Maintaining normothermia in the immediate postpartum period and beyond.
Review definition and classification of temperature ranges; risks of hypothermia; clinical management options for prevention of hypothermia.
Normothermia has been defined by the World Health Organization (WHO) as a neonatal temperature of 36.5–37.5°C (97.7–99.5°F). Any neonatal temperatures above this are considered hyperthermia and those below this range are considered hypothermia. Hypothermia is further separated into mild hypothermia (36–36.5°C; also referred to as “cold stress”), moderate hypothermia (32–35.9°C), and severe hypothermia (<32°C). Hypothermia is frequent in preterm infants. A California-based cohort of 8782 very low birth weight (VLBW) neonates born in 2006–2007 reported a 56.2% rate of hypothermia. A report from 18 hospitals included in the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network reported 38.6% of moderately preterm infants (29–33 weeks) and 40.9% of extremely preterm infants (<29 weeks) had admission temperatures <36.5 °C. A Canadian cohort of 9833 neonates born at <33 gestational age in 2010–2012 reported a 35.8% rate of hypothermia.
The incidence of hypothermia in term infants is not well defined. A single-institution study from a resource-poor setting in Zambia reported 73% of term infants experienced hypothermia. It is likely that resource-rich settings also experience a non-trivial rate of hypothermia in term infants.
Hypothermia has been associated with increased morbidity and mortality. In a population-based study, admission temperature less than 35°C was an independent predictor of death and bronchopulmonary dysplasia (BPD) among neonates born less than 26 weeks. A separate study which included 8782 neonates born between 23 and 32 weeks’ gestation also found strong associations between moderate to severe hypothermia and stage 3–4 retinopathy of prematurity (ROP), late onset sepsis, BPD, intraventricular hemorrhage (IVH), and death.
On the basis of these findings, both obstetric and neonatal organizations have issued guidelines addressing prevention of hypothermia as part of the delivery and resuscitation process. Organizations with such statements or recommendations include the American Academy of Pediatrics (AAP), American College of Obstetrics and Gynecology, American Heart Association, International Liaison Committee on Resuscitation, Neonatal Resuscitation Program, and European Resuscitation Council.
Although the pathophysiology is beyond the scope of this chapter, it should be recognized that the general mechanisms for heat loss are evaporation, conduction, convection, and radiation. Interventions to prevent hypothermia target one or more of these mechanisms. Interventions that are discussed below include delivery room temperature standards, use of a radiant warmer, attention to thermoregulation during transport of preterm infants to the neonatal intensive care unit (NICU), use of occlusive wrap or bag including plastic cap, use of an exothermic mattress, use of heated-humidified gas, and skin-to-skin (kangaroo) care.
Adopt strategies to prevent ...