By: Shubhada Ponkshe
Thermoregulation is a critical physiologic function that is closely related to the transition and survival of the infant. An understanding of transitional events and the physiologic adaptations that neonates must make is essential to helping the nurse provide an appropriate environment and help infants maintain thermal stability.
Optimizing the thermal environment has proven significant for improving the chances of survival for small infants. Understanding the basic physiologic principles and current methodology of thermoregulation is important in the clinical care of these tiny infants.
Thermoregulation is the ability to balance heat production and heat loss in order to maintain body temperature within a certain ‘‘normal’’ range.
Thermoregulation is controlled by the hypothalamus. Thermal stimuli providing information to the hypothalamus are derived from the body’s skin and deep thermal receptors and from thermal receptors in the pre - optic area of the hypothalamus. It is in the hypothalamus that sensory information describing thermal status throughout the body is processed and compared against the temperature set point. Body heat-and therefore body temperature-is modified by alterations in metabolism, motor tone and activity, vasomotor activity, and sweating to produce either heat gain or loss. Neonates are prone to temperature maintenance problems. The intrauterine temperature of 37.9o c (100.2oF) fluctuates very little under normal circumstances.’ At birth, the transition from an intrauterine to extra-uterine environment creates a significant thermal change that challenges the infant’s thermoregulatory abilities. Unless someone gives immediate attention to heat loss, the neonate’s temperature can drop approximately 4.5oC (8.loF) during the first minute after birth.’ Because the infant is dependent on environmental temperature, providing thermal support is a primary nursing objective.
MECHANISMS OF HEAT LOSS:
Because of differences in physiologic function and small body size, neonates are particularly vulnerable to both under-heating and overheating. Transfer of heat between the environment and the infant occurs by conduction, convection radiation and evaporation.
Newborn loses heat by evaporation particularly soon after birth (due to evaporation of amniotic fluid from skin surface), conduction (by coming in contact with cold objects-cloth, tray etc.), convection (by air currents in which cold air replaces warm air around baby-open windows, fans) and radiation (to colder solid objects in vicinity walls)
MECHANISMS OF HEAT GAIN:
The process of heat gain is by conduction, convection and radiation in addition to non-shivering thermo-genesis. Non-shivering thermo-genesis occurs predominantly in the brown adipose tissue. Brown fat is localized around the adrenal glands, kidneys, nape of neck; inter scapular area, and axillary region. Metabolism of brown fat results in heat production. Blood flowing through the brown fat becomes warm and through circulation transfers heat to other parts of the body.
THERMO NEUTRAL ENVIRONMENT:
Range of environmental temperature in which an infant can maintain normal body temperature with the least amount of basal metabolic rate and oxygen consumption and baby thrives well is known as 'Thermo- neutral range of temperature' or 'Neutral Thermal Environment'. For each baby, this range of temperature varies depending on gestational age.
Hypothermia / Cold stress: Occurs when the newborn’s temperature drops below 36.5o C Degrees of Hypothermia:
36o -36.5 o C is mild hypothermia (cold stress);
32 o - 36 o C is moderate hypothermia;
Less than 32 o C is severe hypothermia.
Hyperthermia: Occurs when the newborn’s body temperature rises above 37.5 o C because the environment is too hot for the baby or the baby is overdressed....