USMLE/COMLEX - Step 2 - Hyperkalemia

USMLE/COMLEX - Step 2 - Hyperkalemia Serum potassium greater than 5 mEq/L is defined as hyperkalemia. Increased potassium intake

• Iatrogenic (e.g., IV fluids containing potassium)
• High potassium diet (most fruits, potatoes)

Extracellular potassium shift

• Acidosis
• Hyperosmolarity (e.g., diabetic ketoacidosis, mannitol)
• Insulin deficiency
• Drugs (e.g., beta blockers, succinylcholine)
• Exercise

Extracellular potassium release

• Rhabdomyolysis
• Tumor lysis syndrome
• Pseudohyperkalemia: incorrect blood drawing technique leading to RBC hemolysis (e.g., fist clenching)
• Blood resorption (e.g., hematoma)

Reduced potassium excretion

• NSAIDs (e.g., ketorolac, diclofenac etc.)
• ACE-Is (e.g., captopril, lisinopril etc.)
• ARBs (e.g., valsartan, losartan etc.)
• Potassium sparing diuretics (e.g., spironolactone, triamterene, amiloride)
• Trimethoprim (antibiotic)

Extracellular potassium shift

• Beta-blockers
• Succinylcholine
• Digoxin

Patient can be asymptomatic. Symptoms usually present when serum potassium > 7 mEq/L or serum potassium levels increase rapidly. Common symptoms: GI: Nausea, vomiting, intestinal colic Neuromuscular: Muscle weakness, hyporeflexia, areflexia, flaccid paralysis, paresthesia Cardiac: Cardiac arrhythmias Hyperkalemia can be confirmed by repeating a blood sample to exclude pseduohyperkalemia. ECG, basic metabolic profile, arterial blood gas (ABGs), CBC, liver enzymes ECG Findings:

• Tall, peaked T waves with shortened QT interval
• Widening of QRS complex
• Loss of p waves
• Sine waves

If serum potassium > 6.5 mEq/L or ECG changes attributable to hyperkalemia are observed then following steps are taken. 1st Step: Cardiac membrane stabilization Give IV calcium gluconate or calcium chloride 2nd Step: Intracellular potassium shift Give sodium bicarbonate and/or insulin with glucose to shift potassium from extracellular compartment to intracellular Beta-agonists (e.g., albuterol) can also be used 3rd Step: Potassium elimination Remove potassium from IV fluids and diet Potassium-binding agents, loop diuretics and dialysis can be used to remove potassium from the body Potassium-binding agents (e.g., sodium polystyrene sulfonate, patiromer, sodium zirconium cyclosilicate) are contraindicated in ileus, bowel obstruction, gut ischemia and pancreatic transplants. Dialysis is an appropriate treatment for hyperkalemia in patients with renal failure or therapy-refractory hyperkalemia.