Hyperkalemia

Question 1

What is considered hyperkalemia?

Answer 1

Serum K+ >=5.0mEq/L

Question 2

What is considered hypokalemia

Answer 2

Serum K+<=3.5mEq/L

Question 3

Why is hyperkalemia a problem?

Answer 3

• Cell swelling
• Intracellular alkalosis
• Resting cell membrane potential is reduced–>depolarization
• NM activity: increased excitability–>paralysis
• Cardiac conduction disturbances
• Vasodilation

Question 4

Pseudohyperkalemia

Answer 4

• In vitro hemolysis
• Leukocytosis
• Thrombocytosis
• Fist-clenching during blood drawing

Question 5

Pseudohyperkalemia

Answer 5

• In vitro hemolysis
• Leukocytosis
• Thrombocytosis
• Fist-clenching during blood drawing

Question 6

Can excessive K intake cause hyperkalemia?

Answer 6

Transiently and mildly

Question 7

What can cause hyperkalemia due to “too little out”?

Answer 7

• Low GFR (AKI, CKD)
• Impaired RAAS
• Inadequate distal tubule Na delivery and urine flow

Question 8

Causes of reduced aldosterone synthesis?

Answer 8

• Addison’s (adrenal insufficiency)
• Genetics
• Type IV RTA with hyporeninemic hypoaldosteronism
• Drugs (NSAIDs inhibit renin synth, ACE inhib and ARB, heparin, cyclosporine and tacrolimus)

Question 9

Causes of impaired responsiveness to aldosterone?

Answer 9

• Drugs
• Tubulointerstitial kidney disease
• Pseudohypoaldosteronism

Question 10

Examples of drugs that cause aldosterone resistance?

Answer 10

Amiloride, triamterene, trimethoprim, pentamidine (ENaC)

Spironolactone, eplerenone (A-Receptor)

Question 11

Causes of hyperkalemia due to abnormal internal balance

Answer 11

• Insulin deficiency
• Hypertonicity
• Metabolic acidosis
• Drugs
• Exercise
• Tissue damage, muscle necrosis, cell lysis
• Hyperkalemic periodic paralysis

Question 12

Insulin effect on K

Answer 12

Insulin causes K to go into cells (muscle and liver cells)

• with fasting/DM, plasma K+ increases
• insulin stimulates Na-K ATPase
• Can give insulin and glucose together (give glucose to avoid hypoglycemia)

Question 13

How does hypertonicity cause hyperkalemia?

Answer 13

1. Solvent drag

2. Intracellular [K] increases with decreasing intracellular water so it goes with its concentration gradient

Question 14

What acid/base disturbance causes hyperkalemia?

Answer 14

Metabolic acidosis

Question 15

Clinical manifestations of hyperkalemia

Answer 15

• ECG changes and cardiac arrhythmias (resting membrane potential becomes less negative)
• Muscle weakness/paralysis
• Paresthesias
• Impaired urinary acidification

Question 16

Steps of emergency treatment of severe acute hyperkalemia?

Answer 16

1. Antagonize cardiac effects
2. Move K from the ECF into cells
3. Remove K from the body

Question 17

Mechanisms to antagonize cardiac effects of hyperkalemia

Answer 17

• Calcium gluconate (MOA unclear)

- Ca infusion does NOTHING to serum [K]

Question 18

B2 agonists effect on k

Answer 18

Increase cellular uptake of K by stimulating Na-k ATPase, primarily in the muscle and liver

Question 19

Sodium bicarb effect on K

Answer 19

In theory, H+ leaves cells and K+ enters, but really this is ineffective unless in the setting of metabolic acidosis

Question 20

Emergency treatment of hyperkalemia

Answer 20

K removal

• Loop diuretics
• Cation exchange resin-sodium polystyrene sulfonate (kayexalate): K leaves in stool
• Hemodialysis

Question 21

Management of chronic hyperkalemia

Answer 21

• Reduced intake
• Review medications
• Increase Na intake
• Diuretics
• Kayexalate
• Fludrocortisone