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Thermoregulation for neonates

Temperature control or thermoregulation in the neonate is a critical physiological function that is strongly influenced by physical immaturity, extent of illness and environmental factors (Thomas, 1994). By definition, the term neonate refers to the first 28 days post delivery.

Due to the wide range of post-natal ages and gestations seen on NICU and elsewhere within Great Ormond Street Hospital, this guideline is appropriate for infants up to four weeks of age (post term).

The neonate’s susceptibility to temperature instability needs to be recognised and understood in order to appropriately manage and limit the effects of cold or heat stress (Smith, Alcock and Usher, 2013).

It is essential that neonates are nursed within their ‘neutral thermal environment’ (NTE). This is defined as “the environmental air temperature at which an infant with a normal body temperature has a minimal metabolic rate and therefore minimal oxygen consumption” ( Waldron and Mackinnon, 2007). The maintenance of the NTE is the ultimate aim of neonatal temperature control and management. 

Extended periods of cold stress can lead to harmful side effects which include hypoglycaemia, respiratory distress, hypoxia, metabolic acidosis, necrotizing enterocolitis and failure to gain weight ( McCall et al, 2010). Waldron and MacKinnon (2007) state preventing hypothermia is important to survival and long-term outcome in neonates. Factors that increase the risk of hypothermia include prematurity, interuterine growth retardation, birth asphyxia, congenital anomalies such as gastroschisis and damage to the central nervous system.

Optimum thermoregulation and related nursing care can be addressed in three main areas:

  • method of temperature taking
  • choice of environment
  • temperature instability and intervention

Method of

The acceptable set-point temperature is an axilla temperature of range 36.7 - 37.3°C. This range should be maintained at all times. ( Rationale 1)

Tempadot™ (single-use) is the thermometer in use in this trust ( Rationale 2).

A central temperature is obtained by insertion under the axilla site for three minutes, placing the dots against the trunk ( Rationale 3). It must be read 10 seconds following removal ( Rationale 4).

The axilla temperature should be checked four hourly and recorded ( Merentstein and Gardner, 2011). If their temperature falls outside the normal range, the medical staff should be informed and readings must be  taken more frequently (every 30 to 60 minutes). This should be continued until their temperature has normalised ( Rationale 5).

If a neonate undergoes any change of environment or increased exposure, eg procedures, phototherapy, new transfer to an incubator or cot, they will require 30 to 60 minute temperature checks for the first few hours until the temperature is stable ( Rationale 6)( Merentstein and Gardner, 2011).

For neonates receiving intensive care, peripheral skin temperature is monitored continuously by use of a probe placed on the sole of the foot ( Rationale 7 and Rationale 8)( Turnbell and Petty, 2013).

Allow five minutes for skin temperature to stabilise once applied to foot

Peripheral temperature is recorded hourly and the probe site should be changed every four to six hours.

The ‘toe-core’ temperature difference is taken from the difference between the peripheral temperature reading on the monitor and the central readings done at intervals or continuously.

Continuous central monitoring can be done by placing a probe over the abdomen when supine, or the back when prone avoiding bony prominences and excoriated areas ( Rationale 9). Rectal probes should not be used ( Rationale 10). The difference should be between 1-2°C( Waldron and Mackinnon, 2007)( Rationale 11).

Peripheral monitoring can be discontinued when a neonate:

  • no longer requires cardiovascular support to maintain an adequate blood pressure
  • is peripherally warm and well perfused  

This will require individual assessment ( Rationale 12).

Choice of environment

Incubator

Incubators are now specifically designed to minimise heat losses by radiation, convection, conduction and evaporation whilst allowing clear visibility and access to the neonate. Ambient temperature and humidity are easily controlled. Any neonate less than 1.5 kg should be nursed within an enclosed incubator ( Rationale 13)( Turnbell and Petty, 2013).

Use of an incubator

Before admission pre heat the incubator temperature according to the specific age and gestation and adjust incubator temperature according to individual response ( Rationale 14).


  • Check and record incubator temperature hourly.
  • Alter set temperature according to the neonate’s temperature and adjust by 0.5-1°C every 15-30 minutes, depending on the extent of temperature instability ( Rationale 15 and 16).
  • If a neonate does not require heat provided by an incubator and is at risk of hypothermia, ie body temperature is above 37.5°C, it is necessary to transfer the neonate to a radiant warmer bed (Babytherm) or open cot.
  • Do not leave a neonate inside a switched off incubator ( Rationale 17 and 18).

