Chronic pain in critically ill neonates and infants

Clinicians and researchers agree that, in addition to acutely painful episodes such as heel lancing, infants in the neonatal intensive care unit (NICU) and high dependency unit (HDU) may also experience other types of pain such as chronic pain. Although chronic pain is defined as pain lasting three months or more, such a definition is not appropriate for infants in the NICU or HDU due to their younger age. The aim of this thesis was to develop a clear and clinically valid definition of chronic pain in infants admitted to the NICU and HDU using multiple methodologies. The thesis begins with an exploration of the ethical implications of neonatal and infant pain in the context of clinical pain management. Following this exploration, the thesis begins to develop a definition of chronic pain. First, a systematic review demonstrates that many studies refer to various types of non-acute pain such as chronic pain, however a consistent definition was lacking. Second, analysis of real-world clinical data demonstrates that chronic pain, according to current descriptions, is statistically evident in neonates and infants who underwent major surgery. Third, an expert panel is detailed which leads to a consensus definition of chronic pain in infants in the NICU and HDU, and which is then validated using a global survey of neonatal clinicians. Fourth, exploratory and confirmatory factor analyses of a non-acute pain assessment tool reveal the constructs underlying this instrument commonly used in the NICU and HDU. Fifth, a prognostic and clinical definition of chronic pain in neonates is currently underway in a prospective cohort study to determine whether longer periods of treated pain result in adverse effects on neurodevelopment, psychosocial wellbeing, and growth outcomes. Therefore, this thesis provides 1) an ethical analysis of neonatal pain management, 2) a systematic review of non-acute pain in critically ill neonates and infants, 3) a statistical definition of chronic pain in critically ill neonates and infants, 3) a consensus definition of chronic pain, 4) an analysis of non-acute pain and assessment, and 6) a protocol for a prospective cohort study to develop a prognostic and clinical definition of chronic pain. The thesis takes an important step towards guiding the assessment, prevention, and treatment of chronic pain in neonates and infants in the NICU.