Disorders of Potassium Regulation

Question 1

What are some ways the body balances potassium?

What is the primary route of K+ elimination?

Answer 1

Homeostasis:

• Diet
• GI losses
• urinary losses
• acid-base
• aldosterone, catecholamines, insulin

Primary route of elimination-Renal route

Question 2

Between the ICF and ECF, how is potassium balanced?

Answer 2

It is balanced by the Na+/K+ efflux pump

- Na+ leaves and K+ enters

Question 3

What is the potassium level for diagnosing hypokalemia?

What are some causes? Hyperkalemia?

Answer 3

K+ < 3.5 mEq/L

Causes- diuretics, steroids, amphotericin-B (antifungal) use, GI losses, intracellular K+ shifting

K+ >5.0 mEq/L

Causes-renal failure (most common), ACEi, ARBs, K+ sparing, extracellular K+ shifting

Question 4

What causes intracellular K+ shifts? Extracellular shifts?

Answer 4

Intracellular shifts:

• metabolic alkalosis
• insulin
• beta-agonists (albuterol)

Extracellular shifts:

• metabolic acidosis
• insulin deficit
• beta-blockers (propranolol)
• cellular destruction (from tumor cells lysing)

Question 5

Why does metabolic alkalosis cause hypokalemia?

Answer 5

Metabolic alkalosis is the deficiency of H+ in the ECF. In order to remedy this, H+ from the ICF is exchanged for K+ from the ECF. Therefore, K+ will be depleted from the ECF.

Question 6

Classify moderate and severe hypokalemia in terms of K+ ECF concentrations. What are some symptoms that correlate with these classifications?

Answer 6

Moderate 2.5-3.5 mEq/L

• cramps
• weakness
• myalgias

Severe <2.5 mEq/L

• cardiac arrthimias
• digoxin intoxication

Question 7

When should you consider K+ prophylaxis?

Answer 7

When patients use:

• diuretics (loops or thiazide)
• digoxin with loops
• patients receiving IV fluids (dehydrated)

Question 8

When should you consider K+ treatment?

Answer 8

When patients have:

• persistently low K+
• diarrhea and vomiting
• arrhythmias
• diabetic ketoacidosis

Question 9

What are the treatment regimens for hypokalemia?

Answer 9

IV: 0.1mEq/L = 10mEq/L K+
- consider IV if NPO or symptomatic

ORAL: 1:1 ratio for IV:ORAL

• consider if deficit is mild (K+ <3.0) or asymptomatic
• take with food

Question 10

Give examples of each treatment regimen and what you have to consider for each

Answer 10

IV

• two lines (peripheral and central)
• peripheral = 10-20mEq in 100mL NS over 1 hour
• central = used if burning or venous sclerosis is evident
• can give up to 40mEq/hr ===== monitor EKG

ORAL

• K+ sparing diuretics (amiloride, triamterene, spironolactone)
• only effective in mild hypokalemia

Question 11

What electrolyte should you monitor along with K+?

Answer 11

Magnesium levels because it is part of the cation co-transporter

Question 12

What are medications that can be used to treat hyperkalemia?

Answer 12

Calcium - for heart muscle stabilization
Beta agonist - intracellular K+ shift
Insulin - intracellular K+ shift
Glucose - to prevent hypoglycemia
Kayexalate - potassium binder

Question 13

What two formulations are commonly used as calcium from CBIGK? Which one is use more and why?

Answer 13

CaCl
CaGluconate

Both are IV formulations. CaGluconate is used more because of less incidences of tissue necrosis at site of injection

Question 14

What is the principle of therapy for hyperkalemia?

Answer 14

1 Stabilize heart
2 Decide whether to bind K+ or do intracellular shifts or dialysis
3 How fast can K+ be reduced

Question 15

What is kayexalate’s MOA and what is administered with it? Why?

Answer 15

MOA: exchanges 1mEq Na+ for 1-2mEq K+

Usually administered with sorbitol to promote diarrheal release of K+

FYI: Now it’s formulated with less sorbitol to bad reactions