### Date : 2024-11-01 15:37 ### Topic : Hyperkalemia #medicine #cardiology ---- **Hyperkalemia** is a condition where the serum potassium level is elevated above the normal range, typically defined as a potassium level >5.0 mEq/L. Potassium is essential for maintaining cellular membrane potential, particularly in muscle cells, including cardiac muscle, and abnormalities in potassium levels can lead to serious complications, particularly in the heart. ### 1. **Causes of Hyperkalemia** Hyperkalemia can result from increased potassium intake, impaired potassium excretion, or shifts of potassium from inside cells to the bloodstream. Common causes include: - **Impaired Renal Excretion**: The kidneys are the primary organ for potassium excretion, so any dysfunction can lead to hyperkalemia. - **Chronic Kidney Disease (CKD)** or **Acute Kidney Injury (AKI)**: Reduced kidney function decreases potassium excretion. - **Medications**: Certain drugs impair potassium excretion, including: - **Potassium-sparing diuretics** (e.g., spironolactone, amiloride) - **ACE inhibitors and ARBs** (e.g., lisinopril, losartan) - **NSAIDs**: Can reduce kidney function and potassium excretion. - **Heparin**: Can affect aldosterone secretion, reducing potassium excretion. - **Adrenal Insufficiency (e.g., Addison's Disease)**: Reduced aldosterone levels lead to decreased potassium excretion. - **Increased Potassium Intake**: Rarely a cause on its own but can contribute in patients with kidney disease. - **Dietary Sources**: High-potassium foods (bananas, oranges, potatoes) or potassium supplements. - **Intravenous Potassium**: Excessive IV potassium administration. - **Cellular Shifts**: Conditions that cause potassium to move out of cells into the bloodstream. - **Acidosis**: Hydrogen ions enter cells to buffer the blood, causing potassium to shift out of cells. - **Tissue Breakdown**: Conditions like rhabdomyolysis, tumor lysis syndrome, and hemolysis release potassium from damaged cells. - **Insulin Deficiency**: Insulin promotes potassium entry into cells, so deficiency (as in diabetic ketoacidosis) can raise serum potassium levels. - **Beta Blockers**: Block potassium uptake by cells. ### 2. **Symptoms of Hyperkalemia** Symptoms of hyperkalemia vary with the severity and speed of potassium elevation. Many patients are asymptomatic with mild hyperkalemia. In more severe cases, symptoms can include: - **Muscle Weakness**: Mild weakness initially, progressing to severe weakness or even paralysis. - **Fatigue**: Generalized feeling of tiredness or weakness. - **Paresthesias**: Numbness or tingling, particularly in the extremities. - **Cardiac Symptoms**: The most dangerous effects of hyperkalemia are on the heart. High potassium levels can cause arrhythmias, potentially leading to sudden cardiac arrest. ### 3. **ECG Findings in Hyperkalemia** ECG changes in hyperkalemia progress with the severity of the potassium elevation. The following are common findings, usually in this order as potassium levels rise: - **Peaked T Waves**: Narrow, tall, and "tent-shaped" T waves, typically one of the earliest signs. - **Prolonged PR Interval**: As potassium increases, conduction slows. - **Flattening or Absence of P Waves**: High potassium can reduce atrial depolarization. - **Widened QRS Complex**: The QRS complex broadens, and eventually, the QRS and T wave can merge to form a "sine wave" pattern in severe cases. - **Ventricular Arrhythmias**: Severe hyperkalemia may progress to ventricular fibrillation or asystole, both of which are life-threatening. ### 4. **Management of Hyperkalemia** Treatment depends on the severity of hyperkalemia and the presence of ECG changes or symptoms. The main goals are to stabilize the heart, shift potassium back into cells, and remove excess potassium from the body: - **Stabilize the Cardiac Membrane**: - **Calcium Gluconate or Calcium Chloride**: IV calcium stabilizes the cardiac membrane and reduces the risk of arrhythmias. It does not lower potassium levels but is a first-line treatment in severe hyperkalemia with ECG changes. - **Shift Potassium into Cells**: - **Insulin and Glucose**: IV insulin (typically with glucose to prevent hypoglycemia) drives potassium into cells. - **Beta-2 Agonists** (e.g., albuterol): Inhaled beta-2 agonists promote potassium entry into cells, although they are less effective than insulin. - **Sodium Bicarbonate**: Used in cases of acidosis; helps to shift potassium into cells by correcting pH. Not used in all cases of hyperkalemia, mainly in metabolic acidosis. - **Eliminate Potassium from the Body**: - **Loop or Thiazide Diuretics**: Increase renal potassium excretion in patients with adequate kidney function. - **Sodium Polystyrene Sulfonate (Kayexalate)**: A potassium-binding resin that works in the gut to remove potassium. Its onset of action is slow, so it's used for mild to moderate cases rather than emergencies. - **Patiromer and Sodium Zirconium Cyclosilicate**: Newer potassium binders used for chronic hyperkalemia management; they act in the gut to remove potassium. - **Dialysis**: Used in cases of severe hyperkalemia, especially in patients with kidney failure who cannot excrete potassium. Dialysis rapidly removes potassium from the bloodstream. ### 5. **Prevention of Hyperkalemia** For patients at risk of hyperkalemia (e.g., those with chronic kidney disease or those taking potassium-sparing drugs), prevention strategies include: - **Dietary Restrictions**: Limiting high-potassium foods. - **Medication Review**: Regular monitoring and, if necessary, adjusting medications that increase potassium levels. - **Regular Monitoring**: Periodic blood tests to monitor potassium levels, especially in high-risk patients. ### 6. **Summary of Treatment Steps for Severe Hyperkalemia** In cases of severe hyperkalemia with ECG changes, the treatment sequence generally follows these steps: 1. **Administer Calcium Gluconate** (to stabilize cardiac membranes). 2. **Shift Potassium Intracellularly** with insulin and glucose, beta-2 agonists, and, if acidosis is present, sodium bicarbonate. 3. **Remove Potassium from the Body** using diuretics, potassium binders, or dialysis. ### Summary - **Hyperkalemia** is a potentially life-threatening condition, especially when severe, as it can lead to cardiac arrhythmias. - **Common Causes**: Impaired renal excretion, medications, acidosis, tissue breakdown, and excessive potassium intake. - **ECG Changes**: Peaked T waves, wide QRS, loss of P waves, and eventually, a sine-wave pattern in severe cases. - **Treatment**: Stabilize the heart, shift potassium into cells, and remove potassium from the body. ### Reference: - ### Connected Documents: -