Do not expose an incubator to direct sunlight ( Rationale 19).


Care and interventions, eg suction and nappy care, should be carried out via portholes, avoiding opening the side or roof completely ( Rationale 20).

Where appropriate, the incubator should be changed every seven days, particularly if humidity is being used ( Rationale 21).

This should be recorded in the nursing records.

Use of humidity

Any neonate less than 30 weeks gestation in the first 14 days of life should be nursed in a closed incubator with added humidity. The use of humidity maintains temperature, assists fluid and electrolyte management, decreases insensible water loss and maintains skin integrity ( Merentstein and Gardner, 2011). The optimum level of humidity is determined by gestational age, days of life, skin maturity and underlying pathology.

Sterile water should be used and humidity levels checked hourly.

  • Axilla temperature should be taken before commencing humidity and every 30-60 minutes until the infant's temperature has stabilised then three to four hourly as individually appropriate. Peripheral temperature should be monitored continuously ( Rationale 22). Record set and actual humidity with hourly observations.
  • Fill the container with sterile water ( Rationale 23). 
  • Humidity should be set initially at 85 per cent in the first week of life for gestations 23-30 weeks ( Rationale 24).
  • Humidity should be decreased after seven days ( Rationale 25) and ceased on or before 14 days ( Rationale 26). Aim to wean humidity by five per cent 12 hourly (see table below). 
  • When weaning humidity increase the incubator or Giraffe OmniBed temperature by 0.5 degree increments, alongside 30-60 minute temperature checks aiming to maintain a normal central temperature (36.8-37.2).

 

Humidity should be decreased after seven days and ceased on or before 14 days. Aim to wean humidity by five per cent 12 hourly as below.
 Days  Hours
 Day eight - reduce to 80 per cent  After 12 hours reduce to 75 per cent
 Day nine - reduce to 70 per cent  After 12 hours reduce to 65 per cent
 Day 10 - reduce to 60 per cent  After 12 hours reduce to 55 per cent
 Day 11 - reduce to 50 per cent  After 12 hours reduce to 45 per cent
 Day 12 - reduce to 40 per cent  After 12 hours stop
  • Check the container water level every four hours ( Rationale 27). It will need topping up regularly.
  • Check for condensation inside the incubator regularly and wipe away with a clean/dry cloth ( Rationale 28). 
  • Avoid opening the doors and portholes (and roof if using a Giraffe OmniBed) ( Rationale 29).
  • Nurse the infant with a nappy only. Clothes will become damp. Sheets should be inspected regularly and changed if they become damp ( Rationale 30).
  • Skin should be inspected regularly to check for integrity and any signs of infection ( Rationale 31).
  • The incubator should be changed every 14 days, sent to HSDU for cleaning and the date recorded in the nursing notes ( Rationale 32).
  • If discontinuing humidification before the due date to change the incubator, then the water chamber should be emptied and dried ( Rationale 33).
  • Any technical problems with the incubator should be addressed with biomedical engineering. 

Radiant warmer bed (Babytherm)

A Radiant warmer bed or 'Babytherm' provides heat by a combination of conduction (from below via a gel mattress) and radiation (from above).

They are convenient to use, allow direct access to the neonate and maintain the neonate's temperature during procedures. Disadvantages of radiant warmer beds include a large amount of insensible water loss and convective heat loss.

Use of the radiant warmer bed (Babytherm)

  • When preparing a Babytherm for use, the mattress is switched to ‘on’ at a set temperature of 37°C. 
  • It will take an hour to heat up to the set temperature.

The overhead heater should be turned on and the ‘Manual’ control should be selected rather than 'Servo' ( Rationale 34).

  • The overhead heater should be switched to level 5 (each level or bar represents a 10 per cent increase or decrease in heat from above).

It will take 25 minutes to reach the desired temperature from the overhead heater.

If the neonate is hypothermic


The initial settings need to be higher ( Rationale 35).

Increase the overhead heater in increments of 0.5°C every 15 to 30 minute until the neonate’s temperature is within normal range. 

Assess temperature every 30 minutes to one hour to monitor temperature and success of warming. 

The extended upper range (indicated as > 37°C; ie range 37 - 38.5°C) is chosen plus level/bar 6-10.  Above level six, the heater requires resetting every 15 minutes (press ‘reset’), which is indicated by an alarm.

If the neonate is overheated

  • Turn the temperature down by 0.5°C at 30-60 minute intervals ( Rationale 36).
  • Leave the neonate in an extended position to encourage heat loss.
  • Remove external heat sources eg blankets, swaddling.
    • Prostaglandin infusions and phototherapy can cause hyperthermia in neonates and temperature needs to be assessed frequently.

