Brief Reports

Indian Pediatrics 1999;36: 1135-1141

Evaluation of Physiological and Behavioral Response to Pain Following Heel Prick with Different Techniques for Dextrostix Assessment in Healthy Preterm Neonates

From the Department of Neonatology, KEM Hospital, Parel, Mumbai 400 012, India.
Reprint requests: Dr. Nandkishor S. Kabra, 3/58 Epping Road, Lane Cove, Sydney, NSW 2066, Australia.
e-mail: nskabra@acay.com.au.
Manuscript received: January 6, 1999;
Initial review completed: February 18, 1999;
Revision accepted: June 21, 1999

Modern neonatal intensive care units have emerged to focus exclusively on the care of premature and sick neonates with an aggressive approach to treatment and intensive nursing care(1). As a part of intensive care, invasive procedures are being performed frequently for each acutely sick and fragile baby. In one of recent report, an infant with gestational age of 23 weeks underwent 488 procedures during her total stay in neonatal intensive care(2).

Heel prick is the most frequent, universal and repeatedly performed procedure to obtain blood sample for various investigations and it has been proved beyond doubt that it causes distress(2-4). Frequent heel pricks may make heels tender(5). Various interventions used for relief of pain following heel prick in newborn are to give comfort by gentle stroking and verbal reassurance(6), providing nonnutritive sucking(7), changing from manual heel prick to spring loaded device_autolet(6,8), applying local anesthetic cream like EMLA(6), lidocaine (lignocaine)(9,10), and by giving sucrose(11) or glucose(12) orally before heel prick.

Most of the developed countries are using either lancet or the autolet for heel prick. In developing countries like India 21 to 24 G needles are used for heel prick as they are easily available and are relatively less expensive. Needle induced heel pricks are probably more painful, as there is no control on depth of penetration and tissue injury. There are no studies in neonatal literature regarding the pain due to needle induced heel prick. This study was carried out to measure the physiological and behavioral changes in response to heel prick in healthy preterm neonates by needle and other techniques to evaluate the least painful technique of heel prick.

Subjects and Methods

This prospective study was carried out in the neonatal intensive care unit of King Edward Memorial Hospital, Mumbai over a six months period from January 1997 to June 1997.

Patients

A continuous sample of 40 preterm neonates between gestational age of 28 to 36 weeks (mean 32.9 weeks) with birth weight ranging from 880 to 2000 grams (mean 1558±312 grams), was evaluated between 2 to 25 days (7±4) days of age. The inclusion criteria for study were: (a) Gestational age <37 weeks (assessed by Ballard et al. score)(13); (b) Postnatal age <4 weeks but with maturity scores <37 weeks; (c) Stable condition and not receiving any sedatives or analgesic; (d) Not having any evidence of neurologic disease; (e) Breathing spontaneously and not on ventilator or oxygen supplementation; (f) Not on IV fluids, full feeds either oral or intragastric; (g) State 3 or 4 of arousal on Prechtl and Beintema Scale(14); and (h) Heel pricks being performed as a part of the neonates routine Dextrostix monitoring. Informed consent was obtained from the mother before procedure.

Monitoring

All the neonates were monitored for four physiological parameters-heart rate, respiratory rate, oxygen saturation and noninvasive blood pressure. They were also monitored for behavioral indices, the facial actions and cry. Heart rate and respiratory rate was monitored on Neotrack_502 infant monitor_Corometrics, USA. Oxygen saturation was monitored on Radiometer Copenhagen pulse oximeter. Noninvasive blood pressure (NIBP) was monitored with Omega-1400 TM NIBP-Invivo Research Lab Inc, USA, in which values are updated every five minutes. Behavioral response to pain was monitored by the bedside score_Neonatal facial action coding system (NFCS) developed by Rushforth and Levene(15). Four items of facial actions (brow bulge, eye squeeze, nasolabial furrow and open mouth), and the presence of crying was used as a measure of behavioral response to pain. Each response was given a score of "1" if present and "0" if absent, so that total ranging from 0 to 5 was possible.

