Pain in Preterm Newborns

Abstract

Introduction

Pain is an unpleasant sensory and emotional experience associated with, or resembling the experience of, actual or potential tissue damage. While nociception is objective, pain is subjective. It is a complex, personal experience influenced by biological, psychological, and social factors hence not being equal to nociception. Pain mechanisms start developing early and mature during development. Through life experiences individuals learn the concept of pain. Verbal inability to communicate should not be interpreted as absence of pain. In preterm newborns who are prone to medical interventions due to their immaturity and medical conditions associated with it, recognising, assessing, treating and preventing pain remains a challenge.

Through literature review our aim is to answer the following questions: (1) How do pain mechanisms develop during pregnancy? (2) How do premature birth and procedures in preterm newborns influence pain mechanisms? (3) How do we recognise pain during perinatal period? 

Results

Development of Nociception and Pain: At 8 weeks of gestation (WGA) fetus has a sufficiently developed neural system to respond to touch and noxious stimuli, at 12 WGA pain capacity can be enabled via cortical subplate. Some researchers see these reactions prior to 24 WGA as unconscious and reflexive. Preterm babies of 22-27 WGA share physiology with fetuses of same age [1]. Neurons that modulate and inhibit pain undergo rapid growth beginning at 22 WGA [2].

Effects of Preterm Birth and Procedures on Pain Mechanisms: Repeated painful exposures in preterm babies have potential for deleterious consequences [3]. Procedures may permanently modify individual pain processing and present risk factors for persistent altered neurodevelopment. 

Recognising Pain: Newborns use behavioural (facial expressions, crying, body movement) and physiological (increased heart rate and blood pressure) signals to communicate their experience of pain which can be measured with pain scales, but these signals are not uniquely specific to pain. Prolonged pain can lead to exhaustion, causing newborns to stop expressing it [3].

Conclusions

Pain mechanisms are developed in preterm infants. Because of immaturity pain is difficult to recognise, interpret, and measure. From ethical point of view as well as from the possible consequences on neurodevelopment, further research is needed.

References 

[1] R. Pierucci, “Fetal pain: The science behind why it is the medical standard of care,” The Linacre Quarterly, vol. 87, no. 3, pp. 311–316, 2020. doi:10.1177/0024363920924877

[2] A. C. Rodrigues and R. Guinsburg, “Pain evaluation after a non-nociceptive stimulus in preterm infants during the first 28 days of life,” Early Human Development, vol. 89, no. 2, pp. 75–79, Feb. 2013. doi:10.1016/j.earlhumdev.2012.08.002

[3] E. Keels et al., “Prevention and management of procedural pain in the neonate: An update,” Pediatrics, vol. 137, no. 2, Feb. 2016. doi:10.1542/peds.2015-4271