Abstract
Hyperkalemia is an acute life-threatening metabolic imbalance that is commonly seen in emergency departments. The primary cause is renal disease, but it also results from increased potassium intake in the diet, severe volume contraction, some medications, and other metabolic disturbances. Signs and symptoms suggestive of hyperkalemia must be recognized early so that life-saving interventions can be initiated. Rapid acquisition of an electrocardiogram (ECG) is important for making an early diagnosis because it can provide clues to the diagnosis long before laboratory results become available. Acute care providers are trained in the progression of alterations on the ECG tracings that occur as serum potassium levels rise. The earliest signs of mild hyperkalemia (5.5-6.5 mmol/L) are tall, narrow-based T waves, best seen in the precordial leads. As the potassium level becomes moderately elevated (6.5-8.0 mmol/L), the PR and QRS intervals become progressively longer, and the P waves might be lost. Severe hyperkalemia (> 8.0 mmol/L) often produces fascicular and intraventricular blocks and an eventual "sine wave" appearance which leads to ventricular fibrillation or asystole if immediate treatment is not provided. Hyperkalemia also often produces bradycardic rhythms along the progression of ECG findings, but this manifestation is not well-known or commonly taught. As a result, life-threatening hyperkalemia may be easily missed until laboratory results reveal the diagnosis. Additionally, standard treatments for bradydysrhythmias, such as atropine and electrical pacing, are often ineffective in treating this life-threatening cause of bradycardia. With early recognition of bradyarrhythmia caused by hyperkalemia, however, the proper treatment can be expedited and clinical decline can be averted.