocele repair were the subjects of the study. Subjects were observed postoperatively for six 5-min intervals, commencing with their awakening from anesthesia, using the TPPPS. T,,,o raters independently observed 28 of the children to assess inter-rater reliability. Validity was assessed by relating TPPPS scores to the timing and type of analgesics used, visual analog and numerical scale pain ratings made by parents and nurses, and perioperative vital signs. The TPPPS was found to possess satisfactory internal reliability (Cronbach's alpha = 0.88). inter-rater reliability was good, with kappas for the pain behavior items ranging from 0.53 to 0.78. Preliminary evidence of the scale's validity is provided by the sensitivity of the scale to analgesic regimen, the convergence between TPPPS scores and nurse and parent ratings of postoperative pain, and the associations found between TPPPS scores and perioperative vital signs. Key, words: Postoperative pain; Young children; Pain measurement

Introduction While significant recent efforts have been made to improve pain measurement in infants (Gunnar et al. 1985; Johnston and Strada 1986; Porter et al. 1986; Anand and Hickey 1987; Grunau and Craig 1987; McGrath 1987) and school age and adolescent children (Tesler et al. 1983; Abu-Saad 1984; Jay and Elliot 1986; McGrath 1987; Varni et al. 1987; Beyer and Aradine 1988; Savedra et al. 1990), there have been few attempts to measure pain in children aged 1-5 years old. Measurement of pain in young children is a challenging problem. Methods that show promise for older chil-

Correspondence to: Sally E. Tarbell, Ph.D., 4 Carmel Road, Andover, MA 01810, USA. Tel.: (508) 475-0906.

dren such as visual analogue scales (VAS) (Abu-Saad 1984; Varni et al. 1987) have not been found to be reliable or particularly useful in this age group (Scott et al. 1977; Jay 1988). Other self-report pain measurement methods such as Faces scales, where the child selects among faces that display incremental levels of discomfort, have been used with children as young as 3 years old (Beyer et al. 1990), but such scales cannot be used reliably with the prelingual child. Methods used to measure pain in infants such as analysis of videotaped facial expression (Grunau and Craig 1987) and cry analysis (Johnston and Strada 1986; Porter et al. 1986) are not currently applicable to the clinical setting. Gauvain-Piquard et al. (1987, 1991) are developing an observational scale for measuring pain in children with cancer aged 2-6 years old. Items on the scale

274

include objective behavioral responses, such as 'the child points out painful areas', as well as evaluations of the child's emotional state including depression, which was found to bc so closely associated with pain that the authors suggest that it be considered as a "secondary or general sign(s) of pain" (Gauvain-Piquard et al. 1987). The authors report satisfactory sensitivity and reliability of the Douleur Enfant Gustave-Roussy (DEGR R) (Gauvain-Piquard et al. 1987) and most recently have presented evidence to support its validity (Gauvain-Piquard et al. 1991). As this scale is designed to assess acute pain lasting several days, involving four 4-h observation intervals, it is inappropriate for the measurement of surgical pain in the immediate postoperative recovery period. McGrath et al. (1985) developed the CHEOPS, an observational scale for measuring postoperative pain in children aged 1-7 years, that includes 6 categories of pain behavior, each with items weighted on a 0-3 scale. The child's responses are observed for 5 sec, followed by a 25-sec period for recording. Inter-rater reliability of the scale is quite acceptable, with a greater than 80% agreement rate for all behavior categories. Validity was evaluated by relating CHEOPS scores to concurrent VAS ratings by observers and nurses and to changes in CHEOPS scores during administration of analgesics, both of which provided preliminary evidence of the scale's validity. The clinical utility of the CHEOPS, however, is limited by the very tight observation and recording intervals and by the inclusion of 28 separate behaviors to be evaluated across the 6 behavior categories. It also should be noted that the high correlation, i.e., 0.81, found between the CHEOPS score and the nurse's VAS pain rating may argue for the use of the simpler VAS ratings. Furthermore, in a recent study (Beyer et al. 1990) the CHEOPS was found to be poorly correlated with self-report measures of postoperative pain in children aged 3-7 years, leading the authors to suggest that further validational work is warranted and that a more refined behavioral tool may be necessary to measure postoperative pain in preschoolers.

