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The 2024 Global Year will examine what is known about sex and gender differences in pain perception and modulation and address sex-and gender-related disparities in both the research and treatment of pain.

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The Journal of Pain recently announced the five most downloaded articles of 2013. Our very own Jane Bowering was on the podium with the third most downloaded paper (and the second most read paper in the Journal’s history!!) Well done indeed Jane! Anyway, we have decided to bring all five of the most downloaded articles to you over the coming weeks. Here is an account of one of them, Cong et al on skin-to-skin contact and protective responses in preterm infants. The post is written by Rohan Miegel.

Neonatal intensive care units (NICU) reportedly administer 10-16 painful procedures a day, with most of them being the heel stick. This common procedure involves a warm pack administered for 5mins before the heel being pricked to draw some blood. Much like in the adult population, it is believed pain is not simply forgotten in these young babies. Cong et al. (2012) alludes to the detrimental physiological and behavioural effects of unrelieved pain that can have extending influences in adult-life. These effects are related by fluctuations in the babies body systems, sudden changes in heart rate, blood pressure, respiratory rate and oxygen saturation, that can lead to intraventricular haemorrhage resulting in permanent disability or death. So limiting the pain experience in this population is extremely important. Opioids or other pain relieving drugs have been shown to be ineffective so other avenues must be explored to alleviate the effects of pain. Enter the heroic intervention, kangaroo care…

Kangaroo care (KC) involves laying a nappy-clad infant skin-to-skin on the seated parent’s chest. A blanket is then placed over the infant. This technique has long been used in preterm infant care. In this study, two groups utilized KC, one had 30min before and during the heel stick, and the other just 15mins before and during the heel stick procedure. The control group remained in the incubator, propped up in prone to 30-40 degrees from horizontal and covered by a blanket to simulate KC as much as possible. Each baby had 24-72 hours between trials to washout any lingering effects.

The team attached electrodes on the baby’s chest to measure the beat-to-beat heart rate. This was done to analyse the sympathetic and parasympathic involvement during the application of KC and the painful heel stick. The ideal is for these autonomic processes to remain balanced when undergoing these procedures. Assessing the stress response through an objective measure of heart rate variability enhances rigor of the study. The babies face was also videotaped so behavioural changes could be recorded and analysed. This was interesting to read about, but should not be weighted too heavily with the self-admitted limitation of the trouble of blinding the viewers to the group because the baby’s head would move with the parent’s breathing.

The results were quite interesting. They found that the KC groups (both 30mins and 15mins) showed less heart rate variability than the incubator group. In short, the autonomic responses in these preterm infants were reduced when the child was in close contact with their parent compared to being left in the incubator. The parasympathetic responses were not different between groups.

Thirty minutes of kangaroo care was likely to familiarise the baby with his/her mother, therefore increasing the analgesic effect. This multisensory stimulation of skin, smell, warmth, breath, heartbeat is clearly soothing enough to allow the baby to feel safe enough to not overly stress over the heel stick pain. Cong et al. also mentions the role of oxytocin in kangaroo care. Oxytocin, being crucial in controlling the stress and autonomic function, could be priming the baby to edge into a parasympathetic state and reduce the threat of the situation – although the data would suggest this is not driven by different parasympathetic responses, so more work is required there.

Like many studies, more RCTs with more power are needed to improve confidence in this treatment technique. This study hints at an interesting mechanism that is not contaminated by learned response to pain, but rather incorporates it as something that can be handled if the baby feels safe and protected as is likely in kangaroo care.

This paper shows that the protective responses to heel prick in pre-term infants can be reduced, which clearly implies that the baby is unconsciously judging the condition to be less dangerous, despite identical nociceptive input. That being held by one’s parent does this seems not altogether surprising and is very consistent with the idea that protection will occur according to evaluation of threat, not just nociceptive input. That nociception is not the sole driver of protective responses even in pre-term infants, is pretty cool. This drop in perceived danger could be an evolutionary trait that makes us feel safe and less threatened when in the close presence of our parents, or just a biological reaction to being warm or, perhaps a combination of the two. Regardless, the old adage of ‘a mother’s touch’ may just have more truth behind it than many children would like to admit.

About Rohan Miegel

Rohan MiegelRohan Miegel is currently in his final year of Physiotherapy at the University of South Australia.  He has only recently become involved in research and is taking advantage of any opportunities.  Particular interests include neuroscience, pain, (very recently) cycling, and anything to do with dinosaurs.  He plans to finish his degree then dive more into the world of research.


Cong X, Cusson RM, Walsh S, Hussain N, Ludington-Hoe SM, & Zhang D (2012). Effects of skin-to-skin contact on autonomic pain responses in preterm infants. J Pain, 13 (7), 636-45 PMID: 22595172

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