Newborn Care: Temperature control and hypothermia


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Newborn Care was written for healthcare workers providing special care for newborn infants in level 2 hospitals. It covers: resuscitation at birth, assessing infant size and gestational age, routine care and feeding of both normal and high-risk infants, the prevention, diagnosis and management of hypothermia, hypoglycaemia, jaundice, respiratory distress, infection, trauma, bleeding and congenital abnormalities, communication with parents

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Newborn Care: Temperature control and hypothermia

  1. 1. 7 Temperature control and hypothermia hot, it is preferable to measure axillary (arm Objectives pit) or abdominal skin temperature as the skin is the first part of the body to cool down. When you have completed this unit you NOTE In contrast, the oral or rectal temperature is useful in detecting a fever in older children and should be able to: adults as the body core (centre) is the first part of • Keep infants warm. the body to heat up. • Explain why infants can develop Skin temperature can be measured with: hypothermia. 1. A digital thermometer: The digital • Recognise the signs and list the dangers thermometer is placed in the infant’s axilla of hypothermia. (armpit) for 2 minutes before the reading is • Prevent and treat hypothermia. taken. Thermometers should be stored dry • List the causes and complications of when not in use to prevent cross-infection. pyrexia. 2. A low reading glass mercury thermometer: Used and stored the same as a digital thermometer. Mercury thermometers should no longer be usedMEASURING BODY in children due to the risk of mercuryTEMPERATURE poisoning if the thermometer should break in the mouth. 3. A telethermometer: (electrical7-1 How do you measure an infant’s thermometer). If a telethermometer istemperature? used, the probe is usually placed over the left, lower abdomen or the lower back.An infant’s skin temperature, rather than the Avoid the right, upper abdomen as theoral or rectal temperature, is usually measured. liver produces a lot of heat and this mayAs infants commonly become cold rather than
  2. 2. 132 NEWBORN CARE give too high a reading. Telethermometers presence of many nerves and blood vessels, should be calibrated regularly. and differs in many ways from the ordinary white fat that is found under the skin. When7-2 What is the normal range of body the body temperature drops, the infant breakstemperature? down brown fat and, thereby, produces heat toThis depends on the site where the correct the body temperature.temperature is measured: To a lesser degree the infant is also able to use1. The normal axillary temperature is 36.5– other energy stores to produce heat, such as: 37 °C. • White fat which is found under the skin.2. The normal abdominal skin temperature is • Glycogen which is stored in the liver. 36–36.5 °C. • Milk feeds.All newborn infants have the same range ofnormal body temperature. 7-5 Which infants produce too little heat? NOTE The normal oral temperature is 37–37.5 °C The following infants are often unable to and rectal temperature is 37.5–38 °C. Neither are produce enough heat to maintain a normal routinely used in newborn infants. body temperature: 1. Preterm infants. They are born before adequate stores of brown fat have beenHEAT PRODUCTION deposited.AND LOSS 2. Underweight for gestational age or wasted infants. They have used up their stores of brown fat before delivery.7-3 What determines body temperature? 3. Infected or hypoxic infants. Generalised infection or severe hypoxia prevents theThe body temperature depends on a balance normal breakdown of brown fat and,between: thereby, decreases the production of heat.1. The rate of heat production (how fast heat Infected and hypoxic infants, therefore, is produced). commonly present with a drop rather than2. The rate of heat loss (how fast heat is lost). a rise in body temperature.If the rate of heat production is low or the rateof heat loss is high, then the body temperature Infection in newborn infants causes a fall rathermay fall. Similarly, excessive heat production than a rise in body temperatureor reduced heat loss causes an increased bodytemperature (fever or pyrexia). 7-6 How do infants lose heat?7-4 How do newborn infants produce heat? Infants lose heat from the skin to theAdults and older children are able to increase environment by the following methods:their heat production by shivering and doing 1. Convection. This is the loss of heat fromphysical exercise. Newborn infants cannot the infant’s skin to the surrounding air.shiver or exercise. However, during the first Infants lose a lot of heat by convectionfew weeks of life the infant is able to break when exposed to cold air or draughts.down (metabolise) brown fat which releases 2. Conduction. This is the loss of heat whenlarge amounts of heat. Brown fat is a special the infant lies on a cold surface. Infantstissue laid down in the neck, chest and rapidly lose heat by conduction whenabdomen of the fetus during the last weeks of placed naked on a cold table, weighingpregnancy. It is brown in colour, due to the