TABLE i TODDLER-PRESCHOOLER POSTOPERATIVE PAIN SCALE: PAIN BEHAVIOR CATEGORIES AND SPECIFIC PAIN BEHAVIORS Vocal Pain Expression:

Facial Pain Expression

Bodily Pain Expression:

Verbal pain complaint/Cry Scream Groan, moan, grunt Open mouth, lips pulled back at corners Squint, close eyes Furrow forehead, brow bulge Restless motor behavior/ Rub or touch painful area

Gauvain-Piquard and McGrath's studies exemplify the behavioral observation method of pain measurement, which involves the use of trained observers who watch the child and record the occurrence of specific behaviors indicative of pain or distress during a specified time period. Behavioral observation scales have been used to document pain and distress associated with invasive medical procedures such as bone marrow aspirations and lumbar punctures in children and adolescents (Katz et al. 1980; LeBaron and Zeltzer 1984). Such scales have been found to be among the most reliable and objective means for assessing behavioral indices of pain and distress (Jay 1988). However, with the exception of the D E G R R, most behavioral measure~ at present do not lend themselves readily to clinical application. The primary aim of this study was to develop an observational scale of postoperative pain behavior in children aged 1-5 years for clinical use.

Methods The scale The Toddler-Preschooler Postoperative Pain Scale (TPPPS) consists of 7 items, divided among 3 pain behavior categories: (1) Vocal Pain Expression; (2) Facial Pain Expression; and (3) Bodily Pain Expression (Table I). These behaviors were derived from preliminary studies involving postoperative observations of young children (Tarbell and Cohen 1990; Tarbell 1991; Tarbell et al. 1991) and from other observational studies of children's pain behavior (Katz et al. 1980; Taylor 1983; Abu-Saad 1984; McGrath et ai. 1985; Grunau and Craig 1087; Mills 1989). Originally the TPPPS was comprised of 15 pain behavior items; however, 6 items were eliminated from the scale by the criteria that (I) the pain behavior was present for less than 10% of the patients and (2) the correlation between the pain behavior and the TPPPS score was less than +0,30. The 7 pain behavior items were scored as '1' if the behavior(s) wits i~resent during a 5-rain observation interval and as '0' if the behavior(s) was not present. TPPPS scores were generated by adding up the number of pain behavior items occurring over a 5-rain observation period. Scores on the scale may range from 0 to 7. The codh~, rules for the TPPPS are presented in Table II.

Subjects Seventy-four patients (15 females and 59 males) between the ages of 12 and 64 motlths (mean age: 34 months) consecutively scheduled for inguinal hernia or hydrocele repair were the subjects of the study. Children with other significant medical or neurological disorders were excluded. Written consent was obtained from the parents before the child was enrolled in the study. Six parents declined to have their child enrolled in the study, with the primary reason for refusal being their concern that participation in the study would increase either their own or their child's anxiety related to the surgery. Ethnicity of the subjects was predominantly caucasian (95%), with few Black (4%), Hispanic (1%), and no Asian or Native American children.

Procedure Subjects were observed for 30 min postoperatively with the TPPPS, for 6 consecutive 5-rain intervals, commencing with their awakening from anesthesia. The 7 pain behavior items were scored

275 as they occurred during the 5-min observation intervals. Observa tions were discontinued if the subject fell asleep. Two observers independently rated 28 of the children with the TPPPS to assess inter-rater reliability. The attending recovery room nurse independently completed a VAS and numerical rating for paia at 5 and 10 min after the child was awake, coinciding with the 1st and 2nd TPPPS observation intervals. The type, dose and route of any intra-

a n d / o r postoperative analgesia were noted, as were patient's heart and respiratory rate as recorded by the recovery room nurse. Parents were asked to rate the average level of their child's postoperative pain on a VAS. Validity was assessed by relating TPPPS scores to the timing and type of analgesics used: VAS and numerical scale pain ratings made b~ nurses, VAS pain ratings made by parents, and peri-operative vital signs.

TABLE ii TPPPS: OBSERVATIONAL CATEGORIES AND CODING PROCEDURES

I.

