Hyperkalemia
Hyperkalemia is a serum potassium level above 5.0 mEq/L, most often from decreased kidney excretion, transcellular shifts, or excess intake, with levels above 6.0-6.5 mEq/L or any ECG change constituting a medical emergency from the risk of fatal arrhythmia. Treatment sequences cardiac membrane stabilization with calcium, transcellular potassium shifting with insulin/dextrose and albuterol, then definitive potassium removal with binders, diuretics, or dialysis.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
Hyperkalemia is defined as a serum potassium level greater than 5.0 mEq/L (5.0 mmol/L), with levels greater than 6.0 to 6.5 mEq/L capable of causing fatal cardiac arrhythmias.
- Epidemiology
Hyperkalemia is common in patients with chronic kidney disease (CKD), particularly as GFR declines below 20 mL/min/1.73 m2, and is a frequent cause of hospital admission and dialysis initiation.
- Risk factors
Advanced CKD or oliguric acute kidney injury, particularly with GFR below 20 mL/min/1.73 m2, the dominant risk factor through impaired renal potassium excretion.
- Pathophysiology
Potassium homeostasis depends on both transcellular distribution and renal excretion; hyperkalemia arises when cellular potassium shifts out of cells, renal excretion is impaired, or intake exceeds excretory capacity.
- Clinical features
Many patients are asymptomatic, with hyperkalemia detected incidentally on routine labs, especially in mild to moderate elevations.
- Differential diagnosis
Pseudohyperkalemia: an artifact from hemolysis during sampling, a tight tourniquet, clenched fist, or extreme leukocytosis/thrombocytosis; a repeat plasma specimen is normal.
- Diagnosis
Hyperkalemia is confirmed by a serum (or plasma, if pseudohyperkalemia is suspected) potassium level greater than 5.0 mEq/L, with severity graded by the absolute level and presence of ECG changes…
- Management
First, in any patient with ECG changes or potassium above 6.0 to 6.5 mEq/L, give IV calcium gluconate to stabilize the cardiac membrane, since calcium does not lower serum potassium and is never…
- Complications
Fatal cardiac arrhythmia and cardiac arrest, including ventricular fibrillation and asystole from progression to a sine wave pattern, the end result of untreated severe hyperkalemia and the reason…
- Prognosis
Prognosis is excellent with prompt recognition and treatment of ECG changes, since calcium gluconate rapidly stabilizes the cardiac membrane and prevents progression to fatal arrhythmia.
- Prevention
Monitor serum potassium and creatinine within 1-2 weeks of starting or up-titrating an ACE inhibitor, ARB, or mineralocorticoid receptor antagonist, and periodically thereafter, particularly in patients with CKD or diabetes.
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Acute kidney injury
Acute kidney injury is a sudden rise in serum creatinine or fall in urine output from prerenal, intrinsic, or postrenal causes, defined and staged by KDIGO criteria. Management targets the underlying cause, corrects volume and electrolyte derangements, and escalates to renal replacement therapy for refractory hyperkalemia, acidosis, volume overload, or uremia.
- Rhabdomyolysis
Rhabdomyolysis is necrosis of skeletal muscle with release of myoglobin, creatine kinase, and intracellular electrolytes into the circulation, diagnosed by a serum creatine kinase at least five times the upper limit of normal (typically over 1500 U/L) with a urine dipstick positive for blood but no red cells on microscopy; treatment is aggressive isotonic intravenous fluid to a urine output of 200 to 300 mL/h and correction of hyperkalemia, with acute kidney injury from pigment nephropathy the dominant complication.
- Tumor lysis syndrome (TLS)
Tumor lysis syndrome is a metabolic oncologic emergency in which massive tumor cell breakdown, spontaneous or chemotherapy-induced, releases potassium, phosphate, and nucleic acids into the blood, producing hyperuricemia, hyperkalemia, hyperphosphatemia, and secondary hypocalcemia that can precipitate acute kidney injury, arrhythmia, seizure, and death. Risk-stratified prophylaxis with hydration plus allopurinol or rasburicase before chemotherapy, and aggressive correction of electrolytes with renal replacement therapy when needed, are the cornerstones of management.
- Hypomagnesemia
Hypomagnesemia is a serum magnesium level below 1.7 mg/dL, most often caused by gastrointestinal losses, proton pump inhibitors, or renal magnesium wasting from diuretics and other drugs. It causes concurrent hypokalemia and hypocalcemia and can potentiate cardiac arrhythmias, and treatment is intravenous magnesium sulfate for significant symptoms or slow-release oral repletion for milder deficiency.