From the Guidelines
Hypokalemia workup should start by assessing the severity of potassium deficiency and identifying potential causes, as hypokalemia is often the result of diuresis, potassium-free intravenous fluids, vomiting, diarrhea, and other endocrine and renal mechanisms 1.
Initial Evaluation
- Measure Serum Potassium Levels: Assess for symptoms such as muscle weakness, fatigue, and cardiac arrhythmias, and define hypokalemia as K<3.5 mEq/L 1.
- Basic Laboratory Tests: Include complete blood count (CBC), basic metabolic panel (BMP), magnesium level, and renal function tests (including creatinine and urea).
- Urinalysis: Evaluate for renal potassium wasting by measuring urine potassium, sodium, and creatinine to calculate the transtubular potassium gradient (TTKG).
- Hormonal Evaluation: Consider measuring aldosterone and renin levels, using the aldosterone-to-renin ratio (ARR) for primary aldosteronism screening, especially if spontaneous or diuretic-induced hypokalemia are suspected 1.
- Medication Review: Assess for medications that can cause hypokalemia, such as loop and thiazide diuretics (e.g., furosemide, hydrochlorothiazide), laxatives, and certain antibiotics.
- Dietary Assessment: Evaluate dietary potassium intake and consider the possibility of gastrointestinal losses (e.g., diarrhea).
- ECG: Perform an electrocardiogram to assess for cardiac effects of hypokalemia, such as QT interval prolongation, and be aware that changes on the ECG associated with hypokalemia include broadening of the T waves, ST-segment depression, and prominent U waves 1.
Treatment of hypokalemia depends on the severity and cause, with mild cases (potassium level > 3.5 mEq/L) potentially managed with oral potassium supplementation, and more severe cases or those with significant symptoms requiring intravenous potassium chloride, typically at a rate not exceeding 10 mEq/hour in a general medical setting, with close cardiac monitoring 1. Always prioritize correcting the underlying cause of hypokalemia.
From the Research
Diagnosis of Hypokalemia
- Hypokalemia is defined as a potassium level less than 3.5 mEq/L 2
- It can be due to either potassium deficiency or net potassium shifts from the extracellular to the intracellular compartment 3
- Measurement of spot urine for potassium and creatinine, as well as evaluation of acid-base status, can be used as an initial step in the diagnosis of hypokalemia 3
Evaluation of Hypokalemia
- Serum potassium concentration is an inaccurate marker of total-body potassium deficit 4
- Mild hypokalemia may be associated with significant total-body potassium deficits, and conversely, total-body potassium stores can be normal in patients with hypokalemia due to redistribution 4
- Subsequent evaluations, such as measurement of spot urinary chloride, blood pressure, serum aldosterone, renin, and cortisol levels, may be needed in certain circumstances 3
Treatment of Hypokalemia
- Management consists of intravenous potassium replacement during cardiac monitoring for patients with marked symptoms, ECG abnormalities, or severe hypokalemia (ie, level less than 3.0 mEq/L) 2
- Oral replacement is appropriate for asymptomatic patients with less severe hypokalemia 2
- The speed and extent of potassium replacement should be dictated by the clinical picture and guided by frequent reassessment of serum potassium concentration 4
- Potassium-sparing diuretics might be helpful in cases where renal potassium clearance is abnormally increased from potassium wasting 4
Urgent Treatment of Hypokalemia
- Indications for urgent treatment include severe or symptomatic hypokalemia; abrupt changes in potassium levels; ECG changes; or the presence of certain comorbid conditions 5
- Hypokalemia is treated with oral or intravenous potassium 5
- In cases of hyperkalemia, intravenous calcium is administered to patients with electrocardiography changes, and insulin, usually with concomitant glucose, and albuterol are preferred to lower serum potassium levels in the acute setting 5