Hypernatraemia

E87.0

DESCRIPTION

A serum sodium level >145mmol/L.

  • Mild to moderate symptoms: Lethargy, weakness, irritability
  • Severe symptoms: Convulsions, coma

It is usually due to inadequate water intake (decreased thirst sensation or inability to drink water) or due to gastro-intestinal losses (vomiting, diarrhoea) or renal losses (diabetes insipidus, osmotic diuresis, furosemide).

GENERAL MEASURES

Treat the cause.

Calculate the water deficit:

Water deficit = (total body water)*(1-(140/Na))

Total body water = correction factor * weight.

(The correction factor is 0.6 for men, 0.5 for women and elderly men, and 0.45 for elderly women).

Online calculator: http://www.nephromatic.com/water_deficit.php

MEDICINE TREATMENT

Correction fluid:

  • Oral fluids or via NGT.
  • Dextrose 5%, IV infusion.
    • Monitor for hyperglycaemia. Rate of correction of hypernatraemia should be slower than 10 mmol/L over 24 hours to prevent cerebral oedema.
    • Ongoing obligatory water loss through skin and stool (estimated at 30 mL/hour) must also be replaced.

LoEIII [12]

Desired water replacement in the first 24 hours = Water deficit x 10 mmol/L ÷ (Serum [Na] – 140)

Hourly infusion rate = Desired water replacement in the first day ÷ 24 hours + 30 mL/hour.