HYPONATREMIA: Causes, Assessment, Intervention

 Hyponatremia

Description 

Hyponatremia is a serum sodium level lower than 135 mEq/L.  Sodium imbalance usually is associated with fluid volume imbalance. 

CAUSES 

Increased sodium excretion 

• Excessive diaphoresis
• Diuretics 
• Vomiting 
• Diarrhoea 
• Wound drainage, especially gastrointestinal 
• Renal disease 
• Decreased secretion of aldosterone

Inadequate sodium intake

• Nothing by mouth
• Low-salt diet

Dilution of serum sodium 

• Excessive ingestion of hypotonic fluids or irrigation with hypotonic fluids 
• Renal failure
• Freshwater drowning 
• Syndrome of inappropriate antidiuretic hormone secretion 
• Hyperglycemia 
• Congestive heart failure 

ASSESSMENT 

Cardiovascular 

• Symptoms vary with changes in vascular volume 
• Normovolemic: Rapid pulse rate, normal blood pressure 
• Hypovolemic: Thready, weak, rapid pulse rate, hypotension, flat neck veins, normal or low central venous pressure 
• Hypervolemic: Rapid, bounding pulse, blood pressure normal or elevated, normal or elevated central venous pressure 

Respiratory 

• Shallow, ineffective respiratory movements as a late manifestation related to skeletal muscle weakness 

Neuromuscular 

• Generalized skeletal muscle weakness that is worse in the extremities 
• Diminished deep tendon reflexes 

Cerebral function 

• Headache 
• Personality changes 
• Confusion 
• Seizures
• Coma

Gastrointestinal 

• Increased motility and hyperactive bowel sounds
• Nausea 
• Abdominal cramping and diarrhoea 

Renal

• Decreased urinary specific gravity 
• Increased urinary output

INTERVENTION 

• Monitor cardiovascular, respiratory, neuromuscular,  cerebral, renal, and gastrointestinal status.
• If hyponatremia is accompanied by a fluid deficit, IV sodium chloride infusion are administered to restore sodium content and fluid volume. 
• If hyponatremia is accompanied by fluid excess, osmotic diuretics are administered to promote the excretion of water rather than sodium. 
• If the cause is inappropriate or excessive secretion of antidiuretic hormone,  medications that antagonize antidiuretic hormones, such as lithium and demeclocycline,  may be administered. 
• Instruct client to increase oral sodium intake and inform the client about the foods to include in the diet.