 

Once established in the radiant warmer bed (Babytherm), there are four options to determine what the neonate is laid on and covered with:

Option one: Both mattress and radiant heater on:

  • The neonate should lie directly onto a sheet covering the gel mattress ( Rationale 37). In the intensive care areas, the repose mattress is placed on top of the gel mattress ( Rationale 38).
  • Do not cover with sheets or blankets, cover the baby with bubble wrap, bubbles downwards, or leave exposed ( Rationale 39). Use bubble wrap with extreme caution and observe babies continuously.

Option two: Mattress with no radiant heater:

  • As option one but the neonate should be covered with a blanket ( Rationale 40).

Option three: Radiant heater with no mattress:

  • Ensure that a padded sheet, towel or gamgee, is place between the neonate and mattress while it is turned off. Cover neonate with bubble wrap ( Rationale 41).

Option Four: Neither:

  • As for option three but wrap well with blankets.

Giraffe OmniBed Incubator

This equipment is predominantly located and used on NICU.

The GE Healthcare Giraffe OmniBed can be used as both a closed incubator with or without humidity and as an overhead heater when procedures need to be undertaken which are unable to be performed through the portholes. If opening the Giraffe OmniBed it should be noted that the humidity within will cease.

The lid should remain closed other than when procedures are carried out ( Rationale 42) ( GE Healthcare, 2011).

Open cot

A well neonate who weighs more than 1.5 kg, who no longer requires close monitoring or intensive care, is gaining weight and who is maintaining a stable central temperature in 26-28°C room temperature, can be transferred to a small cot ( Rationale 43).

The neonate should be covered or wrapped in blankets and should wear a hat ( Rationale 44).

Weaning a well neonate from an incubator or Babytherm should be done according to age and gestation ( Merenstein & Gardiner, 2011), turning the incubator or mattress temperature down by 0.5 - 1°C each day and observing central temperature ( Rationale 45).

Larger infants, ie > 4kg, who require warming can be nursed on an open cot with a bear-hugger blanket, heated mattress and/or single overhead heater.

General interventions

 

Maintain a set environmental room temperature of >26°C.

Specific events may precipitate heat loss. The effects of this need to be counteracted ( Rationale 46)

Conduction

 

  • cool x-ray plate
  • theatre table
  • weighing scales
  • stethoscope
  • cold linen
  • cold hands
  • cold mattress

These pieces of equipment should be pre-warmed and covered if possible.

Convection

  • draughts
  • windows

Avoid over-exposure and maintain a 'minimal handling' policy. Use incubator or Giraffe OmniBed portholes for all procedures whenever possible and close these as soon as the procedure is finished.

Keep Babytherm sides up. If using a Giraffe OmniBed use the airflow wall option.

Radiation

  • cold incubator walls
  • direct sunlight

Pre-warm incubators, use curtains and covers over the incubator.

Evaporation

  • cold water
  • wet skin
  • wet nappy
  • wet bed

Keep skin and bed dry.

Before transferring a neonate to theatre, preparing for procedures or general transportation:

Pack an appropriate sized bonnet, blankets, heat pad if available and a clean nappy ( Rationale 47).

Cover as well as possible ( Rationale 48).

Transfer of neonate


During transfers within GOSH the neonate should remain in their incubator or Babytherm. This should be left switched on, at the same setting, to await their return from the radiological or surgical procedure ( Rationale 49).

Ensure the neonate is transferred to a pre-warmed, dry surface in theatre or X-ray ( Rationale 50).

The neonate’s temperature must continue to be monitored during transfers & procedures ( Rationale 51).

If their temperature falls outside normal range, recordings must be taken more frequently, ie 30-60 minutes, until it has normalised. When it has returned to the normal range it may be done four hourly.

Any intervention carried out for temperature instability must be recorded in the child’s health care records ( Rationale 52).

Interventions for cold stress

The signs and associated problems of cold stress are:

  • central temperature < 36.5°C
  • increase in core-toe gap > 2°C
  • mottled and/or pale
  • increased capillary refill time, ie > 2 seconds
  • increased oxygen requirements
  • metabolic acidosis
  • tachycardia
  • hypoglycaemia
  • apnoeas
  • bradycardia

To intervene in this situation:

  • Place a neonate of < 1.5kg in an incubator at the upper range, ie >37°C ( Rationale 54).
  • If using a Babytherm, set the temperature at the upper range, both above & below, and follow guidelines for Babytherm use.
  • Increase the set temperature by 0.5°C every 15 minutes according to the neonate’s response.
  • Take the neonate's temperature every 30-60 minutes until warmed to an acceptable temperature.
  • Identify and eliminate any environmental causes, eg wet bed, over exposure, handling.
  • Promote a flexed position ( Rationale 55).
  • Ensure ventilator gases are adequately warmed to 37°C.

