f. Monitor core temperature (rectal or esophageal) for

72 hours duration of HT.

g. Apply blankets and change gloves and/or water

bottles as frequently as necessary to maintain core

temperature at 33.5 ± 0.5°C.

h. Rewarming can be achieved passively by discontinuing active cooling and monitoring the rise in core

temperature.

i. Gradual rewarming using external heat source, as

for passive cooling, can be used with appropriate

shield to protect the head (Figs. 45.6B, 45.21).

Fig. 45.8. Variability in the rectal temperature during initiation, maintenance, and rewarming phase of

HT. SHC, selective head cooling manual (CoolCap n = 21); WBCmc, whole body cooling manual control (Tecotherm n = 25); WBCsc, whole body cooling servocontrolled (CritiCool n = 28).

332 Section IX ■ Miscellaneous Procedures

Pitfalls

a. There should be minimal variation in ambient

temperature.

b. Some, but relatively less, variability in core temperature compared with passive cooling.

c. Frequent monitoring is required to determine when

the gloves/water bottles need replacing.

2 Gels (5) (Fig. 45.10)

Technique

a. Expose the infant to the ambient temperature in an

open crib with an overhead warmer turned off.

b. Apply two refrigerated gel packs (12 cm × 12 cm, at

7°C to 10°C) across the chest and/or under the head

and shoulders.

c. Remove one gel pack when the core temperature

falls below 35°C.

d. Remove the next gel pack when the core temperature falls below 34.5°C.

e. Turn on the radiant warmer and manually adjust the

heater output every 15 to 30 minutes if the core

temperature falls below 33.5°C and use appropriate

shield to protect the head (Fig. 45.21).

f. Reapply gel packs if core temperature rises above

34°C.

g. After 72 hours, increase the radiant warmer heater

output to achieve rewarming by 0.5°C every 1 hour.

Pitfalls

1. High variability of core temperature.

2. Intensive monitoring and support required to maintain

the desired core temperature.

3. Servocontrolled fan (27)

WBC is achieved using a custom-made, servocontrolled

fan, which directs airflow cephalocaudally over the

infant.

The fan unit consists of a Perspex box (30 × 15 × 10 cm)

containing three fans. The fans are noiseless and are placed

at the head of the infant. The unit produces an airflow of

105 ft/min at 100% power, and is powered on 12V direct

current via a custom-made power supply. The fans are activated when the rectal temperature is at or above the preset

activation temperature, and the power of the fans automatically increase or decrease with fluctuations in the rectal

temperature.