Approach to fever by age and immune status — formative SAQs

SAQ 1 (10)

A 22-day-old term infant presents to ED with a rectal temperature of 38.3 °C. The mother reports poor feeding for 8 hours and says the baby "is not right." The infant is mildly irritable but perfuses well. ^{[1] [6]}

1. State your immediate priority and the work-up this infant must receive. (3) ^[1]
2. Explain why height of fever cannot be used to rule in or rule out serious bacterial infection in this age group. (3) ^[4]
3. Outline your disposition, empiric management principles (no invented drug doses), and the safety-net you give the family. (4) ^{[1] [6]}

Model answer

Immediate priority and work-up. Any fever in a neonate 0–28 days is sepsis until proven otherwise. Immediate priority is ABCDE threat assessment and a full septic work-up — blood culture, complete blood count and differential, urine culture from catheterisation or suprapubic aspirate (not bag), and cerebrospinal fluid from lumbar puncture — with empiric antibiotics and admission regardless of how well the infant appears. ^[1]

Why fever height is unreliable. De and colleagues showed body temperature lacks accuracy for detecting serious bacterial infection in febrile episodes. Neonates have immature thermoregulation and a weak inflammatory response, so they may be hypothermic or only mildly febrile in sepsis. The magnitude of the cytokine response reflects host thermoregulatory capacity, not organism virulence. Behaviour, perfusion, and feeding matter more than the temperature number. ^[4]

Disposition, management, safety-net. Admit for observation and empiric antibiotics. Involve senior paediatric and microbiology input. Give the family a written safety-net: return immediately if feeding worsens, breathing difficulty, reduced interaction, abnormal colour, seizures, or parental concern the baby is worse. Caregiver concern is associated with critical illness, so take the mother's "not right" seriously. ^{[1] [6]}