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ECG Findings

Findings are variable but tend to correlate with increasing serum potassium levels following the order below:

  • Peaked T waves, tented with a narrow base (may be > 10 mm high in precordial leads and/or > 6 mm in limb leads)

  • QRS complex widening

  • PR interval prolongation

  • Decreased P-wave amplitude

  • As potassium levels approach and exceed 8.0 mEq/L:

    • Indiscernible P waves

    • New bundle branch blocks or fascicular blocks

    • Sine wave appearance of QRS-T complex

    • VT, fibrillation, or asystole

Pearls

  1. Hyperkalemia is often missed on the initial ECG as it can produce nonspecific changes.

  2. Acute treatment for hyperkalemia includes insulin and glucose, sodium bicarbonate, and β-agonists in an attempt to drive potassium into the cell. Intravenous calcium may be used to stabilize the myocardium but has no effect on serum potassium levels. These are temporizing measures that must be followed by definitive treatment of the underlying problem, which may include the need for dialysis.

FIGURE 23.47A

Hyperkalemia (potassium of 7.1). (ECG contributor: R. Jason Thurman, MD.)

FIGURE 23.47B

Peaked T waves (arrow), widened QRS (double arrow), and subtle flattening of the P waves are seen in this patient with a serum potassium of 7.1.

FIGURE 23.48A

Severe Hyperkalemia—Sine Wave. (ECG contributors: Sam Parnell, MD, and Tracy Fennessy, MD.)

FIGURE 23.48B

Wide blunted QRS with sine wave appearance. No P waves are visible. Serum potassium was > 8 in this patient.

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