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16 Cards in this Set
- Front
- Back
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Name two activators of the Na/K ATPase pump.
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1) Insulin & 2) Beta-2 Adrenergic Agonists
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How does the hormone aldosterone influence serum potassium levels?
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Aldosterone causes sodium resorption, in exchange for potassium, in the kidney. So if potassium levels get too high, it stimulates release of aldosterone to activate the pumps that reabsorb sodium in exchange for potassium in the distal tubule and collecting ducts.
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What are the normal limits for serum potassium?
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3.5 to 4.8 mmolar
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What is the most important factor in determining serum potassium levels?
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Renal Function: 90% or more of the daily potassium turnover is due to excretion of the kidney.
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What drugs or other factors decrease aldosterone, and thus increase risk of hyperkalemia?
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ACE inhibitors, ARBs, heparin (interferes w/ the enzyme that synthesizes aldosterone), and adrenal insufficiency.
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List several drugs that inhibit renal secretion of potassium.
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Aldosterone Antagonists (spironolactone & eplerenone) and Epithelial Sodium Channel Blockers (triamterene & amiloride (the antibiotic trimethoprim has this effect as well))
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List several drugs or conditions that shift the ECF/ICF equilibrium towards hyperkalemia.
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Insulin insufficiency, beta-2 blockers, digitalis intoxication, succinylcholine, acidosis
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At what serum potassium levels will cardiac conduction disturbances and/or skeletal muscle weakness occur?
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May develop at serum [K+] > 6.5 mmol/L. Cardiotoxicity present in all cases w/ serum [K+] > 8 mmol/L.
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What ECG readings are consistent with hyperkalemia?
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Elevated T-waves appear first. They are not dangerous, but when seen, they should tip one off that the potassium is elevated because they are a classic manifestation of hyperkalemia. As levels continue to rise, the P-waves flatten, the PR interval increases, and the QRS complex widens. These lead to potentially lethal dysrhythmias.
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Above what baseline serum potassium level should an aldosterone antagonist not be added to drug therapy? Above what level should an aldosterone antagonist be discontinued?
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Don't add at [K+] of > 5.0 mmol/L. D/C if [K+] is > 5.5 mmol/L.
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What are the recommendations for spironolactone dosing in patients on an ACE-I?
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Limit spironolactone dose to 25 mg/day if on ACE-I, and avoid spironolactone if on ACE-I and GFR is < 30.
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What are the four steps to treating hyperkalemia?
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1) Minimize K+ intake, 2) Physiological antagonism w/ i.v. Ca2+ bolus 5 to 10 mEq over 3 to 5 min (if acute ECG disturbances are present), 3) Intracellular shift w/ insulin and beta-2 agonist, 4) Removal from the body via renal excretion, dialysis, or Na polystyrene sulfonate.
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How many mEq/g of Ca2+ are there in CaCl2? In Calcium Gluconate?
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CaCl2 = 13.6 mEq/g; CaGluconate = 4.8 mEq/g
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Describe dosing of insulin for treatment of hyperkalemia.
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I.V. push of 10 to 20 units regular insulin + 25 g of 50% dextrose OR i.v. infusion of 500 to 1000 mL of 10% dextrose w/ insulin 20 units over 1 hr.
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Describe use of beta-2 agonists for treatment of hyperkalemia.
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Albuterol 20 mg per nebulizer OR terbutaline 7 mcg/kg s.c. injection
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What is the brand name for sodium polystyrene sulfonate (SPS)?
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Kayexlate
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