12_HST110 Potassium Disorders 2017

Question 1

What are the threshholds for Hyper- and Hypo-kalemia?

Answer 1

Hyperkalemia: [K+] > 5.0 mEq/L

Hypokalemia: [K+] < 3.5 mEq/L

Question 2

What are the factors involved in K+ homeostasis?

Answer 2

Intake (Diet), Shifts (Cells), Output (Sweat, Feces, Urine)

Question 3

Hyperkalemia results from (X), (Y) in release from cells, and decreased urinary excretion

Answer 3

X = Large increases in intake
Y = increases

Question 4

Common causes of Hyperkalemia include…

Answer 4

Oral intake, IV intake

Pseudohyperkalemia
Metabolic acidosis
Decreased Insulin
β-adrenergic blockade
Tissue catabolism

Renal failure
ECV depletion
Hypoaldosteronism

Question 5

Increased intake of K+ Rarely causes hyperkalemia unless:

Intake is massive and acutely overwhelms homeostatic mechanisms

or

(X) function is impaired (more importantly)

Answer 5

X = Renal and/or adrenal

Question 6

Key Concept: Chronic hyperkalemia is ALWAYS associated with an impairment in urinary K+ (X)

Answer 6

X = excretion

Question 7

Hyperkalemia: Transcellular Shift into the ECF can be caused by a number of factors including…

Answer 7

Hyperglycemia
Severe exercise
Cell lysis
Pseudohyperkalemia

Metabolic acidosis

Insulin deficiency
Β-blockers

Question 8

Define Pseudohyperkalemia

Answer 8

Elevation of plasma [K+] due to movement of K+ out of cells during or after the drawing of the blood specimen

Question 9

Hyperkalemia: Decreased Output

Decreased urinary K+ excretion
-(X) (Too few functioning nephrons. Typically when GFR < (Y) mL/min)

-ECV depletion (Effective circulating volume)
Decreases distal (Z) delivery to collecting duct

-Hypoaldosteronism

Answer 9

X = Renal failure
Y = 20
Z = sodium

Question 10

Name 3 causes of Hypoaldosteronism

Answer 10

Decreased RAS activity
Decreased aldosterone synthesis
Aldosterone resistance

All caused crucially by medications

Question 11

Name 2 symptoms of hyperkalemia

Answer 11

Muscle weakness

Abnormal cardiac conduction (Manifests as distinct changes on EKG. Can lead to cardiac arrest and death) (Sine wave)

Question 12

How to treat hyperkalemia

Answer 12

Stabilize cell membranes
(Calcium gluconate)

Shift K+ into cells
(Insulin and glucose
β-adrenergic agonists
Sodium bicarbonate)

Remove excess K+ from body
(Diuretics
Cation exchange resin
Dialysis)

Question 13

Hypokalemia can result from decreased dietary intake, (X) entry into cells, and (X) losses

Answer 13

X = increased

Question 14

Common causes of Hypokalemia include

Answer 14

Low intake
Clay ingestion

Metabolic alkalosis
Increased Insulin
Increased β-adrenergic activity
Periodic paralysis

Diuretics
Vomiting
Mineralocorticoid excess
Bartter’s, Gitelman’s, Liddle’s
Hypomagnesemia

Diarrhea
Vomiting

Question 15

Hypokalemia: Decreased Intake
Urinary K+ excretion can be reduced to <15-25 mEq/day in the setting of K+ depletion
-Decreased secretion by (X) cells
-Increased reabsorption by intercalated cells via (Y)

RARELY the primary cause of hypokalemia in normal individuals

Chronic (Z) ingestion* can bind dietary K+

Answer 15

X = principal
Y = H+-K+-ATPase
Z = clay

Question 16

Hypokalemia: Transcellular Shift into the ICF can be caused by a number of factors including…

Answer 16

Insulin
β-agonists
Pseudohypokalemia
-Leukemia and thrombocytosis (high cell counts)

Metabolic alkalosis

Question 17

All diuretics except (X) can cause hypokalemia by increasing K+ secretion at the (Y). ↑ tubular flow rate, stimulating BK channels. Induce volume depletion, stimulating (Z)

Answer 17

X = K+-sparing diuretics
Y = CD
Z = aldosterone

Question 18

Mineralocorticoid Excess

Primary hyperaldosteronism (e.g. adrenal adenoma)

(X) (glycyrrhetinic acid)
Inhibits 11β-hydroxysteroid dehydrogenase

Syndrome of apparent mineralocorticoid excess (S.A.M.E.)
*Autosomal recessive disorder involving mutation in the enzyme 11β-hydroxysteroid dehydrogenase

(Y) and hypokalemia are common features of these syndromes

Answer 18

X = Licorice
Y = Hypertension

Question 19

What are some symptoms of hypokalemia?

Answer 19

• Muscle weakness
• Polyuria, polydipsia
• –Hypokalemia can cause ADH resistance
• Abnormal cardiac conduction
• –Manifests as acute changes on EKG (flat T wave, U wave)
• –Arrhythmias

Question 20

Treatment of Hypokalemia

Administer (X)

• –A drop in plasma [K+] from 4.0 to 3.0 mEq/L is associated with a loss of 200-400 mEq of total body K+
• –Oral or IV

K+-sparing diuretics
—Can be used in combination with loop or thiazide diuretics to prevent (Y)

Answer 20

X = potassium chloride (KCl)
Y = hypokalemia