Thermoregulation
- A full-term infant is homeothermic
- Has limited ability to regulate body temperature compared with older child
Mechanisms of heat loss
- Evaporation>
- Radiation
- Conduction
- Convection
Mechanisms to conserve heat
- Peripheral vasoconstriction
- Increased heat production by increase metabolic rate and muscle activity
- Non-shivering thermogenesis
Why is neonate prone to loose heat ?
- Increased surface area to body ration
- Limited ability to shiver
- Reduced subcutaneous fat
- Relative deficiency of brown fat and glycogen
Hypoglycaemia
- Commonest neonatal metabolic disorder
- Often has a non-specific presentation
- Clinical features include respiratory distress, tachycardia, tachypnoea, irritability
Predisposing factors
- Diabetic mother
- Prematurity / small for gestational age
- Hydrops foetalis
- Birth asphyxia
- Sepsis
- Hypothermia
Neonatal jaundice
- Physiological jaundice - normal elevation of unconjugated bilirubin in healthy neonate
- Erythroblastosis foetalis - results from materno-foetal Rhesus D Antigen incompatibility
- Kernicterus - deposition of bilirubin in basal ganglia,thalamus and hippocampus
Causes of hyperbilirubinaemia
- Haemolysis - rhesus or blood group incompatibility
- Enzyme defect - G6PD deficiency, pyruvate kinase deficiency
- Red cell structural defect - hereditary spherocytosis or elliptocytosis
- Increased red cell mass - polycythaemia
- Increased red cell sequestration - haematoma
- Reduced hepatic uptake - Gilbert's syndrome
- Reduced hepatic conjugation - Crigler-Najjar syndrome
Investigation
- ABO group and rhesus status
- Coomb's test
- Blood film and reticulocyte count
- Total and direct bilirubin
Treatment
- Phototherapy causes photo-oxidation of bilirubin
- Increases water solubility and increases urinary excretion
- Exchange blood transfusion may be required
Bibliography
Dennery P A, Seidman D S, Stevenson D K. Neonatal hyperbilirubinaemia. N Engl J
Med 2001; 344: 581-590.
Hashim M J, Guillet R. Common issues in the care of the sick neonate. Am Fam Physician 2002;
66: 1685-1692. |