Hyperkalemia in Critical Care: Causes, EKG Patterns & Treatment Approaches

Hyperkalemia can be silent—until it isn't. In critical care, elevated potassium levels can quickly escalate to life-threatening arrhythmias. In this episode of Pulmcast, we review potassium physiology, identify EKG warning signs, and break down both emergency and stepwise non-emergency strategies to manage hyperkalemia.

What Is Hyperkalemia and Why It Matters

• Potassium is the major intracellular cation

• 98% of potassium found in the body is in the cell

• 2% found in extracellular fluid

• All cells maintain a negative voltage in the cell interior (-40 to -80 mV) which creates membrane potential

  • Difference in electric potential between the interior and the exterior of the cell

• Membrane potential functions

  • Provides power to the molecular devices within the cells

  • Helps transmit signals to another part of the cell

    • Action potential in nerve cells

• Depolarization

  • Ion channels open and allows electricity to flow (cell interior becomes less negative quickly)

• Sodium/Potassium Pump maintains the balance of negative ions (aka potassium) inside the cell compared to outside the cell

• Too much extracellular potassium leads to less of a membrane potential (cell exterior and interior match more closely)

  • Makes it easier for depolarization to happen

  • Causes cardiac cells to be more excitable and leads to potentially lethal arrhythmias

Common Causes: Shift, Output, Intake

Shifting of Potassium Out of the Cell

• Acidosis

• Diabetes Mellitus

• Acute Cell Tissue Breakdown (rhabdo, hemolysis, massive transfusion)

• Drugs: Digoxin, Beta Blockers (especially non selective ones)

Impaired renal elimination of potassium

• Renal insufficiency

• Hypoaldosteronism

• Medications that interfere with potassium excretion

  • K sparing diuretics (spironolactone, NSAIDs, and ACEI/ARBs)

• Congestive heart failure (or the drugs associated with them: BB, ACEI)

• Constipation

Increased intake of potassium

• With normal renal function it takes large amounts

• With impaired renal function a smaller increase in potassium can cause severe hyperkalemia

Signs and Symptoms of Hyperkalemia

• Rarely associated with symptoms

• Some patients can complain of nausea, muscle pain, or parathesias

• If patients are symptomatic; always check an EKG

Recognizing Hyperkalemia on EKG

• First: Tall, peaked T waves

• Second: Flattening of the p wave and prolongation of PR interval

  • Can see bradycardia and AV block

• Third: Broad QRS Complexes

• Eventually becomes a sine wave; cardiac arrest and Vfib are imminent

Emergency Stabilization: Calcium & Urgency

• How urgent do you need therapy?

  • Treat it urgently if you have EKG changes or the patient is symptomatic

• Calcium is your mainstay treatment in emergent hyperkalemia

  • Calcium makes outside the cell more positive and increases the gradient of electrical charge so cells aren’t able to depolarize as easily

  • 1-3 minutes to take effect

  • Only lasts 30-60 minutes

• Which type of Calcium?

  • Calcium Gluconate preferred because calcium chloride has a higher concentration of calcium and you want to avoid calcium toxicity

  • Calcium gluconate is safe to give peripherally

  • Calcium chloride can cause tissue necrosis and can be irritating to peripheral veins

• Calcium is in; now what?

  • Rapidly remove potassium from the body

    • Hemodiaylsis

Non-Emergency Management: Insulin, Bicarbonate, Albuterol, Diuretics

• Shift Potassium into the cells (don’t affect total body potassium)

  • Fluids

    • Dilutes total body volume and treats pre-renal AKI

  • D50 + Insulin

    • Insulin shifts potassium out of the vascular space and into the cells

    • D50 given to prevent hypoglycemia

  • Sodium Bicarbonate

    • Reversing acidosis which shifts potassium out of the cells (only works if the patient is acidotic)

  • Albuterol

    • Shifts potassium back into cells

    • Additive to insulin

    • Takes about 15-30 minutes to work, lasts 2-3 hours

    • 10 mg continuous neb (not the usual 2.5 mg)

• Remove potassium from the body

  • Loop diuretic

    • Increases renal excretion of potassium (only effective if kidneys are working)

  • Kayexelate (sodium polystyrene sulfonate)

    • Removes potassium from the gut in exchange for sodium

    • Takes 1-2 hours to work

    • Lasts 4-6 hours

    • Associated with bowel necrosis and sodium retention

Summary: Rapid Stabilization + Removal

• Hyperkalemia is defined as a potassium > 5.5 outside the cell

• caused either by intracellular shift of potassium outside the cell, decreased renal excretion of potassium or increased exogenous intake of potassium

• patients are typically asymptomatic but when it’s not, it’s usually life threatening and associated with EKG changes

• Calcium is used to stabilize the heart by making the outside of the cell more positive and shifting the membrane potential closer to normal

• For life threatening hyperkalemia, stabilize the myocardial membrane potential with calcium then rapidly remove potassium with a measure such as dialysis

• In a patient with hyperkalemic arrest you can use albuterol with insulin/d50 to rapidly shift potassium inside the cell

• To remove potassium from the body more slowly you can use Lasix (a loop diuretic) in patients with good renal function or kayexlate to remove potassium via bowel excretion – but both take longer to work

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Attribution

“Fantasy", "Chimera", "Charmed”, “Skepto”, “Sunday Afternoon”, “Trader Ho Hey”, “Love Sprouts” and “Lucky Charms” by Podington Bear is licensed under CC BY-NC 3.0 / Song has been decreased in length from original form