A 42-year-old man with bipolar II disorder has been on lithium 1200 mg daily for 18 months. He presents to the emergency department with confusion, coarse tremor, ataxia, and vomiting. Serum lithium level is 2.8 mEq/L (therapeutic: 0.6–1.2). Serum creatinine is 1.6 mg/dL (baseline 0.9), and urine output is 300 mL in 8 hours. What is the most appropriate immediate next step?

Explanation

## Clinical Diagnosis: Acute Lithium Toxicity (Severe) **Key Point:** Serum lithium >2.0 mEq/L with neurological signs (confusion, tremor, ataxia) and rising creatinine indicates severe acute lithium toxicity with acute kidney injury. This is a medical emergency requiring immediate hemodialysis. **High-Yield:** Lithium toxicity severity correlates with serum level AND clinical presentation: | Serum Li^+^ (mEq/L) | Clinical Features | Management | |---|---|---| | 1.5–2.0 | Mild tremor, nausea, diarrhea | Supportive care, monitor | | 2.0–3.5 | Coarse tremor, confusion, ataxia, vomiting | Hemodialysis | | >3.5 | Seizures, coma, cardiac arrhythmias, pulmonary edema | Urgent hemodialysis + ICU | **Mnemonic: LITHIUM toxicity signs** — **L**ethargy, **I**ncontinence, **T**remor (coarse), **H**ypertension/Hyperthermia, **I**ncreased reflexes, **U**nsteady gait, **M**uscle rigidity. ## Management Algorithm for Acute Lithium Toxicity ```mermaid flowchart TD A[Acute Lithium Toxicity Suspected]:::outcome --> B{Serum Li Level + Symptoms?}:::decision B -->|Mild: 1.5-2.0 + GI symptoms| C[Supportive Care + Monitor]:::action B -->|Moderate-Severe: >2.0 + Neuro Signs| D[STOP Lithium Immediately]:::action D --> E[IV Access + Fluid Resuscitation]:::action E --> F[Check Renal Function + ECG]:::action F --> G{Serum Cr Rising or Neuro Deterioration?}:::decision G -->|Yes| H[Urgent Hemodialysis]:::urgent G -->|No| I[Supportive Care + Serial Li Levels]:::action H --> J[Repeat HD if Li Rebound >1.5]:::action ``` **Clinical Pearl:** Lithium is not protein-bound and has a small volume of distribution; hemodialysis efficiently removes it. However, lithium can rebound from intracellular stores 4–6 hours post-dialysis, necessitating repeat sessions. ## Why This Case Requires Hemodialysis 1. **Serum lithium 2.8 mEq/L** — well above therapeutic range and in the severe toxicity zone 2. **Neurological signs** — confusion, tremor, ataxia indicate CNS penetration 3. **Rising creatinine (1.6 from baseline 0.9)** — acute kidney injury reduces lithium clearance, worsening toxicity 4. **Oliguria (300 mL/8 hrs)** — further impairs renal excretion **Tip:** Do NOT rely on supportive care alone in severe toxicity. Do NOT use activated charcoal (lithium is not absorbed by charcoal). Do NOT attempt to alkalinize urine (minimal effect on lithium reabsorption; wastes time). [cite:KD Tripathi 8e Ch 30; Harrison 21e Ch 297]