Hyperkalemia Recognition
Hyperkalemia is one of the most dangerous electrolyte imbalances because it directly affects cardiac conduction. A potassium level above 6.0 mEq/L is a medical emergency — the heart can stop without warning if the electrical system is disrupted.
Core Concept
Normal serum potassium is 3.5-5.0 mEq/L. Hyperkalemia (>5.0 mEq/L) most commonly results from renal failure (decreased excretion), potassium-sparing diuretics, ACE inhibitors/ARBs, massive tissue destruction (burns, crush injuries), and metabolic acidosis (hydrogen ions shift into cells, potassium shifts out).
The cardiac effects follow a predictable ECG progression: first peaked T waves, then widened QRS complex, then flattened P waves, and finally a sine wave pattern preceding cardiac arrest. The earliest ECG change — peaked T waves — is a critical NCLEX recognition point.
Treatment follows three principles: stabilize the cardiac membrane (IV calcium gluconate), shift potassium into cells (insulin + glucose, sodium bicarbonate, albuterol), and remove potassium from the body (kayexalate, dialysis, loop diuretics).
Watch Out For
Don't confuse hyperkalemia with hypokalemia symptoms. Hyperkalemia causes muscle weakness that can progress to flaccid paralysis, while hypokalemia also causes weakness but with additional cramping, decreased bowel sounds (paralytic ileus), and U waves on ECG.
Calcium gluconate does NOT lower potassium — it stabilizes the cardiac membrane to prevent fatal dysrhythmias while you use other interventions to actually lower the level. This is a common misconception tested on NCLEX.
Clinical Pearl
IV calcium gluconate is always the FIRST intervention in severe hyperkalemia with ECG changes — it acts within minutes to stabilize the heart. Then give insulin with glucose (insulin drives potassium into cells; glucose prevents hypoglycemia). Remember the mnemonic for hyperkalemia signs: "MURDER" — Muscle weakness, Urine output changes, Respiratory distress, Decreased cardiac contractility, ECG changes, Reflexes decreased.
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