Letters to the Editor

Indian Pediatrics 2000;37: 689-691

Comparison of Pain Response to Venipuncture Between Term and Preterm Neonates

We read with interest the recent communication on this subject(1). Although the neonate has a functioning nociceptive system it has only limited ways of communicating the sensation of pain. Behavioral responses to pain are more consistent and specific than physio-logical measurements in all age groups(2,3). Amongst behavioral pain measures, cry and facial expression are the two most widely accepted indicators of pain in infants. A short latency to onset of cry and a long duration of the first cry cycle, in combination with facial expression (specially brow bulging, eyes squeezed shut, open mouth and deepening of nasolabial furrrow) are typical of the reaction to acute invasive procedure in neonates(2).

The behavioral pain score(4) used by authors in the above study based on four criteria, viz., facial expressions, movements, response to handling and consolability and rigidity of limbs and body, was originally intended for intubated neonates and hence cry was not included as a criteria. So it is not clear why the authors considered a tool for behavio-ral assesment of healthy neonates which was used in ventilated and sick neonates and was not validated. Moreover, the behavioral state has also been reported to modify the pain response in neonates(2), which was not considered in the present study. We fully agree with the authors that gestational age affects the pain behavior in neonates. Acute detection of pain in premature neonates requires evaluation of factors which influence their responses and severity of illness(3). So special multi-dimensional scales such as premature infant pain profile (PIPP) have been developed for premature babies(5). We feel usage of appropriate pain assessment tool could have further strengthened the final outcome in the study. Despite obvious limitations, behavioral measurement of pain in preverbal children is of major importance, when treating pain and evaluating the effectiveness of therapy. There is need for development of tools that are valid and easy to use in clinical situations.

Srikanta Basu,
Veena R. Parmar,
Department of Pediatrics,
Government Medical College Hospital,
Sector 32, Chandigarh 160 047, India.

1. Singh H, Singh D, Soni RK. Comparison of pain response to venipuncture between term and preterm neonates. Indian Pediatr 2000; 37: 179-181.

2. Grunau RVE, Craig KD. Pain expression in neonates: Facila action and cry. Pain 1987; 28: 395-410.

3. Stevens BJ, Johnston C, Horton L. Factors that influence behavioral pain responses of premature infants. Pain 1994; 59: 101-109.

4. Pokela ML. Pain relief can reduce hypoxemia in distressed neonates during routine treatment procedures. Pediatrics 1994; 93: 379-383.

5. Stevens B, Johnston C, Petryshen P, Taddio A. Premature infant pain profile: Development and initial validation. Clin J Pain 1996; 12: 13-22.

Neonatal responses to painful stimuli can be categorized as: (a) behavioral, (b) physio-logic, and (c) metabolic and hormonal. Certainly, behavioral responses including facial expressions, motor responses (body move-ments, response to handling and consolability, rigidity of limbs and body) and cry, are important parameters while assessing response to pain. An elaborate assessment of cry itself includes aspects like duration, fundamental frequencies and spectrography(1). However, preterms differ from term babies in these parameters with spontaneous activity even without pain stimulation. Such complex requirements have necessitated multi-dimentional scales like Premature Infant Pain Profile, for preterm babies(2). Since this study was aimed at comparing paing response in preterm and term babies, a simpler combination of behavioral and physiological parameters was used. We did analyze the presence of audible cry (Table I) but since its detailed features are confounded by normal cry patterns of preterm babies, this element was excluded from the publication.

Regarding the influence of behavioral state on pain response, we recognize that the initial state of alertness is of considerable significance. As indicated in our report, the time interval between feed and the procedure was kept similar in the two groups. Moreover, prepara-tion of local site and handling prior to actual pain stimulus do alter the preceding behavioral state resulting in comparable alert and awake state in healthy babies as in this study(3).

Harmesh Singh,
Daljit Singh,
R.K. Soni,
Department of Pediatrics,
Dayanand Medical College and Hospital,
Ludhiana, Punjab, India.

1. Marshall RE. Neonatal pain associated with caregiving procedures. Pediatr Clin N Amer 1989; 36: 885-902.

2. Stevens B, Johnston C, Petryshen P, Taddio A. Premature infant pain profile: Development and initial validation. Clin J Pain 1996; 12: 13-22.

3. Singh H, Singh D, Soni RK. Comparision of Pain responses to venipuncture between term and preterm neonates. Indian Pediatr 2000, 37: 179-181.