If the cause of decreased peripheral temperature is not due to cold stress, ie central temperature stable but an increase in core - toe gap, the neonate’s perfusion status should be assessed ( Rationale 56).

The neonate should be observed and the following aimed for: 

  • capillary refill time < 2 seconds
  • pink colour
  • skin warm to touch
  • no increase in heart rate above normal
  • palpable peripheral pulses
  • blood pressure within normal range for age, gestation and condition

Interventions for heat stress

The signs and associated problems of heat stress are:

  • central temperature above 37.3°C and rising
  • increased peripheral temperature and decrease in core-toe gap, ie < 1°C
  • tachycardia
  • tachypnoea
  • restlessness
  • dehydration
  • stress

To intervene in this situation ( Rationale 57):

  • Check environmental temperature and reduce by 0.5°C at 30-60 minute intervals.
  • Remove excess layers and clothing.
  • If under a Babytherm, turn radiant heater off and choose the extended lower range (<35°C).  
  • Turn the temperature down by 0.5° at 30-60 minute intervals ( Rationale 53).


If the cause is not environmental consider infection as a cause of the pyrexia. This must be reported to the child’s doctor and the policy for the management of the pyrexial neonate followed.

Rationale

Rationale 1: To allow normal physiological function and body metabolism. 

Rationale 2: They are safe, quick and non-invasive to use. 

Rationale 3: The axilla is the safest and most accurate site for central temperature readings.

Rationale 4: To meet manufacturer’s guidelines.

Rationale 5: Four hourly is the general recommended interval unless instability occurs.

Rationale 6: It can take up to two hours for a central and peripheral temperature to stabilise following a change to the thermal environment or prolonged exposure in relation to nursing or medical procedures 

Rationale 7: Peripheral temperature is valuable as one parameter in the assessment of perfusion.

Rationale 8: The foot is recommended as the most 'peripheral' site 

Rationale 9: Abdominal/liver skin temperature is closest to the body’s central temperature and is non-invasive ( Drager Ltd, 1997).

Rationale 10: Rectal probes should not be used due to a risk of perforation. 

Rationale 11: Less than 1°C may indicate heat stress while greater than 2°C may indicate cold stress, hypovolaemia or infection. 

Rationale 12: The length of time required for optimum perfusion will depend on: extent of illness, peripheral shutdown and the nature and timing of surgery (if applicable).

Rationale 13: They have a greater physiological predisposition to heat loss due to relatively large surface area to volume ratio.

Rationale 14:  To reduce the risk of heat loss via convection in a cold incubator.

Rationale 15: To avoid rapid over or under heating.

Rationale 16: To avoid sudden swings in temperature.

Rationale 17: To avoid overheating.

Rationale 18: To avoid sudden changes to their temperature and adverse cooling.

Rationale 19: To avoid overheating of the incubator.

Rationale 20: The pre-term neonate has high 'trans-epidermal' water losses due to a thin, poorly keratinised skin (stratum corneus). This matures by 21 days post-natal age trans-epidermal water loss is a major cause of heat loss in the premature neonate.

Rationale 21: To meet the Infection Control Policy. 

Rationale 22: To monitor for temperature instability and monitor toe/core temperature gap because this can highlight energy expenditure of the infant to maintain neutrothermia. 

Rationale 23: To prevent bacterial growth. 

Rationale 24: This level of humidity is optimal to minimise trans-epidermal water loss.

Rationale 25: To aid stratem corneum formation. High levels of humidity have been shown to delay this process.

Rationale 26: Due to rapid maturation of skin (stratem corneum) post birth.

Rationale 27: To avoid the container drying out and causing the humidity function becoming ineffective.

Rationale 28: Condensation can reduce visibility of the infant and can also drip onto the infant's skin causing cooling and temperature instability.

Rationale 29: To reduce the loss of humidity from the incubator.

Rationale 30: Damp clothes will cause the infant to become cold and they can also harbour bacteria. It is easier to view skin integrity.

Rationale 31: If the skin becomes damp it will cause temperature instability. It also can become a breeding ground for bacteria and fungus and effect the skin integrity which is already underdeveloped.