Vocal expression of pain

A. Verbal pain complaint/Cry Verbal pain complaint: any word, phrase, or statement that refers to pain, hurt or discomfort. Coding rules Must be a statement, not a question. Code only discrete, intelligible words. Examples: "'It hurts"; "Ow"; "Oh; "You're hurting me". Cry: tears in the eyes or running down the face a n d / o r making sobbing sounds. Coding rules Do not code crying initiated at separation from parents, unless child is undergoing a potentially painful medical procedure, e.g.i.v, removal, transfer fr:~m bed after surgery, bandage or tape removal. Examples: sobbing, tears in eyes, tears falling down cheeks. B. Groan, moan, grunt: deep, low-pitched vocalizations expressing pain, hurt or discomfort. Coding rules Must occur during or after potentially painful procedure/surgery. Child must be awake, not undergoing anesthetic induction or awakening from anesthesia. Examples: non-inteliigible, low-pitched sounds. May be drawn out (moan) or abrupt (grunt). C. Scream: acute, loud, high pitched cry Coding rules Must occur during/after petentially painful medical procedure/surgery. High pitch distinguishes scream from crj. Examples: sharp, shrill, harsh, high-pitched vocalization, shriek.

!!. Facial expression of pain A. Open mouth, lips pulled back at corners: open mouth, lips pulled back at corners with a downward pull on the jaw. Coding rules Child must be awake. Must occur during or after a potentially painful medical procedure/surgery. B. Squint/close eyes" eyelids taut, stiff, closed or nearly closed with wrinkling of the skin at the lateral aspect of the eyes. Coding rules Child must be awake. Must occur during or after a potentially painful medical procedure/surgery. C. Brow bulge/forehead furrow: bulging, creasing, or furrows above a n d / o r between the eyebrows. Coding rules Child must be awake. Must occur during or after a potentially painful medical procedure/surgery.

IIi. Bodily expression of pain A. Restless motor behavior: Rub/touch painful area Restless motor behavior: unrestrained motor activity. May appear random or to lack goal direction. The body a n d / o r head is never still. Coding rules Child must be awake. Must occur during or after a potentially painful medical procedure/surgery. Examples: twisting and turning of torso a n d / o r head while lying down, flailing of arms and/or legs, arching, repetitive fine motor activity. Rub/touch painful area: touching, rubbing, massaging body area where medical procedure/surgery has been performed. Coding rules Child must be awake. Must occur during or after a potentially painful medical procedure/surgery. Examples: child rubs incisional area, i.v. site.

27h

Results

Descriptil'e statistics The actual time subjects were observed ranged from 2 to 6 observation intervals, i.e., 10-30 min with a mean of 5.7 observation intervals. Scores on the TPPPS ranged from a low of 0 to a high of 7. The mean TPPPS score for the 6 observation intervals was 2.1 with a standard deviation of 1.6. The variability of TPPPS scores appears acceptable in spite of a negative skew, given that the surgical procedures being evaluated are not the most painful procedt~res which a yom~g child may undergo.

Reliability To assess differences in the behavioral expression of pain in children aged 1-2 and 3-5 years and the necessity for conducting reliability analyses separately for these 2 groups, their mean TPPPS scores were compared. Due 'o the lack of significant differences found between the 1-2 (n = 37) and the 3-5 (n = 37) year old age groups, on their pain category and total TPPPS scores (Vocal pain category score t test: t = 1.41, df= 72, P=0.16; Facial pain category score t test: t = 1.53, dr= 72, P = 0.13; Bodily pain category score t test: t--1.17, df= 72, P = 0.24; total TPPPS score t test: t = 1.59, df= 72, P = 0.12) separate analyses were not performed.

