Potassium - Kim (EXAM 2)

Does potassium dominate in the ICF or ECF?

ICF

What are the 3 physiologic functions of potassium?

- Cell metabolism and growth

- Glycogen and protein synthesis

- Electrical action potential in cardiac, skeletal, and nerve tissues (potassium is responsible for repolarization of the cell as it rushes outside the cell)

What percent of potassium resides in the plasma? What is a normal potassium level?

0.4% ; Normal Level: 3.5-5

The majority of potassium is excreted in the _____.

Urine; This is why AKI affects potassium!

If you stimulate the sodium potassium pump, how will that affect plasma potassium levels?

What conditions cause stimulation of the sodium potassium pump?

This shovels more K+ into the ICF. Therefore, you will have lower potassium levels in the plasma.

Conditions that stimulate the sodium potassium pump include insulin excess, beta adrenergic agonists, alpha-1 antagonists, and aldosterone

If you inhibit the sodium potassium pump, how will that affect plasma potassium levels?

What conditions cause inhibition of the sodium potassium pump?

This prevents K+ from entering the ICF. Therefore, you will have higher potassium levels in the plasma.

Conditions that inhibit the sodium potassium pump include insulin deficit, beta adrenergic antagonist, alpha-1 agonist, and digoxin toxicity

What conditions induce a release of potassium from the cells? What does this do to plasma potassium?

- Injury (cellular damage)

- Exercise (muscle breakdown)

- Catabolism (breaking down)

- Hyperosmolarity (e.g. if we have high glucose, that will drag water outside the cell... ends up dragging potassium along with it)

This causes an increase in plasma potassium.

What conditions induce an intracellular shift of potassium? What does this do to plasma potassium?

Anabolism (building up)

This causes a decrease in plasma potassium.

How does metabolic acidosis affect plasma potassium?

Increase in plasma potassium (H+ enters the cell in exchange for K+ which leaves the cell)

How does metabolic alkalosis affect plasma potassium?

Decrease in plasma potassium (H+ leaves the cell in exchange for K+ which enters the cell)

How do we define metabolic acidosis? (i.e. pH < ___)

7.35

How do we define metabolic alkalosis? (i.e. pH > ___)

7.45

If pH increases by 0.1, then K+ ___ by ___.

decreases; 0.6 mEq/L

If pH decreases by 0.1, then K+ ____ by ____.

increases; 0.6 mEq/L

pH = 7.0. K+ = 4.4. Calculate the corrected potassium.

Normal pH = 7.4. Therefore, pH needs to go up by 0.4. This is a 4 fold increase in pH (in increments of 0.1). Therefore, we expect a 4 fold decrease in potassium (in increments of 0.6 mEq/L). Therefore, the corrected potassium is 4.4 - (4*0.6) which equals 2.

pH = 7.6. K+ = 4.4. Calculate the corrected potassium.

Normal pH = 7.4. Therefore, pH needs to go down by 0.2. This is a 2 fold decrease in pH (in increments of 0.1). Therefore, we expect a 2 fold increase in K+ (in increments of 0.6 mEq/L). Therefore, the corrected potassium is 4.4 + (2*0.6) which equals 5.6.

How does aldosterone affect potassium levels?

Aldosterone promotes sodium conservation and potassium wasting!

How do we define hypokalemia?

Serum potassium < 3.5

What are 2 risk factors for hypokalemia?

- Hospitalization

- Diuretic use

What are a few reasons for hypokalemia?

- Insufficient dietary intake (minimum is 1.6-2 g)

- Medications which cause intracellular shift of K+

- Metabolic alkalosis (recall that in these conditions, H+ will leave the cell to correct the alkalosis in exchange for K+ which is shoved into the cell, causing hypokalemia in the plasma)

- Excessive K+ loss through diarrhea, skin, renal losses

- Hypomagnesemia (recall that Thambi mentioned that hypomagnesemia can cause resistant hypokalemia)

Which medications cause hypokalemia due to an intracellular shift of K+?

