Neuroendocrine Mechanisms of Pain in Newborn Children

Abstract

From the first days of their lives, newborns experience primary pain due to neonatal screening, primary treatment and blood collection for laboratory analysis. As a result of untreated analgesia, the risk of developing neurological consequences is high and prevention is necessary.

For a long time, painful reactions in newborns did not attach importance. All newborns are faced with painful procedures soon after birth, and often even in utero. Newborns are sensitive to pain, but they cannot signal about it, based on anatomical and physiological characteristics and a set of pathological processes.

The pain perception system begins to develop in early pregnancy (starting from 6-9 weeks of gestation) and is fully formed by 21-23 weeks of intrauterine development. All anatomical structures necessary for the pain impulses are ready at the time of delivery: the nerve fibers are sufficiently myelinated already in the second trimester of pregnancy and are completely myelinated by the 30-37th week of intrauterine development. Afferent pain tracts are present even in newborns with a minimum gestational age: by the 8-14th week, most neuropeptides, transmitters of pain, are determined, by the 20th, nociceptors are developed, and in the cerebral cortex there is a normal number of neurons - 10 billion or functional changes. Even premature babies are able to experience pain and react to it with hypertension, tachycardia, an increase in intracranial pressure, and a pronounced neuroendocrine reaction. Moreover, newborns have a higher pain threshold than older ones. Simons et al. proved that each newborn undergoes an average of 14 painful procedures daily and 39.7% of them do not receive any analgesia. The problem of pain prevention in the neonatal period stands at the intersection of medicine, philosophy, ethics, deontology of morality. This is why the dissemination and improvement of strategies to prevent neonatal pain needs to be supported not only from an evidence-based perspective, but also from a humanitarian perspective. The International Association for the Study of Pain (IASP) defines pain as “an unpleasant sensory and emotional experience with actual or possible tissue damage, or a condition that is verbally described as consistent with such damage. Newborns who have spent a long time in the intensive care unit have different pain thresholds and other characteristics of pain sensitivity compared to healthy newborns. Long-term neurological consequences include changes in neuropsychic development and social behavior, later development of attention and learning ability. Repeated pain in a child can cause the development of intraventricular hemorrhage, ischemia and periventricular leukomalacia, leads to the development of DIC syndrome, metabolic acidosis, and forms a state of constant stress, or hyperalgesia. Such conclusions are prompted by the opinion about insufficient myelination of nerve fibers and the maturity of nociceptors, as well as the system of neurotransmitters, high concentrations of endorphins, and increased BBB permeability.