The cold preterm on admission — moderate hypothermia with hypoglycaemia

Clinical information for the examiner

Setting: Tertiary neonatal unit, 15 minutes after birth by emergency caesarean for preterm labour. The delivery room was noted to be cool (below 25 C). The infant was wrapped in a towel that is now damp. No plastic wrap was used; no hat was applied. [1]

On your arrival:

• Axillary temperature 35.0 C; infant is pale, grunting, with mild subcostal recession. [9]
• Heart rate 150, SpO₂ 90% in air, capillary refill 3 seconds, peripherally cool. [9]
• Bedside glucose 1.6 mmol/L. [9]

Task 1 — Classification and physiology (3 marks)

The candidate should classify and explain. [9]

1. Classification: 35.0 C is moderate hypothermia (WHO band 32.0–35.9 C); target normothermia is 36.5–37.5 C. [9]
2. Why the preterm: high surface-area-to-mass ratio, thin skin with high transepidermal water loss, small brown-fat and glycogen stores, non-shivering thermogenesis only, immature hypothalamus. [3]
3. Four pathways: evaporation (dominant at birth, wet skin), radiation (cold walls), convection (drafts), conduction (cold surfaces). [1]

Pass criterion: candidate names the WHO band, the four pathways, and why the preterm is the extreme. [9]

Task 2 — The metabolic cascade (2 marks)

The candidate should describe the cascade. [9]

• Heat loss exceeds thermogenesis → glycogen exhaustion and hypoglycaemia (glucose 1.6 mmol/L). [9]
• Anaerobic glycolysis → metabolic (lactic) acidosis. [9]
• Cold and acidosis → pulmonary vasoconstriction (PPHN risk); fluctuating cerebral flow → intraventricular haemorrhage risk. [9]
• Hogeveen review: admission hypothermia in very preterm infants is independently associated with death and major morbidity, with a dose-response gradient. [9]

Pass criterion: candidate links the cold to hypoglycaemia, acidosis and the systemic complications, and states that the glucose is non-negotiable. [9]

Task 3 — Immediate management (3 marks)

Active external rewarming plus glucose correction. [9]

• Radiant warmer or servo-controlled incubator; remove damp towel; apply hat; continuous monitoring. [9]
• Target rewarming roughly 0.5 C per hour; watch for apnoea. [9]
• Correct the glucose: 10% dextrose bolus (typically 2 mL/kg) then continuous dextrose infusion; recheck. [9]
• Consider empiric antibiotics if sepsis suspected. [9]

Pass criterion: candidate gives active external rewarming with a target rate, corrects the glucose, and monitors for apnoea. [9]

Task 4 — Prevention bundle (2 marks)

The warm chain and plastic wrap for the very preterm. [3]

• Warm delivery room (above 25 C), immediate drying and a dry towel, hat, radiant warmer. [10]
• Plastic wrap without drying for infants under 32 weeks — Cochrane-supported and the highest-ranked delivery-room strategy in the network meta-analysis. [3] [4]
• Early breastfeeding (or expressed milk), delayed bathing, warm transport, continuous monitoring. [10]