- Beta adrenergic agonists

- Phosphodiesterase inhibitors such as theophylline and caffeine

- Excess insulin

- Barium or verapamil overdose

What are the 5 causes of hypokalemia via renal losses?

- Hyperaldosteronism (remember that aldosterone promotes sodium reabsorption and potassium wasting)

- Diuretics (e.g. loop and thiazide)

- High dose penicillin, AG, amphotericin B

- Renal tubular acidosis

- High sodium diet

What is evidence of hypokalemia in an ECG?

The only thing she REALLY emphasizes is flat T wave / T wave inversion

What is our goal K+ measurement for correcting hypokalemia to avoid adverse cardio events?

>= 4.0 mEq/L

What are the signs and symptoms of hypokalemia?

Hypertension + Stroke

What is the first step in treating hypokalemia?

Treat the underlying cause + treat hypomagnesemia + avoid drugs that decrease potassium

How do we define mild hypokalemia numerically?

3.1-3.4 mEq/L

If the patient has mild asymptomatic hypokalemia, how would you treat this?

Diet, oral supplement, or parenteral

How do we define moderate hypokalemia numerically?

2.5-3.0 mEq/L

If the patient has moderate asymptomatic hypokalemia, how would you treat this?

Oral supplement or parenteral

How do we define severe hypokalemia numerically?

< 2.5 mEq/L

If a patient has severe or symptomatic hypokalemia, how would you treat this?

Parenteral plus or minus oral supplement

How do you estimate a potassium deficit?

K+ LEVEL OF 3 OR MORE: Each 0.1 mEq/L decrease in potassium level represents a 10 mEq deficit

K+ LEVEL OF LESS THAN 3: Each 0.1 mEq/L decrease in the potassium level represents a 20 mEq deficit

If my potassium level is currently 2.2, what is my potassium deficit?

3.0 - 2.2 = 0.8 (so 8 * 20 = 160)

4,0 - 3.0 = 1 (so 10 * 10 = 100)

160 + 100 = 260 mEq

If K = 3.8 and pH = 7.3, what is the corrected potassium and potassium deficit?

First, let's look at pH. You need to increase to 7.4 which is a 1 fold difference (in increments of 0.1). Therefore, you should decrease potassium level by 1 * 0.6.

3.8 - 0.6 = 3.2!

4.0 (goal potassium) - 3.2 = 0.8

To calculate potassium deficit, you must multiply 8 * 10 = 80 mEq!

How do we provide oral potassium supplements?

Divide dose into no more than 40mEq every 3-4 hours (this will help mitigate GI side effects)

What is the prophylactic dose of oral potassium supplements? In what situation might this be appropriate?

10 - 20 mEq per day. This might be appropriate if a patient is on a potassium wasting diuretic (such as loop diuretic)

What are adverse effects associated with oral potassium supplements?

- N&V

- Diarrhea

- Abdominal pain/ discomfort

- GI ulceration/ bleeding

- Esophageal irritation

How do we administer potassium parenterally?

IVPB or continuous infusion

Name 3 INCORRECT ways to administer potassium parenterally.

- IM

- IV Push

- SC

You can cause burning, irritation, or death.

What is the rate of administration of potassium for peripheral access?

10 mEq/hr

What is the rate of administration of potassium for central access?

20 mEq/hr (can go up in life threatening instances)

Do you need to do cardiac monitoring for potassium administration in peripheral or central access?

Central!

What are some potential adverse events when administering potassium supplement parenterally?

- Burning sensation

- Phlebitis

- Fluid overload

- Cardiac arrhythmias

How do we define hyperkalemia?

- Serum K > 5

What population is at risk for hyperkalemia?

Acute and chronic renal disease

What can cause pseudo-hyperkalemia?

- Hemolysis

- Use of K+ EDTA

- Thrombocytosis, leukocytosis, and erythrocytosis

Bursting of cells releases intracellular K+ and makes it seem like the pt has hyperkalemia

Do not treat pseudo-hyperkalemia!

