Oxford Handbook of Midwifery (125 page)

All of these will result in a reduced fluid:solids ratio, which will result

in the baby receiving inadequate fluids. If either is occurring, advise the

mother appropriately. If neither of the above are occurring, advise the mother to offer the baby small amounts of extra boiled, cooled water between feeds and, if constipation still persists, to seek medical attention.

Regurgitation

Regurgitation is the effortless posseting of small amounts of milk following a feed. It usually occurs after a large feed and is usually of no importance. A newborn baby may have swallowed liquor amnii, blood, or mucus shortly before or during the process of being born. If following birth he or she vomits watery fluid or mucus, possibly streaked with blood, reassure the mother that it is usually of no significance.

Vomiting other than this may well be abnormal and should be referred to the paediatrician. Possible causes may be:

The colour, quantity, frequency, and timing in relation to feeding should be observed and recorded, and whether or not it is projectile.

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Care of the newborn

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Neonatal temperature control

Temperature is controlled from the heat-losing centre and the heat- promoting centre of the hypothalamus, an area of the brain near to the pituitary gland. The mechanisms controlled by these centres are immature in the newborn, especially if premature.
^1,2

• The newborn temperature should be maintained between 36.5°C and 37°C.
  
• Hypothermia in the newborn is defined as a temperature below 35°C.
  ¹
  ,
  2
  

  Non-shivering thermogenesis
  

  Newborns have a limited ability to sweat and shiver. Non-shivering ther- mogenesis (NST) is used by newborns to keep warm, and is initiated by:
  

• Oxygenation
  
• Separation from the placenta: cutting the cord maximizes NST
  
• Cutaneous cooling: cold receptors in the skin stimulate noradrenaline and thyroxine release, which stimulate brown fat.
  

  Brown fat
  

• It is found around the neck and between the scapulae, across the clavicle line and the sternum.
  
• It also surrounds the major thoracic vessels and pads the kidneys.
  
• The cells contain a nucleus, glycogen, mitochondria (which release energy), and multiple fat vacuoles in the cytoplasm (a source of energy).
  
• The presence of the mitochondrial enzyme, thermogenin, means that,
  when the fat is oxidized, it releases heat rather than other forms of
  

  energy.
  

• It has a high concentration of stored triglycerides, a rich capillary network, and is densely innervated.
  
• It increases in amount during gestation.
  ²
  

  Heat loss
  

  Heat is lost during birth, resuscitation, and transportation. Mechanisms of heat loss are:
  

• Conduction
  from cold surfaces
  
• Radiation
  from surrounding objects
  
• Convection
  from the air
  
• Evaporation
  : insensible water loss from the skin, especially in the preterm infant.
  

  Thermoneutrality
  is the environmental temperature at which minimal rates of oxygen consumption and energy expenditure occur.
  ²
  

  Effects of hypothermia (cold stress)
  

• Increases pulmonary vascular resistance, reducing oxygenation.
  
• Decreases surfactant production and efficiency, giving rise to atelectasis which worsens hypoxia.
  
• Poor perfusion causes an increase in anaerobic metabolism, worsening acidosis.
  

  NEONATAL TEMPERATURE CONTROL
  

  589
  

Hyperthermia

Hyperthermia is unusual in the newborn and is normally the result of envi- ronmental factors or pyrexia due to sepsis.

Usually in sepsis there is a vast difference between core and peripheral temperatures.
Low core temperatures indicate thermal stress.
A difference between core and peripheral temperatures of >2–3°C indicates thermal stress can be due to:

The factors that lead to hyperthermia are:

Sweating, seen on the forehead and temples, can occur in term babies in response to overheating. This can lead to:

Maintaining the neonatal temperature

Assessment

The different methods of assessing the baby's temperature are:

Care at birth

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Care of the newborn

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• Drying and wrapping the baby in warm towels will enable it to maintain its temperature.
  
• ‘Kangaroo care’ helps to keep the baby warm. Putting the baby in skin- to-skin contact on the mother’s chest stimulates the mother to alter her temperature to the needs of the baby.
  ²
  ,
  3
  

  Premature babies
  

• Delivery rooms can be cool and draughty, which increases convective heat loss.
  
• The body temperature of a 1kg infant can decrease by 1°C every 5min.
  
• Set the radiant warmer to maximum and have warm towels ready.
  
• Remember, the head is a large surface area for heat loss, so place a hat on the baby if he or she requires extensive resuscitation and transfer to the NICU.
  
• During resuscitation and transportation to the NICU use plastic bags to contain the infant’s body. The plastic next to the skin helps to cut down the trans-epidermal fluid loss through the immature skin of premature babies.
  
• Once the baby is in the incubator environment, the 87% humidity will also help the baby to warm up.
  ²
  ,
  3
  

  Equipment used to maintain temperature in the newborn
  

  Radiant heaters
  

• Provide dry heat directly on to the skin.
  
• Are used mainly at delivery or during interventions.
  
• Increase insensible, evaporative, and convective heat loss.
  

  The infant will increase its metabolic rate as it tries to produce neutral thermal conditions. Radiant heaters are not used for long with very premature
  

  or ill babies.
  

  Incubators
  

• Provide an enclosed protected space.
  
• As a result of their double-glazed design, they reduce radiation heat loss, surrounding the infant with a ‘curtain’ of heat even when the doors are open.
  
• Enable the administration of humidity (87%) to help cut down evaporation (insensible) heat and fluid loss.
  
• Enable the administration of oxygen.
  
• Reduce noise, because the portholes and doors are cushioned.
  

  Controlling temperature
  

  Incubators control temperature in three ways:
  

• Servo control: if the infant’s temperature decreases, the incubator will increase its heat automatically to compensate. This is not used for premature infants as the decrease in temperature needs to be
  

  observed as an early and subtle sign that the infant is becoming unwell, perhaps with an infection.
  

• Air temperature: this can be altered according to the changes in the infant’s condition and is the method used for premature and ill babies as it allows for an observation to be recorded and recognized as a sign that the baby is unwell.
  
• Air temperature probe: this hangs near to the infant and maintains a consistent set temperature, leading to less fluctuation.
  

  NEONATAL TEMPERATURE CONTROL
  

  591
  

  Radiant hood warmer
  

  This can be used independently of the incubator’s main source. It is pre- ferred for very premature infants as it: