Thermoregulation in the Neonate
THERMOREGULATION IN THE NEONATE By: Shubhada Ponkshe [pic] INTRODUCTION: 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.
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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. [pic] 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: [pic] 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 emperature’ or ‘Neutral Thermal Environment’. For each baby, this range of temperature varies depending on gestational age. THERMAL INSTABILITY: 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.
RISK FACTORS FOR THERMOREGULATION PROBLEM: Premature, Small for gestational age, Neuro problems, Endocrine, Cardiac / respiratory problems, Large open areas in the skin, Sedated Infants, Drug exposure. These conditions make newborns are at risk because Infants have more skin surface per pound of body weight than older children or adults, more skin means more radiant heat and more insensible water loss. Less brown fat and glycogen stores decreased ability to maintain flexion increased body surface area compared to weight. SIGNS AND SYMPTOMS OF HYPOTHERMIA / COLD STRESS:
Peripheral vasoconstriction: acrocyanosis, cold extremities, decreased peripheral perfusion. CNS depression: lethargy, bradycardia, apnea, poor feeding Increased pulmonary artery pressure: respiratory distress, tachypnea Chronic signs: weight loss, failure to thrive PREVENTION OF HYPOTHERMIA: Hypothermia can be prevented by maintaining a neutral thermal environment and reducing heat loss. For prevention in reduction of heat consider the four ways by which the neonate experiences heat loss and intervene appropriately. Convective heat loss can be prevented by: Providing warm ambient air temperature • Placing infants less than 1500 grams in incubators • Keeping portholes of the incubator closed • Warming all inspired oxygen • On open warmers keeping sides up and covering infant if possible • Using Infant Servo Temperature Control Radiant heat loss can be prevented by: • Avoiding placement of incubators, warming tables and bassinets near cold windows, walls, air conditioners, etc.. • Placing a knit hat on the infant’s head • Wrapping tiny babies in saran or “bubble” wrap • Increase environmental temperature Conductive heat loss can be prevented by: Placing a warm diaper or blanket between the neonate and cold surfaces • Placing infant on pre-warmed table at time of delivery • Warming all objects that come in contact with the neonate • Admitting infant to a pre-warmed environment • Skin to skin contact Prevention of hypothermia is the best treatment but if it occurs anyway, the following is a list of what you can do to relieve the cold stress. MANAGEMENT OF HYPOTHERMIA / COLD STRESS: Management of mild hypothermia / cold stress: • Hypothermia can be prevented by maintaining a neutral thermal environment and reducing heat loss. Cover adequately – remove cold clothes and replace with warm clothes • Warm room/bed • Take measures to reduce heat loss • Ensure skin-to-skin contact with mother; if not possible, keep next to mother after fully covering the baby • Breast feeding • Monitor axillary temperature every ? hour till it reaches 36. 50 C, then hourly for next 4 hours, 2 hourly for 12 hours thereafter and 3 hourly as a routine Management of moderate Hypothermia / Cold stress :(32oc to 35. 9oc) • Skin to skin contact • Warm room/bed • Take measures to reduce heat loss • Provide extra heat: 200 W bulbs, Heater, warmer, incubator, apply warm towels.
Management of severe Hypothermia / Cold stress: (< 320C) • Take measures to reduce heat loss • Provide extra heat preferably under radiant warmer or air heated incubator rapidly warm till 340C, and then slow re-warming. • IV fluids: 60-80 ml/kg of 10% Dextrose • Oxygen, Inj. Vitamin K 1mg in term & 0. 5 mg in preterm • If still hypothermic, consider antibiotics assuming sepsis • Monitor HR, BP, Glucose HYPERTHERMIA: 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. RISK FACTORS FOR HYPERTHERMIA: • Excessive environmental temp Sepsis • Dehydration • Alterations in the hypothalamic control mechanism due to birth trauma, anomalies, drugs SIGNS OF HYPERTHERMIA: • Tachypnea • Apnea • Tachycardia • Flushing • Hypotension • Irritability • Poor Feeding • Skin Temp > Core Temp MANAGEMENT OF HYPERTHERMIA: • Place the baby in a normal temperature environment (25 to 280C), away from any source of heat • Undress the baby partially or fully, if necessary • Give frequent breast feeds • If temperature > 390C, sponge the baby with tap water; don’t use cold / ice water for sponge • Measure the temperature hourly till it becomes normal
NURSES RESPONSIBILITIES DURING INTERVENTIONS FOR AT RISK INFANTS: • Always be prepared to intervene • Rewarm slowly (0. 5? C per hour) • Monitor closely (vital signs every 15 – 30min) • Core temp • Skin temp will be higher than axillary • Blood pressure because Rewarming may lead to vasodilatation & hypotension • Heart rate and rhythm because bradycardia & arrhythmias common with hypothermia Monitor: • Respiratory rate and effort: Increased distress, Apnea • Oxygen saturations: Hypoxemia / desaturations, be prepared for ( need for respiratory support, Monitor acid/base status • Blood glucose: Monitor- nfant at increase risk for hypoglycemia • Assess infant temp every 15-30 minutes • As infants core temp reaches set temp and infant is not showing signs of deterioration increase set temp again. • Continue process until temp within normal range While caring infant in incubator: • Incubator better control than warmer • Set temp 1 – 1. 5? C above core temp • Open incubator portholes and doors only when necessary • Blanket over incubator • Cluster care • Incubators and radiant warmers are designed to work using skin temperature to regulate the thermal environment Skin Servo Monitoring:
As temperature is higher in brown fat areas, avoid placing the temperature probe over brown fat deposit areas, such as the axilla, neck, or back. Because as the core temperature will be higher than the skin temp. , the warming device will cool the environment. The infant will then need to burn fat and calories to stay warm Temperature Probe Placement: Secure the temperature probe at/or about the costal margin of the chest, midway between the xiphoid and the navel. This placement should assure accurate skin temperature measurement. Never lay infants on the probe, as this will also cause a falsely high temperature to be registered.
Skin temperature Probes: Do not lay infant on skin probe Do not place over: Bony prominences Areas of brown fat deposits Poorly vascular areas Excoriated areas Keep probe exposed to heat source Keep probe securely attached SUMMARY Hypothermia in the newborn is due more to a lack of knowledge than to lack of equipment. Hypothermia is a preventable condition that has well documented impact on morbidity and mortality. Therefore, assisting the infant to maintain a normal body temperature and preventing hypothermia during stabilization is critical.
This is the gift from god so prevent them from thermoregulation crises. [pic] Review Questions: 1. Why is brown fat so important for infants? 2. What is NTE (Neutral Thermal Environment)? 3. Write the four ways a newborn may lose heat to the environment 4. Write down the points of “Warm chain” REFERANCES: 1. The ACoRN Editorial Board, ACoRN, Acute Care of At-Risk Newborns, Vancouver, BC, 2005. 2. Health Canada, Family-Centred Maternity and Newborn Care: National Guidelines, Minister of Public Works and Government Services, Ottawa, 2000. . Karen Thomas, Thermoregulation in Neonates neonatal network / March 1994vol. 13 no. 2 4. Thermal control of the newborn: a practical guide. WHO/FHE/MSM/93. 2. essential Newborn nursing for small hospital in resource restricted countries: learner’s guide. Publication of WHO-CC for training & research in newborn care, department of pediatrics, AIIMS, New Delhi, 2009. 5. Nursan Dede C?? nar a, Tuncay Muge Filiz Journal of Neonatal Nursing (2006) 12, 69e74. www. intl. elsevierhealth. com/journals/jneo ———————– [pic] [pic] [pic]