Among hospitalized patients with acute hyperkalemia (serum K⁺ >6.5 mEq/L), what is the most common underlying etiology?

Explanation

## Most Common Cause of Acute Hyperkalemia in Hospitalized Patients **Key Point:** Acute kidney injury (AKI) with reduced urine output is the most common cause of acute hyperkalemia in hospitalized patients. AKI can develop rapidly (hours to days) from sepsis, hypotension, nephrotoxic drugs, or contrast exposure, and leads to sudden inability to excrete potassium. **High-Yield:** Acute hyperkalemia (K⁺ >6.5 mEq/L) typically occurs in one of two settings: 1. **Acute kidney injury** — loss of filtration capacity 2. **Massive transcellular shift** — rhabdomyolysis, tumor lysis, hemolysis, or severe acidosis In the hospital setting, AKI is far more frequent than the other causes combined. ### Epidemiology of Acute Hyperkalemia Causes | Cause | Frequency | Clinical Context | |-------|-----------|------------------| | **Acute kidney injury** | ~50–60% | Sepsis, hypotension, nephrotoxins, contrast | | Tumor lysis syndrome | ~10–15% | Acute leukemia, lymphoma (post-chemotherapy) | | Rhabdomyolysis | ~10–15% | Crush injury, statins, sepsis, exertion | | Adrenal insufficiency | ~5–10% | Acute adrenal crisis (rare in acute hyperkalemia) | | Other (hemolysis, acidosis, drugs) | ~10–20% | Variable | **Clinical Pearl:** In the ICU, sepsis-induced AKI is the single most common precipitant. Patients on ACE inhibitors, ARBs, or NSAIDs are at even higher risk when AKI develops. **Mnemonic — ACUTE Hyperkalemia (Acute causes):** - **A**cute kidney injury - **C**ell lysis (tumor, rhabdo, hemolysis) - **U**nderlying acidosis - **T**ranscellular shift - **E**xcessive intake (rare in acute setting) In hospitalized patients, **A** (AKI) dominates.