A total of six persons were assigned for this specific aspect of the study recordings and remained constant throughout the study. The first person was responsible for performing heel prick, second for counting time, third for sampling values of heart rate from monitor, fourth for sampling values of respiratory rate from monitor, fifth one for recording_values of  pulse-oximetry second and the sixth person recorded facial actions - cry and NIBP. The seventh person was required only when heel pricks were performed with giving comfort to the baby, and was the staff nurse on duty caring for baby. She was asked to comfort the baby by gentle stroking and verbal reassurance and this was performed with idea of minimizing the effect of pain by the application of nursing care.

Heel Pricks

The heel prick was performed in the baby's own warmer or infant care trolley by single investigator. Infants were fully clothed apart from the foot that was to be used for sampling. Before skin preparation: the Neotrack 502 monitor was applied to measure changes in heart and respiratory rates. Radiometer Copenhagen pulse oximeter sensor was placed over the right wrist to measure oxygen saturation. NIBP monitor was applied to left arm with appropriate sized cuff to measure changes in blood pressure. Facial actions and cry were observed as behavioral indices of pain. The heel prick was performed using the following protocol. The whole procedure period was divided into 4 consecutive 5-minute periods (Fig. 1).

Fig 1. Study protocol for heel prick

(i)Control 1 (C-1) period was baseline or waiting period of 5 minutes when the baby was not disturbed; (ii) Dummy (D) period of 5 minutes duration mimicked the Procedure (P) period using the same heel but it was not pricked. The investigator, after exposing the foot and placing it in the required position, warmed the heel, cleaned it with an alcohol swab, and squeezed for 10 seconds; but no heel prick was given; (iii) Control 2 (C-2) period was baseline or waiting period of 5 minutes following Dummy period in which the baby was not disturbed (Exactly like C-1); and (iv) Procedure (P) period was 5 minutes period in which the investigator, after exposing the foot and placing it in required position, warmed the heel, cleaned it with alcohol swab, pricked the heel and squeezed the heel to collect blood on Dextrostix. Following this a cotton swab was placed on the prick site until the bleeding ceased.

Recording in the C-1, D, C-2 and P periods was done for 10 seconds, as a pilot study had shown that this was the average time taken for the heel prick blood collection for Dextrostix in our unit. During the study, first heel prick was performed with 24G disposable needle (Becton-Dickinson, Singapore). Same neonates had further heel pricks on next three consecutive days in three different ways in the follow- ing order: Lancet (International Mediaids, Singapore), Autolet - a spring loaded device (Autoclix - Lancet - Boheringer Mannheim India Ltd.), and a nurse comforting the baby by gentle stroking and vocal reassurance during the heel prick being performed by 24 G disposable needle, respectively.

Variability and Analysis

The mean and standard deviation of the one-second value of the heart rate, respiratory rate, oxygen saturation was recorded over the first 10 seconds of each 5-minutes period. Standard deviation around the mean in each neonate was taken as simple measure of variability. The NIBP and facial actions and cry was also recorded in C-1, D, C-2 and P periods. To differentiate between the physiological and behavioral response to nonpainful (non tissue injury/handling) from painful (tissue injury) stimuli, comparison was made between the Dummy (D) and Procedure (P) period.

Data gathered in the Dummy and Procedure period was compared by using paired `t' test for  each method of heel prick. Comparison of the needle against other three techniques of the heel prick was done by paired `t' test, by comparing the mean difference between the `P' and `D' period of each method of heel prick. Significance was accepted for p value <0.05. Wilcoxon matched pairs signed ranks test was used for further analysis of NFCS score data, as the p values were highly significant on paired `t' test. All the statistical analysis was per-formed by SPSS package.

Results

Table I^__ Difference (Between Procedure and Dummy Period) in Absolute Values and Variability Values (Mean and 95% Confidence Intervals) of the Physiological Parameters and NFCS score.

The results of the study are tabulated in Table I. Though there was a trend of increase in mean heart rate from dummy to procedure period with all techniques of heel prick except with autolet, it was statistically significant only with needle. There was a trend of increase in heart rate variability with all techniques of heel prick except with needle, and it was statistically significant with lancet and autolet. There was a trend of drop in respiratory rate from dummy to procedure period with all techniques of heel prick except comfort, and it was statistically significant for autolet. There was statistically significant increase in diastolic blood pressure for needle induced heel prick.

Fig. 2. Comparative distress of heel prick measured by difference in mean heart rate between procedure and dummy period.

