Potassium homeostasis Flashcards
98% of potassium is intracellular or extracellular?
intracellular
what % shift in distribution of potassium can be lethal?
2%
what are the causes of hypokalemia?
- decreased intake
- increased entry into cells
- increased GI loss
- increased urinary losses
what are the symptoms of hypokalemia?
- muscle weakness
- rhabdomyolysis
- renal dysfunction
- hyperglycemia
how does hypokalemia manifest on ECG?
U waves
what are the treatment options for hypokalemia?
- treat underlying cause
- oral or IV K+
- KCl, K phos, K citrate, KHCO3, K acetate
when administering potassium the IV dose should not exceed what level?
10-20 mmol / hour
why use KCl when administering potassium?
- metabolic alkalosis is commonly associated with hypokalemia
- administration of KCl will help both the hypokalemia and the metabolic alkalosis
what drugs caused drug-induced hyperkalemia?
- NSAIDs
- ACEI
- aldosterone antagonists
- renin inhibitors
what are the EKG manifestations of hyperkalemia? severe hyperkalemia?
- hyperkalemia: peaking and narrowing of the T wave with a short QT interval
- severe hyperkalemia: widening of QRS, decreased amplitude, loss of P wave
what is the first change seen on the ECG in a patient with hyperkalemia?
tall peaked and symmetrical T wave
what is the best initial therapy for severe hyperkalemia (muscle weakness, EKG changes)?
antagonism of deleterious membrane action
what is the dosing for hyperkalemia / calcemia?
10 mL 10% Ca2+ gluconate over 2-5 minutes
what does glucose and insulin do to treat hyperkalemia?
shifts potassium into cells by increasing activity of Na/K ATPase
what does NaHCO3 do to treat hyperkalemia?
shifts potassium to intracellular space
which therapy has the greatest value in hyperkalemic patients with coexisting metabolic acidosis?
NaHCO3
NaHCO3 has the greatest value in patients with what concurrent condition?
metabolic acidosis
when is NaHCO3 cautioned for hyperkalemia therapy?
volume overload / hypernatremia
what do beta agonists do for hyperkalemia?
shift potassium to intracellular space (Na/K ATPase)
when are beta agonists cautioned for hyperkalemia therapy?
tachycardia, angina pectoris
what do diuretics do for hyperkalemia?
increased urinary potassium losses by increasing urine flow rates
what does cation exchange resins do for hyperkalemia?
exchanges K for Na
when are cation exchange resins cautioned for hyperkalemia?
- constipation
- bowel injury
- volume overload
what is the fastest and most efficient means to lower serum potassium for hyperkalemia? when is it used?
- dialysis
- used when conservative measures fail or are likely to fail