  3. 3. TEMPERATURE CONTROL AND HYPOTHERMIA 133 scale or X-ray plate, or are wrapped in a 4. Wet infants lose heat by evaporation. cold blanket or towel. Infants are wet after delivery, after a bath,3. Evaporation. This is the loss of heat from and when lying in a wet nappy. an infant’s wet skin to the surrounding 5. Infants with poor muscle tone. Hypotonic air. Infants lose heat by evaporation after infants, such as preterm or ill infants lie delivery or after a bath. Even an infant in a with their arms and legs spread out. They, wet nappy can lose heat by evaporation. therefore, expose a greater area of skin for4. Radiation. This is the loss of heat from an heat loss than do well, term infants who infant’s skin to distant cold objects, such as hold their arms and legs flexed against the cold windowpanes, walls and the incubator body. hood. Many people find radiation difficult to understand as the loss of heat from a warm to a distant cold object is not affected HYPOTHERMIA by the temperature of the surrounding air. Even if the room and incubator are warm, an infant may still radiate heat to a cold 7-8 What is hypothermia? windowpane. The closer the infant is to the An abdominal temperature below 36 °C cold window, the more heat will be lost. or an axillary temperature below 36.5 °C is Curtains reduce radiant heat loss at night abnormally low. These infants need to be when windows are coldest. warmed. Therefore, a working definition of hypothermia (low body temperature) is a7-7 Which infants lose too much heat? body temperature below these values. OnceThe following infants commonly lose too the body temperature falls below 35 °C themuch heat and, therefore, may drop their body infant is in danger of complications relatedtemperature: to being too cold. As the rectal temperature is normally higher than that at other sites, a1. Small infants. All small infants have rectal temperature below 35 °C is particularly a large surface area in relation to their dangerous. body weight. Therefore, preterm and underweight for gestational age infants 7-9 Which infants are at the greatest risk of tend to lose heat rapidly. hypothermia?2. Infants with little subcutaneous fat. Preterm, underweight for gestational Infants who produce too little heat or lose too age and wasted infants all have very little much heat are at the greatest risk. These high- WHITE fat under their skin (subcutaneous risk infants are: fat) to insulate their body against heat 1. Preterm infants loss. Most white fat is deposited under the 2. Underweight for gestational age infants skin during the last weeks of pregnancy. 3. Wasted infants Therefore, preterm infants are born before 4. Infants who have not been fed they are able to build up stores of white 5. Infected infants fat. Underweight for gestational age and 6. Hypoxic infants wasted infants also have little white fat as 7. Wet infants they have used up their white fat before 8. Infants exposed to a cold environment delivery. 9. Infants who are nursed naked and not3. Infants in a cold environment may covered lose heat by conduction, convection, 10. Infants nursed close to a cold window evaporation or radiation. Heat loss is greatest if an infant is left naked and not covered.
  4. 4. 134 NEWBORN CARE7-10 How do you prevent hypothermia? 7. Monitor the skin or axillary temperature in all infants who are at an increased risk1. Identify all infants at high risk of of hypothermia. It is essential to detect any hypothermia. This includes all infants who drop in temperature as soon as possible. are likely to produce too little heat or lose too much heat.2. Provide energy (calories) by oral, A woollen cap prevents radiant heat loss from the nasogastric tube or intravenous feeding. infant’s head This is very important in infants who are born with little brown and white fat. Early feeding with breast milk or milk formula 7-11 What is the best environmental feeds helps to reduce the incidence of temperature? hypothermia by providing the infant with The best environmental (e.g. room or energy needed to produce heat. incubator) temperature depends on:3. Provide a warm environment for all infants. The smaller the infant, the warmer 1. The weight and gestational age of the the required environment. Most infants infant. The lower the weight and the under 1800 g need some source of warmth. earlier the gestational age, the higher is You should: the required environmental temperature. • Use skin-to-skin care (kangaroo Infants that are underweight for gestational mother care) whenever possible. age or wasted also need a higher • Never place an infant in a cold environmental temperature. incubator. 2. The postnatal age of the infant. The • Keep the incubator ports closed. greater the postnatal age the lower is the • Always wrap an X-ray cassette in a required environmental temperature, i.e. as towel before use. the infant gets older, a lower environmental • Warm and humidify oxygen whenever temperature is needed. possible. 3. Illness. Sick infants need a higher • Do not nurse an infant near a cold environmental temperature. window. For example, a 1000 g preterm infant on day • Have curtains in the nursery. 