huermd rehabihty Internal reliability of the TPPPS was assessed by computing Cronbach's alpha for the 7-item scale. This analysis was performed for TPPPS scores aggregated over the 6 observation intervals and for each observation interval separately. The aggregated TPPPS scores are presented as they provide a broader sample of possible TPPPS scores and thus should be a more stable estimate of the reliability of the TPPPS. Also, the TPPPS scores aggregated over the 6 observation intervals may be considered as composite scores that may have clinical utility of their own, beyond that which is offered by the single interval TPPPS scores. The results for the aggregated TPPPS are presented first. The overall alpha coefficient for the aggregated TPPPS scores is 0.88. Separate alpha coefficients for each of the 3 pain behavior categories were not computed due to the low number of items in each category. The aggregated scale mean was 1.98 with a standard deviation of 1.53. The mean individual item score was 0.28, with item scores ranging from 0.08 (Scream) to 0.40 (Verbal pain complaint/Cry), and item standard deviations ranging from 0.17 to 0.33. Correlation coefficients among the items range from a low of 0.31 between Furrow forehead/brow bulge and Scream, and a high of 0.76 between Squint/close eyes and

Mouth open, lips pulled back at corners. Item-total correlations ranged from 0.41 (Scream) to 0.82 (Furrow forehead/brow bulge). The alpha coefficient for the TPPPS for each of the 6 observation intervals ranged from 0.82 to 0.86. Interval TPPPS score means ranged from 1.36 to 3.27, with the highest mean TPPPS scores found in the first and second observation intervals. The mean inter-item correlations ranged from 0.39 to 0.47, while the mean item-total correlations ranged from a low of 0.56 to a high of 0.64. Results from both the aggregate and the individual interval reliability analyses show that the TPPPS demonstrates acceptable internal reliability (Cronbach 1951).

biter-rater reliability Inter-rater reliability checks were conducted for 38% (28 of 74) of the children. These were accomplished through direct observations in which two investigators independently and simultaneously recorded the child's pain behavior using the TPPPS. Inter-rater agreement for the TPPPS was calculated with the kappa statistic. The kappa statistic allows for measurement of observer variability for categorical data, controlling for chance levels of agreement that can eccur when the behaviors being observed occur at a low frequency. Results are presented f o r 9 pain behavior items, as inter-rater reliability was calculated before analyses were performed to assess internal reliability, which resulted in the combining of 2 sets of pain behavior items (i.e., Verbal pain complaint and Cry; Restless motor behavior and Rub body part). Inter-rater reliability as measured by the kappa statistic for each of the pain behaviors ranged from 0.53 to 0.78 (mean: 0.67), with values above 0.41 considered indicative of acceptable levels of inter-rater agreement (Landis and Koch 1977) (see Table III).

TABLE !II K.~PPA STATISTICS FOR INDIVIDUAL PAIN BEHAVIORS 28)

(n =

Pain behavior

Kappa

Verbal pain complaint Cry Scream Groan, moan, grunt Mouth open, lips pulled back at corners Squint/close eyes Furrow forehead/brow bulge Restless motor behavior Rub or touch painful area

0.77 O.67 0.78 0.55 0.65 0.68 0.53 0.68 0.76

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Validity To protect against possible type-I errors in the repeated testing performed to assess validity, only those results at the P = 0.01 level or less are considered significant. Discriminant validity TPPPS scores before and after postoperative analgesic administration. If the TPPPS is measuring pain, then scores should be lower after administration of analgesics. A comparison was made between the mean TPPPS scores b~fore (mean: 4.53) and after (mean: 2.35) the administration of postoperative medication. In this analysis, the intervals during which postoperative analgesic was given and all subsequent observation intervals were considered as post-medication intervals. There were 25 patients who were observed with the TPPPS both before and after they received postoperative analgesics. These patients had higher mean TPPPS scores than the remainder of the sample, as assessed by their TPPPS score during the first postoperative observation interval (group with postoperative analgesia: mean TPPPS score = 4.68; group without postoperative analgesia: mean TPPPS score = 2.50, t = 4.96, df = 24, P < 0.0001). Thus this subsample is biased by its higher TPPPS scores than the remainder of the sample; however, it is expected that those patients with higher levels of observed discomfort would be more likely to receive postoperative analgesics. The results of this analysis (t = 5.18, df = 24, P < 0.0001) show a significant decrease in the mean TPPPS score after administration of postoperative analgesia, thus providing preliminary evidence that the TPPPS is measuring pain. The differences between TPPPS scores before and after the administration of postoperative analgesia may also be examined through a multiple baseline design, whereby data from individual patients receiving analgesics at different observation intervals are presented as case illustrations for the results presented above. Five patients were chosen who best illustrate the differences in TPPPS score before and after the administration of postoperative analgesics. Again, if the TPPPS is measuring pain, there should be a visible trend

