Neonatal hypothermia and thermoregulation — formative SAQs

SAQ 1 — The cold preterm on admission (10 marks)

A 28-week gestation, 950 g infant is delivered by emergency caesarean for preterm labour. The delivery room was noted to be cool. The infant arrives in the neonatal unit 15 minutes after birth, wrapped in a towel that is damp. The axillary temperature is 35.0 C, the infant is pale and grunting, and the bedside glucose is 1.6 mmol/L. [9]

a) Classify this infant's temperature by the WHO band and state the target normothermic range. (2 marks) [9]

The axillary temperature of 35.0 C places this infant in the moderate hypothermia band (32.0–35.9 C). The target normothermic range is 36.5–37.5 C. Moderate hypothermia is the band in which admission hypothermia in preterm infants most commonly sits, and in very preterm infants it is independently associated with mortality and major morbidity. [9]

b) List the four physical pathways of heat loss and state which dominates at birth and why. (3 marks) [1]

The four pathways are evaporation (water converting to vapour from the wet skin), radiation (heat radiating from the skin to cooler surrounding walls), convection (moving air carrying heat away — drafts, transport), and conduction (heat lost to a cold surface in direct contact — scales, cold towels, a cold mattress). Evaporation dominates at birth because the infant is wet with amniotic fluid and the skin-to-air gradient is large; this is why immediate drying is the single highest-yield warm-chain step. [1]

c) Describe your immediate management of this infant, including the rewarming strategy and the metabolic priority. (3 marks) [9]

The management is active external rewarming: place the infant under a pre-warmed radiant warmer or in a servo-controlled incubator, remove the damp towel, apply a hat, and monitor continuously, targeting a rewarming rate of roughly 0.5 C per hour. The metabolic priority is to correct the hypoglycaemia — give a bolus of 10% dextrose (typically 2 mL/kg) followed by a continuous dextrose infusion — because thermogenesis consumes glucose and hypoglycaemia disables thermogenesis. Watch for apnoea during rewarming. [9]

d) State the delivery-room interventions that would have prevented this, citing the evidence base for the very preterm. (2 marks) [3]

A warm delivery room (above 25 C), immediate drying and a change to a dry towel, a hat, and — specifically for the very preterm (under 32 weeks) — plastic wrap without drying under a radiant warmer. The Cochrane review of interventions to prevent hypothermia at birth in preterm infants found that plastic wraps reduce hypothermia, and the JAMA Pediatrics network meta-analysis ranked the combination of plastic bag, cap and radiant warmer as the highest delivery-room strategy. [3] [4]

SAQ 2 — A cold term infant and the warm chain (10 marks)

A term infant, born after an uneventful labour, is found to have an axillary temperature of 35.6 C at the routine check at four hours of age. The infant is in a cot beside the mother, wrapped in a single blanket, and the room window is open. The infant is alert and pink but feels cool peripherally. [10]

a) Classify this temperature and give two immediate management steps. (2 marks) [9]

An axillary temperature of 35.6 C is moderate hypothermia (32.0–35.9 C). Two immediate steps are to add warmth — close the window, add layers and a hat, and consider skin-to-skin contact or a radiant warmer — and to check the bedside glucose, because a cold infant is hypoglycaemic until proven otherwise. [9]

b) The infant does not rewarm adequately within an hour despite these measures. What is the key differential diagnosis, and what investigation is now indicated? (3 marks) [9]

Hypothermia in a term infant that persists despite adequate warming is a red flag for sepsis, hypoglycaemia, or a metabolic/endocrine cause (congenital hypothyroidism, inborn errors of metabolism). A cold infant in a warm environment has sepsis until proven otherwise. The indicated investigation is a septic screen (blood culture, inflammatory markers), with confirmation of the newborn bloodspot and targeted metabolic and endocrine testing if the picture persists. [9]

c) State the WHO warm chain, naming at least seven of its steps. (3 marks) [10]

The warm chain: (1) a warm delivery room above 25 C, free of drafts; (2) immediate drying and change to a dry towel; (3) skin-to-skin contact or a radiant warmer; (4) early breastfeeding within the first hour; (5) postponed bathing and weighing (at least 24 hours); (6) appropriate clothing and bedding — a hat and layers; (7) a warm environment during procedures; (8) warm transport; (9) continuous temperature monitoring in the high-risk infant; (10) staff education. [10]

d) For a stable preterm infant, describe kangaroo mother care and its evidence-based benefits. (2 marks) [6]

Kangaroo mother care is sustained skin-to-skin contact, with the infant prone on the parent's chest between the breasts, covered with a blanket and a hat. Meta-analyses (including Boundy) confirm that it reduces mortality, hypothermia, and serious illness in stable preterm and low-birth-weight infants, supports breastfeeding, and is feasible in both well-resourced and low-resource settings. [6]