A 48-year-old woman with bipolar I disorder on lithium 1000 mg daily presents with acute onset confusion, coarse tremor, and severe diarrhea. Her serum lithium level is 2.1 mEq/L. Which of the following interventions is NOT indicated in the acute management of severe lithium toxicity?

Explanation

## Management of Acute Severe Lithium Toxicity ### Correct Answer Rationale **Key Point:** Thiazide diuretics are **contraindicated** in lithium toxicity. They reduce glomerular filtration and increase proximal tubular reabsorption of lithium, thereby **increasing** serum lithium levels and worsening toxicity. ### Acute Lithium Toxicity Management Algorithm ```mermaid flowchart TD A[Severe lithium toxicity<br/>Serum Li >2.0 mEq/L<br/>+ CNS/cardiac signs]:::outcome --> B[STOP lithium immediately]:::action B --> C[IV normal saline<br/>aggressive hydration]:::action C --> D{Serum Li level<br/>& clinical response?}:::decision D -->|Li >2.5 or<br/>no improvement| E[Hemodialysis]:::action D -->|Li 1.5-2.5 &<br/>improving| F[Continue IV fluids<br/>+ supportive care]:::action E --> G[Monitor electrolytes<br/>cardiac function]:::action F --> G H[AVOID: Thiazides<br/>NSAIDs, ACE-I]:::urgent --> I[These increase<br/>Li reabsorption]:::outcome ``` ### Why Each Intervention Is Correct (Except the Answer) | Intervention | Indication | Mechanism | |--------------|-----------|----------| | **IV saline + hydration** | ✓ First-line | Increases GFR and urine flow; dilutes serum Li; enhances renal clearance | | **Hemodialysis** | ✓ For severe cases | Removes lithium directly; indicated if Li >2.5 mEq/L or persistent CNS/cardiac toxicity | | **Thiazide diuretics** | ✗ **CONTRAINDICATED** | Reduces GFR and increases proximal tubular reabsorption → **increases** serum Li | | **Electrolyte correction** | ✓ Essential | Hyponatremia, hypokalemia worsen neurotoxicity; cardiac monitoring prevents arrhythmias | ### High-Yield Pharmacology **High-Yield:** Lithium clearance depends on **glomerular filtration rate (GFR)**. Any drug that reduces GFR or increases tubular reabsorption will increase lithium levels: **Mnemonic: DRUGS THAT INCREASE LITHIUM LEVELS (SANE)** - **S**alt depletion (diuretics, NSAIDs) - **A**CE inhibitors / ARBs - **N**SAIDs - **E**lder age (reduced GFR) **Clinical Pearl:** Thiazides are particularly dangerous because they cause both volume depletion (reducing GFR) and direct increase in proximal tubular lithium reabsorption via Na^+^-Li^+^ exchange in the proximal tubule. ### Correct Management Steps for Severe Toxicity 1. **Discontinue lithium immediately** 2. **Aggressive IV normal saline** (0.9% NaCl) — target urine output 200–300 mL/hr 3. **Monitor serum Li, Na^+^, K^+^, Cr, ECG** every 2–4 hours 4. **Hemodialysis** if: - Serum Li >2.5 mEq/L - Severe neurological symptoms (seizures, altered mental status) - Renal impairment - Cardiac arrhythmias 5. **Supportive care:** Antiemetics, electrolyte replacement, cardiac monitoring **Warning:** Do not use loop diuretics or thiazides. Do not restrict sodium intake (this increases Li reabsorption). Do not use NSAIDs.