What are the symptoms and treatment of hypokalemia (low potassium levels)?

Symptoms and Treatment of Hypokalemia

Hypokalemia, defined as serum potassium level <3.5 mEq/L, presents with various symptoms depending on severity and requires prompt treatment to prevent serious complications. 1

Classification of Hypokalemia

• Mild: 3.0-3.5 mEq/L 1
• Moderate: 2.5-2.9 mEq/L 1
• Severe: <2.5 mEq/L 1

Symptoms of Hypokalemia

Cardiac Manifestations

• ECG changes including T-wave flattening, ST-segment depression, and prominent U waves 1
• Cardiac arrhythmias, particularly ventricular arrhythmias 1
• First or second-degree atrioventricular block or atrial fibrillation 1
• Risk of progression to ventricular fibrillation, pulseless electrical activity (PEA), or asystole if untreated 1
• Increased risk of digitalis toxicity in patients taking digoxin 1, 2

Neuromuscular Symptoms

• Muscle weakness, which may be vague between 3.5 and 3.0 mEq/L but becomes more pronounced below 2.7 mEq/L 2
• Flaccid paralysis in severe cases 1, 3
• Paresthesia (abnormal sensations) and depressed deep tendon reflexes 1
• Respiratory difficulties due to respiratory muscle weakness, potentially leading to respiratory arrest 1, 3

Gastrointestinal Symptoms

• Decreased smooth muscle motility leading to ileus 3
• Constipation 4

Urinary Symptoms

• Urinary retention due to decreased smooth muscle motility 3

Causes of Hypokalemia

Decreased Intake

• Inadequate dietary potassium 5

Increased Losses

• Gastrointestinal losses: vomiting, diarrhea, fistulas 1, 5
• Renal losses: diuretic therapy (most common cause), primary hyperaldosteronism, secondary hyperaldosteronism, Bartter syndrome, Gitelman syndrome 1, 5, 4
• Magnesium deficiency causing renal potassium wasting 1

Transcellular Shifts

• Insulin administration 5, 3
• Catecholamine excess 3
• Familial periodic hypokalemic paralysis 3
• Thyrotoxic hypokalemic paralysis 3

Treatment of Hypokalemia

General Principles

• Address the underlying cause 5
• Route of administration depends on severity and symptoms 6
• Oral replacement is preferred if:
  • Patient has functioning gastrointestinal tract 6
  • Serum potassium >2.5 mEq/L 5
  • No ECG changes, neurologic symptoms, cardiac ischemia, or digitalis therapy 6

Oral Potassium Replacement

• Potassium chloride is indicated for treatment of hypokalemia with or without metabolic alkalosis, in digitalis intoxication, and in patients with hypokalemic familial periodic paralysis 7
• For metabolic acidosis, use alkalinizing potassium salts (potassium bicarbonate, citrate, acetate, or gluconate) 7
• Controlled-release potassium chloride preparations should be reserved for patients who cannot tolerate liquid or effervescent preparations due to risk of gastrointestinal ulceration and bleeding 7

Intravenous Potassium Replacement

• Indicated for severe hypokalemia (≤2.5 mEq/L), ECG abnormalities, or neuromuscular symptoms 5
• Slow infusion is recommended; bolus administration is potentially dangerous 1
• In diabetic ketoacidosis, potassium replacement should begin with fluid therapy if potassium is low, and insulin treatment should be delayed until potassium is ≥3.3 mEq/L to avoid arrhythmias or cardiac arrest 1

Special Considerations

• Concurrent magnesium deficiency should be addressed, as it can make potassium repletion difficult 1
• Monitor serum potassium levels frequently during replacement therapy 6
• For patients on diuretics, consider using a lower dose of diuretic or adding potassium-sparing diuretics 7, 6
• For patients with chronic kidney disease, hypertension, or heart failure, maintaining normal potassium levels is particularly important to prevent disease progression 6

Prevention

• Maintain adequate dietary potassium intake (WHO recommends at least 3,510 mg per day) 5
• Monitor potassium levels in high-risk patients (e.g., those on diuretics, digoxin, or with heart failure) 7
• The American Heart Association recommends maintaining serum potassium at ≥4.0 mEq/L in patients with heart failure 1

Common Pitfalls

• Failing to address magnesium deficiency when treating hypokalemia 1
• Overlooking secondary hyperaldosteronism as a cause of hypokalemia in volume-depleted patients 1
• Administering potassium too rapidly, which can cause cardiac arrhythmias 1
• Relying solely on serum potassium levels, which may not accurately reflect total-body potassium deficit 6