Sodium

Sodium is the bulk cation of the extracellular fluids. It is the principal osmotically active solute responsible for the maintenance of the intravascular and interstitial fluids.
The amount of sodium in the body is determined by the balance between intake and excretion.

Sodium content of many infant formulas is high compared with breast milk. Sodium dietary intake of older children and adolescents varies but usually high because of ingestion of fast foods and junk foods. The sodium excretion occurs through the urine, sweat and feces. The kidney is the principal organ for the regulation of sodium output.

Serum sodium of more than 150meq/liter is termed as hypernatremia. In the pediatric age group, the causes of hypernatremia are divided into 2:

1. Primary sodium excess
– improperly  mixed formula or rehydration solution
– accidental substitution of Nacl for glucose in infant formulas
– excessive sodium bicarbonate during resuscitation
– hypernatremic enemas
– ingestion of sea water
– hypertonic saline intravenous administration
– NACl used to induce vomiting
– intentional salt poisoning
– high breast milk sodium

2. Primary water deficit
– diabetes insipidus
– diabetes mellitus
– gastroenteritis
– inadequate breast feeding
– intentional withholding of water intake
– increased insensible water loss
– inadequate access to free water

When the serum sodium is below 130meq/l , it is termed as hyponatremia. Hyponatremia is caused by conditions  that create primary sodium deficits resulting in the depletion of sodium. The pediatric causes of hyponatremia are:

1. Renal losses
– prematurity
– acute tubular necrosis
– diuretics
– renal salt wasting

2. Extrarenal losses
– vomiting and diarrhea
– third space loss
– burns
– nasogastric drainage
– cystic fibrosis
– excess sweating

3. Nutritional deficits

4. Water excess with water gain
– hypothyroidism
– drugs
– excess parenteral fluid administration
– psychogenic polydipsia
– tap water enemas

5. Excess of Sodium and Water
– nephrotic syndrome
– cirrhosis
– cardiac failure
– acute and chronic renal failure