What level of potassium can cause cardiac arrest?

From the Guidelines

Severe hyperkalemia, typically defined as a potassium level above 6.5 mEq/L (or mmol/L), can cause cardiac arrest, though cardiac effects may begin at lower levels. Potassium levels between 6.0-7.0 mEq/L are considered dangerous, with increasing risk of fatal cardiac arrhythmias as levels rise. The heart is particularly vulnerable to high potassium because it disrupts normal electrical conduction by affecting the resting membrane potential of cardiac cells. This leads to a progression of ECG changes: tall, peaked T waves initially, followed by PR prolongation, P wave flattening, QRS widening, and eventually sine wave pattern and asystole.

Key Considerations

• The clinical signs associated with severe hyperkalemia include flaccid paralysis, paresthesia, depressed deep tendon reflexes, or shortness of breath 1.
• Emergency treatment for severe hyperkalemia includes calcium gluconate to stabilize cardiac membranes, insulin to shift potassium into cells, sodium bicarbonate if acidotic, and beta-agonists like albuterol 1.
• Patients with chronic kidney disease, those taking certain medications (ACE inhibitors, potassium-sparing diuretics), or those with adrenal insufficiency are at higher risk and should monitor potassium levels regularly 1.

Treatment Approach

• Dialysis may be needed for very high levels or in patients with kidney failure, as it is the most effective way to remove excess potassium from the body 1.
• The treatment approach should be individualized based on the patient's underlying condition, the severity of hyperkalemia, and the presence of any symptoms or ECG changes.
• It is essential to note that the risk of cardiac arrest and arrhythmias increases with the severity of hyperkalemia, and prompt treatment is crucial to prevent these complications 1.

From the Research

Hyperkalemia and Cardiac Arrest

• Hyperkalemia is a condition where serum potassium levels exceed 5.5 mmol/l, which can lead to fatal dysrhythmias and muscular dysfunction 2.
• Severe hyperkalemia can cause cardiac arrest, with progressively more severe elevations in potassium leading to abnormalities in cardiac depolarization and repolarization and contractility 3.
• The level of potassium that can cause cardiac arrest is not strictly defined, but serum potassium levels above 5.0 mEq/L can lead to cardiac conduction disturbances and increase the risk of cardiac arrest 4.

Potassium Levels and Cardiac Effects

• Serum potassium levels above 5.5 mmol/l can lead to hyperkalemia, which can cause cardiac dysrhythmias and increase the risk of cardiac arrest 2.
• Potassium levels above 5.0 mEq/L can lead to cardiac conduction disturbances, including abnormalities in cardiac depolarization and repolarization and contractility 3, 4.
• Severe hyperkalemia, typically defined as serum potassium levels above 6.0-6.5 mEq/L, can lead to life-threatening cardiac arrhythmias and cardiac arrest 5, 6.

Treatment of Hyperkalemia

• Treatment of hyperkalemia includes measures to stabilize cardiac membranes, shift potassium from extracellular to intracellular stores, and promote potassium excretion 5.
• Acute treatment of hyperkalemia may include intravenous calcium, insulin, sodium bicarbonate, diuretics, and beta agonists, as well as dialysis in severe cases 5, 4, 6.
• Newer potassium binders, such as patiromer and sodium zirconium cyclosilicate, may be used in chronic or acute hyperkalemia 2, 4.