Minerals in newborn (Calcium, phosphate and magnesium)

Hypocalcaemia

Definition

• Serum total calcium <1.7 mmol/l or ionised calcium <0.7 mmol/l
• Treatment is often started at lower levels

Risk groups

• Preterm
• Infant diabetic mother
• Asphyxiated infants
• During exchange transfusion

Treat if

• serum total calcium <1.5 mmol/l or
• symptomatic

Use oral route where possible

See

• enteral supplements for oral use
• calcium monograph for iv replacement

Hypercalcaemia

A rising serum calcium is sometimes seen in preterm babies who are totally parenterally fed.  This is secondary to hypophosphataemia which may need treatment with intravenous phosphate.

Hypophosphataemia

Definition

• Serum phosphate <1.5 mmol/l
• Treatment levels will depend on clinical situation

Risk groups

• Preterm
• Breast milk fed
• Parenteral nutrition

Treat if

• Preterm, breast fed and serum phosphate <1.0mmol/l
• Preterm, parenteral nutrition and serum calcium >2.9mmol/l

Note :

• Some formula fed preterm babies may need extra phosphate supplementation if the serum phosphate is <1.0mmol/l and not increasing with the formula milk.  This is a Consultant decision.
• Preterm babies with alkaline phosphatase >1000u/l may need phosphate supplementation even if serum phosphate within acceptable range.  This is a Consultant decision.

Use oral route where possible

See

• enteral supplements for oral use
• phosphate monograph for iv replacement

Hypomagnesaemia

Definition

Serum magnesium <0.7mmol/l

Diagnosis

Check serum magnesium in unexplained convulsions or persistent hypocalcaemia

Management

• Magnesium sulphate 50%
• 0.2ml/kg intramuscular, as a single dose
• Rarely oral maintenance therapy required, 0.2ml/kg/day

Treatment with magnesium may cause neuromuscular blockade with transient weakness and hypotonia.