Hypernatraemia

Introduction

A high concentration of sodium in the blood is known as hypernatraemia. It  is as plasma sodium of more than 145 Millimoles per liter.
Majority of cases result from water loss in the absence of sodium loss, when the thirst mechanism is impaired, or (infrequently) due to primary sodium gain

Clinical features

Mainly neurologic:

  • Altered mental status
  • Weakness
  • Neuromuscular irritability
  • Focal neurological deficits
  • Occasionally coma and seizures

As in hyponatraemia severity of the clinical features are related to the rapidity of onset and the magnitude of the rise in plasma sodium concentration

Treatment objectives

  • Correct water deficit
  • Stop on-going water loss.

Calculation of water deficit

Deficit = (Plasma Na -140)/140 × 0.5(males) or 0.4 (females) × body weight in kg

  • Water replacement in glomerulo nephropathy
  • Mineralocorticoid excess (primary deficit should be corrected slowly over 48-72 hours to prevent cerebral oedema
  • Water replacement can be given by mouth or nasogastric tube pressure
  • Glucose 5% injection is also suitable for water replacement, being a hypotonic fluid mmHg