Hyperkalemia - Symptoms, ECG Changes & Mnemonic (MURDER)

By -VHTC

16 July

What Is Hyperkalemia?

Hyperkalemia is defined as a serum potassium concentration >5.0 mmol/L. It is a potentially life-threatening electrolyte imbalance that requires immediate attention—especially when it impacts cardiac conduction and neuromuscular function.

Why Is Potassium Important?

Potassium (K⁺) is vital for:

Nerve impulse transmission
Muscle contraction
Cardiac action potentials
Cellular metabolism

Even minor deviations from normal levels can disrupt these processes, making hyperkalemia a critical clinical emergency.

Normal Potassium Levels

Category	Potassium Range (mmol/L)
Normal	3.5 – 5.0
Mild Hyperkalemia	5.1 – 5.9
Moderate	6.0 – 6.9
Severe	≥7.0

Hyperkalemia - Symptoms, ECG Changes & Mnemonic (MURDER)

Causes of Hyperkalemia

Hyperkalemia can result from:

1. Increased Potassium Intake

Overuse of potassium supplements
Potassium-rich foods in renal failure patients

2. Impaired Renal Excretion

Acute or chronic kidney disease
Addison’s disease
Potassium-sparing diuretics (spironolactone)

3. Cellular Shift (Intracellular to Extracellular)

Burns or trauma
Acidosis (e.g., diabetic ketoacidosis)
Rhabdomyolysis
Tumor lysis syndrome

4. Medications

ACE inhibitors
ARBs
NSAIDs
Heparin
Beta-blockers

Mnemonic MURDER: Signs & Symptoms of Hyperkalemia

To remember the classic signs and symptoms of hyperkalemia, use the powerful mnemonic:

MURDER

M – Muscle cramps
U – Urine abnormalities (oliguria, anuria)
R – Respiratory distress
D – Decreased cardiac contractility
E – EKG changes
R – Reflexes altered (hyperreflexia or areflexia)

Let’s break it down further:

Muscle Cramps

Patients may experience weakness, twitching, or cramps, starting in lower limbs and potentially progressing to paralysis.

Urine Abnormalities

Due to impaired renal function, urine output may decline. This worsens potassium retention and the condition itself.

Respiratory Distress

As muscles weaken, even the diaphragm and intercostal muscles may be affected, leading to breathing difficulties.

Decreased Cardiac Contractility

Potassium interferes with action potentials, decreasing the force of cardiac contractions. This can cause hypotension or cardiac arrest.

EKG Changes (see detailed section below)

T-wave and QRS complex abnormalities are hallmark features of potassium imbalance.

Reflexes Altered

Initially, hyperreflexia may be seen, but as the condition worsens, reflexes may diminish due to nerve conduction issues.

ECG Changes in Hyperkalemia

ECG is a vital tool in assessing the severity of hyperkalemia.

Serum K⁺ Level (mmol/L)	ECG Change
5.5 – 6.5	Tall, peaked T waves
6.5 – 7.5	Loss of P wave, prolonged PR interval
7.5 – 8.5	Widened QRS complex
>8.5	Sine wave pattern → Cardiac arrest imminent

Key Points:

Peaked T waves are often the first sign.
Progression leads to QRS widening, ventricular fibrillation, and asystole.
Always correlate ECG changes with potassium levels.

Complications: Why Hyperkalemia Can Be Fatal

Hyperkalemia is dangerous because:

It causes life-threatening arrhythmias.
Sudden potassium shifts can result in asystole or ventricular fibrillation.
Respiratory muscle paralysis can lead to hypoventilation and hypoxia.

Diagnosis and Laboratory Findings

Key Diagnostic Tests:

Serum potassium (>5.0 mmol/L)
Blood urea and creatinine (renal function)
ABG (acidosis may worsen K⁺ levels)
Serum glucose (for diabetic causes)
EKG (for cardiac involvement)

Pseudohyperkalemia

A false elevation due to hemolysis during blood draw. Always confirm with repeat testing.

Treatment of Hyperkalemia

Management depends on the severity and presence of ECG changes:

1. Cardiac Stabilization

Calcium gluconate IV → Stabilizes cardiac membranes (doesn’t reduce K⁺)

2. Shift K⁺ Into Cells

Insulin + glucose infusion
Sodium bicarbonate (if acidosis is present)
Beta-2 agonists (e.g., salbutamol)

3. Remove K⁺ From Body

Loop diuretics (furosemide)
Sodium polystyrene sulfonate (Kayexalate)
Hemodialysis (for severe or refractory cases)

4. Stop Offending Agents

Discontinue:

ACE inhibitors
Potassium-sparing diuretics
NSAIDs

Prevention and Monitoring

Who Should Be Monitored Closely?

CKD patients
Patients on RAAS blockers
Diabetics
Individuals with a history of hyperkalemia

Preventive Measures

Low-potassium diet (avoid bananas, oranges, potatoes)
Regular blood tests
Adjusting medications carefully
Hydration and renal function monitoring

Clinical Case Study

Case: Dialysis-Dependent Patient with Muscle Weakness

A 65-year-old male on hemodialysis presents with muscle cramps and palpitations. ECG shows tall T waves and QRS widening. Serum potassium: 7.4 mmol/L.

Management:

IV calcium gluconate administered immediately
Followed by insulin-glucose infusion
Emergency dialysis performed

Outcome:

Symptoms resolved
Potassium normalized to 4.6 mmol/L
Discharged with adjusted diet and medication

FAQs on Hyperkalemia

Q1: What is the most common cause of hyperkalemia?

Renal failure is the most common cause.

Q2: Is hyperkalemia always symptomatic?

No, mild cases can be asymptomatic. Severe hyperkalemia often presents with neuromuscular and cardiac symptoms.

Q3: Can hyperkalemia be reversed?

Yes, with timely intervention using medications or dialysis.

Q4: What foods should I avoid in hyperkalemia?

Bananas, oranges, spinach, potatoes, tomatoes, and salt substitutes.

Q5: When should I go to the hospital?

If you experience palpitations, severe muscle weakness, or breathing difficulties, seek emergency care.

Final Takeaway

Hyperkalemia is a silent killer if not recognized early. But with tools like the MURDER mnemonic, you can quickly recall its red-flag signs and act promptly. Whether you're a medical student, nurse, or patient, understanding this condition is vital.

Stay alert for:

Muscle cramps
ECG changes
Decreased cardiac output

And always act fast—because hyperkalemia doesn’t knock twice.