Hypokalemia

What is there to know about the kidneys and potassium?

Kidney is primary route of potassium elimination

• Freely filtered but almost entirely reabsorbed

• Potassium is secreted through collecting duct

  • Regulated via aldosterone activity

Potassium levels in the body are mainly regulated where

distal collecting duct and, to some extent, in the loop of Henle

What happens when Aldosterone is activated in the DCT

it increases the activity and expression of:

• Na/K ATPase pumps: Moves sodium out of and potassium into cells.

• ENaC (Epithelial Sodium Channels): Facilitates sodium reabsorption.

• Potassium Channels: Allows potassium to move from cells into the urine.

Aldosterone promotes sodium reabsorption (along with water) into the bloodstream, which helps to concentrate urine.

What do principal cells do?

secrete potassium into urine→ contribute to potassium excretion

Intercalated cells do what?

use a K/H antiporter to allow potassium to be reabsorbed back into the bloodstream while secreting hydrogen ions into the urine.

What happens if there is an increase in sodium load in the ultrafiltrate?

enhance potassium excretion.

What happens if there is a blockade of the ENaC channel?

reduces sodium reabsorption and potassium excretion, leading to potential hyperkalemia.

What happens if given an aldosterone antagonist?

Less sodium is reabsorbed, which decreases the drive for potassium to be secreted into the urine.

What happens if we have decreased renal flow?

decrease potassium excretion and potentially lead to hyperkalemia.

What happens if we have metabolic acidosis?

initially cause hyperkalemia as potassium shifts out of cells, but chronic acidosis can lead to potassium depletion due to increased renal potassium loss

Mild hypokalemia

K: 3-3.5mEq/L

Moderate hypokalemia

K: 2.5-3mEq/L

Severe Hypokalemia

K: <2.5mEq/L

T/F: Serum potassium is a good reflection of total body potassium

False

Common Causes of Hypokalemia

GI losses

• Vomiting/diarrhea

• NG suction

• Fistula

Diuretics

Hypomagnesemia

• Impairment of Na/K/ATPase pump

• Increased K renal wasting

What drugs increase renal excretion of K+?

Diuretics

Acetazolamide

Amphotericin

Corticosteroids and Mineralcorticoids

Cisplatin

Penicillins

Think: DAACCP

What drugs increase fecal excretion of K+?

Sorbitol

Sodium polystyrene sulfonate

What drugs lead to intracellular shifts resulting in K+ loss?

Beta 2 agonists and insulin/glucose

What can shift Potassium from ECF to ICF causing hypokalemia?

insulin, Beta 2 adergenic agonists, alkalosis, alpha adrenoreceptor agonists

Hypokalemia symptoms

Neuromuscular

• Hyperpolarization of resting membrane potential → ↓ muscle contraction

• Cramping, weakness, fatigue

• Lower extremities → upper extremities → respiratory muscles

Cardiovascular

• Arrhythmias: heart block, atrial flutter

• EKG abnormalities: T-wave inversion, narrowing QRS, bradycardia, S depression

Goals for hypokalemia:

Maintain potassium levels between 4–4.5 mEq/L

Prevent dangerous heart rhythms (arrhythmias)

Alleviate symptoms and address the underlying cause

If Potassium Level are between 3–3.5 mEq/L

Encourage foods high in potassium

• Add on potassium supplementation if there is an underlying heart condition or if the patient is taking digoxin

If Potassium Levels are <3 mEq/L

Start potassium supplementation to raise blood potassium levels.

If patient is asymptomatic but has hypokalemia

give them oral supplementation

If patient is severe/symptomatic

give them IV supplementation

What foods are high in K+?

Fruits / Vegetables / Meats

Dried fruits

Bananas, oranges, kiwi

Squash, broccoli, lentils  Potatoes & Tomatoes

Vegetable juices

Peanut butter, nuts

Yogurt, Milk  Granola, bran

Chocolate

Daily Potassium Intake Recommendations

50 mEq/day

To prevent hypokalemia what should be given?

give Potassium Chloride (KCl) 20 mEq/day

According to the JNC VII how much potassium should be taken each day to prevent HTN and CV complications

100mEq/L

What is there to know about hypokalemia defecit?

For every 1 mEq/L decrease in blood potassium, there is a total body potassium deficit of approximately 100–400 mEq.

• To treat hypokalemia, 40–100 mEq of KCl per day is usually given, depending on the severity of the deficit and patient need

What are the supplements for hypokalemia?

Potassium chloride (KCl)

• Most common

Potassium phosphate

• use if also have Concomitant hypophosphatemia

Potassium bicarbonate

• can use if also have Metabolic acidosis

Comparing Potassium formulations

Klor-Con (KCl): wax matrix→ easier to swallow but has higher GI erosions

K-dur (KCl): microencapsulated→ lower GI erosions

Intravenous Potassium Supplementation Guidelines for treating hypokalemia

• Preparation:

  • Potassium is prepared in a sodium chloride solution (either normal saline (NS) or half-normal saline (½ NS)).

• Administration Rates:

  • Peripheral IV Administration: Typically 10–20 mEq in 100 mL of solution, infused over 1 hour.

  • Central IV Administration: Higher concentration of 40 mEq in 100 mL, infused over 1 hour (used in cases needing rapid correction).

• Monitoring:

  • Continuous ECG Monitoring (Telemetry): Required if the infusion rate is greater than 10 mEq per hour to monitor for heart rhythm changes.

  • Re-check Potassium Levels: After each 40 mEq dose to ensure levels are safe and avoid hyperkalemia

What are the alternative hypokalemia treatments?

Remove offending agent(s) if able

• i.e Loop / thiazide diuretics

Use potassium sparing diuretics

• i.e HCTZ/Triamterene combination (Dyazide)

Supplement loop / thiazide diuretics with low-dose daily KCl

What should be done if a patient has hypomagnesemia and hypokalemia?

You must first fix hypomagensia

The goal is to correct serum magnesium levels to 1.5–2.5 mEq/L.

Oral Magnesium Supplementation:

• Magnesium oxide: 400–800 mg PO BID

Intravenous Magnesium Supplementation:

• Magnesium sulfate: 2–4 g IV, infused over 2–4 hours.

Potassium Correction Related to Hypomagnesemia

For each 0.1 mEq/L increase in serum potassium, it is recommended to administer 10 mEq K to help raise the potassium level appropriately

Potassium Chloride (KCl) Conversion to elemental potassium

10 mEq KCl = 10 mmol KCl = 750 mg KCl = 390 mg elemental potassium.