U of U PA School Hyperkalemia and Hypokalemia

What is potassium? What does it do?

Main intracellular cation - 30x more in ICF than ECF

Maintain electrochemical gradient

What causes a intracellular potassium influx?

Alkalosis

Insulin

Catecholamines

How does alkalosis cause a potassium influx?

Intracellular hydrogen ion leave cell to balance pH, potassium moves in cell to maintain electroneutrality

Causes low serum potassium - hypokalemia

How does insulin cause a potassium influx?

Drives potassium into cell

Can treat hyperkalemia

How do catecholamines cause a potassium influx?

Beta activation causes potassium uptake by cells

Albuterol can treat hyperkalemia

Beta blockers can increase serum potassium

What causes a potassium efflux?

Cell lysis

Potassium concentration state dependent acidosis

Aldosterone/Addisons

How does cell lysis cause potassium efflux?

Intracellular contents - potassium - spill out into serum causing hyperkalemia

Crush injuries and rhabdomyolysis

How does acidosis cause potassium efflux?

When serum hydrogen ions are high, they move into cell and potassium leaves to maintain electroneutrality

Increases serum potassium

How does Addisons cause a potassium efflux? What does this cause?

No aldosterone = no potassium excreted and sodium not reabsorbed

Causes

-Hypotension

-Hyperkalemia

-High hydrogen ions

What should be checked if a patients potassium is not responding to treatment?

Magnesium levels

How do magnesium and potassium interact?

Magnesium blocks potassium excretion

When magnesium levels are low, potassium can be excreted easier

Affected by diuretics

What causes hyperkalemia? (5)

Decreased excretion

Drugs

Diabetes

Acidosis

Cell lysis

What causes decreased excretion of potassium?

AKI/CKD

Low aldosterone - Addisons

What drugs cause hyperkalemia? (6)

ACEi/ARBS - decrease aldosterone effect

Beta blockers - decrease cellular potassium uptake

Bactrim

Non-depolarizing paralytics

NSAIDs

Spironolaction/potassium sparing diuretics - block aldosterone

How does diabetes affect potassium levels?

Insulin decreases serum potassium

Lack of insulin increases serum potassium

DKA can cause hypokalemia due to osmotic diuresis

How can lysis occur to cause hyperkalemia?

Crush injuries

Rhabdomyolysis

Tumor lysis in chemo

What are the signs and symptoms of hyperkalemia?

Cell hyperexcitability

-Muscle depolarizes and is unable to repolarize for another contraction

--Ileus

--Weakness and respiratory failure

--Muscle cramps

--Decreased cardiac contractility

What lab and EKG changes are indicative of hyperkalemia?

Serum k+ levels >5.0 mEq/L

Peaked T waves

What are the steps to treating hyperkalemia? (6)

Aim for target around 4-4.5

Stabilize

Shift

Eliminate

Bind

Dialysis

How should stabilization be done for hyperkalemia?

Calcium gluconate or calcium chloride to stabalize the cardiac membrane potential

-Give in all cases where potassium >6.5 or EKG changes present

How do calcium gluconate or calcium chloride stabalize in hyperkalemia? What can they cause?

Restore electrochemical gradient between resting and threshold potential

Can cause spike in BP

How should shifting be done for hyperkalemia?

Insulin

-IV aspart 10U + 1 amp D50

-Check glucose before and q15 X4

Aerosolized or IV albuterol

Insulin will eventually let potassium out, this allows kidneys to clear potassium

How should elimination be done in hyperkalemia?

Lasix, increased dose in AKI/CKD

What is used for binding in hyperkalemia?

Kayexalate/sodium polystyrene sulfonate - oral GI cation exchanger

Sodium zirconium cyclosilicate - $$$ - oral GI cation exchanger - safer

Bind potassium in stomach and excrete in stool

Why is dialysis done for treating hyperkalemia?

Done for patients does not have renal capability to clear potassium

What causes hypokalemia?

Decreased intake (diet/eating disorder)

Increased losses

Transcellular shift

What can cause increased losses in hypokalemia? (4)

Vomiting/diarrhea

Excess aldosterone and corticosteroids - hyperaldosteronism and Cushings

Hyperosmotic diuresis in DKA due to huge renal losses of potassium

Diuretics - loop and thiazide

What causes a transcellular shift of potassium in hypokalemia? (4)

Alkalosis

Drugs

-Insulin

-Epinephrine

-Albuterol

At what level do symptoms begin for hypokalemia?

<3 mEq/L

What are the signs and symptoms of hypokalemia? (4)

Muscle weakness

-Ileus

-Respiratory distress

-Muscle cramping

Nausea and vomiting

What EKG changes are associated with hypokalemia?

T wave flattening with prominent U wave

PR interval prolongation

What is the treatment for mild to moderate hypokalemia?

Oral potassium chloride

Oral potassium phosphate

Oral potassium bicarb

What is the treatment for severe hypokalemia?

IV potassium chloride max 20 mEq/hour

Need large central vein and slow infusion

IV magnesium concurrent

When is empiric potassium replacement used?

Prescribing potassium with loop diuretics to prevent hypokalemia

-1/2 po Lasix dose = potassium dose approximately

How does elevated glucose cause hypertonic hyponatremia?

Elevated glucose draws water into ECF from ICF diluting sodium