Potassium Flashcards
What is the most prevelant intracellular cation?
K
What is the intracellular concentration?
140
What is the normal serum level of K?
3.5-5
What is potassium required for?
cellular metabolism and growth, protein and glycogen synthesis
What does K determine?
the resting membrane potential across the cell membrane (cardiac conduction activity)
What determines the plasma potassium level?
relationship between K intake, GI and urinary excretion, hormones, acid base balance, and body fluid tonicity
What does insulin do to K?
How?
insulin increase uptake of K into the cell
it stimulates Na/K ATPase
What does NE do to K?
How?
increase uptake of K into the cell
stimulates Na/K ATPase
What does aldosterone do to K?
How?
promotes the excretion of K
through its effects on the Na/K ATPase in the collecting duct
What does an increase in K in the ECF do?
increases Angitensin II which stimulates Aldosterone
What role does PH play on K?
in metabolic acidosis, the cells uptake H, and push out K
Is the relationship between serum potassium and TBK linear?
How can you estimate?
no
a drop in 1 Meq/L (4-3) is equivalent to -200 to -400 in TBK, an increase in 1 Meq/L (3-4) is equivalent to 100-200 + in TBK
How is Hypokalemia defined?
decreased intake of K, increased movement into the cells, or most commonly increased losses from the urine, loss from GI or sweat
Give example of how hypokalemia can occur?
Give specific examples.
increase in extracellular Ph, icnreased insulin, , vomiting, diuretics, increased urinary loss in metabolic acidosis, polyuria
What are the most common causes of durg induced hypokalemia?
loop and thiazide
What are the 3 ways that drugs induce hypokalmia?
trancellular potassium shift, increased renal potassium loss, excess potassium loss in stool
Give examples of trancellular shifts?
B-adrenergic agonists, chlorquine, insulin overdose
Give examples of increased renal potassium loss?
diuretics, drugs associated with magnesium depletion
Give examples of potassium loss in stool?
phenolphthalein
What is the 2nd most common cause of hypokalemia?
GI loss of potassium rich fluids through vomiting and diarrhea
What percent of people also have hypomagnesia?
40%
What does hypokalemia do?
decreases intracellular potassium by impairing the function of the Na/K ATPase pump- promotes renal K wasting by unknown mechanism
When symptoms of hypokalemia occur how do they occur?
impairment of cardiovascular and/or muscular activity
What are 3 cardiac manifestations of hypokalemia?
hypertension, arrhythmias, ECG changes