Potassium (K⁺) is one of the most vital electrolytes in the human body, playing a critical role in:
- Cell metabolism
- Nerve impulse transmission
- Cardiac and skeletal muscle contraction
- Acid-base balance
Normal serum potassium levels range from 3.5 to 5.0 mEq/L.
Both hyperkalemia (>5 mEq/L) and hypokalemia (<3.5 mEq/L) can lead to dangerous cardiac dysrhythmias, respiratory failure, and even death if untreated. Nurses, doctors, and medical students must master potassium imbalances for safe clinical practice and exam readiness (NCLEX, USMLE, NEET-PG, etc.).
Potassium Homeostasis
Potassium is mostly found inside cells (intracellular fluid), with only a small fraction circulating in blood. The body maintains potassium balance through:
- Kidneys – primary regulator (excretes excess potassium).
- GI tract – absorption from food and excretion.
- Hormones – insulin and aldosterone shift potassium into cells.
Any disruption in this balance leads to either hyperkalemia or hypokalemia.
Hyperkalemia (>5.0 mEq/L)
Signs & Symptoms (TIGHT & CONTRACTED)
- Muscle cramps and weakness
- Urine abnormalities (oliguria)
- Respiratory distress
- Decreased cardiac contractility (↓ HR, ↓ BP)
- ECG changes: tall peaked T waves, widened QRS, flat P waves, prolonged PR interval
- Reflex changes (↑ deep tendon reflexes)
Risk Factors
- Medications: potassium-sparing diuretics (Spironolactone), ACE inhibitors, NSAIDs
- Excessive intake: rapid potassium infusion, salt substitutes
- Decreased excretion: kidney disease, dialysis patients, adrenal insufficiency (Addison’s disease)
- Other causes: tissue damage, acidosis, hyperuricemia, hypercatabolism
Management
- Monitor ECG continuously
- Stop IV/PO potassium intake
- Potassium-restricted diet
- Administer potassium-excreting diuretics
- Prepare patient for dialysis (severe cases)
- IV calcium gluconate (protects heart)
- IV sodium bicarbonate (shifts K⁺ into cells)
Note: Avoid salt substitutes or potassium-containing foods.
Hypokalemia (<3.5 mEq/L)
Signs & Symptoms
- Weak, thready, irregular pulse
- Orthostatic hypotension
- Shallow respirations
- Anxiety, confusion, lethargy, coma
- Paresthesias (tingling sensations)
- Hyporeflexia (weak reflexes)
- Decreased bowel sounds (constipation)
- Nausea, vomiting, abdominal distention
- ECG changes: ST depression, shallow or inverted T wave, prominent U wave
Risk Factors
- Actual body potassium loss: vomiting, diarrhea, NG suction, excessive sweating
- Inadequate intake: fasting, NPO (nothing by mouth)
- Potassium shift into cells: alkalosis, hyperinsulinism
- Dilutional states: water intoxication, IV therapy with K⁺-deficient fluids
Management
- Oral potassium supplements (mild cases)
- IV potassium chloride (severe cases)
- Potassium-retaining diuretics (spironolactone)
- Encourage potassium-rich diet (bananas, oranges, potatoes, spinach, avocados)
Critical Rule: Potassium is NEVER given IV push, IM, or subcutaneous — it must always be diluted and administered via infusion pump, as rapid administration can cause fatal arrhythmias.
ECG Changes in Potassium Imbalance
| Condition | ECG Findings |
|---|---|
| Hyperkalemia | Tall peaked T waves, flat P waves, widened QRS, prolonged PR interval |
| Hypokalemia | ST depression, shallow or inverted T waves, prominent U wave |
Relationship Between Sodium and Potassium
Potassium and sodium are opposites in balance:
- ↑ Sodium = ↓ Potassium
- ↓ Sodium = ↑ Potassium
This is due to their exchange in the sodium-potassium pump, which maintains cellular homeostasis.
Clinical Importance
- Hyperkalemia: Medical emergency due to risk of sudden cardiac arrest.
- Hypokalemia: Dangerous due to risk of muscle paralysis and arrhythmias.
- Potassium monitoring is essential in patients on diuretics, ACE inhibitors, or dialysis.
Quick Potassium Imbalance Reference Table
| Feature | Hyperkalemia (>5) | Hypokalemia (<3.5) |
|---|---|---|
| Symptoms | Muscle cramps, ↓ HR, ↓ BP, ECG changes | Weak pulse, constipation, lethargy, ECG changes |
| ECG | Tall T waves, flat P, wide QRS | ST depression, shallow T, U wave |
| Risk Factors | Kidney disease, K-sparing diuretics, acidosis, excess intake | GI loss, fasting, alkalosis, insulin therapy, water intoxication |
| Treatment | Stop K⁺ intake, dialysis, IV Ca²⁺, diuretics | K⁺ supplements (PO/IV), diet ↑ K⁺, K-retaining diuretics |
| Danger | Cardiac arrest | Respiratory failure, arrhythmias |
FAQs
Q1. What foods are rich in potassium?
Bananas, oranges, potatoes, spinach, tomatoes, avocados, and beans.
Q2. Why is hyperkalemia more dangerous than hypokalemia?
Because it can cause sudden, fatal arrhythmias within minutes.
Q3. Why can’t potassium be given IV push?
Because rapid infusion can cause instant cardiac arrest.
Q4. Which drugs commonly affect potassium levels?
- Increase K⁺: spironolactone, ACE inhibitors, NSAIDs
- Decrease K⁺: loop and thiazide diuretics, laxatives
Q5. How is potassium imbalance monitored?
Through serum potassium levels, ECG monitoring, and clinical symptoms.
