Potassium K

Elemental K+ is the major intracellular cation of the body. The normal intracellular concentration is 100 to 150 meq/L, while the normal extracellular concentration is 3.5 to 5.0 meq/L. The total body K+ store ranges from 35 to 55 meq/kg or 3500 meq in a healthy 70-kg man. Approximately 70 to 75 percent of total body K+ is found in muscle tissue; therefore, in patients with severe muscle wasting, total body stores may be as low as 20 to 30 meq/kg. Daily intake of K + ranges from 50 to 150 meq. Foods high in K+ include oranges, grapefruit, tomatoes, bananas, avocados, and raisins. K+ is excreted predominantly by the kidneys (90 percent) and with some loss in the stool and by sweating. K+ is filtered freely through the glomerulus and then reabsorbed in the proximal and ascending tubules. It is secreted in the distal tubule in exchange for Na+. In healthy individuals, the kidneys are able to excrete up to 6 meq/kg per day. Even in severe K + deficit, 5 to 15 meq/L may be excreted.

In the absence of an acid-base disturbance, measuring extracellular [K+] is a reasonably accurate way to assess total body K+ in relatively healthy patients. A decrease in measured serum [K+] from 4 to 3 meq/L represents a total body deficit of approximately 200 to 400 meq. An increase in measured serum [K+] from 4 to 5 meq/L represents a total body K+ increase of approximately 100 to 200 meq/L. Extracellular K+ represents about 2 percent of total body K+, or 70 meq, and is influenced by two important variables: total body K+ stores, and distribution between the ICF and ECF spaces. Significant and rapid intracellular to extracellular shifting occurs in response to severe injury (i.e., surgical stress, trauma, or burns), acid-base imbalance, catabolic states, increased extracellular osmolality, or insulin deficiency. These shifts are important when viewed in light of the role of K + in maintaining the resting membrane potential. The normally balanced intracellular-extracellular gradient facilitates propagation of electrical impulses. This is particularly important in the functioning of the heart.

Was this article helpful?

0 0
Diabetes Sustenance

Diabetes Sustenance

Get All The Support And Guidance You Need To Be A Success At Dealing With Diabetes The Healthy Way. This Book Is One Of The Most Valuable Resources In The World When It Comes To Learning How Nutritional Supplements Can Control Sugar Levels.

Get My Free Ebook

Post a comment