A 52-year-old woman with bipolar I disorder has been on lithium 900 mg daily for 3 years with good mood stabilization. She presents to the emergency department with confusion, coarse tremor, ataxia, and slurred speech for 2 days. Her husband reports she had gastroenteritis 3 days ago with vomiting and diarrhea, and has been drinking less water. Serum lithium level is 2.8 mEq/L (normal therapeutic range 0.6–1.2 mEq/L). Serum creatinine is 1.4 mg/dL (baseline 0.9 mg/dL). What is the most appropriate immediate management?

Explanation

## Acute Lithium Toxicity Management **Key Point:** Acute lithium toxicity with neurological symptoms (confusion, tremor, ataxia) and markedly elevated serum level (2.8 mEq/L) requires aggressive fluid resuscitation and cessation of the drug. ### Clinical Context This patient has **acute-on-chronic lithium toxicity** precipitated by volume depletion from gastroenteritis. The combination of: - High serum lithium level (2.8 mEq/L, >2× therapeutic ceiling) - Acute neurological signs (CNS toxicity) - Elevated creatinine (renal impairment from dehydration) - Reduced fluid intake (vomiting/diarrhea) warrants immediate intervention. ### Management Algorithm for Lithium Toxicity ```mermaid flowchart TD A["Lithium toxicity suspected<br/>(tremor, confusion, ataxia)"]:::outcome --> B{"Serum Li+ level?"}:::decision B -->|"< 1.5 mEq/L<br/>mild symptoms"| C["Hold lithium<br/>Increase fluids PO<br/>Monitor levels"]:::action B -->|"1.5–2.5 mEq/L<br/>moderate symptoms"| D["IV normal saline<br/>Hold lithium<br/>Q6h levels"]:::action B -->|"> 2.5 mEq/L<br/>severe/neuro signs"| E{"Renal function?"}:::decision E -->|"Normal GFR"| F["IV saline + monitor<br/>Consider HD if worsening"]:::action E -->|"Impaired GFR"| G["Hemodialysis<br/>+ IV saline"]:::urgent D --> H{"Improving?"}:::decision H -->|"Yes"| I["Continue supportive care<br/>Reassess lithium need"]:::action H -->|"No"| G ``` ### Rationale for Option 0 1. **IV Normal Saline:** Restores intravascular volume, increases glomerular filtration rate (GFR), and enhances renal clearance of lithium. This is the cornerstone of acute toxicity management. 2. **Hold Lithium:** Prevents further accumulation; the drug has no antidote. 3. **Frequent Monitoring (Q6h):** Lithium has a narrow therapeutic index; levels must be rechecked frequently to guide further intervention. 4. **Target Level <1.5 mEq/L:** Neurological symptoms typically resolve once the level drops below this threshold. **High-Yield:** In acute toxicity with neurological signs and level >2.5 mEq/L, hemodialysis is indicated if renal function is severely impaired or if the patient does not improve with IV fluids within 6–12 hours. ### When Hemodialysis Is Indicated - Serum lithium >3 mEq/L (acute ingestion) - Serum lithium >1.5 mEq/L with severe neurological symptoms and renal failure - Failure to improve with conservative management **Clinical Pearl:** Lithium is freely filtered by the glomerulus and reabsorbed in the proximal tubule (competing with Na^+^). Volume depletion → increased proximal reabsorption → higher serum levels. Conversely, saline loading suppresses reabsorption and increases clearance. [cite:Kaplan & Sadock's Synopsis of Psychiatry 12e Ch 31] --- ## Why Each Distractor Is Wrong | Option | Reason | |--------|--------| | **Option 1** | Continuing lithium at the same dose while the patient is acutely toxic is dangerous and will worsen toxicity. Oral fluid intake alone is insufficient when serum level is 2.8 mEq/L and renal function is impaired; IV saline is required for rapid volume restoration. | | **Option 2** | Hemodialysis is not the first-line immediate intervention for this patient. While her creatinine is elevated, it is only mildly so (1.4 mg/dL), and IV saline may restore renal perfusion. HD is reserved for severe toxicity (level >3 mEq/L), profound renal failure, or failure to improve with fluids. Restarting lithium immediately after HD is contraindicated; the drug should not be reintroduced until the patient is stable and the indication is reassessed. | | **Option 3** | Activated charcoal is ineffective for lithium (a small inorganic ion) and is not indicated in toxicity management. This is a common misconception from general toxicology; lithium is not absorbed by charcoal. | --- ## Key Monitoring Parameters - **Serum lithium:** Q6h until stable, then daily until <1.5 mEq/L, then weekly - **Serum creatinine & electrolytes:** Baseline, then daily - **Urine output:** Monitor for adequate renal perfusion - **Neurological exam:** Assess for improvement in tremor, confusion, ataxia **Mnemonic for Lithium Toxicity Severity — TREMOR:** - **T**remor (fine → coarse) - **R**eflex hyperreflexia - **E**xcitability, agitation - **M**uscle rigidity - **O**rgan dysfunction (renal, cardiac) - **R**igidity, seizures (severe)