Thermal regulation and effects on nutrient substrate metabolism

Abstract

One of the most stimulating and rewarding aspects for many clinicians practicing neonatology is the application of basic physiological principles to the understanding of disease processes and to determining optimal management. This is particularly true in the area of thermal regulation. Those who carried out the early and pioneering work were also pioneers in neonatal physiology. Their work was of immeasurable value in reducing neonatal mortality and morbidity, and has informed subsequent technological advances. The current generation of practicing neonatologists has been fortunate enough to be taught by these “masters” and learn from their works. It is our responsibility to hand on to our juniors enthusiasm and respect for the application of physiology to neonatal care. This chapter covers normal physiological changes, the challenges to these, the impact of disturbed thermal regulation, and therapeutic strategies. Changes in the thermal environment at birth Fetal temperature rises and falls with maternal temperature and is maintained at 0.5°C above that of the mother. Fetal heat loss is via the placenta and amniotic fluid. At birth, a fall in body temperature is physiological; indeed stimulation of peripheral thermal receptors is a trigger for spontaneous breathing. The usual rectal temperature of the newborn baby is 36.5–37.0°C with skin temperature 0.5°C below this. Physiological responses first described 40 years ago are triggered by the postnatal fall in temperature resulting in heat conservation and heat production.