1 may need an environmental temperature • Not bath small or sick infants. of 37 °C to keep warm while a healthy term4. Insulate the infant. Dress the infant infant on day 5 may need an environmental and use a woollen cap. The head of the temperature of only 20 °C. newborn infant loses a lot of heat by radiation as the surface area of the scalp In clinical practice each infant must be handled is large, the brain produces a lot of heat as an individual and the above factors, which and there is little hair for insulation. A influence the infant’s temperature needs, woollen cap is more effective than booties must be regarded only as guidelines. The or leggings. It is best if all these are used. A environmental temperature for each infant woollen cap is particularly important if the should be adjusted in order to give a normal infant is receiving headbox oxygen which abdominal skin or axillary temperature. This has not been warmed. Most infants in can be achieved automatically if a servo- incubators should wear a woollen cap. controlled incubator or radiant warmer is used.5. All wet infants must be dried immediately The infant’s energy and oxygen needs are and then wrapped in another, warm, dry lowest when the skin temperature is normal towel. Do not leave an infant in a wet and the infant is nursed at the correct towel. Remember to dry the infant’s head. environmental temperature. Both energy6. Treat any infection or hypoxia. and oxygen needs increase if the infant’s skin
  5. 5. TEMPERATURE CONTROL AND HYPOTHERMIA 135temperature is either above or below normal. ‘bubble wrap’ over the infant reduces waterInfants gain weigh fastest when they are kept loss. As soon as ill infants have improvedat the correct environmental temperature. they should be moved out of a radiant heater and into a closed incubator or KMC. The environmental temperature should be 4. Warm room. Most healthy, term infants adjusted to give a normal axillary or skin can be nursed in a cot or bassinet in a temperature warm nursery, ward or home. The room temperature should be about 20 °C. The NOTE The neutral thermal environment (best room infant should be dressed to prevent heat or incubator temperature) is that environmental loss by radiation to cold windows or walls. temperature at which the skin temperature is 5. Hot room. Many low birth weight infants normal and the infant’s metabolic rate is at its can be kept warm in a bassinet if they are lowest. In this state the infant uses the least amount of oxygen and energy. The energy in nursed in a room where the temperature feeds, therefore, can be used for growth rather is kept at 25–30 °C. The smaller the infant, than for generating heat. It is important to ensure the higher the required room temperature that all infants are nursed as close as possible to will be. However, keeping the mother and their own neutral thermal environment. infant together with KMC is preferable. 6. Dressing the infant. The infant can be7-12 How do you keep an infant warm? kept warm by covering the body with anThere are a number of ways to keep an infant insulating layer and, thereby, preventingwarm: heat loss by convection to cold air and radiation to cold objects in the room. This1. Maternal body heat (skin-to-skin care). is done by dressing the infant in a nappy, Infants can very easily and effectively be jacket, woollen hat and booties. A woollen kept warm by placing them naked against cap is most important in preventing heat the mother’s bare breasts. The infant loss by radiation. Often infants in closed should wear a woollen cap and nappy. Both incubators are dressed. mother and infant should be covered. The mother’s body heat will keep the infant 7. Thermal blanket. An infant can be kept warm. This simple method is an important warm for hours if wrapped in a thermal part of kangaroo mother care (KMC). blanket, silver swaddler or heavy gauge aluminium foil normally used for cooking. This is an effective method of preventing Kangaroo mother care is the best method of heat loss during transport if KMC or a keeping a well infant warm transport incubator is not available. The infant must be warm and dry before being2. A closed incubator. This is the traditional wrapped in a thermal blanket. Never put a way of nursing most small or sick infants cold infant into a thermal blanket or use a as the temperature can be carefully thermal blanket in an incubator. controlled. Today more and more infants 8. Perspex heat shield. A transparent perspex are being nursed with KMC rather than in shield can be placed over an infant in an an incubator. incubator to reduce heat loss by radiation.3. Radiant warmers (overhead radiant heaters). A radiant warmer is used for A woollen cap and perspex heat shield reduces resuscitating an infant or for nursing a very sick infant in an intensive care unit. heat loss by radiation in infants nursed in an Water loss by evaporation is higher than in incubator a closed incubator. A thick plastic sheet or
