The WHO defines the normal temperature of a neonate at 36.5– 37.5°C, and gradations of hypothermia including mild (36-36.5°C), moderate (32-36°C) and severe (<32°C). Even at warm ambient temperatures, neonates can have difficulty retaining heat, especially as amniotic and other fluid evaporates off their skin. Cold stresses on neonates can lead to hypoglycemia, respiratory distress, hypoxia, acidosis, and other pathologies.
Mechanism of Action
Infant warmers can be used over the course of hours (for example during transport) or over the course of weeks (for example in a NICU). Electric devices include incubators that heat the air around the neonate, radiant warmers that use an overhead heat lamp, and heated mattresses that continuously warm the surface underneath the baby. Thermal mass devices typically store and release heat, sometimes using phase change materials which can maintain a constant temperature over hours. Insulative devices are often used in conjunction with other technologies, and include hats, blankets, and occlusive wraps. Skin-to-skin contact has also proven extremely effective, especially as a component of Kangaroo mother care (KMC) wherein the caregiver provides direct body heat, exclusive breastfeeding, and early recognition and response to complications.
Current Use in High-Resource Settings
High end, full featured incubators are common in high-resource NICUs, offering automated temperature and humidity control as well as vital signs monitoring, in-bed weight scale, integrated x-ray cassette trays, overhead phototherapy, etc. Radiant warmers and heated mattresses are also used. Among 669 US hospitals surveyed, 82% use kangaroo mother care, often in combination with these high tech solutions.
Application in Low-Resource Settings
Radiant warmers are more common in low-resource hospitals. Relative to incubators, they are lower cost and offer greater access to the patient. Their major drawback is evaporative water loss, which can be significant in low birth weight babies whose skin is relatively permeable. The WHO has endorsed KMC in all settings noting that “Almost two decades of implementation and research have made it clear that KMC is more than an alternative to incubator care. It has been shown to be effective for thermal control, breastfeeding, and bonding in all newborn infants, irrespective of setting, weight, gestational age, and clinical conditions.” While the practice is increasing in popularity, there has still been resistance to what may be viewed as low tech, unproven, or a mark of poverty.
Related Technologies in Development
Information Blanket, Neonuture, Rice University Warming Crib