toward decreased TPPPS scores for the postanalgesic observation intervals, which is in fact the case as shown in Table IV. The type of medications administered postoperatively was not controlled in this study, and a majority of patients (17 of 25; 68%) received a narcotic analgesic, such as morphine or fentanyl, which may generally suppress behavior. In order to assess better whether the TPPPS is measuring a specific reduction in pain behaviors, rather than a general suppression of behavior produced by a sedative medication, a comparison was made for patients receiving postoperative acetaminophen or:ly, which should have no sedative effects. Eight patients received only acetaminophen for their postoperative pain, of whom 3 received the medication 10 min before observations with the TPPPS were discontinued. As acetaminophen achieves therapeutic efficacy approximately 20 min after oral administration, only those patients for whom observations with the TPPPS were available for 15 min or more after its administration were considered. Due to the small number of patients available for this comparison (n = 5), no statistical test was performed, However, 4 of 5 patients had lower TPPPS scores after administration of acetaminophen, while 1 patient had no change in his TPPPS score. TPPPS scores and the timing of analgesic administration. To determine whether the TPPPS is sensitive to differences in the timing of analgesic administration, a chi-square analysis was performed. Patients were first divided into 3 groups of approximately equal numbers according to the magnitude of their mean TPPPS score (i.e., low, n - 24; moderate, n = 24; and high, n = 26) and then grouped according to when they received analgesics (i.e., intra-operatively, postoperatively, intraaiid postoperatively, or never). The results of this analysis are presented in Table V. A majority of patients with low TPPPS scores received intra-operative analgesics only, whereas those with high TPPPS scores were more likely to receive both intra- and postoperative analgesics. These preliminary results indicated that the TPPPS is sensitive to differences in the liming of analgesic administration

"IABLE IV CHANGES IN TPPPS SCORE BY INTERVALOF ANALGESICADMINISTRATION * (n = 5) Observation interval Patient 1 Patient 2 Patient 3 Patient 4 Patient 5

1

2

3

4

5

6

7 5

0 4

0 0

0 0

0 0

0 0

5

6

3

0

0

0

4 1

3 !

5 1

3 6

4 7

0 0

* TPPPS scores after the administration of an analgesic are designated by bold type.

_78 TABLE V

T A B L E Vii

MEAN TPPPS SCORE BY TIMING OF A N A L G E S I C ADMINIST R A T I O N * (n = 74)

P O S T O P E R A T I V E A N A L G E S I C S BY MEAN TPPPS S C O R E * (n = 74)

TPPS

Administration

TPPPS score

score

Intra-operative

Low
Postoperative

lntraand Post-

Never

0 (I1%)

2 (8%)

2 (8%)

2 (8%)

8(33%)

2 (8%)

3 (12%)

14(54%)

4(15%)

Low < 1.17 Moderate !.00-3.00 High 3.01-5.33

Acetaminophen

Opiate

Other

No analgesia

1 (4%)

0 (0%)

! (4%)

22 (92%)

3 (13%)

7 (29%)

0 (0%)

14 (58%)

5 (19%)

11 (42%)

1 (4%)

9 (35%)

* Chi square = lq.54, d f = 6, P < 0.003.

* Chi square = 21.611. tO'= 6. P < 0.001.

but did not reveal why such differences were found. For example, why did patients who received analgesic medication both intra- and postoperatively have higher TPPPS scores than those who received medication intra-operativcly only? Further analyses were thus conducted to determine whether the type of analgesics given to patients with low TPPPS scores differed significantly from those with high TPPPS scores. The results from these analyses are presented below.

