Urea and electrolytes

Urea and electrolytes

1. Na+

   • extracellular cation
   • Hyponatremia (Na <120 mmol/L)
     • due to either loss of sodium or overload of water or both.&nbsp; The following list contains the relatively common and important causes of hyponatraemia.&nbsp; For more complex cases, it is necessary to have simultaneous samples of both blood and urine for estimation of osmolality and electrolytes.
     • + edema
       • CCF
       • Liver failure
       • nephrotic syndrome
     • +dehydration
       • diarrhea
       • Addison's disease
       • Renal salt wasting
     • +normal volume
       • D + V follwed by drinking excess water
       • diuretics
         • Monitoring: Prior to the initiation of therapy and after 2/52, 3/12, 6/12 and then 6-12/12&nbsp; or more frequently in the elderly or in patients with renal disease, disorders affecting electrolyte status or those patients taking other drugs eg corticosteroids, digoxin.
         • may occur w/in 1-2 weeks of initiation of therapy but may develop after many years of therapy
       • ACE inhibitors
     • + innapprop ADH secretion
       • drug therapy
       • chest disease
       • CNS disease
     • complications varied
       • from seizures and coma in younger ppl,&nbsp; wherby chronic diuretic therapy can bring down hugely in old ppl w/little effect

2. K+

   • intracellular cation
   • hyperkalemia (K >5.5 mmol/L)
     • hemolysis and delayed separation over-night storage in a 'fridge'
     • renal failure
     • potassium retaining diuretics (eg spironolactone)
     • ACE inhibitors
   • hypokalemia (K < 3.5 mmol/L)
     • diuretics
     • D + V
     • ileostomy
     • chronic purgative abuse
     • excessive liquorice
     • elderly pts w/poor nutrition (catabolic state)

3. Urea

   • waste product formed from 2 ammonia + 1 CO2, allows excretion of excess nitrogen from body
   • Low
     • pregnancy
     • starvation
     • chronic liver disease
   • High
     • renal failure
       • high urea with a normal creatinine often points to dehydration or CKD.
     • dehydration
     • transiently after eating high protein meal
     • following a significant gI bleed

4. Creatinine

   • waste product formed from creatine in muscles, renally excreted serves as measure of renal function
   • high
     • dehydration
     • dietary intake
     • renal failure
     • body building
   • low
     • low or falling muscle mass
       • eg very old, malnourished

5. bicarbonate

   • important anion (-) in acid base balance balances H+
   • low
     • metabolic acidosis
       • renal failure
       • GI fluid losses
   • high
     • respiratory acidosis
       • CO2 retention in COPD