What can cause hyperkalemia (increased potassium load)?

- Dietary source

- Medications such as penicillin

- Protein-calorie supplements

- Stored blood

- Anaerobic exercise

- Rhabdomyolysis

What can cause hyperkalemia due to transcellular shift?

- Hyperosmolality (glucose, mannitol dragging K+ out with water)

- Somatostatin (this decreases insulin secretion)

- Succinylcholine

- Exercise

- B-adrenergic blokers

- Hyperkalemic periodic paralysis

What medications can impair potassium excretion, causing hyperkalemia?

- Spironolactone, eplernone, triamterene, amiloride (potassium sparing diuretics)

- Trimethoprim

- NSAIDs

- ACEi/ ARB

- Tacrolimus, cyclosporine

What are 2 conditions that can impair potassium excretion?

- HRHA (hyporeninemic hypoaldosteronism)

- Adrenal insufficiency

What are signs and symptoms of hyperkalemia? (Hint: there are 2 different buckets of signs and symptoms)

Cardiac! EKG changes and arrhythmias (AV block, ventricular, cardiac arrest)

Neuromuscular! Muscle twitching, cramping, paraesthesias, generalized weakness, flaccid paralysis, decreased or absent deep tendon reflexes

What changes will you see in EKG due to hyperkalemia?

Big one is tall, peaked T-wave!

What is step 1 of treating hyperkalemia?

Treat the underlying cause + Assess for pseudohyperkalemia

What do we classify as mild hyperkalemia?

5.1 - 5.9

How do we treat mild hyperkalemia?

Kayexalate (SPS) plus or minus redistribution drugs

What do we classify as moderate hyperkalemia?

6.0 - 7.0

How do we treat moderate hyperkalemia?

Kayexalate (SPS) +/- redistribution drugs OR furosemide if kidney function is intact

In recitation, Dr. Kim mentions that the easiest course of action is to start with the furosemide if their kidney function is intact. However, since this population of patients typically has impaired kidney function (#1 cause is CKD), we typically have to turn to SPS + redistribution drugs. We like to administer these together since the redistribution drugs offer an immediate effect of "hiding" the potassium in the cells while the binding drugs such as SPS promote permanent elimination.

What do we classify as severe hyperkalemia?

> 7

How do we treat severe hyperkalemia?

IV Calcium + Kayexalate (SPS) + redistribution drugs

*You always give IV calcium to address cardiac problems associated with severe/symptomatic hyperkalemia (i.e. you see a peak T wave, you give IV calcium)

What is our membrane stabilizing drug for hyperkalemia?

Calcium! You administer this until peak T-wave is resolved.

Dosing: 1g IVP over 2-3 minutes, may repeat in 5-10 min

Duration: 30-60min (gives you half an hour to an hour to think about what yu want to do with the potassium that is in the IVF)

Note this medication may cause phlebitis, tissue necrosis, and hypercalcemia

What 3 medications are our intracellular shift drugs for hyperkalemia?

Insulin plus or minus glucose (note this can cause hypoglycemia) --> she mentions she would administer the D5W for anyone with glucose < 200

Albuterol (note this can cause tachycardia so this is not a good option for a patient already experiencing high HR)

NaHCO3 (ONLY TO BE USED IN METABOLIC ACIDOSIS) (note this can cause alkalosis, hypernatremia, and edema)

What 4 medications are our elimination drugs for hyperkalemia?

- Sodium polystyrene sulfonate

- Sodium zirconium cyclosilicate

- Furosemide (may or may not show benefit, don't give to someone who cannot sufficiently make urine, remember that a huge cause of hyperkalemia is CKD)

- Dialysis (note this can cause rebound hyperkalemia)

What adverse events can SPS cause?

hypernatremia (due to Na-K exchange), nausea, constipation, colonic necrosis

What adverse events can sodium zirconium cyclosilicate cause?

edema (due to Na-K exchnage)