What is Hypernatraemia?

Hypernatraemia is a condition when the sodium levels in blood increase beyond the normal levels. Clinically it is defined as plasma sodium levels more than 145mEq/L.

Elderly people with poor thirst sensations (impaired thirst mechanisms) are at high risk of developing Hypernatraemia.

Understanding Hypernatraemia?

It is much less common compared to Hyponatraemia (decreased sodium levels) as even a little rise in the sodium concentration above the normal limits makes a person very thirsty. The intake of water rapidly balances the sodium levels. Hypernatraemia develops, more commonly in elderly, when the thirst mechanism fails or when a person fails to gain access to water.

All body cells require sodium for better functioning and equilibrium. Hence, the levels are very tightly maintained between 135-145mEq/L. The most sensitive cells to get affected by any fluctuation of sodium are the brain cells (neurons).

Since cells now face an imbalance of sodium on their outside compared to their insides (the levels outside the cells are higher than the levels inside the cells), the cells try to re-attain equilibrium by moving water to the exteriors.

Since the sodium is in excess outside the cells, water from inside the cells oozes out to correct the imbalance and this causes the cells to get dehydrated, and that is the reason a person feels thirsty.

If the condition persists for a long time, i.e. days, weeks, months, the cells adapt by accumulating organic solutes inside and thus building up concentration inside the cell to match the outside.

How common is Hypernatraemia?

1% hospitalized patients and those seeking long term treatment.

In the elderly, the fatality is as high as 70% due to age-related kidney dysfunction that is likely to be present. In the elderly, the kidney is less likely to efficiently handle the changes in electrolytes even if treatment is rapidly started.

What are the symptoms of Hypernatraemia?

  1. Extremely thirsty
  2. Dry mouth
  3. Muscle rigidity, twitching, brisk reflexes
  4. Rhabdomyolysis (rupture of muscle cells) causing sudden kidney shut down.
  5. Irritability and mental confusion
  6. Convulsions
  7. Disorientation and coma

What are the risk factors for Hypernatraemia?

Elderly are especially at risk since the kidney is aged and not as capable of managing electrolytes as it was in youth. At the same time the thirst mechanism that should get triggered on developing higher concentrations also gets impaired with age.

Bedridden patients who are at the mercy of care givers for their food and water intake may also develop Hypernatraemia due to inadequate intake of water.

What are the causes of Hypernatraemia?

  1. Excessive water loss
    • Vomiting diarrhea
    • High-grade fever
    • Patient on ventilator
    • Kidney dysfunction
    • Hypothalamic dysfunction (central diabetes insipidus)
    • Thyroid disease
    • Inability to swallow
    • Hot environment
  2. Increased salt intake
    • Excess ingestion of salt
    • Hypertonic saline administration, especially in elderly

What are the complications with Hypernatraemia?

Neurological complications appear sooner in elderly compared to younger individuals. In extreme cases, the mortality in elderly is 70% compared to 50% in children.

Thrombosis (formation of clots) and bleeding in the brain are likely. It may lead to seizures.

Seizures may cause muscle break down and this may lead to sudden rapid increase in sodium. Muscle damage leads to sudden kidney shutdown also. Multi-system dysfunction sets in soon.

How is Hypernatraemia diagnosed?

  • Plasma sodium levels > 145mEq/L
  • Haematocrit usually >50%
  • Raised blood urea levels
  • Urine specific gravity >1.010

How is Hypernatraemia treated?

Identification and treatment of the underlying cause is the cornerstone of treatment. In acute conditions giving patients water to drink can cure the ailment.

In Hypernatraemia developing over days and weeks correction is made gradually otherwise the cells may swell due to uptake of suddenly excessive water. Correction is done with half normal saline (0.45% against 0.9% normal saline)

Normal urine output of about 1500ml/day is targeted.

How to take care of someone with Hypernatraemia?

Caregivers should be sensitive to the water requirements of their elderly dependants especially if they are on any long term medication.

  • Water intake should be regulated and ensured as per the guidelines given by the physician.
  • High salt foods like pickles, papads, bakery products and added salt in food should be avoided.
  • If the patient is diabetic, blood sugar should be strictly controlled.
  • Vomiting and diarrhea in elderly need to be reported immediately and treated aggressively.

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