[Nociception in newborn and premature babies]

Abstract

Background: The somatosensory system of preterms and newborns differs substantially from adults. These differences are of considerable preclinical and clinical interest. Maturation of A- and C-fibre synaptic connections in the dorsal horn and development of descending inhibition from the brainstem all take place postnatally in the rat. In early stages of development there is no definite spatial separation in the dorsal horn between the nociceptive and the non-nociceptive system. In preterms but not in adults non-noxious stimuli can induce central sensitization. Many neurotransmitters and signalling molecules involved in pain pathways are expressed early in the developing nervous system but do not reach adult levels for a considerable period. More important, receptors are frequently transiently overexpressed or expressed in areas during development where they are not seen in the adult and may have a different functional profile. The descending pain inhibitory system that provides an important protection against central sensitization develops later than the ascending nociceptive system. Thus, during a critical period of time the immature nociceptive system is highly vulnerable. For example, neonatal circumcision in the absence of analgesia results in increased pain responses during subsequent routine vaccination months later.

Conclusions: In view of the changing nature of neonatal somatosensory and pain pathways and the vulnerability of the developing nervous system to alterations in sensory stimulation it is important that preterms and newborns need the care of a specialist for prevention and treatment of pain to avoid suffer and long-term changes in the nervous system.