Before We Start
Recognizing the problem versus finding its source
MURDER (the companion mnemonic) walks through the signs and symptoms of high potassium. MACHINE goes one level deeper — the seven distinct mechanisms that can actually cause potassium to climb in the first place.
💡 Memory Trick
MACHINE: Medications · Acidosis · Cellular destruction · Hypoaldosteronism · Intake · Nephrons · Excretion. Seven genuinely different root causes, each requiring a different fix.
The Key Points
Seven causes, and the specific fix each one implies
M
Medications — several common drug classes can raise potassium
ACE inhibitors, NSAIDs, and potassium-sparing diuretics can all raise serum potassium, through different mechanisms tied to how each drug class affects kidney handling of potassium.
💊 A patient on an ACE inhibitor for blood pressure control who also starts a potassium-sparing diuretic is at compounded risk for hyperkalemia, since both drug classes push potassium in the same direction.
A
Acidosis — both metabolic and respiratory
In acidosis, hydrogen ions shift into cells in exchange for potassium moving out into the bloodstream, raising serum potassium levels even without any actual excess total-body potassium.
💊 A patient in diabetic ketoacidosis can present with an elevated serum potassium level despite actually having a total-body potassium deficit, since the acidosis itself is temporarily shifting potassium out of cells.
C
Cellular destruction — releasing intracellular potassium into circulation
Burns, traumatic injury, and hemolysis all destroy large numbers of cells at once, releasing the potassium normally held inside those cells directly into the bloodstream.
💊 A patient with extensive burn injuries is at real risk for hyperkalemia in the acute period, purely from the sheer volume of cell destruction releasing intracellular potassium into circulation.
H/I/N/E
Hypoaldosteronism, Intake, Nephrons, and Excretion — the remaining four mechanisms
Hypoaldosteronism (as in Addison's disease) removes the hormonal signal the kidneys normally use to excrete potassium. Excessive dietary Intake can overwhelm normal excretion capacity. Renal failure (Nephrons) directly impairs the kidney's ability to filter and excrete potassium. And impaired Excretion more broadly covers any situation where potassium isn't being eliminated at a normal rate.
💊 A patient with renal failure has fundamentally reduced capacity to excrete excess potassium through any mechanism, which is why hyperkalemia is such a common and closely monitored complication in this population specifically.
🏥 Clinical Scenario
A patient with newly diagnosed renal failure is found to have an elevated potassium level, and the care team is also reviewing whether the patient's home ACE inhibitor should be continued.
Step 1
Identify the primary MACHINE cause at play: The renal failure itself falls under "Nephrons" — impaired kidney function directly reduces the body's ability to excrete potassium through its normal route.
Step 2
Identify a compounding cause: The home ACE inhibitor falls under "Medications" — continuing it on top of impaired renal excretion would compound the hyperkalemia risk rather than existing as an isolated, unrelated concern.
Step 3
Recognize why identifying both causes matters: A patient can have more than one MACHINE mechanism contributing simultaneously — recognizing both the renal cause and the medication-related cause here changes the treatment plan beyond addressing potassium in isolation.
Step 4
Conclusion: MACHINE is most useful not just for naming one cause, but for checking whether multiple mechanisms are stacking together in the same patient, since that changes what actually needs to be addressed.
📌 NCLEX Application
NCLEX questions test whether you can identify which MACHINE mechanism explains a described hyperkalemia case — a specific medication, an acid-base disturbance, tissue destruction, an endocrine cause, dietary intake, or renal impairment — and often expect you to recognize when more than one mechanism is contributing at once.
⚠️ The Trap — Assuming Hyperkalemia Always Means Excess Total-Body Potassium
A common trap is assuming an elevated serum potassium level always reflects excess total-body potassium. In acidosis specifically, potassium shifts out of cells into the bloodstream without any actual increase in the body's total potassium — the serum level rises while the underlying cause is a redistribution, not a true excess, which changes how the situation should be corrected.
✓ Quick Self-Test
Answer before checking:
1. What does MACHINE stand for?
2. How does acidosis raise serum potassium without an actual excess of total-body potassium?
3. Name two medication classes that can cause hyperkalemia.
4. Why does cellular destruction (burns, trauma, hemolysis) raise potassium?
5. How does MACHINE relate to the MURDER mnemonic?
Answers:
1. Medications, Acidosis, Cellular destruction, Hypoaldosteronism, Intake, Nephrons, Excretion.
2. Hydrogen ions shift into cells in exchange for potassium moving out into the bloodstream, raising the serum level through redistribution rather than true excess.
3. ACE inhibitors and potassium-sparing diuretics (also NSAIDs).
4. Because it releases the potassium normally held inside those destroyed cells directly into the bloodstream.
5. MURDER teaches the signs and symptoms of hyperkalemia; MACHINE teaches the underlying causes — they're companion mnemonics covering different aspects of the same condition.