  6. 6. 136 NEWBORN CAREThe most appropriate method should be 7-15 What metabolic problems arechosen for each individual. There is no excuse common in hypothermic infants?for an infant ever becoming hypothermic 1. Hypoglycaemia. This is a common causebecause hypothermia is preventable. Skin-to- of death in cold infants and the mostskin care by the mother, father, family member, important complication of hypothermia.nurse, doctor or paramedic is always available. Cold infants use a lot of energy in an attempt to warm themselves. As a result Hypothermia is preventable they use up all their energy stores, resulting in hypoglycaemia. 2. Hypoxia. When haemoglobin becomes7-13 When does a small infant no longer cold it takes up, but will not release,need an incubator? oxygen. The oxygen is trapped in the haemoglobin and not released to the bodyMost small infants are able to maintain their cells. The cold infant, therefore, appearsbody temperature in a warm room when they centrally pink even while dying of hypoxia.reach a weight of 1800 g. However, many small Hypothermia also increases the oxygeninfants can maintain their body temperature needs of the body and this make themuch sooner with KMC. Most well infants hypoxia worse.can be moved from an incubator to KMC by 3. Metabolic acidosis. Due to poor1600 g. peripheral perfusion, blood does not carry enough oxygen to the cells. The resulting7-14 How do you recognise a hypothermic hypoxia causes a metabolic acidosis.infant? NOTE A cold infant increases its metabolic rate toHypothermic infants present with the produce heat and rapidly breaks down glucose.following signs: This in turn increases the oxygen needs of the cells, aggravating any hypoxia. The resultant1. They are cold to the touch. anaerobic metabolism of glucose causes an2. They are lethargic, hypotonic, feed poorly excess lactic acid production. Disseminated and have a feeble cry. intravascular coagulopathy is also common in3. Their hands and feet are usually pale or marked hypothermia. blue, but their tongue and cheeks are pink. Note that they are not centrally cyanosed. The pink cheeks may incorrectly suggest Hypothermic infants often die of hypoglycaemia that the infant is well.4. Peripheral oedema or sclerema (a woody 7-16 How do you treat hypothermia? or plastic feel to the skin).5. Shallow, slow respiration or signs of 1. Warm the infant in a closed incubator, respiratory distress. overhead radiant warmer or warm room.6. Bleeding from the mouth, nose or needle Skin-to-skin care is a very effective method punctures. Hypothermic infants often die of warming a cold infant. The incubator of massive pulmonary haemorrhage. temperature should be set at 37 °C until the skin temperature returns to normal. WarmThe more severe the hypothermia (especially water (37 °C) has also been used to correctif the body temperature falls below 35 °C) the hypothermia.more clinical signs will be present. 2. Provide energy while the infant is being warmed. Hypoglycaemia may occur during warming. Energy can be given as oral or nasogastric milk, or intravenous
  7. 7. TEMPERATURE CONTROL AND HYPOTHERMIA 137 maintenance fluid containing 10% dextrose is not cooled. Prolonged pyrexia can also water (e.g. Neonatalyte). lead to dehydration and increases the body’s3. Provide oxygen. Although centrally pink, oxygen and energy needs. cold infants are often hypoxic. Therefore, give 30% oxygen (FiO2 0.3) while the infant is being warmed. A normal oxygen CASE STUDY 1 saturation in a cold infant does to exclude tissue hypoxia as oxygen is trapped in the A preterm female infant is brought to the red cells. nursery from the labour ward wrapped in a4. Give 4% sodium bicarbonate. Most wet towel. The axillary temperature is 32.5 °C. hypothermic infants have a metabolic The infant’s estimated gestational age is 35 acidosis. If intravenous fluid is given, add weeks. The cheeks and tongue are pink but 10 ml 4% sodium bicarbonate to 100 ml of the hands and feet are grey and feel cold. The maintenance fluid (Neonatalyte). Obtain infant is lethargic. a blood gas analysis if possible and half correct any base deficit. 1. Does the infant have hypothermia? Give5. Observations. Monitor and record the your reasons. infant’s temperature, pulse, respiration, skin colour and blood glucose concen- Yes. An axillary temperature below 36 °C tration until they are normal and stable. is below the normal range and is defined as6. Antibiotics. Give parenteral antibiotics if hypothermia. there are any signs of infection. 2. What is the probable cause of thePYREXIA peripheral cyanosis in this infant? The peripheral cyanosis was almost certainly caused by hypothermia, and should, therefore,7-17 What is pyrexia? disappear when the infant’s temperaturePyrexia or fever (high body temperature) is returns to normal. Cold infants are oftendefined as an abdominal skin temperature centrally pink even if they are hypoxic.of 37 °C or more, or an axillary temperatureof 37.5 °C or more. As newborn infants can 3. Why do you think this infant is cold?only sweat a little, they are unable to cool Because the infant was not well dried afterthemselves and, therefore, easily become too birth and wrapped in a second warm, dryhot. towel. This is a common error. The labourPyrexia may be caused by: ward may also have been cold. Therefore body heat would be lost by both evaporation and1. A high environmental temperature. This convection. In addition, the infant is preterm. is usually due to the incubator or room Preterm infants lose heat rapidly as they have being too hot for the infant’s needs, or the little subcutaneous fat. infant being placed in the sun or too close to a heater. 4. How should this infant have been kept2. Infection. However, most infants become warm in the labour ward? hypothermic when infected. The easiest way to have kept this infant warm7-18 Is pyrexia dangerous? after delivery would have been to dry her well and then place her in the KMC position, nakedYes. Pyrexia is an important cause of recurrent against the mother’s breasts. The mother’s skinapnoea which can result in death if the infant would have kept the infant warm.
