Q1. What are diseases of water balance?

Total body water and tonicity is tightly controlled by renal actions of antidiuretic hormone (ADH), renin angiotensin-aldosterone system, norepinephrine and by the thirst mechanism. Abnormalities in water balance are presented as sodium disturbances-hyponatremia and hypernatremia.

Q2. How do we describe hyponatremia?

Hyponatremia [Na+ <136 meq/l] is a common abnormality in hospitalized patients and is associated with increased morbidity and mortality. A frequent cause of hyponatremia is impaired renal water excretion either due to low extracellular fluid volume or inappropriate secretion of ADH. The determination of the cause of hyponatremia through total body water and urine assessment is essential in guiding treatment of hyponatremia.

In acute and severe forms, hyponatremia may lead to neurological symptoms which makes rapid correction with hypertonic saline essential.

Q3. What is the role of monitoring in hyponatremia?

Frequent monitoring of sodium is essential in the treatment of sodium disorders. Rapid correction of sodium concentration may lead to osmotic demyelination syndrome, brain injury and possibly death, Hence, serum sodium correction with normal saline or through the introduction of a vasopressin receptor antagonist must not occur at more than 0.5 mmol/h, or more than 12 mmol/d. Patients should be in a setting where they can be easily monitored.

Q4. Does the type of hyponatremia affect treatment?

Although there are several approaches to the management of hyponatremia, a commonly used approach practiced by nonexpert clinicians starts with an examination of extracellular fluid (ECF) volume status. Since diabetes is commonly prevalent in adult population, clinicians should be alert about ruling out hyperosmolar hyponatremia caused by hyperglycemia as a probable cause of hyponatremia. The clinical history and physical examination of the patient may provide important diagnostic clues which may help in classifying the type of hyponatremia (hypovolemic, euvolemic or hypervolemic) and guide appropriate treatment.

Q5. When should hypertonic saline be administered?

Any patient who presents with neurologic compromise or seizures as a result of hyponatremia needs urgent correction of serum sodium level, irrespective of the rate of the fall in sodium. Correction is accomplished by use of intravenous hypertonic sodium chloride, usually at a concentration of 3%, at 1-2 mL/Kg/h in a monitored setting The cause of hyponatremia should be determined from the patient’s history and physical examination and should be managed based on the volume status of the patient.