Diseases of Potassium Regulation Flashcards
Cortisol is prevented from activating the aldosterone receptor by ___________.
the enzyme 11-ß-hydroxysteroid dehydrogenase (11ßHDH) which converts it to cortisone
Low serum potassium can result from three things. What are they?
Spurious (high WBC) Decreased total body potassium (decreased intake or increased GI/renal losses) Transcellular shift (due to stress)
What medications and physiological states can cause hypokalemia from cell shift?
Stress
ß2 agonists
Alcohol or drug withdrawal
Insulin excess
Through what urine test can you decide if hypokalemia is renal or extrarenal?
Urine potassium less than 20 mEq/L = extrarenal
Urine potassium greater than 20 20 mEq/L = renal
What is a cause of extrarenal hypokalemia in a patient with metabolic acidosis?
Diarrhea
Nonselective ß-blockers do what to serum potassium?
They prevent serum potassium from moving into cells. (Selective ones do not.)
There are two causes of extrarenal hypokalemia. Both will have urine K less than 20 mEq/L. What are they and how can you differentiate?
Diarrhea (indicated by metabolic acidosis) Decreased intake (indicated by normal pH)
There are three kinds of true hypokalemia from renal causes (as shown by urine potassium greater than 40 mEq/L). What are they?
Metabolic alkalosis (indicated by high pH) Decreased magnesium (indicated by normal pH) Metabolic acidosis (such as in renal tubular acidosis or DKA)
How can you differentiate the two types of hypokalemia from renal causes presenting in metabolic alkalosis?
Test the urine chloride. Cl less than 20 mEq/L indicates overuse of diuretics. Cl greater than 20 mEq/L with high BP indicates primary hyperaldosteronism or Cushing’s, and Cl greater than 20 mEq/L with low BP suggests Bartter’s or Gitelman’s syndromes.
If someone has symptomatic hypokalemia, then give them ____________.
up to 40 mEq/L potassium and monitor their ECG
If a patient has hyperkalemia, first ___________.
do an ECG; if that is normal, then do another lab to confirm that the hyperkalemia is real
What can cause acute hyperkalemia (transcellular shift)?
Inadequate insulin management in a diabetic
Nonselective ß-blockers
Rhabdomyolysis
Hyperkalemia is almost never caused by _____________.
increased dietary intake
Go through the C A BIG K Drop mnemonic.
Calcium Albuterol (or other ß-agonist) Bicarbonate Insulin Glucose Kayexalate Dialysis
Anion gap acidosis causes more _________ than non-anion gap acidosis.
hypokalemia
