Hyponatremia

• Sodium accounts for 90% of the extracellular cations 
• Important for electrolyte and water balance because accounts for half of the osmolarity of the ECF
• Normal serum concentration: 135-145 mEq/L
• important in generation and transmission of nerve impulses and the regulation of acid base balance
• regulated by kidneys, ADH, aldostorone

• Hypo = low (less than 135 mEq/L) 
• decreased osmolarity 
• cells are swollen: associated w ECF hypo-osmolarity from excess water. To restore balance, fluid shifts out of the ECF and into the cells, leading to cellular edema
• 

• Direct Loss of Na+
  • GI losses: diarrhea, vomiting, fistulas, NG suction
  • Renal losses: diuretics, adrenal insufficiency, Na+ wasting renal disease
  • Skin losses: burns, wound drainage
• Excess water in ECF which dilutes Na+ conc
  • SIADH: syndrome of inappropriate secretion of antidiuretic hormone (retain water)
  • Heart failure
  • Excessive hypotonic IV fluids
  • Excessive water intake (polydipsia

• irreversible neurological damage or death from brain herniation can occur
• rapid, weak thready pulse
• postural hypotension
• Brain Swelling : headache, lethargy, headache, confusion, apprehension
• nausea vomiting
• low BP

• water excess treatment: fluid restriction, for severe symptoms (seizures): small amts of IV hypertonic saline solution is admin to restore the serum sodium level while the body is returning to a normal water balance
• sodium-containing fluid loss treatment: fluid replacement w sodium-containing solutions
• oral rehydration fluids containing electrolytes may help prevent it (home setting)

Nursing 

• monitor serum sodium levels and pts response to therapy to avoid rapid correction or over correction
• record I&O