Comparison of Pain Response to Heel Prick and
Behaviour is the main source of expression of pain in non-verbal neonates. It is considered that there is increased sensitivity of pain in preterm babies as pain threshold is directly related to gestational age. Preterm babies having low threshold are highly sensitive to pain and term babies having higher threshold have lesser sensitivity to pain.
The early and abundant expression of putative neurotransmitters mediating nociception together with the delayed appearance of neurotransmitters associated with descending inhibitory fibers is responsible for increased excitability in the dorsal horn of the premature spinal cord. The magnitude of hormonal, metabolic, cardiovascular and immune response to invasive procedures is high in preterm and term babies. Because of high magnitudinal response, higher plasma concentration of analgesia and anesthesia are required to produce effect in neonates as compared to older age group.
There is still uncertainty about the extent of perception of pain by preterm babies as compared to term babies. Thus there is need to define differences in the common behaviours that consistently appear with painful stimuli in term and preterm babies. There is a gap in knowledge regarding this, hence present study was undertaken.
METHOD
The present study, a prospective study was carried out in the Department in Pediatrics in a reputed medical college hospital in Karnataka, India. The ethical clearance for the study was obtained from the institutional review board. The sample size for the study was determined to be 70. Healthy term neonates between 37 weeks to 42 weeks of gestational age, who required blood sampling for bilirubin or blood sugar estimation within the first week of life, were selected for the study. Selected cases were equally divided into 2 groups. In group 1, blood sampling was done by venepuncture and group 2; blood sampling was done by heel prick. Babies with significant morbidity like Septicemia, Birth Asphyxia, Congenital Malformation, neurological involvement and those received Nalaxone were excluded from the study.
Mothers of the selected neonates were always present during blood samplings & informed consent was taken before the procedure.
The state of arousal of neonates was assessed before the procedure using Prechtl and Beintema score as:
1. Eyes closed, regular respiration, no movements.
2. Eyes closed irregular respiration.
3. Eyes open, no gross movements
4. Eyes open, continual gross movements, no crying 5. Eyes open or closed, fussing or crying
Neonates in state 5 were not included in the study.
The Dorsum of the hand was selected and venepuncture was done using a 24 gauge hypodermic needle. A cotton wool ball was applied to prevent bleeding. For the heel prick group, the heel was wiped with alcohol and pricked with a lancet to collect blood.
A cotton wool ball was applied to prevent bleeding.
The pain during the procedure was scored in terms of behavioral pain score as
1. Brow Bulge 2. Eye Squeeze 3. Nasolabial Furrow 4. Open mouth 5. Cry
Each response was given a score of 1 if present and
‘0’ if absent. Total score ranging from 0 to 5 were possible. Oxygen saturation was monitored using pulse oximeter. Heart rate, respiratory rate and behavioural scores were monitored by single observer.
Heart rate, respiratory rate and saturation were measured before and after the procedure. The maximum response during first five minutes of procedure was taken into consideration and the results were compared between groups I and II. The data collected was analyzed for statistical significance by student t test for continuous numerical values and the results were expressed in frequency, percentages, mean and SD. P< 0.05 was considered as significant.
RESULTS
In present study 70 term neonates were selected, to know the difference in the behavioural pattern that appear with painful stimuli and also to compare the pain response to venepuncture & heel prick . Among selected neonates, 42 were males and 28 were females.
(Table 1)
Table 1. Gender distribution
Group Male Female
Group I: Term Venepuncture 21 14
Group II: Term Heel prick 21 14
Most of the babies selected were having a score of 3 in Prechtl & Beintema score. In this study almost all neonates exhibited brow bulge & eyes squeeze during the procedure. Nasolabial furrow & open mouth were next commonly observed response. Cry as a response was consistently high in heel prick group when compared to venepuncture group. (Table2)
20 Manupraksh 80-84.pmd 81 8/27/2012, 6:39 PM
There was significant difference in behavioral pain response score (p<0.002) between venepuncture and heel prick group. The mean behavioural pain response score for venepuncture being 4.086 & for the heel prick 4.723, which suggest that response was high in heel prick. (Table 3a, 3b)
In this study, venepuncture and heel prick groups exhibited increase in mean heart rate , respiratory rate during the first five minutes of procedure resulting in significant statistical differences (P<0.01). The O2 Saturation fell significantly during the procedure (P< 0.01) (Table 4 & 5)
When pain response to venepuncture and heel prick compared, there were no statistically significant differences in heart rate, respiratory rate & Spo2 changes before & during first five minutes of procedure. The behavioural pain response score was statistically significant in heel prick group (Table 6).
There was no statistical significant difference in the male & female preterm infants in behavioural response score. (Table 7)
DISCUSSION
Until recently, it was believed that neonates &
infants do not feel pain due to immaturity of their nervous system.
Previous studies have clearly shown that the anatomical, physiological & neurochemical structures which convey pain are well developed in both preterm
& term neonates20. Most of the term & preterm neonates admitted to NICU undergo repeated multiple diagnostic & therapeutic procedures that result in pain
& discomfort.
