Indian Pediatrics 2000;37: 179-181
Comparison of Pain Response to Venipuncture Between Term and Preterm Neonates
Harmesh Singh, Daljit Singh and R.K. Soni
From the Departments of Pediatrics and Social and Preventive Medicine, Dayanand Medical College and Hospital, Ludhiana, Punjab, India.
Reprint requests: Dr. Harmesh Singh, 18-E, Tagore Nagar, Ludhiana, Punjab.
Manuscript received: May 19, 1999;
Initial review completed: July 15, 1999;
Revision accepted: August 18, 1999
Pain in neonates has been historically underestimated, under treated and only recently has become the focus of clinical and research attention(1,2). Previously, it was thought that neonates do not feel pain because of inadequate myelinization of the sensory nerves, immaturity of pain receptors and cortex and reduced localization of pain(3,4). However, recent studies(4,5) have documented pain perception by the newborn babies although babies can't verbalize or report pain(6). Behavior is the main source of expression in nonverbal infants(7).
There is still considerable uncertainty about extent of perception of pain by the preterm babies as compared to term babies(8). Thus there is a need to define difference in the common behaviors and other parameters that consistently appear with painful stimuli in term and preterm babies. The present study was therefore conducted to compare responses of term and preterm neonates to venipuncture.
Subjects and Methods
Fifty term and 100 preterm infants less than 7 days of age who required blood sampling for bilirubin estimation and workup were assessed for their responses to venipuncture performed in a standard manner. Healthy neonates between 32 weeks to 42 weeks gestational age were eligible. Babies with significant morbidity like septi-cemia, birth asphyxia, major congenital mal-formations, and neurological involvement were excluded. The selected cases were divided into three groups: Group I_Term, Group II-Preterm, 35-37 weeks gestation and Group III_Preterm, 32-34 weeks gestation. Pain during the procedure was scored in terms of the behavioral pain score(4). Heart rate, respiratory rate, and oxygen saturation (Nellcor N-180 pulse oximeter) were monitored continuously from 10 minutes before to 15 minutes after the procedure. The maximal change in the above parameters were noted. The data so collected were statistically analyzed by using Fisher's Z test.
The mean postnatal age (days) in groups I, II and III was 3.20±2.09, 2.58±1.89 and 2.92±2.05, respectively. The time of last feed (minutes) was comparable in all the groups (group I=119.40±5.30, group II = 112.20±5.40, group III=107.40±5.20). The mean birth weight (kg) was 3.20±1.06 in group I, 2.40±1.10 in group II and 1.70±1.14 in group III, respectively.
Table I__Changes in Heart Rate, Respiratory Rate and Oxygen Saturation in Response to Venipuncture
Values depict means±SD.
*p <0.05; ** p <0.01.
The mean heart rate (Table I) increased during the procedure in all the groups and showed a significant difference (p <0.01) when compared to that recorded prior to venipuncture. There was a significant rise in respiratory rate during the procedure in all the groups as com-pared to the baseline (p <0.01). All newborns in three groups experienced a significant decrease in oxygen saturation during the procedure (p <0.01).
The mean total behavioral pain score during venipuncture was significantly higher in Group I (7.46±3.34) and group II (5.90±3.10) as compared to the baseline values (group I = 0.70±1.72; group II=0.54±1.37, respective-ly) (p <0.01). However, in group III there was no significant change in the mean total pain score during the procedure.
Most of the preterm neonates are admitted to hospital NSCUs and undergo repeated multiple diagnostic and therapeutic procedures that result in pain and discomfort. Frequent and prolonged pain may be potentially harmful to the developing nervous system and may threaten the physiological stability of premature and sick infants(9).
The present study clearly indicates that all the neonates responded to painful stimuli in one or the other way. Various other studies have also reported that neonates have a characteristic and predictable response to painful stimuli(10,11). Physiologic changes in response to painful stimuli had been uniformly reported by previous studies both in term and preterm babies(10). A significant increase in heart rate was reported by Williamson and Williamson(12) (54.1±17.8 bpm) and Rawlings et al.(13) (43 bpm) in response to circumcision. These changes are comparable to that observed in the present study. Similarly Owens and Todt(14) reported that an average increase in HR was 49±27.5 bpm over the preceding rate during heel warm-ing. These authors did not compare the changes between term and preterm babies. The statisti-cally significant rise in respiratory rate in the present study is in accordance to that reported earlier(15). A significant decrease in oxygen saturation in response to painful stimuli was also reported by previous studies(16,17). Similar findigns were recorded in the present study. Potentially injurious hypoxia occur even during essential routine care procedures(18,19).
The mean total behavioral pain score was significantly higher in term and 35-37 weeks preterm babies but showed no significant change in the 32-34 weeks neonates. Craig et al.(19) also reported diminished bodily activity in preterm neonates compared to full term babies and increasing facial activity with the gestational age of the newborns. On the other hand Stevens(17) found that premature neonates were capable of responding in a manner similar to full term neonates but factors altering this response were not clearly delineat-ed. It has been documented that gestational age had a main multivariate effect in the premature infant responding less robustly(20).
As behavioral pain score response during venipuncture showed a significant difference between full term and preterm babies and changes in physiologic parameters were uniformly present in all the groups, it can be concluded that gestational age influences the pain response in newborn babies. Thus assessment of pain requires attention to the gestational age of the neonates.
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