Hypokalemia

Question 1

What is the definition of hypokalemia?

Answer 1

Potassium concentration < 3.5 mEq/L

Question 2

What are the clinical features of hypokalemia?

Answer 2

1. Asymptomatic
2. Musculoskeletal - muscle weakness, cramps, paralysis, decreased reflexes
3. CVS - hyperpolarization of cells, delayed conduction, arrhythmias
4. ECG changes - flat inverted T waves, prominent U waves, ST depression

Question 3

What ECG changes are seen in hypokalemia?

Answer 3

flat inverted T waves
prominent U waves
ST depression

Question 4

What is the differential diagnosis of hypokalemia?

Answer 4

1. Intracellular shift
2. Renal loss
3. GI loss

Question 5

What can cause hypokalemia via shift into the intracellular space?

Answer 5

medications (beta 2 agonist, phosphodiesterase inhibitors, calcium channel blockers, exogenous insulin)
hyperthyroidism
delirium tremens
familial periodic paralysis

Question 6

What can cause renal loss of potassium resulting in hypokalemia?

Answer 6

medications (diuretics, exogenous mineralocorticoids, penicillin, cisplatin)
mineralocorticoid excess (primary hyperaldosteronism, Cushing disease, renin secreting tumors)

Question 7

How might penicillin affect potassium levels?

Answer 7

It may cause hypokalemia via renal loss of potassium.

Question 8

How might cisplatin affect potassium levels?

Answer 8

It may cause hypokalemia via renal loss of potassium.

Question 9

What is the management of hypokalemia?

Answer 9

1. Treat underlying cause
2. Replace potassium orally or intravenously
3. Monitor ECG

Question 10

How would you dose and administer potassium for treatment of hypokalemia?

Answer 10

Central line preferred if it can’t be given orally. 20 mEq KCL in 100cc NS infused at 10 - 20 mEq/hr.