TPPPS scores and the type of analgesics admhzistered intra- and postoperatit'ely. Significant differences were found in TPPPS scores for patients receiving different analgesics intra- and postoperatively, indicating that the TPPPS is sensitive to variations in analgesic regimen (See Tables VI and VII). Patients receiving only local bupivacaine infiltrations to their incision sites were more likely to have high TPPPS scores, whereas those receiving local bupivacaine infiltrations and an i.v. opiate were more likely to have low TPPPS scores. it is likely that the intra-operative analgesia administered to patients with high TPPPS scores, a majority of whom received only local bupivacaine infiltrations to their incision sites, was not adequate to treat their pain, thus requiring the addition of a postoperative analgesic. Furthermore, an examination of the differences in the types of analgesic provided to patients

postoperatively shows that those with higher TPPPS scores were more likely to receive a more potent analgesic such as an i.v. opiate, as compared to those with low pain scores the majority of whom received no postoperative analgesics. It should be noted that observers using the TPPPS were not blind to the administration of postoperative medications; however, they were typically not aware of medications given intra-operatively until a chart review conducted after the TPPPS ratings were completed. Thus, the comparisc as performed to assess the discriminant validity of the TPPPS for intra-operative analgesics provide the best test of the ability of the TPPPS to distinguish patients on the basis of the analgesics they received. Given that analgesic regimen was not controlled for in this study and that observer ratings were typically not blinded to the analgesics used, these results should be interpreted as very preliminary evidence of the discriminant validity of the TPPPS.

Concurrent calidity Relationship between TPPPS scores and pain ratings by nurses and parents. The convergence between TPPPS scores and (11 nurses' VAS and numerical pain ratings for the first and second observation intervals and (2) parents' VAS rating of the child's postoperative pain was examined. Results are presented in Table VIII.

T A B L E VIll TABLE V! MEAN TPP:'S SCORE ANALGESIA ~ (n = 74)

BY TYPE OF

INTRA-OPERATIVE

RELATIONSHIP BETWEEN AND PARENT RATINGS

TPPPS SCORES A N D

Nurse TPPPS score

Local i.v. Opiate bupivacaine

Local+ i,v. opiate

Other

NOne

0(0)

2 (8%)

Low <1.17 Moderate

4(17%)

6(25%)

12(50¢~)

1.18-3.00 High

7(29%)

7(29%)

5(21%)

1(4%)

4(17%)

3.01-5.33

13(50c)~)

4(15%)

2 (8%)

0(0%)

7(27~)

* Chi square = i9.07,

df =

8, P < (,~.00!.

NURSE

Parent

VAS ! V A S 2 Numerical I Numerical2 VAS (n = 57) (n = 46) (n = 49) (n = 47) (n = 55) Mean TPPPS score 0,25 TPPPS score Interval 1 0.55 * TPPPS score Interval2 0.36 * * P < 0.01.

0.56 *

0.30

0.66 *

0.45 *

0.51 *

t).6(I *

0.63 *

0.61 *

q.42 *

0.32

0.57 *

0.43 *

279

These findings indicate a moderate and positive relationship between the TPPPS scores and pain ratings made by nurses and parents. In order to determine whether the TPPPS scores offer any more information than is available from the VAS and numerical scale pain ratings alone, analyses were conducted to evaluate whether the VAS and numerical ratings could distinguish among patients receiving different intra-operative analgesic regimens. These analyses were performed only for the first and second observation intervals as VAS and numerical ratings were not made for intervals 3-6 and included only those patients who had received no postoperative medications during the observation intervals. The VAS ratings made by the nurses and parents arid the nurses numerical scale ratings did not distinguish patients on the basis of their intra-operative analgesia (nurses' VAS interval 1: F (3, 49)= 0.07, n.s.; nurses' VAS interval 2: F (3, 34)= 0.53, n.s.; nurses' numerical rating interval 1: F (3, 41)= 0.49, n.s.; nurses numerical rating interval 2: F (3, 33)= 0.78, n.s.; parents' VAS rating: F (3, 4 4 ) = 0.88, n.s.). TPPPS scores did distinguish among patients receiving different intra-operative analgesic regimens both on average for the 6 observation intervals as reported above and for the second observation interval ( F (3, 53)=5.64, P < 0.002). The TPPPS scores for the first observation interval were not significantly related to intra-operative analgesia ( F (3, 61) = 1.28, n.s.).

