Among patients presenting to a tertiary care hospital in India with acute symptomatic hyperkalemia (K⁺ >6.5 mEq/L with ECG changes), what is the most common underlying cause?

Explanation

## Acute Symptomatic Hyperkalemia: Most Common Cause **Key Point:** Acute kidney injury (AKI) with oliguria is the most common cause of **symptomatic hyperkalemia** requiring emergency treatment in hospital settings. ### Why AKI with Oliguria Is Most Common **High-Yield:** AKI causes rapid potassium accumulation because: 1. **Sudden loss of renal function** — GFR drops to <5 mL/min/1.73m² over hours to days 2. **Oliguria** — urine output <400 mL/day means <1–2 mEq K⁺ excretion/day 3. **Rapid rise in serum K⁺** — can increase 0.5–1.0 mEq/L per day without dialysis 4. **Acute presentation** — patients develop ECG changes and symptoms quickly In a busy tertiary hospital in India, the most common causes of AKI are: - Sepsis (most frequent) - Nephrotoxic drugs (aminoglycosides, NSAIDs, cisplatin) - Contrast-induced nephropathy (CIN) - Prerenal azotemia from dehydration **Clinical Pearl:** Symptomatic hyperkalemia (peaked T waves, widened QRS, bradycardia, cardiac arrhythmias) is almost always **acute**, not chronic. Chronic hyperkalemia in CKD stage 4–5 is usually asymptomatic because the rise is gradual and the body adapts. ### Comparison of Causes of Acute vs. Chronic Hyperkalemia | Cause | Onset | Severity | Symptoms | ECG Changes | Frequency in Hospital | |-------|-------|----------|----------|-------------|----------------------| | AKI with oliguria | Hours–days | Severe (K⁺ >6.5) | Yes | Yes | **Most common** | | Rhabdomyolysis | Hours–days | Severe | Yes (if AKI develops) | Yes (if K⁺ >6) | Common (but often secondary to AKI) | | DKA | Hours–days | Moderate–severe | Yes | Variable | Common in uncontrolled DM | | K⁺ supplementation | Days–weeks | Mild–moderate | Rare | Rare | Uncommon (requires excess intake) | **Warning:** Do not confuse the most common cause of **chronic** hyperkalemia (CKD with reduced excretion) with the most common cause of **acute symptomatic** hyperkalemia (AKI). The question specifies "acute symptomatic," which points to AKI. ### Mechanism: Why AKI Causes Rapid Hyperkalemia ```mermaid flowchart TD A[Acute Kidney Injury]:::outcome --> B[GFR drops to <5 mL/min]:::action B --> C[Oliguria: UOP <400 mL/day]:::action C --> D[K+ excretion <1-2 mEq/day]:::action D --> E[Serum K+ rises 0.5-1.0 mEq/L/day]:::action E --> F{K+ >6.5 mEq/L?}:::decision F -->|Yes| G[Peaked T waves, widened QRS]:::outcome F -->|Yes| H[Cardiac arrhythmias, bradycardia]:::urgent I[Transcellular shift from acidosis<br/>+ Tissue breakdown from AKI] --> E ``` **Mnemonic:** **ACUTE** — Acute Kidney Injury with Oliguria is the most Common cause of Urgent hyperkalemia needing Treatment in Emergency settings.