FEN: Hypokalemia

Question 1

What is normal plasma potassium concentration?

Answer 1

3.5-5 mEq/L

Question 2

What is the primary intracellular cation?

Answer 2

K+ (maintains electroneutrality with na+, the primary EC cation)

Question 3

List two receptors that promote cellular uptake of K+

Answer 3

1. B2-adrenergic stimulation (caused by epinephrine) promotes cellular uptake of K+ 2. Insulin promotes cellular uptake of K+

Question 4

Why does plasma potassium concentration directly correlate with the movement of K+ in and out of cells?

Answer 4

1. Passive shifts occur based on the concentration gradient across cell-membrane 2. E.g. diarrhea-induced hypokalemia shifts K+ out of cells passively, minimizing reduction in plasma K+ concentration

Question 5

Long term potassium homeostasis is maintained by what body function?

Answer 5

renal excretion

Question 6

List four principle causes of hypokalemia

Answer 6

1. reduced K+ dietary intake 2. Increased K+ shift into cells 3. Increased GI losses of K+ 4. Increased renal losses of K+

Question 7

Why is reduced intake seldom the cause of hypokalemia?

Answer 7

Renal excretion is minimized because of increased renal tubular absorption

Question 8

List four causes of increased K+ shift into cells

Answer 8

1. alkalosis (most common) 2. insulin or carbohydrate (e.g. dextrose) 3. B2 receptor stimulation (stress-induced epi release, B-agonist like albuterol or dobutamine) 4. Hypothermia

Question 9

List four causes of increased GI loss of K+

Answer 9

1. vomiting 2. diarrhea 3. intestinal fistula 4. chronic laxative abuse

Question 10

List two causes of renal loss of K+

Answer 10

1. mineralocorticoid excess (e.g. aldosterone) 2. diuretic use (e.g. loop, thiazides)

Question 11

What other serum electrolyte derangement is commonly associated with hypokalemia and requires supplementation to correct K+?

Answer 11

Hypomagnesemia

Question 12

What cause of hypokalemia is most commonly associated with concomitant hypomagnesemia?

Answer 12

Increased renal loss of K+

Question 13

At what serum potassium do hypokalemia symptoms typically occur?

Answer 13

less than 3 mEq/L

Question 14

List four principle symptoms of hypokalemia

Answer 14

1. muscle weakness 2. ECG changes 3. cardiac arrhythmias 4. rhabdomyolysis

Question 15

Describe what muscle groups are affected by hypokalemia symptoms

Answer 15

1. Most commonly occurs in lower extremities 2. Progress to trunk, upper extremity, respiratory muscles 3. GI tract as well

Question 16

List 5 manifestations of hypokalemia in GI tract muscle weakness

Answer 16

1. Paralytic ileus 2. Abdominal distention 3. Nausea 4. vomiting 5. Constipation

Question 17

List two manifestations of hypokalemia on ECG changes

Answer 17

1. flattened T waves 2. elevated U wave

Question 18

List four manifestations of cardiac arrhythmias in hypokalemia

Answer 18

1. bradycardia 2. heart block 3. ventricular tachycardia 4. ventricular fibrillation

Question 19

How does rhabdomyolysis occur in hypokalemia?

Answer 19

Reduced blood flow to skeletal muscle

Question 20

What narrow therapeutic index drug can cause toxicity in the setting of hypokalemia despite normal serum concentrations?

Answer 20

digoxin

Question 21

How to estimate K+ deficit?

Answer 21

1. Assuming a normal distribution of K+ between EC and IC compartments 2. A K+ deficit can be estimated as 200-400 mEq of K+ for every 1 mEq/L reduction in plasma potassium.

Question 22

Under what circumstances and how often should K+ be monitored when monitored closely?

Answer 22

1. Symptomatic or K+ less than 3 mEq/L 2. Every 2-4 hours after infusion

Question 23

In patients with no signs of symptoms of hypokalemia with K+ between 3-3.5, what is preferred way to give potassium?

Answer 23

Oral KCl 40-80 mEq/day (doses greater than 60 mEq should be divided to avoid GI adverse effects) (recheck K+ daily)

Question 24

When can high dose oral K+ be given, and how much?

Answer 24

1. Oral KCl 120 mEq/day in divided doses 2. In patients with K+ 2.5-3 mEq/L without signs or symptoms

Question 25

What is treatment for patient with K+ 2-2.5 mEq/L

Answer 25

1. IV KCl 10-20 mEq/hour 2. Consider continuous ECG monitoring 3. recheck K+ frequently (every 2-4hours)

Question 26

What is treatment for patient with K+ \<2 mEq/L

Answer 26

1. IV KCl 20-40 mEq/hour 2. Requires continuous ECG monitoring 3. recheck K+ frequently (every 2-4hours)

Question 27

What patients are candidate for oral potassium supplementation?

Answer 27

1. Without ECG changes or symptoms of hypokalemia

Question 28

What is typical infusion rate potassium in hypokalemia?

Answer 28

1. Normal: 10-20 mEq/hour 2. Maximum: 40 mEq/hour

Question 29

What is the maximum concentration of compounded K+ preparation that can be safetly administred through a peripheral vein to avoid irritation?

Answer 29

60-80 mEq per 1 L (e.g. of NS)

Question 30

What crystalloid should potassium not be compounded with in setting of hypokalemia?

Answer 30

1. Avoid mixing K+ in dextrose, which can cause insulin release with subsequent IC shift of K+

Question 31

What additional monitoring is required for patients receiving K+ infusions at rates faster than 20 mEq/hour?

Answer 31

ECG

Question 32

Dose adjustments for normal potassium dosing must be made for what insufficiency?

Answer 32

1. renal insufficiency 2. e.g. kidney dysfunction, older adults

Question 33

What is the preferred potassium salt in the treatment of hypokalemia with concurrent metabolic ALKALOSIS?

Answer 33

1. Potassium chloride 2. because these patients typically lose Cl- through diuretics or GI loss

Question 34

In patients with metabolic ACIDOSIS, what potassium salts can be used (oral and IV?)

Answer 34

1. IV: potassium acetate 2. Oral: potassium bicarbonate