Rationale 32: Humidity in the incubator can cause pooling of water at the bottom which creates an environment for microbial growth. Changing the incubator regularly minimises this. Fourteen days is as per manufacturing guidelines.

Rationale 33: As per manufacturing guidelines to prevent organism growth.

Rationale 34: The 'Servo' may cause overheating due to the heater responding to the cool skin temperature ( Drager Ltd, 1997).

Rationale 35: To avoid the complications associated with cold stress, ie decreased surfactant, increased oxygen consumption, respiratory distress and hypoxia, metabolic acidosis, hypoglycaemia, weight loss and apnoea. 

Rationale 36: To avoid the complications of heat stress associated with increased fluid losses, hypernatraemia, recurrent apnoeas, convulsions, increased metabolic rate and tachycardia. 

Rationale 37: To achieve optimum heat transfer from the heat pad, via the gel mattress, to the neonate (by conduction).

Rationale 38: To aid pressure area care.

Rationale 39: Blankets may block radiative heat transfer from above to the neonate. Bubble wrap provides an insulation layer to prevent heat loss from convective air currents. The bubbles placed downwards maximise the air trapped between the sheet and neonate.

Rationale 40: When there is no radiative heat from above, a blanket can be used.

Rationale 41: To avoid heat loss from the neonate to the cool mattress by conduction and watch continuously with bubble wrap to prevent suffocation. 

Rationale 42: As per manufacturer's usage policy.

Rationale 43: If well insulated by clothes, blankets and/or swaddling, in the ideal room temperature, will be able to maintain an adequate central temperature.

Rationale 44: The head has a large surface area for heat loss so should be covered. 

Rationale 45: The environmental temperature must be altered slowly due to the immature heat conserving mechanisms at this age and limited ability to adapt to sudden or extreme changes.

Rationale 46: To prevent heat loss by all means. 

Rationale 47: To provide optimal insulation.

Rationale 48: To prevent heat loss during transfer/change to the Neutral Thermal Environment 

Rationale 49: To maintain a NTE at all times. 

Rationale 50: To prevent the neonate being exposed to a cold, wet surface and losing heat by conduction and evaporation.

Rationale 51: To prevent cold/heat stress.

Rationale 52: To provide an accurate record.

Rationale 53: Once switched off, the mattress retains heat for 15 minutes.

Rationale 54: To avoid the complications of cold stress.

Rationale 55: To decrease surface area for heat loss.

Rationale 56: It could be due to vasoconstriction from shock, hypovolaemia, post-operative stress or handling.

Rationale 57: To avoid the complications of heat stress. 

References

Reference 1
Drager Product Information (1997) Closed and open incubators. Hemel Hempstead: Drager.

Reference 2
GE Healthcare (2011) giraffe omnibed . Accessed 18/6/14.

Reference 3

Merenstein, G.B. and Gardner, S.L. (2011) Handbook of Neonatal Intensive Care. St Louis: Mosby Elsevier, pp117-123.

Reference 4

McCall, E.M., Alderdice, F., Halliday, H.L., Jenkins, J.G. and Vohra, S. (2010) Interventions to prevent hypothermia at birth in preterm and/or low birthweight infants. Cochrane Neonatal Group www.thecochranelibrary.com

Reference 5

Smith, J. Alcock, G. and Usher, K. (2013) Temperature measurement in the preterm and term neonate: A review of the literature. Neonatal Network , 32 (1), pp. 16-25.

Reference 6

Thomas, K. (1994) Thermoregulation in Neonates. Neonatal Network, 13 (2), pp. 15-21.

Reference 7

Turnbull, V. and Petty, J. (2013) Evidence-based thermal care of low birthweight neonates, Part one. Nursing Children and Young People, 25 (2), pp. 18-22.

Reference 8

Waldron, S. and MacKinnon, R. (2007) Neonatal thermoregulation. Infant, 3 (3), pp. 101-104. 

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Document control information

Lead author(s)

Heather Parsons, Practice Educator, NICU 

Original author
Lindsay Warner, Sister, NICU
Annette Rathwell, NICU 

Additional authors
Emma Peacock, SSN, NICU
Tara O'Regan, SN, NICU

Document owner
Heather Parsons, Practice Educator, NICU

Approved by
Guideline Approval Group

First introduced: 5 December 2007
Date approved: 25 March 2014
Review schedule:
Two years
Next review:
12 May 2017
Document version:
3.0
Replaces version:
2.0