Yes, infection can definitely cause hypothermia in neonates and is a critical diagnostic consideration.
Infection is a well-established cause of hypothermia in neonates, occurring in approximately 50-80% of hypothermic infants, and should be presumed present until proven otherwise. 1, 2, 3, 4
Why Infection Causes Hypothermia
Neonates, particularly those under 3 months, have immature thermoregulatory systems and can present with hypothermia rather than fever when infected. Both fever AND hypothermia (core temperature <36°C) are recognized diagnostic criteria for sepsis in international guidelines 2. The inflammatory response in neonates may paradoxically suppress temperature rather than elevate it.
Clinical Evidence
The relationship between infection and hypothermia is substantial:
- In infants <3 months with hypothermia (≤34°C), infection was diagnosed in 53% of cases 3
- In neonates specifically, infection was present in 80 of 138 (58%) hypothermic children, with respiratory tract infections being most common, particularly right upper lobe atelectasis from aspiration pneumonia 4
- Among infants <60 days evaluated for serious bacterial infection (SBI), 9% had confirmed SBI, including UTI, bacteremia, meningitis, and pneumonia 5
Key Clinical Indicators of Infection in Hypothermic Infants
When infection is present alongside hypothermia, look for:
- Bradycardia (not tachycardia, as expected in older patients)
- Altered mental status (lethargy, poor interaction, irritability)
- Anemia
- Abnormal leukocyte counts (leukocytosis >12,000 or leukopenia <4,000)
- Abnormal glucose levels (hypo- or hyperglycemia)
- Elevated absolute band counts and immature-to-total neutrophil ratio 5
- Uremia
- Repeat episodes of hypothermia after initial warming 6
The presence of two or more of these variables significantly increases the likelihood of infection 3.
Diagnostic Approach
For Late-Onset Hypothermia (>3 days old):
Infection is much more common in this group. Gastric aspirate examination is highly valuable: abnormal in 82% of infected babies versus only 13% of non-infected babies 7. The most common pathogen is Escherichia coli 4.
For Early-Onset Hypothermia (<3 days old):
Infection is less common, and gastric aspirate is usually normal 7.
Critical Management Recommendation
Given the high mortality and morbidity associated with infection in hypothermic infants, and the absence of rapid reliable indicators to definitively exclude infection in individual cases, empiric antibiotics should be administered to ALL infants younger than 3 months with hypothermia on hospital admission 3. This recommendation stands despite the fact that only about 25% of hypothermic infants undergo full sepsis evaluation in practice 5.
Common Pitfalls to Avoid
- Waiting for fever: Hypothermic neonates with sepsis may never develop fever
- Assuming environmental causes: Even well-appearing infants can have serious infections
- Relying on single indicators: No single test reliably excludes infection
- Delaying antibiotics: Mortality is higher in infected hypothermic infants 3
The clinical diagnosis of septic shock in children explicitly includes hypothermia as a presenting sign, alongside altered mental status and signs of inadequate tissue perfusion 1.