Table 2. Behavioural pain score
Facial actions Term Term
Venepuncture Heel prick
Brow bulge 35 35
Eyes squeeze 34 35
Nasolabial furrow 31 35
Open mouth 25 33
Cry 18 29
Table 3a. Behavioral pain score Behavioural Pain score Number of babies
Term Term
Venepuncture Heel prick
2 4 -
3 7 2
4 6 5
5 18 28
Table 3b. Mean total behavioural pain score
Groups Mean B.P.S.
I 4.086
II 4.743
Table 4. Changes in heart rate, respiratory rate & Spo2 in response tovenepunctre in term neonates
Variables Before During 1st 5 min Mean 95% CI P value
of procedure difference for mean
HR 127.71±15.038 149.26±17.68 +21.543 17.25+25.836 .000
RR 47.54±8.41 60.06±15.05 +12.114 8.19+16.04 .000
Spo2 95.8±2.08 91.2±2.99 -4.6 -5.63-3.56 .000
Table 5. Changes in heart rate, respiratory rate & Spo2 in response to heel prick in term babies
Variables Before During 1st 5 min Mean 95% CI P value
of procedure difference for mean
HR 130.37±12.21 147.943±11.36 +17.57 14.31 to+20.83 .000
RR 45.94±10.38 59.57±9.3 +13.63 10.49 to+16.77 .000
Spo2 96.37±1.85 90.6±2.56 -5.77 -6.58 to-4.96 .000
Table 6. Comparison of pain response in term neonates for venepuncture & heel prick
Variables Group I Group II p value
(term venepuncture) (Term heel prick)
Before HR 127.71 130.37 .42
RR 47.94 45.94 .379
Spo2 95.8 96.37 .229
During1st 5 min. HR 149.25 147.94 .713
RR 60.057 59.57 .872
Spo2 91.2 90.6 .371
Frequent & prolonged pain may be potentially harmful to the developing nervous system & may threaten the physiological stability of premature & sick infant.4, 6
Table 6a. Comparison of pain response in term neonates for venepuncture & heel prick
Group I (TV) Group II (TH) p value State of arousal score 3.057 3.086 .82 Behavioural
response score 4.086 4.723 .002*
* Highly significant.
Venepuncture & heel prick are the common methods of collecting blood in neonates. The present study clearly indicates that all newborns responded to painful stimuli in one or the other way. Various studies also reported that neonates have characteristic
& predictable response to painful stimuli.
J. Alison Rush forth et al 7 study reported that 90%
of term and 84% of preterm babies exhibited an increase in behavioural response to heel prick. In term babies the brow bulge & nasolabial furrow were seen most often (83%). Eyes squeeze was observed in 78%
of babies where as open mouth and cry were seen in 75% of term babies.
Table 7. Comparison pain response between Male & Female term neonates (Venepuncture and heel prick group)
Variable Male Female T P value
State of arousal 3.048± .6228 3.11±. 315 .467 .642
Behavioural response score 4.476±.92 4. 32±.94 .683 .492
In our study, brow bulge & eyes squeeze were most often seen facial action (97-100%). Open mouth was seen in 82% of term babies & cry in 67%.
When comparing the physiological parameter in response to pain, Harmesh Singh et al8, in their study reported that mean heart rate was increased during the procedure in both the groups with statistically significant differences (p<0.01). There was significant rise in respiratory rate during the procedure as compared to baseline (P<0.01). All newborn experienced a significant decrease in oxygen saturation during procedure (p<0.01).
Neil M C In tosh et al 9 studies concluded that mean heart rate & respiratory rate increased significantly
with pain. In our study, it was observed that heart rate
& respiratory rate increased significantly in both the groups following venepuncture and heel prick procedures (p<0.001) & on the other hand oxygen saturation was decreased significantly (p<0.001).
Similar responses were also seen in studies done by Brown. L. et al10, Owen ME et al11, Berg.K. M. et al12, Lindli V.et al13, Gonsalves S. et al14.
In a study conducted by Vibhuti S Shah, 15 neonatal pain response and its adverse effects and maternal anxiety were assessed in 27 neonates using neonatal infants Pain scale [NIPS]. It was concluded that NIPS scores were higher in heel stick group compared to venepuncture group. This suggests that venepuncture is less painful than heel prick in newborns.
In our study, there was significant difference in behavioral pain response score (p<0.002) between venepuncture and heel prick group. The mean behavioural pain response score for venepuncture being 4.086 & for heel prick 4.723, which suggest that response was high in heel prick. Changes in physiological parameters i.e. heart rate, respiratory rate
& oxygen saturation were uniformly present in both the groups. This implies pain response to heel prick was high compared to venepuncture.
Greisburg R et al 16 & Grunau et al 17, in their study concluded that female newborn babies of all gestational age expressed more facial features of pain than male babies. J. Alison Rush forth et al 7 study concluded that term female babies were associated with increased pain scores compared to male babies.
In contrast to above studies, there was no statistical
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significance in behavioral response scores in male &
female term babies in our study.
In Summary, the behavioural response score was increased in both the groups. In response to pain, there was increase in heart rate and respiratory rate, where as oxygen saturation was decreased in both the groups.
The study revealed that term neonates who underwent heel prick had higher pain score than venepuncture.
There was no difference in pain response score in male or female babies in both the groups.
CONCLUSION
Pain response was more during heel prick than venepuncture. Like adults, babies do experience pain.
Hence it is necessary to use analgesia during any painful procedures.
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