  8. 8. 138 NEWBORN CARE5. What should be the management of this 2. What error was made when the infant’sinfant? temperature was determined?The infant should be removed from the wet The temperature should not be taken overtowel and dried well. Do not forget to dry the liver as this is a very warm organ. Thethe infant’s head. Then place the infant in skin temperature should have been takena prewarmed closed incubator set at 37 °C over the left side of the abdomen. An axillaryor under an overhead radiant heater. If temperature could also have been taken.neither is available, skin-to-skin care (KMC)or a warmed room can be used. Give 30% 3. When should this infant be fed?head box oxygen while the infant is beingwarmed. Energy must be given intravenously As this infant is at high risk of hypoglycaemiaas an infusion of maintenance fluid (e.g. it should be given a feed as soon as possible.Neonatalyte). As soon as possible, nasogastric Check the blood glucose concentration.milk feeds must be started to preventhypoglycaemia. Careful observations should 4. How should the infant be kept warmbe kept until the infant is warm and appears during the next few days?clinically normal. It should be dressed and given a woollen cap. If the room becomes cold at night, the infant6. What investigations do you think should can be kept warm in the mother’s bed or bebe done when the infant arrives in the given KMC.nursery?The blood glucose concentration must bedetermined and the temperature must be CASE STUDY 3carefully monitored with a digital or lowreading thermometer until the infant is warm. A term female infant is brought to an outlyingAny hypoglycaemia must be treated. clinic on a cold winters day. The mother delivered 30 minutes before and has to be referred to hospital because of a retainedCASE STUDY 2 placenta. The infant’s axillary temperature is 34.5 °C but the infant appears active. NeitherA 5 day old male term infant is bathed in a the clinic nor the ambulance has an incubator.cold ward. Afterwards the infant appears wellbut feels cold. A telethermometer reading 1. How can you warm this infant in theover the right upper abdomen gives a result clinic?of 34 °C. The infant, which weighed 2400 g You can use a heater, warm room or warmat birth and is clinically wasted, is rapidly water to correct the infant’s temperature.warmed by placing it next to a wall heater. One of the staff or a family member could give skin-to-skin care. The infant can also be1. Give 3 probable reasons why this infant warmed by placing her skin-to-skin againstbecame hypothermic. the mother and wrapping both in blankets.The infant is underweight for gestational ageand is also wasted. Both these conditions may 2. When should the infant be moved tocause hypothermia as the infants have little hospital?white and brown fat. In addition the infant If possible, it is best to warm the infant firstprobably became cold after the bath because before moving it to hospital.he was not well dried and the room was cold.
  9. 9. TEMPERATURE CONTROL AND HYPOTHERMIA 1393. How can the infant be kept warm in the wrapped around the infant. Remember thatambulance? the infant must be warmed before it is placed in a thermal blanket. Skin-to-skin care can beThe infant should be warmly dressed if you provided by the ambulance crew if necessary.have clothes. If not, provide skin-to-skin care This is a simple but very effective method ofor wrap the infant in a blanket. A thermal keeping an infant warm during transportblanket (or aluminium foil) can also be