Potassium Disorders

What is the primary route of potassium elimination?

kidney

How is potassium filtered through the kidney?

freely filtered but almost entirely reabsorbed?

What is potassium secretion regulated by?

aldosterone activity

Where is potassium predominantly regulated?

the distal collecting duct

What channels are up regulated through aldosterone?

Na/K/ATPase, ENaC, and K channels

Which cells of the collecting duct allow for potassium reabsorption through K/H antiporter?

intercalated cells

What is the action of principal cells?

K secretion into urine

What is the action of intercalated cells?

K reabsorption into bloodstream

Mild Hypokalemia Range

3-3.5 mEq/L

Moderate Hypokalemia Range

2.5-3 mEq/L

Severe Hypokalemia Range

<2.5 mEq/L

True or False: Serum potassium is a poor reflection of total body potassium

True

What are common causes of hypokalemia?

GI losses

Diuretics

Hypomagnesemia

What drugs cause hypokalemia through renal mechanisms?

diuretics, acetazolamide, amphotericin, corticosteroids, mineralocorticoids, cisplatin, penicillins

What drugs cause hypokalemia through fecal mechanisms?

Sorbitol and sodium polystyrene sulfonate

What drugs cause hypokalemia through intracellular shifts?

beta 2 agonists, insulin, and glucose

What are the two ways hypokalemia can present clinically?

Neuromuscular and Cardiovascular

How does hypokalemia present in the neuromuscular system?

cramping, weakness, and fatigue caused by hyperpolarization of resting membrane potential

How does hypokalemia present in the cardiovascular system?

arrythmias, heart block, atrial flutter, EKG abnormalities (t-wave inversion, narrowing QRS, bradycardia, ST depression

Treatment Goals of Hypokalemia

K 4-4.5 mEq/L, prevent arrythmias, reverse symptoms, correct underlying cause

Treatment Goals of Hypokalemia when [K] is 3-3.5 mEq/L

increase potassium rich foods, potassium supplementation IF underlying cardiac disease (or on digoxin)

Treatment Goals of Hypokalemia when [K] is < 3 mEq/L

potassium supplementation

Treatment Goals of asymptomatic hypokalemia

oral supplementation

Treatment goals of severe/symptomatic hypokalemia

IV supplementation with close monitoring

Food that are high in potassium

dried fruits, bananas, orange, kiwi, squash, broccoli, lentils. potatoes, tomatoes, vegetable juices, peanut butter, nuts, yogurt, yogurt, milk, granola, bran, chocolate

What is the recommended daily allowance of potassium?

50 mEq/day

What are the types of potassium supplementation?

potassium chloride (KCl), potassium phosphate, potassium bicarbonate

What are adverse side effects of PO potassium supplementation?

GI-irritation, erosion

What are adverse side effects of IV potassium supplementation?

thrombophlebitis, hyperkalemia, pain/burning at infusion site

What kind of formulation is Klor-Con?

wax matrix

What kind of formulation is K-dur?

microencapsulated

What fluid/solution is IV potassium supplementation prepared in?

NS or ½ NS

How do you provide IV peripheral potassium administration?

10-20 mEq/100 mL infused over 1 hour

How do you provide IV central potassium administration?

40 mEq/100 mL infused over 1 hour; and continuous ECG monitoring if >10 mEq/hr (telemetry)

In order to avoid hyperkalemia, when do you have to recheck potassium after IV supplementation?

after each 40 mEq supplementation

Alternative Hypokalemia Treatments

Removing offending agents, use potassium sparing diuretics, supplement with low-dose KCl

True or False: You must correct hypomagnesemia first

TRUE!

Magnesium Normal Range

1.5-2.5 mEq/L

What kinds of supplements are used for hypomagnesemia?

magnesium oxide and magnesium sulfate

What is the dose for magnesium oxide?

400-800 mg PO BID

What is the dose for magnesium sulfate?

2-4g IV infused over 2-4 hours

How many mEq of K are needed for each 0.1 mEq/L increase in serum K

10 mEq

For every 1 mEq/L K deficit is how much total body K deficit

100-400 mEq

What are the causes of hyperkalemia?

increased dietary K intake

decreased renal K excretion

renal tubular unresponsive to aldosterone

psuedohyperkalemia

rhabdomyolysis

burn injuries

drugs

What is the clinical presentation of hyperkalemia?

usually asymptomatic; palpitations, ECG changes

What is hyperkalemia?

