Thermoregulation, the body’s ability to maintain a stable core temperature, presents a profound challenge for newborns born before 32 weeks of gestation. These extremely preterm infants are highly vulnerable to rapid heat loss and cold stress. They have a significantly greater surface area-to-mass ratio compared to full-term babies, causing them to lose heat quickly. Their immature skin, which is thin and poorly keratinized, results in excessive evaporative heat and water loss, known as insensible water loss. Furthermore, these infants have not yet fully developed the insulating brown adipose tissue (brown fat), the primary mechanism for non-shivering heat generation in newborns.
Immediate Thermal Stabilization Protocols
The first moments of life focus on preventing the catastrophic drop in body temperature that occurs upon exiting the warm, humid environment of the womb. Interventions to maintain a normal temperature (36.5°C to 37.5°C) must be applied within 60 seconds of birth. The resuscitation room temperature is often increased to 23°C to 25°C to reduce heat loss to the surrounding air and surfaces.
A central protocol for infants less than 32 weeks is the immediate use of a polyethylene wrap or bag without first drying the skin. This plastic barrier acts as a vapor shield, significantly reducing evaporative heat loss from the wet, immature skin. The infant is immediately placed beneath a pre-warmed radiant warmer, which provides external heat. A hat is also applied to the head to minimize heat loss from the large surface area of the skull.
This combination of interventions minimizes heat loss through evaporation, conduction, convection, and radiation. Specialized chemical warming mattresses may also be used with the radiant warmer and plastic wrap to provide conductive heat. This rapid, multi-pronged approach prevents the initial, rapid cooling phase, which is associated with higher rates of serious complications. The goal is to ensure the infant’s temperature is within the target range before admission to the Neonatal Intensive Care Unit (NICU).
Specialized Incubator Management and Humidity Control
Once stabilized, the preterm infant is transferred to a specialized incubator environment designed to provide a sustained, controlled atmosphere, called the neutral thermal environment (NTE). The NTE is the temperature range where the infant’s metabolic rate and oxygen consumption are at their lowest while maintaining a normal body temperature. Achieving this requires high-tech equipment, such as double-walled incubators, which minimize radiant and convective heat loss to the cooler external surfaces.
The incubator’s temperature is regulated using a servo-control system. This system uses a temperature probe placed on the infant’s abdomen to automatically adjust the heat output. It constantly monitors the infant’s skin temperature, aiming to keep it around 36.5°C, rather than maintaining a fixed air temperature. The probe placement is specific, avoiding areas of brown fat or bony prominence, to ensure an accurate reading of the infant’s overall thermal status.
The incubator environment also requires high humidity, often set between 80% and 90% initially, especially for infants less than 28 weeks’ gestation. This high moisture level is essential because it reduces the gradient between the immature skin and the air, dramatically lowering insensible water loss. Reducing evaporative heat and water loss prevents dehydration, electrolyte imbalances, and unnecessary calorie expenditure. As the infant’s skin matures, typically after the first week or two, the humidity is gradually reduced to prevent the risk of skin infection.
Strategies for Minimizing Heat Loss During Routine Care
Maintaining thermal stability requires procedural discipline from the NICU staff, as routine care activities can disrupt the controlled environment and cause cold stress. One strategy involves minimizing the frequency and duration of opening the incubator portholes and doors for necessary access. Every time the incubator is opened, the internal temperature and humidity levels drop, forcing the infant to expend energy to stay warm.
Procedures that require the infant to be fully exposed, such as linen changes or weighing, must be conducted with caution and speed. Ideally, these procedures are performed while the infant remains in the controlled environment of the incubator or, if removal is necessary, under a pre-warmed radiant warmer. Bundling the infant within the incubator with warmed blankets and hats, even under servo-control, adds a layer of insulation to reduce convective and radiant losses.
Any fluids or blood products administered intravenously must also be warmed to body temperature before infusion to prevent conductive heat loss. For internal transport within the hospital, such as for X-rays or surgical procedures, specialized transport incubators are used. These portable units are fully self-contained with external power sources and are pre-warmed to ensure the infant is never exposed to an uncontrolled environment, providing a continuous thermal bridge from one location to the next.