HyperK MACHINE Mnemonic
MACHINE is a mnemonic for remembering the causes of hyperkalemia (elevated serum potassium above 5.0 mEq/L). Hyperkalemia is a life-threatening electrolyte imbalance that can cause fatal cardiac dysrhythmias. Recognizing the causes, ECG changes, and treatments for hyperkalemia is heavily tested on the NCLEX because potassium is the most dangerous electrolyte when abnormal.
The Mnemonic
"MACHINE"
Breakdown
Medications
ACE inhibitors, ARBs, potassium-sparing diuretics (spironolactone, triamterene), NSAIDs, and potassium supplements can all cause hyperkalemia. Always review the medication list when potassium is elevated. ACE inhibitors and ARBs reduce aldosterone, decreasing potassium excretion.
Acidosis
Metabolic acidosis can cause potassium to shift out of cells into the bloodstream as hydrogen ions move into cells (H+/K+ exchange). Correcting the acidosis can lower the potassium level.
Cellular Destruction
Any condition that causes massive cell destruction releases intracellular potassium into the bloodstream. Examples include crush injuries, tumor lysis syndrome, hemolysis, rhabdomyolysis, severe burns, and massive blood transfusions.
Hypoaldosteronism
Aldosterone promotes potassium excretion in the kidneys. Conditions that reduce aldosterone (Addison's disease, adrenal insufficiency) impair the kidney's ability to excrete potassium, leading to hyperkalemia. Addison's disease causes both hyperkalemia and hyponatremia.
Intake Excess
Excessive dietary potassium intake or IV potassium administration can cause hyperkalemia, especially in patients with renal impairment. IV potassium must always be diluted and infused slowly (never IV push, which can cause cardiac arrest). Maximum rate is typically 10-20 mEq/hour.
Nephropathy (Renal Failure)
The kidneys excrete most of the body's daily potassium load. Acute or chronic kidney disease significantly impairs potassium excretion, making hyperkalemia one of the most dangerous complications of renal failure. Monitor potassium closely in all patients with decreased GFR.
Excretion Impaired
Beyond renal failure, anything that impairs potassium excretion contributes to hyperkalemia. This includes dehydration, oliguria, urinary obstruction, and medications that reduce renal potassium secretion. Adequate urine output is essential for maintaining normal potassium levels.
Clinical Relevance
Severe hyperkalemia is a medical emergency. ECG changes can progress from peaked T waves to widened QRS to sine wave pattern to cardiac arrest, but the ECG can look normal even when potassium is high. NCLEX treatment priority: (1) IV calcium gluconate to stabilize cardiac membranes, (2) IV insulin with dextrose to shift potassium into cells, (3) sodium bicarbonate for acidosis, (4) Kayexalate (sodium polystyrene sulfonate) to remove potassium from the body, (5) dialysis for refractory cases.
Study Tips
- Severe hyperkalemia = medical emergency. First intervention is IV calcium gluconate to protect the heart.
- Never give IV potassium by push. Always dilute and infuse slowly. Rapid IV potassium causes cardiac arrest.
- Peaked T waves are usually the first ECG change of hyperkalemia, but a normal ECG does not rule it out.
- Insulin drives potassium into cells (give with dextrose to prevent hypoglycemia). This is a temporary measure, not a cure.
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FAQs
Common questions about this mnemonic
IV calcium gluconate does not lower the potassium level. Instead, it stabilizes the cardiac cell membranes to protect the heart from the dysrhythmogenic effects of hyperkalemia. It works within minutes and provides a window of safety while other interventions (insulin, Kayexalate, dialysis) are initiated to actually lower the potassium. Think of it as buying time for the heart.
Hyperkalemia classically causes peaked (tall, narrow) T waves first, followed by a prolonged PR interval and flattened P waves, then a widened QRS complex, and finally a sine wave pattern progressing to ventricular fibrillation or asystole. These changes do not reliably match a specific potassium level, and some patients with high potassium have a normal ECG. The progression can be rapid and fatal.