A 52-year-old woman with bipolar disorder has been on lithium carbonate 900 mg daily for 3 years with good mood stabilization. She presents to the emergency department with confusion, coarse tremor, and ataxia for the past 6 hours. Her husband reports she had gastroenteritis with vomiting and diarrhea for 2 days and continued taking her regular lithium dose. On examination: BP 128/82 mmHg, HR 96/min, temperature 37.2°C, generalized hyperreflexia, and nystagmus. Serum lithium level is 2.8 mEq/L (normal therapeutic range 0.6–1.2 mEq/L). Serum creatinine 1.1 mg/dL, sodium 138 mEq/L. What is the most appropriate immediate management?

Explanation

## Clinical Presentation of Lithium Toxicity **Key Point:** This patient has acute lithium toxicity (serum level 2.8 mEq/L) manifesting with neurological signs: confusion, coarse tremor, ataxia, hyperreflexia, and nystagmus. The precipitant is volume depletion from gastroenteritis, which reduces glomerular filtration and lithium clearance. ## Severity Classification of Lithium Toxicity | Severity | Serum Level (mEq/L) | Clinical Features | Management | |----------|---------------------|-------------------|-------------| | Mild | 1.5–2.0 | Fine tremor, nausea, polyuria | Fluid replacement, hold dose | | Moderate | 2.0–3.5 | Coarse tremor, confusion, ataxia, hyperreflexia | IV saline, hold lithium, frequent monitoring | | Severe | >3.5 | Seizures, arrhythmias, coma, renal failure | Hemodialysis indicated | **High-Yield:** At a level of 2.8 mEq/L with moderate neurological symptoms but stable vital signs and normal renal function, this is moderate toxicity. The first-line approach is aggressive hydration with normal saline to restore intravascular volume, enhance glomerular filtration, and promote lithium excretion. ## Management Algorithm ```mermaid flowchart TD A[Lithium toxicity suspected]:::outcome --> B{Serum Li+ level & clinical severity?}:::decision B -->|Mild: 1.5-2.0 mEq/L| C[Hold lithium, oral fluids, monitor]:::action B -->|Moderate: 2.0-3.5 mEq/L| D[IV normal saline, hold lithium]:::action B -->|Severe: >3.5 mEq/L OR renal failure| E[Hemodialysis + IV saline]:::action D --> F[Check Li+ q6h until <1.5]:::action E --> G[Repeat dialysis if needed]:::action F --> H{Improving clinically?}:::decision H -->|Yes| I[Resume at lower dose when Li+ <0.8]:::action H -->|No| J[Consider hemodialysis]:::urgent ``` **Clinical Pearl:** Normal saline is preferred over hypotonic fluids because it restores volume depletion (the primary cause here) and maintains the sodium gradient that reduces passive lithium reabsorption in the proximal tubule. Lithium is freely filtered and reabsorbed along with sodium; volume depletion increases reabsorption and worsens toxicity. **Mnemonic: LITHIUM TOXICITY MANAGEMENT — VHD** - **V**olume replacement (normal saline first-line for moderate toxicity) - **H**emodialysis (for severe toxicity, renal failure, or unresponsive cases) - **D**iscontinue lithium until levels normalize **Warning:** Hypertonic saline (option C) is contraindicated—it increases serum sodium, which paradoxically increases lithium reabsorption in the proximal tubule and worsens toxicity. Activated charcoal (option D) does not bind lithium effectively and is not indicated.