Features
Implications
- Foetal haemoglobin (HbF) forms, 70-90% of the haemoglobin molecules at birthDrops to around 5% HbF by 3 months with HbA predominating
- Foetal haemoglobin contains less 2,3-DPG and combines more readily with oxygen
- Allows the foetus is able to retrieve oxygen from maternal blood
- Haemoglobin levels change rapidly with age:
- Newborn born with levels 180-200 g/L
- Levels drop over 3-6 months to 90-120 g/L
- Stabilises thereafter to at approximately 130 g/L
- Haemoglobin levels should be interpreted in an age dependent manner
- Development of the coagulation system not complete until about 6 months of age
- Vitamin K dependent factors are 70% of adult values at birth
- Vitamin K is given at birth to prevent haemorrhagic disease of the newborn
- Coagulation screening tests are prolonged in normal infants up to the age of 6 months, which is reflected in values for the normal ranges
- Total blood volume smaller in children than infants
- Relative blood volume per unit mass larger in the newborn and decreases with age
- Lower total blood volume leads to reduced tolerance for blood loss during surgery or trauma
- Transfusion is generally recommended when 15% of the circulating blood volume has been lost
- Higher relative blood volume required to support higher basal metabolic rate
- Affects pharmacokinetics of certain drugs