#32 - Potassium Flashcards
Which 5 things can change the INTERNAL regulation of potassium?
- insulin
- catecholamines
- acid/base balance
- plasma tonicity
- cell lysis/proliferation
T/F: EKG is an important part of the workup in potassium disorders.
TRUE - Cardiac death can occur due to altered potassium, and urgent intervention may be needed. You can track changes via serial EKG monitoring.
Goals of therapy for hyperkalemia - 3
- stabilize the cardiac membrane
- shift potassium intracellularly
- remove excess K+
T/F: Hyperkalemia, but not hypokalemia, can lead to cardiac dysrhythmias.
False. They both lead to cardiac dysrhythmias.
T/F 2/3 of patients die if their hyperkalemia is not treated.
True.
Normal range for potassium
3.5-5.0 mEq/L
T/F The Potassium gradient is largely maintained by the Na/K ATPase pump, which pumps K out of the cell.
False. The pump pumps K+ INTO the cell (98% of K+ in the body is inside cells)
What does “internal balance” of K+ refer to?
the distribution of K+ between intracellular fluid and extracellular fluid
What does “external balance” of K+ refer to?
regulation of potassium through K+ intake and excretion (mainly kidney)
Which cell is most responsible for K+ excretion in the kidney?
Principle cell, in the collecting duct.
K+ excretion in the kidney is dependent on 2 things:
- distal sodium delivery
- aldosterone
Describe excretion of K+ in the kidney, including role of Na and aldosterone
sodium arrives in collecting duct. Sodium comes into the principal cell through ENaC,–>
charge in urine becomes negative—> negative charge attracts which pulls potassium out of the principal cell into the lumen.
Aldosterone activates ENaC (Na channel), and K channel, helping both steps of the process.
Insulin effect on K+
Insulin lowers K+
Insulin activates the Na/K ATPase pump, pushing K inside the cells of the liver/ muscle.
Catecholamines effect on K+
Catecholamines lower K+
Norepinephrine and epinephrine activate the Na/K ATPase through B2 adrenergic receptors.
How does being acidotic affect your K+?
Raises K+
If your bloodstream is acidotic, it will send H+ ions inside the cell to reduce acidity, in exchange for K+ ions, which leak out of the cell, raising your K+.
How does plasma tonicity affect K+?
Increased plasma tonicity (eg, increased sugar in blood) = increased K+, since it follows water out of the cells. (solvent drag)
How does diabetes cause hyperkalemia (2 ways)
- increased sugar in the bloodstream causes efflux of water to balance tonicity, dragging K+ with it.
- low insulin does not allow for as much K+ absorption into the muscle and liver with meals, raising K+.
How does cell lysis/cell proliferation affect potassium?
- Cell lysis releases intracellular K+ (tumor lysis)
- Cell proliferation eats up K+
Therefore, cancer can cause hypokalemia or hyperkalemia
Why does volume depletion decrease distal sodium delivery?
through ADH and aldosterone - increased Na uptake IN THE PROXIMAL tubules, before it gets to the collecting duct.
4 ways hyperkalemia can happen through disorders of EXTERNAL balance
- kidney disease (acute or chronic)
- decreased distal sodium delivery to the collecting duct (volume depletion)
- mineralocortidoid (aldosterone) deficiency (ACEi’s, ARBs)
- distal tubular dysfunction (interstitial nephritis)
What drugs can cause hyperkalemia through messing with aldosterone?
- ACE inhibitors
- ARBs.
- Spironolactone (aldosterone antagonist.)
2 main symptoms that hyperkalemia can cause
- mm weakness (ascending)
- cardiac toxicity
Treatment for hyperkalemia
1 - Calcium gluconate to protect heart (membrane stabilization)
2-EKG monitor
3-Glucose+insulin to push K+ inside cells
How should Calcium gluconate be dosed?
it acts in 1-3 minutes. Repeat the dose if EKG changes don’t go away instantly.
