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Total Body Potassium and ECF Estimates

Total Body Potassium and ECF Estimates


Total Body Potassium

Background


Total Body Potassium

Key facts:

  • Potassium is the major intracellular cation. 98% of the total body potassium is in the intracellular compartment with only 2% located extracellularly (plasma).
  • The ratio of intracellular to extracellular potassium is the major determinant of the resting membrane potential. It  helps establish the resting membrane potential in neurons and muscle fibers.
  • Potassium has very little effect on osmotic pressure unlike sodium in the ECF.
  • Potassium is excreted, both actively and passively, through the renal tubules, especially the distal convoluted tubule and collecting ducts.
  • The primary substance regulating the serum potassium concentration is aldosterone.
  • The daily intake of potassium in the western diet is between 80-120 mmol.
  • The kidney is the major route of potassium excretion, accounting for 90% of potassium loss daily. The remaining 10% is excreted through the gastrointestinal tract.
  • The kidney is responsible for long term potassium homoeostasis.

Potassium Content in the Body

  • Dependent on sex, age, and, most importantly, muscle mass which contains 60 to 75% of total body potassium.
  • Total body potassium estimates for normal adult women and men:
    Female: approximately 40 to 45 mmol/Kg
    Male:  50 to 55 mmol/kg of body weight.
    Elderly:  Values are 20% less (decrease in muscle mass).
    Intracellular (ICF):  ~2% of total body potassium.

 

Required Entries


Data points:




Weight: 

Patient Height: 


Gender: 

Is the patient elderly (65 years of age or older) ?

 


heart

 
 






Reference top of page

Cheng YL, Yu AW. ELECTROLYTES - Water-Electrolyte Balance: in Encyclopedia of Food Sciences and Nutrition (Second Edition), Oxford: 2003. https://doi.org/10.1016/B0-12-227055-X/00395-3.

Potassium Content in the Body:
The total body potassium content is dependent on sex, age, and, most importantly, muscle mass (which contains 60-75% of total body potassium), and is approximately 40-45, and 50-55 mmol per kilogram of body weight for normal adult women and men, respectively. These values decrease with age and are 20% less in the elderly because of a decrease in muscle mass.

 

References top of page

 

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  6. Kamel KS, Quaggin S, Scheich A, et al. Disorders of potassium homeostasis: an approach based on pathophysiology. Am J Kidney Dis 1994;24:597–613.
  7. Kardalas E, et al. Hypokalemia: a clinical update. Endocrine Connections (2018) 7, R135–R146.
  8. Kim GH, Han JS. Therapeutic approach to hypokalemia. Nephron. 2002;92(suppl 1):28-32.
  9. Lippi G, Favaloro EJ, Montagnana M, Guidi GC. Prevalence of hypokalaemia:the experience of a large academic hospital. Intern Med J. 2010;40(4):315-316.
  10. Rastergar A, Soleimani M. Hypokalaemia and hyperkalaemia. Postgrad Med J 2001;77:759–764.
  11. Viera AJ, Wouk N. Potassium Disorders: Hypokalemia and Hyperkalemia.Am Fam Physician. 2015;92(6):487-495.
  12. Weiner ID, Wingo CS. Hypokalemia-consequences, causes, and correction. J Am Soc Nephrol. 1997;8(7):1179-1188.
Total Body Potassium and ECF Estimates