Serum concentration > 5.5 mEq/L

What ECG change is seen in hyperkalemia with a [K] of 6-7?

peaked t-waves

What ECG change is seen in hyperkalemia with a [K] of 7-8?

prolonged PR interval

What ECG change is seen in hyperkalemia with a [K] of 8.5-9.5?

loss of P wave

What ECG change is seen in hyperkalemia with a [K] of 8-9?

widening of QRS

What ECG change is seen in hyperkalemia with a [K] of >9

sine-wave pattern

What factors affect potassium?

acid/base imbalance, hyperosmolality, cell lysis/destruction, renal failure, drugs

How do ACEi/ARBs/direct renin inhibitors induce hyperkalemia?

hypoaldosteronism, impaired K excretion

How to beta blockers induce hyperkalemia?

impaired cellular uptake, inhibit renin release

How does digoxin induce hyperkalemia?

inhibition of Na/K/ATPase

How do potassium containing drugs induce hyperkalemia?

exogenous K load

What are examples of potassium containing drugs?

potassium supplements, KCl, Penicillin G

How do aldosterone antagonists (MRAs) induce hyperkalemia?

block aldosterone’s effects

How do potassium sparing diuretics induce hyperkalemia?

blocks Enac Na channel → impaired K secretion

How does heparin induce hyperkalemia?

blocks aldosterone production

How does cyclosporine/tacrolimus induce hyperkalemia?

impaired K secretion

How do NSAIDs induce hyperkalemia?

impaired K secretion

What causes transcellular shift of K out of the cell into the serum?

acidosis

hyperglycemia

beta-blockers

alpha agonists

increase in osmolality

exercise

True or False: the serum potassium concentration does not accurately reflect total body potassium

True!

What stages of CKD does hyperkalemia become present?

4 and 5

What mechanisms are present in CKD in relation to potassium regulation?

nephrons adapt to excrete more potassium and maintain normokalaemia

increase in fecal K excretion can maintain normokalaemia

reduced capacity for K excretion — struggle with large potassium loads

What are the acute treatment goals of hyperkalemia?

prevent arrythmias, reversal of symptoms, [K] < 5.5 mEq/L within minutes/hours

What are the chronic treatment goals of hyperkalemia?

maintain [K] 4-5 mEq/L, prevent symptoms and arrythmias

What defines emergency hyperkalemia?

[K] > 7 mEq/L or [K] 5.5-6.9 mEq/L with ECG changes

What are the steps in the treatment of a hyperkalemic emergency?

1. determine ECG abnormalities

2. Transient therapy to quickly shift potassium into cells

3. remove excess potassium from the body

How do you initially treat emergent hyperkalemia if there are ECG abnormalities?

1 g IV calcium gluconate and continuous ECG monitoring

What is the most common transient therapy to quickly shift potassium into cells?

regular insulin 10U IV + 25g dextrose if euglycemic

What is the best transient therapy to quickly shift potassium into cells if the patient is acidotic?

50-100 mEq IV sodium bicarbonate

What can be considered for transient therapy to quickly shift potassium into cell if you are unable to gain intravenous access?

albuterol nebulizer if unable to gain intravenous access

What are the three methods/pathways to remove excess potassium from the body?

through stool, urine, or blood

How do you remove excess potassium from the body through the stool?

sodium polystyrene sulfonate 15-30g PO

How do you remove excess potassium from the body through urine?

intravenous loop diuretics

How do you remove excess potassium from the body through blood?

emergent hemodialysis

onset/duration of calcium gluconate or chloride

1-2 min/10-30 min

MOA of calcium gluconate or chloride

raises cardiac threshold potential; reverses ECG effects

onset/ duration of action of furosemide

5-15 mins/4-6 hours

MOA of furosemide

inhibits renal Na+ reabsorption → increased urinary K+ loss

onset/duration of action of regular insulin

30min/ 2-6 hours

MOA of regular insulin

stimulates intracellular K uptake → intracellular K redistribution

onset/duration of action of dextrose 10% or 5%

30min/ 2-6 hours

MOA of dextrose 10% or 5%

stimulates insulin release → intracellular K redistribution

onset/duration of action of sodium bicarbonate

30min/ 2-6 hours

MOA of sodium bicarbonate

raises serum pH → intracellular K redistribution

onset/duration of action of albuterol

30 min/ 1-2 hours

MOA of albuterol

stimulates intracellular K+ uptake → intracellular K+ redistribution

onset/duration of action of hemodialysis

immediate/variable

MOA of hemodialysis

direct removal from serum

onset/duration of action of sodium polystyrene sulfonate

1 hour/ variable

MOA of sodium polystyrene sulfonate

resin exchanges Na for K

onset/duration of action of patiromer

hours/ variable

MOA of partiromer

resin exchanges Ca for K

onset/duration of action of sodium zirconium cyclosilicate

1 hour/ variable

MOA of sodium zirconium cyclosilicate

resin exchanges Na for K

Overall chronic treatment of hyperkalemia

avoid drugs that promote hyperkalemia

low potassium diet

avoid salt substitutes

chronic oral medications

What are examples of low potassium foods?

apples, berries, grapes, pears, peaches, asparagus, corn, peppers, rice, pasta, white bread, coffee, tea, etc.