Fever is a common symptom in infants and young children. Measuring temperature accurately is an important clinical skill as an increase in body temperature may be indicative of illness. Body temperature is a precisely controlled homeostatic mechanism. When an increase in body temperature occurs, this is as a result of the body’s natural defence mechanisms attempting to repair itself by increasing its metabolic rate and making it a hostile environment for invading pathogens.

A normal core body temperature for a newborn infant will be between 36.5°C and 37.6°C. In an older child, a temperature between 36.5°C and 37.5°C is normal. A temperature of more than 37.5°C is defined as pyrexia. Accurate assessment of body temperature is an important part of the baseline assessment of the infant and child and the ongoing measurement indicates their responsiveness to treatment.

Clinical hypothermia is a core body temperature of less than 35°C. It may be defined as mild, moderate, deep or profound. Hypothermia may be as a result of prolonged exposure to cold, drug-induced or metabolic disorders.

Hyperthermia is a significant rise in body temperature that is not attributable to infection. Some of the possible causes of hyperthermia are drug reaction, stroke, malignant hyperpyrexia or a malignancy.

The age and preference of the child will determine how the temperature will be measured. The correct thermometer and site should be used when possible. Both of these will determine the reading (see table in the Figure).

• Infants under 4 weeks of age: use electronic thermometer in the axilla.
  
• Infants aged 4 weeks–5 years:
  
  
  
  • electronic thermometer in the axilla;
    
  • chemical dot thermometer in the axilla;
    
  • infrared tympanic thermometer.
  
  
• 5 years +: axilla or sublingual route.

For repeated measurements of temperature it is not advised to use the chemical dot thermometers.

thermometer

protective disposable cover

disinfectant wipes

observation chart

Make yourself familiar with the manufacturer’s instructions for whichever device you are using.

Explain the procedure to the child and their parents. Consent should be obtained at this point.

• Axilla measurement: loos’en clothing around this area. Remove thermometer probe from base unit and place protective cover over probe. Ensure correct mode is set on base unit. Place probe in the mid-axilla and hold in place. Ensure child keeps upper arm down and in contact with their chest wall. When audible alarm sounds, ask child to lift arm up and remove probe.
  
• If a chemical dot thermometer is being used, ensure the chemical active strip is placed facing the torso and leave in situ for three minutes as per manufacturer’s instructions.
  
• Tympanic measurement: Children < 1 year of age:
  
  
  
  • Gently pull the pinna of the ear straight back and for children > 1 year of age, pull the pinna up and back. This will enable the ear canal to be straightened so the temperature will be recorded from the tympanic membrane as it will be in direct line of sight with the probe. Cover the probe with a disposable cover and insert gently into the ear canal and press the button to begin the measurement. When the audible alarm sounds, remove the probe from the ear canal, note the reading and dispose of the probe.
    
  • Sublingual: Place the probe into the sublingual pocket under the tongue and remove when the audible alarm is heard. This route should not be used if the child has had recent food or fluids to drink or if the child is unable to hold the thermometer in the sublingual pocket.
    
  • Once the probe has been removed, dispose of the probe cover in the appropriate clinical waste bin, clean the device as per manufacturer’s instructions and return it to its base.
    
  • Wash your hands.
  
  
• Document the temperature in the patient’s chart, noting the site and type of thermometer used. Note trends and correlate measurement with other clinical measurements (e.g. heart rate). Report abnormalities and implement care as per care plan.