Figure 2 shows the magnitude of difference of mean heart rate between the procedure and the dummy period of four techniques of heel prick. The comparison of needle with autolet reached statistical signficance (p=0.026). With autolet there was drop in mean heart rate (per min) from dummy (D) period (148.8±2.5) to procedure (P) period (147.5±2.7). The difference of P-D = _ 1.2 is negative. The values of mean heart rate (per min) for autolet in Control-1 and Control-2 period were 144.9±2.5, and 145.5±2.7 respectively. We have compared values of P and D periods to differentiate between the response to handling (dummy period-D) and response to pain (procedure period-P). It is clear from the above description that for the autolet the mean heart rate was not decreased below the normal.

There was statistically highly significant change in NFCS score from dummy to procedure period with all techniques of heel prick. While comparing the relative distress (difference between the procedure and dummy period) of needle with other three techniques for various physiological and behavioral parameters it was observed that the relative distress of needle for heart rate was statistically significant against autolet, but not against lancet and comfort. Relative distress of needle against other three techniques was statistcially insignificant for other physiological parameters and NFCS score.

Discussion

Heel pricks are frequently used to obtain blood from neonates for day to day care and they are known to cause distress(3,4). Very premature babies as young as 26 weeks of gestational age are capable of responding differentially to painful (tissue damage) and nonpainful (handling) stimuli. Their differential response to these two conditions is multi-dimensional, which includes both physiological and behavioral components that contribute to the total response independently(16). Pain in neonates can be assessed by physiological, behavioral and neurochemical changes (1,17,18).

In our study all the four techniques were equally effective in obtaining in satisfactory sample for Dextrostix.

Physiological Response

Various studies have recorded statistically significant increase in mean heart rates with lancet(3,6,19), whereas in the present study statistically significant increase in mean heart rates was not observed with lancet. In these studies(3,6,19), to obtain sufficient sample of the blood the duration of heel prick was prolonged and heel prick was deep as the blood was collected for various biochemical or hematological investigations, as compared to present study where the procedure was carried out for evaluating Dextrostix which required a single drop of blood and was of shorter duration.

Owens and Todt(3) studied 20 full term neonates and found statistically significant increase in mean heart rates when comparison was made between the baseline with procedure period. Craig et al.(19) studied 56 fullterm and preterm mixed group of neonates and found statistically significant increase in mean heart rates when comparison was made between procedure with the baseline period. In the same study when the comparison was made between swabbing with procedure period, the change in mean heart rate was not significant; which is similar to our study. McIntosh et al.(6) did not find statistically significant change in the difference of mean heart rates between procedure and dummy period when they compared lancet with autolet and comfort. They found significant increase in heart rate variability with lancet, but not with autolet and comfort. Johnston et al.(16) did not find significant change in heart rate variability between the dummy and the procedure period of heel prick with lancet. These authors also postulated that the heart rate variability was related to the gestational age of the neonates. In our study heart rate variability was significant with lancet and autolet probably due to the cumulative effect of heel pricks as the sequence of performing heel prick on consecutive days was needle-lancet-autolet and comfort. The comfort used probably has protected against the heart rate variability.

We found statistically significant decrease  in respiratory rate from dummy to procedure with autolet, the drop was to the extent 49.3±1.8 to 44.7±1.9, but this is clinically insignificant as such change in respiratory rate is considered normal in preterm neonates. McIntosh et al.(6) and Craig et al.(19) found significant drop in mean respiratory rates with various techniques of heel prick.

Johnston et al.(16) found significant drop in oxygen saturation with lancet which may probably be related to relatively more premature neonates (gestational age 26-31 weeks) in their study and also the blood collection was done for longer period as compared to our study. Various studies have shown that the more intense and prolonged the stimulus is, more will be the fall in TcPo2 or oxygen saturation in preterm neonates(20,21). McIntosh(23) observed change in systolic and diastolic blood pressure in response to handling the baby. Brown(4) found significant increase in systolic blood pressure when the heel prick was performed with lancet. In our study we did comparison between procedure and dummy period (not the baseline period). We fou nd statistically significant increase in diastolic blood pressure with needle induced heel prick.

