Over the last 30 years, step by step, with the improvement of neonatal care, and increasingly supported by the development of innovative technologies, a particular and very delicate discipline has developed that deals with the transfer of infants in serious or critical conditions from first-level centers to neonatal intensive care units. This is the Neonatal Emergency Transport Service (NETS).

In a 2019 issue of AirMed&Rescue, authors Ian Braithwaite and Cath Harrison published a very interesting article, in which many aspects of neonatal transport were discussed. In this article, I would like to focus my attention on a very important, hidden, and often overlooked point of neonatal transport. The impact of hypothermia in the management of neonatal transport, in particular, the transport of the premature infant.

Neutral thermal environment challenge

Maintaining a neutral thermal environment is one of the major physiological challenges a newborn faces after delivery, becoming ever more important as smaller, and less mature, infants are able to survive pre-term birth. There are significant differences in thermal regulation by infants and adults; adults use peripheral vascular constriction, inhibition of sweating, voluntary muscle movements, involuntary muscle movements (chills), and shiver-free thermogenesis to combat hypothermia. These responses are almost totally lacking in infants. The key to a neutral thermal environment is to establish a narrow range of body temperature in which metabolic and oxygen demands are at their lowest, thus ensuring the correct balance between heat production and loss. This target is very hard to obtain, and maintain, during air transport, particularly during a rotor-wing transport. These conditions are obviously strongly aggravated if the newborn is flying at high altitude (low temperatures), with possible reduction in the fraction of available oxygen (worsening the already precarious metabolism with high risk of lactic acidosis), and possible inadequate production of heat by the transport incubator due to the considerable temperature gap between the intra-incubator environment and the external environment (the aircraft cabin). 

Risk of increase mortality

Normal neonate temperature ranges from 36.5°C to 37.7˚C, while cold stress may occur when a baby’s temperature drops to 36˚C. Below this is hypothermia – moderate is between 32°C and 36°C, and severe is considered to be below 32°C. It is well known that infants exposed to cold temperatures are at risk for increased mortality, and that this is particularly true for premature infants, who are often suffering respiratory distress, thus making their ability to respond to hypothermia even more difficult.

Hypothermia is a real and dangerous enemy of neonatal air transport, resulting in a variety of physiological stresses

Hypothermia is a real and dangerous enemy of neonatal air transport, resulting in a variety of physiological stresses. Main patho-physiologic mechanisms include increased oxygen consumption, which becomes significantly higher during respiratory distress, metabolic-lactic acidosis, hypoglycemia, decreased cardiac output, and increased peripheral vascular resistance.   
Literature (Mank A et al., Hypothermia in Preterm Infants in the First Hours after Birth: Occurrence, Course and Risk Factors. PLoS One. 2016; 11(11): e0164817) reports that a high number of low birthweight infants are admitted to neonatal intensive care units with body temperatures that would be considered hypothermic, thus pointing out that, although many people tend to ignore this aspect, one of the main objectives of the air medical transfer of neonates lies in the correct management of the patient’s temperature.
So, essentially, whenever there may be difficult conditions during a transport related to maintaining the correct body temperature (equipment not completely adequate, inverter onboard not producing sufficient power to generate the necessary amount of voltage, humidification and heating of inhaled gases not available, the need for high-altitude flight, adverse weather conditions, winter season etc), all are aggravated by the possible transfer of a premature newborn, and the choice to perform an air transfer should be carefully evaluated, and possibly avoided. If the decision is taken to perform a transfer, perfect pre-transport stabilization must always be guaranteed.

Options for equipment

Recently, equipment has become available on the market intended to provide active cooling, which is used for the transport and treatment of infants with hypoxic ischemic encephalopathy (HIE), which may occur in about 1.5 per cent of term or near-term births as a result of hypoxic and/or ischemic insults during labor and delivery. Unless treated properly and immediately to the correct standard of care, the condition will almost certainly be fatal, or lead to long-term deficits. Not every hospital is equipped to handle it. Due to the fact that not all hospitals are able to offer adequate treatment, neonatal transport becomes mandatory. Each NETS must be able to offer the correct treatment, and therefore cooling in transport must be guaranteed. Basically, every NETS should be equipped with such equipment. 

equipment has become available on the market intended to provide active cooling

The devices we used is the CritiCool® MINI, by Belmont Medical Technologies, which provides active cooling and is extremely quick and easy to get started, with intuitive touchscreens that clearly display exactly what you need to know. A notable advantage of using this device is that it also has the ability to heat, and therefore, although not the main reason why they are generally purchased, they can be used to great effect in maintaining the body temperature of premature babies during transport. The availability of a heated mattress, and a servo mechanism capable of regulating the temperature by monitoring the rectal temperature of the newborn, offer guarantees of safety in use.

Generally, this type of appliance is powered both by 220-volt current and by battery; batteries generally last no more than 60 minutes and these make them unwieldy during long flights if a reliable source of electrical support is not available. The recommended solution is to equip the NETS with portable batteries provided with an adequate set of adapters. The number and power of batteries must be commensurate with the length of the flight. The use of these devices can ensure the correct control of body temperature even in very premature babies in safe conditions.

Temperature management

In conclusion, hypothermia must be considered a serious, and often underestimated, risk that newborns can encounter during neonatal transport. The longer the time the infant spends in hypothermia, the greater the risk of increased morbidity and mortality rates. The members of the neonatal transport team must be fully aware of the possibility of hypothermia occurring and must provide for all the necessary precautions to avoid the risk, both with appropriate pre-transport stabilization and by equipping themselves with suitable equipment