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Measuring body temperature7-1 How do you measure an infant’s temperature?An infant’s skin temperature, rather than the oral or rectal temperature, is usually measured. As infants commonly become cold rather than hot, it is preferable to measure axillary (arm pit) or abdominal skin temperature as the skin is the first part of the body to cool down. Note In contrast, the oral or rectal temperature is useful in detecting a fever in older children and adults as the body core (centre) is the first part of the body to heat up.Skin temperature can be measured with:
A low reading glass mercury thermometers should no longer be used in children due to the risk of mercury poisoning if the thermometer should break in the mouth. 7-2 What is the normal range of body temperature?This depends on the site where the temperature is measured:
All newborn infants have the same range of normal body temperature. Note The normal oral temperature is 37–37.5 °C and rectal temperature is 37.5–38 °C. Neither are routinely used in newborn infants.Heat production and loss7-3 What determines body temperature?The body temperature depends on a balance between:
If the rate of heat production is low or the rate of heat loss is high, then the body temperature may fall. Similarly, excessive heat production or reduced heat loss causes an increased body temperature (fever or pyrexia). 7-4 How do newborn infants produce heat?Adults and older children are able to increase their heat production by shivering and doing physical exercise. Newborn infants cannot shiver or exercise. However, during the first few weeks of life the infant is able to break down (metabolise) brown fat which releases large amounts of heat. Brown fat is a special tissue laid down in the neck, chest and abdomen of the fetus during the last weeks of pregnancy. It is brown in colour, due to the presence of many nerves and blood vessels, and differs in many ways from the ordinary white fat that is found under the skin. When the body temperature drops, the infant breaks down brown fat and, thereby, produces heat to correct the body temperature. To a lesser degree the infant is also able to use other energy stores to produce heat, such as:
7-5 Which infants produce too little heat?The following infants are often unable to produce enough heat to maintain a normal body temperature:
7-6 How do infants lose heat?Infants lose heat from the skin to the environment by the following methods:
7-7 Which infants lose too much heat?The following infants commonly lose too much heat and, therefore, may drop their body temperature:
Hypothermia7-8 What is hypothermia?An abdominal temperature below 36 °C or an axillary temperature below 36.5 °C is abnormally low. These infants need to be warmed. Therefore, a working definition of hypothermia (low body temperature) is a body temperature below these values. Once the body temperature falls below 35 °C the infant is in danger of complications related to being too cold. As the rectal temperature is normally higher than that at other sites, a rectal temperature below 35 °C is particularly dangerous.
7-9 Which infants are at the greatest risk of hypothermia?Infants who produce too little heat or lose too much heat are at the greatest risk. These high-risk infants are:
7-10 How do you prevent hypothermia?
7-11 What is the best environmental temperature?The best environmental (e.g. room or incubator) temperature depends on:
For example, a 1000 g preterm infant on day 1 may need an environmental temperature of 37 °C to keep warm while a healthy term infant on day 5 may need an environmental temperature of only 20 °C. In clinical practice each infant must be handled as an individual and the above factors, which influence the infant’s temperature needs, must be regarded only as guidelines. The environmental temperature for each infant should be adjusted in order to give a normal abdominal skin or axillary temperature. This can be achieved automatically if a servo-controlled incubator or radiant warmer is used. The infant’s energy and oxygen needs are lowest when the skin temperature is normal and the infant is nursed at the correct environmental temperature. Both energy and oxygen needs increase if the infant’s skin temperature is either above or below normal. Infants gain weigh fastest when they are kept at the correct environmental temperature. Note The neutral thermal environment (best room or incubator temperature) is that environmental temperature at which the skin temperature is normal and the infant’s metabolic rate is at its lowest. In this state the infant uses the least amount of oxygen and energy. The energy in feeds, therefore, can be used for growth rather than for generating heat. It is important to ensure that all infants are nursed as close as possible to their own neutral thermal environment. 7-12 How do you keep an infant warm?There are a number of ways to keep an infant warm:
The most appropriate method should be chosen for each individual. There is no excuse for an infant ever becoming hypothermic because hypothermia is preventable. Skin-to-skin care by the mother, father, family member, nurse, doctor or paramedic is always available.
7-13 When does a small infant no longer need an incubator?Most small infants are able to maintain their body temperature in a warm room when they reach a weight of 1800 g. However, many small infants can maintain their body temperature much sooner with KMC. Most well infants can be moved from an incubator to KMC by 1600 g. 7-14 How do you recognise a hypothermic infant?Hypothermic infants present with the following signs:
The more severe the hypothermia (especially if the body temperature falls below 35 °C) the more clinical signs will be present.
7-16 How do you treat hypothermia?