Behavioral Response

Change in NFCS score in response to heel prick was significant with all four techniques of heel prick. Other workers(15,16,19,23,24) observed similar significant changes in facial expressions in response to heel prick with lancet.

We did not include duration and latency of cry in our study due to non-availability of video camera and audiotapes. However, we felt that the duration and latency of cry had increased from autolet followed by comfort, lancet to needle in that order. The fact that the order of performing heelprick with various techniques was not randomized, is a limitation of this study.

We conclude that autolet, followed by needle with comfort are less painful techniques of heel prick. In practice whenever possible the least painful technique of heel prick should be used.

Acknowledgement

We thank Dr. P.M. Pai, Dean Seth G.S. Medical College and KEM Hospital for granting us permission to publish this article.

References

1. Parker F. Pain in the newborn. Clin Perinatol 1989; 16: 549-564.

2. Barker DP, Rutter N. Exposure to invasive procedures in neonatal intensive care unit admissions. Arch Dis Child 1995; 72; F47-F48.

3. Owens ME, Todt EH. Pain in infancy: Neonatal reaction to heel lancet. Pain 1984; 20: 77-86.

4. Brown L. Physiologic response to cutaneous pain in neonates. Neonatal Network 1987; 5: 18-21.

5. Fitzgerald M, Millard C, McIntosh N. Cutaneous hypersensitivity following peripheral tissue damage in newborn infants and its reversal with topical anesthesia. Pain 1989; 39: 31-36.

6. McIntosh N, Veen LV, Brameyer H. Alleviation of the pain of heelprick in preterm infants. Arch Dis Child 1994, 70: F177-181.

7. Field T, Goldson E. Pacifying effects of nonnutritive sucking on term and preterm neonates during heelstick procedures. Pediatrics 1984; 74: 1012-1015.

8. Harpin VA, Rutter N. Making heel pricks less painful. Arch Dis Child 1983; 58: 226-228.

9. Wester U. Analgesic effect of lidocaine ointment on infant skin in neonates. Acta Pediatr 1993; 82: 791.

10. Rushforth JA, Griffiths G, Thorpe H, Levene MI. Can topical lignocaine reduce behavioral response to heel prick? Arch Dis Child 1995; 72: F49-F51.

11. Abad F, Diaz NM, Domenech E, Robayana M, Rico J. Oral sweet solution redues pain-related behavior in preterm infants. Acta Pediatr 1996, 85: 854-858.

12. Skogsdal Y, Eriksson M, Schollin J. Analgesia in newborns given oral glucose. Acta Pediatr 1997; 87: 217-220.

13. Ballard JL, Novak KK, Driver M. A simplified score for assessment of fetal maturation of newly born infants. J Pediatr 1979; 95: 769-774.

14. Prechtl HFR, Beintema DJ. The neurological examination of the full term newborn infant. Clin Dev Med 1964; 12: 1-49.

15. Rushforth JA, Levene MI. Behavioral response to pain in healthy neonates. Arch Dis Child 1994; 70: F174-F176.

16. Johnston CC, Stevens BJ, Young F, Horton L. Differential response to pain in premature neonates. Pain 1995; 61: 471-479.

17. Anand KJS, Hickey PR. Pain and its effects in human neonates and foetus. N Engl J Med 1987; 317: 1321-1329.

18. Gupta P, Sharma KN. Neonatal pain. Indian Pediatr 1993; 30: 1263-1269.

19. Craig KD, Whitfield MF, Grunau RVE, Linton J, Hadjistavropoulos. Pain in the preterm neonate: Behavioral and physiological indices. Pain 1993; 52: 287-299.

20. Speidel BD. Adverse effects of routine procedures on preterm infants. Lancet 1978; 1: 864-865.

21. Danford DA, Miske S, Headley J, Nelson RM. Effects of routine care procedures on transcutaneous oxygen in neonates: A quantitative approach. Arch Dis Child 1983; 58: 20-23.

22. McIntosh N. Massage in preterm infants. Arch Dis Child 1994; 70: F80.

23. Grunau RVE, Craig Kd. Pain expression in neonates: Facial action and cry. Pain 1987; 28: 395-410.

24. Johnston CC, Stevens BJ. Experience in a neonatal intensive care unit affects pain response. Pediatrics 1996; 98: 925-930.