Hyponatraemia

What are the symptoms and signs of hyponatraemia? Calculate the sodium deficit in a 70 Kg adult male with serum sodium of 122mmol/L. How will you replace the deficit?

Hyponatremia is a plasma sodium concentration less than 135 mEq/L.

S/S of hyponatraemia:

·        Nausea/vomiting

·        Visual disturbances

·        Depressed levels of consciousness

·        Agitation,confusion,coma

·        Muscle cramps,weakness and myoclonus

·        Coma and death

Sodium deficit in a 70kg male with serum sodium of 122mmol/L

Na+ deficit = TBW*(140-122)

TBW is approximately 60% of body weight in males(TBW is total body water)

Na+ deficit = 70*0.6*(135-122)=756 mEq/L

Replacement of the deficit:

The optimal rate of correction seems to be 0.6 to 1 mmol/L/hr until the sodium concentration is 125 mEq/L; correction then proceeds at a slower rate.
 One half the deficit can be administered over the first 8 hours, and the next half can be administered over 1 to 3 days if symptoms remit. Sodium concentration should be monitored every 1 to 2 hours during rapid correction.
Menstruanting female patients are at greater risk for developing significant neurologic sequelae after hyponatremia., Estrogens seem to alter the function of Na⁺/K⁺-ATPase in the rat brain, which could alter the brain's compensatory mechanisms for hyponatremia.
Management of hyponatremia involves elimination of the underlying condition when possible (e.g., stop TURP syndrome as soon as possible).

The use of normal saline (308 mOsm/L) alone may worsen the hyponatremia, depending on the patient's serum and urine osmolality  Severe coma or seizures can be managed with one or more approaches, including 3% hypertonic saline (513 mEq/L), fluid restriction, or furosemide