Pyrexia7-17 What is pyrexia?Pyrexia or fever (high body temperature) is defined as an abdominal skin temperature of 37 °C or more, or an axillary temperature of 37.5 °C or more. As newborn infants can only sweat a little, they are unable to cool themselves and, therefore, easily become too hot. Pyrexia may be caused by:
7-18 Is pyrexia dangerous?Yes. Pyrexia is an important cause of recurrent apnoea which can result in death if the infant is not cooled. Prolonged pyrexia can also lead to dehydration and increases the body’s oxygen and energy needs. Case study 1A preterm female infant is brought to the nursery from the labour ward wrapped in a wet towel. The axillary temperature is 32.5 °C. The infant’s estimated gestational age is 35 weeks. The cheeks and tongue are pink but the hands and feet are grey and feel cold. The infant is lethargic. 1. Does the infant have hypothermia? Give your reasons.Yes. An axillary temperature below 36 °C is below the normal range and is defined as hypothermia. 2. What is the probable cause of the peripheral cyanosis in this infant?The peripheral cyanosis was almost certainly caused by hypothermia, and should, therefore, disappear when the infant’s temperature returns to normal. Cold infants are often centrally pink even if they are hypoxic. 3. Why do you think this infant is cold?Because the infant was not well dried after birth and wrapped in a second warm, dry towel. This is a common error. The labour ward may also have been cold. Therefore body heat would be lost by both evaporation and convection. In addition, the infant is preterm. Preterm infants lose heat rapidly as they have little subcutaneous fat. 4. How should this infant have been kept warm in the labour ward?The easiest way to have kept this infant warm after delivery would have been to dry her well and then place her in the KMC position, naked against the mother’s breasts. The mother’s skin would have kept the infant warm. 5. What should be the management of this infant?The infant should be removed from the wet towel and dried well. Do not forget to dry the infant’s head. Then place the infant in a prewarmed closed incubator set at 37 °C or under an overhead radiant heater. If neither is available, skin-to-skin care (KMC) or a warmed room can be used. Give 30% head box oxygen while the infant is being warmed. Energy must be given intravenously as an infusion of maintenance fluid (e.g. Neonatalyte). As soon as possible, nasogastric milk feeds must be started to prevent hypoglycaemia. Careful observations should be kept until the infant is warm and appears clinically normal. 6. What investigations do you think should be done when the infant arrives in the nursery?The blood glucose concentration must be determined and the temperature must be carefully monitored with a digital or low reading thermometer until the infant is warm. Any hypoglycaemia must be treated. Case study 2A 5 day old male term infant is bathed in a cold ward. Afterwards the infant appears well but feels cold. A telethermometer reading over the right upper abdomen gives a result of 34 °C. The infant, which weighed 2400 g at birth and is clinically wasted, is rapidly warmed by placing it next to a wall heater. 1. Give 3 probable reasons why this infant became hypothermic.The infant is underweight for gestational age and is also wasted. Both these conditions may cause hypothermia as the infants have little white and brown fat. In addition the infant probably became cold after the bath because he was not well dried and the room was cold. 2. What error was made when the infant’s temperature was determined?The temperature should not be taken over the liver as this is a very warm organ. The skin temperature should have been taken over the left side of the abdomen. An axillary temperature could also have been taken. 3. When should this infant be fed?As this infant is at high risk of hypoglycaemia it should be given a feed as soon as possible. Check the blood glucose concentration. 4. How should the infant be kept warm during the next few days?It should be dressed and given a woollen cap. If the room becomes cold at night, the infant can be kept warm in the mother’s bed or be given KMC. Case study 3A term female infant is brought to an outlying clinic on a cold winters day. The mother delivered 30 minutes before and has to be referred to hospital because of a retained placenta. The infant’s axillary temperature is 34.5 °C but the infant appears active. Neither the clinic nor the ambulance has an incubator. 1. How can you warm this infant in the clinic?You can use a heater, warm room or warm water to correct the infant’s temperature. One of the staff or a family member could give skin-to-skin care. The infant can also be warmed by placing her skin-to-skin against the mother and wrapping both in blankets. 2. When should the infant be moved to hospital?If possible, it is best to warm the infant first before moving it to hospital. 3. How can the infant be kept warm in the ambulance?The infant should be warmly dressed if you have clothes. If not, provide skin-to-skin care or wrap the infant in a blanket. A thermal blanket (or aluminium foil) can also be wrapped around the infant. Remember that the infant must be warmed before it is placed in a thermal blanket. Skin-to-skin care can be provided by the ambulance crew if necessary. This is a simple but very effective method of keeping an infant warm during transport VideoKeeping the baby warm
Video by the Global Health Media Project made available under a Creative Commons Attribution-NonCommercial-NoDerivatives License The cold baby
Video by the Global Health Media Project made available under a Creative Commons Attribution-NonCommercial-NoDerivatives License The hot baby
Video by the Global Health Media Project made available under a Creative Commons Attribution-NonCommercial-NoDerivatives License |