Phase changing material: an alternative method for cooling babies with hypoxic ischaemic encephalopathy

Therapeutic hypothermia for hypoxic ischaemic encephalopathy (HIE) has been proved effective. Standard equipment is expensive, while ice packs used in low resource settings are labour intensive and associated with wider temperature fluctuations.

To assess the feasibility of using phase changing material (PCM) as an alternative method for providing therapeutic hypothermia.

We retrospectively analysed 41 babies with HIE who had been cooled with PCM (OM 32 or HS 29) to a target rectal temperature of 33-34°C. Rectal temperature was continuously monitored and recorded every hour. If the rectal temperature was >33.8°C, cool gel packs were applied, and if the temperature was <33.2°C, the baby was covered with sheets and the warmer output turned on till the temperature stabilized at 33.5°C. The unit's standard protocol for cooling was followed for monitoring and treatment. The outcome measures were stability and fluctuation of the rectal temperature and the need for interventions to maintain the target temperature.

The mean (±SD) temperature during the cooling phase was 33.45 ± 0.26°C. Throughout the cooling phase, the target temperature range was maintained in 96.2% of the time. There was no temperature reading <32°C. With HS 29, ice packs were not used in any baby, and the warmer was used for a median of 7 h (interquartile range 1.5-14).

PCM provides a low cost and effective method to maintain therapeutic hypothermia. However, careful monitoring is required during induction and the rewarming phase to avoid hypothermia outside the therapeutic range.