Potassium Balance

Question 1

Regulation of K+ homeostasis?

Answer 1

1. Cellular shifts of potassium (99% intracellular)
2. Renal K+ excretion (90%)
3. GI K+ excretion (10%)

Question 2

Distribution of total body K+

Answer 2

Intracellular fluid - 3500 mEq (140-150mEq/L):
1. Muscles - 2700 mEq
2. Liver - 250 mEq
3. Erythrocytes - 250 mEq
4. Bone - 300 mEq
Intracellular fluid - 70 mEq (3.5-5.5mEq/L):

Question 3

Enter potassium (k) intracellular (3)?

Answer 3

1. Insulin (very fast)
2. Beta Adrenergic Agonists
3. Alkalosis
4. alpha Adrenergic Antagonists

Question 4

Exit potassium (k) intracellular (3)?

Answer 4

1. Acidosis
2. Hyperglycemia
3. Beta blockers

Question 5

Hypokalemia - DDX(5)?

Answer 5

1. PseudoHypoKalemia
2. Cell Shift
3. Inadequate Intake
4. GI Loss
5. Renal Loss

Question 6

Hypokalemia - PseudoHypoKalemia

Answer 6

Uptake by metabolically active cells:

Acute Myeloid Leukemia with marked leukocytosis

Question 7

Hypokalemia - Cell shift

Answer 7

1. Alkalosis
2. Insulin (Insolinoma, Exogenous)
3. Beta andgrenrics (Beta mymetics)
4. Anabolism (B12 for pernicious anemia, TPN, leukemia\lymphoma)
5. Hypokalemic Periodic Paralysis

Question 8

Hypokalemia - Inadequate Intake

Answer 8

Unusual as a sole casue

Question 9

Hypokalemia - GI Loss

Answer 9

Urinary K+ < 20 mEq/L
Diarrhea - most common casue
Vomiting - Due to renal K+ loss

Question 10

Hypokalemia - Renal Loss

Answer 10

Urinary K+ > 20 mEq/L

Coupling of Distal Sodium Delivery + HyperAldosternism

Question 11

Hypokalemia - ECG abnormalities

Answer 11

changes are not necessarily related to the serum potassium level:

1. ST depression
2. decrease in the amplitude of the T wave
3. increase in the amplitude of U waves which occur at the end of the T wave

Question 12

Hypokalemia - TX

Answer 12

1. Address underlying cause
2. Chronic tx: KCl - liquid or slow K
3. Acute tx: IV KCl (40-80 mEq/L, rate < 20/h)

Question 13

Hyperkalemia - DDX(4)?

Answer 13

1. PseudoHyperKalmia
2. Excess K+ intake
3. Cell Shift
4. Impaired Renal excretion

Question 14

Hyperkalemia - Cell shift

Answer 14

1. Cell injury: Rhabdomyolysis, tumor lysis, massive hemolysis, ischemia
2. Toxin\Drugs: Digoxin, succinycholine
3. DKA, nonketotic hyperosmolar state
4. Hypercalemic periodic state

Question 15

Hyperkalemia - Impaired K+ Renal excretion

Answer 15

1. HypoAldosteronism
2. Primary decrease in Na+ Delivery
3. Abnormal cortical Collecting Duct (low flow)