What are the signs and symptoms of hyperkalemia (elevated potassium levels)?

Signs of Elevated Potassium (Hyperkalemia)

Most Critical Finding: ECG Changes

The most important sign of hyperkalemia is the presence of ECG changes, which may appear before any symptoms and indicate severe cardiotoxicity requiring immediate treatment. 1

Progressive ECG Manifestations by Severity

Mild Hyperkalemia (>5.0 to <5.5 mEq/L):

• Often no ECG changes at this level 2
• May be asymptomatic and discovered incidentally on routine blood work 2

Moderate Hyperkalemia (5.5 to 6.0 mEq/L):

• Peaked or tented T waves - the earliest and most common ECG finding, typically appearing at K+ >5.5 mmol/L 1, 3
• Flattened or absent P waves 1
• Prolonged PR interval 1, 3
• Widened QRS complex 1, 3
• Deepened S waves 1

Severe Hyperkalemia (>6.0 mEq/L):

• Merging of S and T waves 1, 3
• Progressive QRS widening 1
• Development of sine-wave pattern (also called "tombstone" pattern) 1, 4
• Idioventricular rhythms 1
• Ventricular fibrillation or asystolic cardiac arrest 1, 3

Clinical Symptoms

Hyperkalemia typically presents with non-specific symptoms, making ECG monitoring essential for early detection. 5, 6

Neuromuscular Manifestations:

• Muscle weakness or paralysis 5, 6
• Paresthesias 6
• Symptoms predominantly related to muscular dysfunction 6

Cardiac Manifestations:

• Cardiac arrhythmias 2, 5
• Bradycardia in severe cases 3
• Risk of sudden cardiac arrest 2, 1

Critical Clinical Pearls and Pitfalls

Important caveat: Patients with chronic kidney disease, diabetes, or heart failure may tolerate K+ levels up to 6 mEq/L without any signs of arrhythmia or ECG changes. 2, 1 This tolerance develops over time in chronic hyperkalemia, but does not eliminate the danger 1.

The absence of ECG changes does not rule out dangerous hyperkalemia - not all patients develop ECG changes at the same potassium level, and individual variability exists. 1, 3

Pseudo-hyperkalemia Consideration:

• Suspect when ECG findings don't match laboratory values 1
• Caused by K+ release from blood or tissue during sampling 2
• Repeat measurement with appropriately sampled blood or arterial sample if suspected 2
• Consider whether hemolysis occurred in the test tube versus in the body 2

When to Treat Emergently

Hyperkalemia with K+ >6.5 mEq/L OR any ECG changes is a medical emergency requiring immediate treatment. 5 The risk for life-threatening arrhythmias and sudden arrhythmic death varies widely between patients, and arrhythmias may occur at different thresholds. 2