Define Cold Stress, moderate and severe Hypothermia in newborn. Enumerate the symptoms and signs of hypothermia in a newborn. Outline management of Severe Hypothermia.
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Hypothermia in the Newborn: Definitions, Signs, and Management
1. Definitions (WHO Classification)
Normal axillary temperature in a newborn: 36.5°C to 37.5°C
Cold Stress
Cold stress is a pre-hypothermic physiological state in which the newborn is losing heat faster than it can produce it, triggering compensatory mechanisms - vasoconstriction and non-shivering thermogenesis via brown fat - to maintain core temperature. The WHO uses "cold stress" synonymously with mild hypothermia, defined as an axillary temperature of 36.0°C to 36.4°C.
In physiological terms, cold stress exists even at temperatures still within the normal range: whenever heat loss demands an increase in metabolic heat production (increased O2 consumption, glucose utilisation), cold stress is occurring. It precedes actual hypothermia and is detectable by peripheral cooling (cold hands/feet) before axillary temperature falls. The baby with cold feet but normal axillary temperature is in cold stress.
Moderate Hypothermia
Axillary temperature 32°C to 35.9°C (some guidelines narrow this to 32-36°C).
The compensatory mechanisms are still active but are becoming inadequate. Metabolic rate is high, oxygen consumption is elevated, and glucose stores are being depleted.
Severe Hypothermia
Axillary temperature below 32°C.
Compensatory mechanisms have failed. The infant is at immediate risk of metabolic collapse, cardiovascular compromise, and death. This is a medical emergency.
2. Symptoms and Signs of Hypothermia in the Newborn
Signs in neonates are non-specific and may mimic sepsis; always confirm with thermometry.
General Signs
| Category | Signs |
|---|---|
| Temperature | Cold skin to touch, cold extremities (feet cold first), cold abdomen indicates severe hypothermia |
| Colour | Pallor, peripheral cyanosis (acrocyanosis), mottling of skin |
| Activity/Tone | Lethargy, hypotonia, poor cry, reduced spontaneous movements |
| Feeding | Poor sucking, feeding refusal |
| Cardiovascular | Bradycardia, prolonged capillary refill time (>3 sec), weak pulse |
| Respiratory | Slow, shallow or irregular breathing; apneic episodes |
| Metabolic | Hypoglycaemia (may cause tremors, jitteriness), metabolic acidosis |
| Neurological | Weak or absent reflexes; in severe cases, unconsciousness or seizures |
| Skin | Oedema of face and extremities; in severe cases, sclerema (hardening of subcutaneous tissue - a very grave sign) |
Specific Signs by Severity
Cold Stress / Mild Hypothermia (36.0-36.4°C)
- Cold feet, warm abdomen
- Slight pallor
- Baby may still be feeding and active
Moderate Hypothermia (32-35.9°C)
- Cold feet AND cold abdomen
- Significant lethargy, weak cry
- Poor feeding
- Mild bradycardia
- Hypoglycaemia
Severe Hypothermia (<32°C)
- Whole body cold to touch
- Very lethargic or unresponsive
- Absent/very weak suck and cry
- Marked bradycardia or arrhythmias
- Apnoea or gasping
- Sclerema
- Shock (cold periphery + CRT >3 sec + fast/weak pulse)
- Hypoglycaemia + metabolic acidosis
Important note: Cold stress lowers arterial oxygen tension and increases metabolic acidosis. In preterm infants with respiratory distress syndrome, even mild cold stress can result in tissue hypoxia and neurological damage. Hypothermia and hypoglycaemia together are also classic signs of severe neonatal sepsis - always screen for infection.
3. Management of Severe Hypothermia (<32°C)
Severe hypothermia in a newborn is a medical emergency requiring immediate, structured intervention.
Step 1 - Immediate Assessment (ABCDE)
- Airway: Clear airway. Suction if obstructed.
- Breathing: If apnoeic/gasping → give positive pressure ventilation (PPV) with bag-and-mask + oxygen.
- Circulation: Check pulse, CRT, colour. If in shock (CRT >3 sec, weak fast pulse) → give 10-20 mL/kg normal saline or Ringer's lactate IV over 5-10 minutes.
- Blood glucose: Check immediately and treat hypoglycaemia (glucose <45 mg/dL) with IV dextrose (2 mL/kg of 10% dextrose bolus, then maintenance).
- Disability/Temperature: Confirm temperature with a low-reading thermometer.
Step 2 - Rapid Active External Rewarming
- Place the infant under a radiant warmer (set 1.0-1.5°C above body temperature, increasing as temperature rises).
- Alternatively, use a warmed incubator.
- Remove all wet/cold clothing and replace with dry, pre-warmed blankets.
- Do not use hot water bottles or electric heating pads directly on skin (risk of burns).
- Keep the room temperature at least 25-28°C.
- Place a hat on the head (significant heat loss via scalp).
- Target rewarming rate: approximately 1°C per hour to avoid rewarming complications (hypotension, cardiac arrhythmias from rapid fluid shifts).
- If no equipment is available and the infant is not in respiratory failure or shock: skin-to-skin (Kangaroo Mother Care) with mother/father/caregiver in a warm room is acceptable, though a radiant warmer is preferred for severe cases.
Step 3 - Monitoring During Rewarming
- Record axillary temperature every 15-30 minutes until ≥36.5°C, then every 1-2 hours.
- Continuous cardiorespiratory monitoring (heart rate, RR, SpO2).
- Repeat blood glucose every 30-60 minutes - hypoglycaemia can recur during rewarming.
- Monitor CRT and perfusion to detect rewarming hypotension.
Step 4 - Treat Hypoglycaemia
- If unable to feed: IV 10% dextrose at maintenance rate (first day: 60-80 mL/kg/day).
- Once rewarmed and stable, encourage breastfeeding or expressed breast milk.
Step 5 - Antibiotics (Screen for Sepsis)
- Severe hypothermia can be a manifestation of serious bacterial infection (sepsis, meningitis).
- After taking cultures (blood, CSF if indicated), start empirical antibiotics (e.g., ampicillin + gentamicin) unless sepsis is clearly excluded.
Step 6 - Oxygen Therapy
- Maintain SpO2 ≥90% (≥95% in term infants).
- Supplement O2 via nasal cannula or headbox as needed.
- Support ventilation with bag-and-mask or intubation if apnoea persists.
Step 7 - Supportive Care
- Feeding: Resume once temperature >35°C and infant is alert enough to feed. Give feeds every 2-3 hours; avoid fasting.
- Fluid balance: Monitor input/output. Avoid both dehydration and fluid overload.
- Sclerema: If present, indicates very severe illness. Continue rewarming; treat sepsis aggressively; prognosis is guarded.
- Parents: Inform and involve in Kangaroo care once stable.
Step 8 - Referral
- If severe hypothermia is present in a peripheral facility without a radiant warmer or incubator: wrap the baby in pre-warmed clothes and blankets, provide skin-to-skin contact during transport, and refer urgently to a facility with NICU capabilities.
Summary Table: WHO Classification and Management
| Category | Temperature | Management |
|---|---|---|
| Normal | 36.5-37.5°C | Maintain warmth |
| Cold Stress / Mild | 36.0-36.4°C | Skin-to-skin KMC, warm room, feed |
| Moderate | 32-35.9°C | KMC or radiant warmer; check glucose |
| Severe | <32°C | Radiant warmer, O2/PPV, IV glucose, IV fluids if shocked, antibiotics, continuous monitoring |
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