A 28-year-old man with bipolar II disorder has been stable on lithium 750 mg/day for 18 months. He presents to the emergency department with confusion, coarse tremor, hyperreflexia, and muscle rigidity. Serum lithium level is 2.8 mEq/L. Renal function is normal (creatinine 0.9 mg/dL). What is the most appropriate immediate management?

Explanation

## Acute Lithium Toxicity: Management ### Clinical Presentation of Severe Toxicity The patient exhibits the **classic triad of severe lithium toxicity**: 1. **Neurological signs:** Confusion, coarse tremor, hyperreflexia, muscle rigidity 2. **Serum lithium level:** 2.8 mEq/L (markedly elevated; therapeutic range 0.6–1.2 mEq/L) 3. **Acute onset:** Suggests acute overdose or acute-on-chronic toxicity **Key Point:** Lithium toxicity is **dose-dependent and unpredictable**. Even small increases in serum level can precipitate severe neurological manifestations. The narrow therapeutic index (therapeutic level ≈ toxic level) makes lithium a high-risk drug. ### Severity Grading of Lithium Toxicity | Serum Level | Presentation | Management | |---|---|---| | **0.6–1.2 mEq/L** | Therapeutic; mild tremor, GI upset | Continue monitoring | | **1.5–2.0 mEq/L** | Mild–moderate toxicity: nausea, diarrhea, coarse tremor, confusion | Supportive care; check renal function | | **2.0–3.5 mEq/L** | **Moderate–severe toxicity: ataxia, hyperreflexia, rigidity, altered mental status** | **Hemodialysis** | | **> 3.5 mEq/L** | **Life-threatening: seizures, coma, cardiac arrhythmias** | **Urgent hemodialysis** | **High-Yield:** This patient's level of 2.8 mEq/L with neurological signs falls into the **moderate–severe category** requiring **hemodialysis**. ### Why Hemodialysis Is Indicated ```mermaid flowchart TD A[Lithium level > 2.0 mEq/L]:::urgent --> B{Neurological symptoms?}:::decision B -->|Yes| C[Hemodialysis]:::action B -->|No| D[Supportive care + monitor]:::action A --> E{Renal impairment?}:::decision E -->|Yes| C E -->|No| F[Check hydration status]:::action C --> G[Remove lithium; prevent recurrence]:::outcome ``` **Clinical Pearl:** Hemodialysis is the **gold standard** for severe lithium toxicity because: 1. **Lithium is water-soluble** — efficiently removed by dialysis 2. **Rapid clearance** — reduces serum level by 30–50% per session 3. **Prevents redistribution** — lithium in intracellular compartment (brain, muscle) slowly equilibrates with serum; repeated dialysis sessions may be needed 4. **Supports organ function** — allows time for renal clearance to resume ### Management Algorithm 1. **Immediate steps:** - **Discontinue lithium** — no further doses - **Establish IV access** — normal saline (0.9%) to maintain hydration and promote renal clearance - **Arrange hemodialysis** — urgent if level > 2.5 mEq/L or neurological symptoms present 2. **During hemodialysis:** - Monitor serum lithium levels pre- and post-dialysis - Repeat dialysis if rebound occurs (lithium re-equilibrates from intracellular stores) - Monitor ECG for arrhythmias 3. **Post-dialysis:** - Continue supportive care (fluids, electrolyte monitoring) - Do NOT restart lithium immediately - Consider alternative mood stabilizer (valproate, lamotrigine, atypical antipsychotic) **Warning:** Do NOT attempt to "correct" the level by continuing lithium or increasing the dose — this will worsen toxicity. Do NOT rely on supportive care alone at this level; the patient is at risk of seizures and cardiac complications. ### Why Normal Renal Function Does Not Exclude Hemodialysis **Key Point:** Even with normal baseline renal function (creatinine 0.9 mg/dL), acute lithium toxicity can overwhelm the kidneys' ability to excrete lithium. Hemodialysis is **not** contraindicated by normal renal function; it is **indicated by the serum level and symptoms**. [cite:KD Tripathi 8e Ch 30; Harrison 21e Ch 297]