Relationship between TPPPS scores and peri-operative rital signs. Small, positive correlations were found between the intra-operative systolic blood pressure high and low readings and the mean TPPPS scores (see Table IX). No significant correlations were found between the high and low intra-operative diastolic blood pressures, heart rate readings and the mean TPPPS scores. A small, positive correlation was found between the mean postoperative respiratory rate and the mean TPPPS scores (r = 0.35, P < 0.01). Mean postoperative heart rate was not significantly correlated with the mean TPPPS scores (r = 0.24, P > 0.01, n = 74). Blood pressure was not recorded postoperatively. These findings are consistent with previous research on pain in TABLE IX CORRELATIONS BETWEEN INTRA-OPERATIVE SIGNS AND MEAN TPPPS SCORES (n = 74) Vital sign

Pearson R

Diastolic BP (low) Diastolic BP (high) Systolic BP (low) Systolic BP (high) Heart rate (high) Heart rate (low)

0.21 0.23 0.32 * 0.35 * 0.14 0.00

* P < 0.01.

VITAL

infants in which the administration of a painful stimulus was associated with vital sign changes, specifically increases in blood pressure (Maxwell et al. 1986).

Discussion

The primary aim of this study was to develop a observational scale to measure postoperative pain in children aged 1-5. The ultimate goals of this research are to provide an objective method: (1) to clinically evaluate postoperative pain in young children; and (2) to study the efficacy of surgical, anesthesiological and behavioral interventions used to manage postoperative pain in this population. The latest version of the Toddler-Preschooler Postoperative Pain Scale consists of 7 items, a number small enough to facilitate clinical use, while still possessing satisfactory internal consistency. Tests of interrater reliability reveal good interrater agreement. The sensitivity of the TPPPS to analgesic regimen, the convergence between TPPPS scores and nurse and parent ratings of postoperative pain, and the associations found between TPPPS scores and peri-operative vital signs provide preliminary evidence of the scale's validity. The limited number of items which comprise the TPPPS and the simple method of scoring behaviors for their presence or absence provide for the scale's clinical utility; however, the TPPPS may best meet the goals of clinical utility without sacrificing validity if the number of observation intervals was reduced. As the TPPPS scores for the first two 5-min observation intervals correlate well with the mean TPPPS score (ir~erval l TPPPS, r = 0.74, P < 0.01; interval 2 TPPPS, r = 0.75, P < 0 . 0 1 ) , this may well be possible. It is unlikely, however, that fewer than 2 observation intervals would be desirable as revealed by the inability of the TPPPS score to distinguish among patients receiving different intra-operative analgesic regimens at the first observation interval. Further testing of the TPPPS also may reveal whether the current observation period of 5 min may be reduced to a shorter time interval. In order to control for surgical protocol, th, ~, range of patients in the current study was restricted to patients undergoing an inguinal hernia or hydrocele repair. If the TPPPS is to be broadly applicable to postoperative pain measurement in young children, a more diversified sample is required. It will be necessary to use the TPPPS with children undergoing surgical procedures considered more painful, including major abdominal, thoracic and orthopedic surgeries. Additionally, given the disproportionate number of males undergoing hernia and hydrocele repair, and the limited ethnic diversity in the present sample, findings regarding the reliability and validity of the TPPPS will

280

necessarily be restricted to the population of children tested in this study until further validational work is done on a broader sample of patients and surgical procedures. While the TPPPS was found to be sensitive to the timing and type of analgesic regimen, further study is indicated to specifically control for analgesic factors that may complicate the interpretation of TPPPS scores, such as the sedative properties of many analgesic medications. It also would be optimal to provide for blind ratings by observers using the TPPPS. Finally, validation of observational measures of postoperative pain, such as the TPPPS, will have to take place in the recovery room and not in the setting of other types of acute pain such as a phlebotomy clinic where more experimental control is possible, as the presentation of postoperative pain may be uniquely affected by the child's response to anesthesia and the recovery room environment.

Acknowledgements The authors gratefully acknowledge Dr. Craig Edelbrock for his consultation on the development of the TPPPS, and the nurses of the Day Surgery Unit of the University of Massachusetts Medical Center for their assistance with data collection. This research is supported in part by a grant from the National Institute of Mental Health (1 RO3 M H45440-0 ! ).

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