Chapter 7 ■ Temperature Monitoring 47

7. Probes for both thermistors and thermocouples are

available in different configurations for different sites.

For example:

a. Surface skin probe

b. Tympanic membrane thermocouple probe

F. Precautions

1. Do not apply skin probes to broken or bruised skin.

2. Do not apply skin probes over clear plastic dressings.

3. Do not use fingernails to remove skin surface probes.

4. Do not force core probes during insertion.

5. Do not reuse disposable probes.

6. Shield skin probe with reflective pad if used with radiant warmer or heat lamp.

7. When using servocontrol mechanisms for environmental control, take intermittent temperatures at other sites

to monitor effectiveness (18,19).

Fig. 7.5. Skin probe properly placed on infant (note that probe

has protective foil cover and lies flat on the skin surface).

G. Technique

1. Skin surface probe (Table 7.1)

a. Prepare the skin using an alcohol pad to ensure

good adhesion to the skin.

b. Cover probe with a reflective cover pad (foil-covered

foam adhesive pad, incorporated in the disposable

probe) (Fig. 7.5). Probe must be covered with an

aluminum foil disk to reflect back the added heat

from devices such as radiant warmers, phototherapy

lights, infrared warming lights, and any other external radiant heat-generating sources (20).

c. Apply probe over the liver in the supine infant.

d. Apply probe to the flank in the prone infant.

e. Ensure that skin probe is free of contact with bed

(Fig. 7.6).

Table 7.1 Site for Temperature Monitoring

Site Range (°C) Application

Surface

1. Abdomen over

liver

36–36.5 Servocontrol

2. Axillary 36.5–37 Noninvasive approximation of core

temperature

Core

1. Sublingual 36.5–37.5 Quick reflection of body change

2. Esophageal 36.5–37.5 Reliable reflection of changes

Target temperature in whole-body

cooling protocols

33.5

3. Rectal 36.5–37.5 Slow reflection of changes

Target temperature in head cooling

protocols associated with mild

systemic hypothermia

34–35

Fig. 7.6. Newborn infant with skin probe free of

contact from bed surface.

48 Section II ■ Physiologic Monitoring

Table 7.2 Potential Pitfalls of Servocontrolled Heating Devices

Skin << Core Skin > Core Skin > Core

Increased heater output Cold stress

Shock (vasoconstricted)

Hypoxia

Acidosis

Dislodged probe (early)

Servo fails to shut off

Vasodilators (e.g., tolazoline)

Shock (vasodilated)

Dislodged probe (late)

Servo fails (late)

Decreased heater output Probe uninsulated (radiant heat)

Servocontrol malfunction Fever, overheating

Internal cold stress Unheated endotracheal oxygen, exchange transfusion

Note: Changes in heater output may not be indicated; therefore, it is necessary to intermittently monitor the infant’s core temperature (axillary optimal).

2. Application of core probe (Table 7.1)

a. Choose probe size according to site (i.e., rectum or

esophagus).

b. Esophageal probe

(1) Does not need lubrication prior to placement,

but may need to be warmed to be more pliable

prior to insertion.

(2) Estimate the length of insertion needed to place

the tip of the probe in the lower third of the

esophagus. Subtract 2 cm from the sum of the

distance from the mouth to the tragus of the ear

and the distance from the ear to the xiphoid

(Fig. 7.4).

(3) Insert probe through nostril until the desired

length is reached.

c. Rectal probe

(1) Lubricate probe before placing in rectum.

(2) Probe should be placed approximately 3 cm

beyond anal sphincter; further advancement

will increase risk of perforation.

d. Do not force either probe.

3. Connect the probe to the monitor.

4. Monitor energy output changes.

5. Reposition or replace the probe if temperature recorded

does not correlate with that recorded using an electronic thermometer. Skin surface temperature will be