Iowa Neonatology Handbook: Temperature

Servocontrol: Incubator and Radiant Warmer

Edward F. Bell, MD
Peer Review Status: Internally Peer Reviewed

1. Careful attention to providing the best possible thermal environment increases the chance of survival and the quality of outcome, particularly in the small premature infant.
   
   Servocontrol is an electronic feedback system which functions as a thermostat to maintain a constant temperature at the site of a thermistor probe (usually on the skin over the abdomen) by regulating the heat output of an incubator or radiant warmer. Maintaining a constant abdominal skin temperature between 36.0 and 36.5ÁC is the simplest way to provide a "thermoneutral" environment, minimizing the number of calories needed to maintain normal body temperature and reducing the risks of cold stress or overheating.
   
   Although either skin or air temperature control can be used safely for most infants, skin temperature servocontrol is probably better for very young, small (below 1500 g) infants because the desired control temperature is more easily determined. Servocontrol is the only acceptable method of heat regulation for the infant cared for under a radiant warmer.
2. The following guidelines apply to both the incubator and radiant warmer:
   1. Insert probe plug securely into hole in heater unit.
   2. Choose the desired abdominal skin temperature, usually 36.5ÁC. Some older infants will require a lower set point, e.g., 36.0ÁC to avoid overheating.
   3. Check the setting of the control panel. Adjust if necessary.
   4. Attach the probe to the exposed abdominal skin at mid-epigastrium, halfway between the xiphoid and the umbilicus. If the infant is prone, attach the probe to the skin over either flank (not between the scapulae). The probe should not be placed in the axilla.
   5. Under the radiant warmer, protect the probe with a foil-backed shield.
   6. Read the skin temperature from the temperature gauge on the heater unit. If it registers below the set point (36.5ÁC), the heater should be on. Check the heater indicator light or dial. If the heater is not on, check all connections.
   7. If the skin temperature does not rise as quickly as you think it should, make sure the heater is on and WAIT. Increasing the set point will not cause faster warming.
   8. When the abdominal skin temperature reaches the chosen set point, check the axillary or rectal temperature to be sure it is within the normal range (36.5 to 37.4ÁC).
   9. Adjust the set point slightly if the axillary (or rectal) temperature is abnormal. Do not change the set point if the axillary (or rectal) temperature is normal.
   10. Check frequently to be sure the probe is in solid contact with the skin. Poor contact will cause overheating. Entrapment of the probe under the arm or between the infant and mattress will cause underheating
   11. Record incubator air temperatures along with infant skin and axillary (or rectal) temperatures. A clearly decreasing (or increasing) trend in incubator temperature may indicate the development of sepsis or a neurological problem.

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