A 38-year-old woman with bipolar I disorder has been stable on lithium 900 mg daily for 3 years. She presents to the emergency department with confusion, coarse tremor, hyperreflexia, and rigidity. Serum lithium level is 2.8 mEq/L (normal therapeutic range 0.6–1.2 mEq/L). She denies intentional overdose but reports a 3-day history of acute gastroenteritis with diarrhea and vomiting. What is the most appropriate immediate management?

Explanation

## Lithium Toxicity Management ### Clinical Presentation **Key Point:** This patient exhibits signs of severe lithium toxicity (neurotoxicity syndrome): confusion, coarse tremor, hyperreflexia, and rigidity with a serum level >2.5 mEq/L. ### Pathophysiology of Toxicity Lithium is not metabolized and is entirely dependent on renal clearance. Dehydration from gastroenteritis reduces glomerular filtration rate (GFR), causing lithium accumulation. At toxic levels, lithium: - Displaces Na⁺ and K⁺ intracellularly - Inhibits inositol monophosphatase (disrupting phosphatidylinositol signaling) - Causes neuronal dysfunction and cerebral edema ### Management Algorithm ```mermaid flowchart TD A[Lithium toxicity suspected]:::outcome --> B{Serum level & symptoms?}:::decision B -->|Mild: 1.5-2.0 mEq/L, GI symptoms| C[Stop lithium, hydrate, recheck in 4-6 hrs]:::action B -->|Moderate: 2.0-2.5 mEq/L, neuro signs| D[Stop lithium, IV fluids, monitor closely]:::action B -->|Severe: >2.5 mEq/L, altered mental status| E[STOP lithium immediately]:::urgent E --> F[Aggressive IV saline resuscitation]:::action F --> G[Hemodialysis indicated]:::action G --> H[Lithium removed 30-50% per session]:::outcome D --> I[Recheck level in 4-6 hrs]:::decision I -->|Still elevated| G I -->|Declining| J[Continue supportive care]:::action ``` ### Why Hemodialysis? **High-Yield:** Hemodialysis is the ONLY effective method to remove lithium from the body because: - Lithium is water-soluble and has low protein binding - Renal clearance alone is inadequate in severe toxicity - Each session removes 30–50% of total body lithium - Rebound increase in serum level can occur 4–8 hours post-dialysis (repeat sessions often needed) ### Supportive Measures 1. **Discontinue lithium immediately** — ongoing dosing worsens toxicity 2. **IV fluid resuscitation** — restores GFR and enhances renal clearance 3. **Correct electrolyte abnormalities** — hypokalemia and hyponatremia worsen neurotoxicity 4. **Monitoring** — ECG (QT prolongation), neurological status, renal function **Clinical Pearl:** Activated charcoal is NOT effective for lithium (inorganic ion, not absorbed by charcoal). Do NOT delay hemodialysis with futile interventions. **Warning:** Switching to valproate without removing lithium prolongs toxicity and risks dual-agent toxicity. [cite:KD Tripathi 8e Ch 12]