A 52-year-old man with bipolar disorder has been on lithium 900 mg daily for 3 years with good mood stabilization. He presents to the emergency department with tremor, confusion, ataxia, and slurred speech for 6 hours. His wife reports he had acute gastroenteritis with vomiting and diarrhea for 2 days and continued taking lithium. Serum lithium level is 2.8 mEq/L (therapeutic range 0.6–1.2 mEq/L). Serum creatinine is 1.4 mg/dL (baseline 1.0 mg/dL). What is the most appropriate immediate next step in management?

Explanation

## Clinical Assessment of Lithium Toxicity This patient presents with **severe lithium toxicity** (acute-on-chronic) with neurological signs (tremor, confusion, ataxia) and a dangerously elevated serum lithium level (2.8 mEq/L). ### Key Point: **Acute lithium toxicity with serum levels >2.5 mEq/L and neurological manifestations requires urgent hemodialysis.** Lithium is not protein-bound and has a small volume of distribution, making it highly dialyzable. ### Pathophysiology of Toxicity **Key Point:** Dehydration from gastroenteritis reduces renal lithium clearance, causing accumulation and toxicity. Lithium competes with Na^+^ for reabsorption in the proximal tubule; volume depletion increases proximal reabsorption of lithium. ### Management Algorithm for Lithium Toxicity ```mermaid flowchart TD A[Lithium toxicity suspected]:::outcome --> B{Serum Li level & symptoms?}:::decision B -->|Mild: <1.5 mEq/L, GI symptoms only| C[Stop lithium, IV fluids, monitor q6h]:::action B -->|Moderate: 1.5-2.5 mEq/L, neuro signs| D[Stop lithium, IV saline, hemodialysis if renal impairment]:::action B -->|Severe: >2.5 mEq/L, CNS/cardiac signs| E[URGENT: IV saline + immediate hemodialysis]:::urgent C --> F[Recheck level in 6-8 hrs]:::action D --> G[Hemodialysis; recheck post-dialysis]:::action E --> G G --> H[Resume lithium only after level <0.5 mEq/L]:::action ``` ### Immediate Management Steps 1. **IV Normal Saline:** Restores intravascular volume → increases glomerular filtration → enhances renal lithium clearance. 2. **Hemodialysis:** Gold standard for severe toxicity. Lithium clearance by dialysis is 5–7 times greater than renal clearance. 3. **Monitoring:** Recheck serum lithium 4–6 hours post-dialysis (rebound elevation can occur due to redistribution from intracellular to extracellular compartment). ### High-Yield: **Lithium has NO antidote. Management is supportive (fluids) + removal (dialysis).** ### Clinical Pearl: In this case, the patient has: - Serum Li 2.8 mEq/L (severe) - Acute neurological signs (confusion, ataxia) - Worsening renal function (Cr 1.4, baseline 1.0) These are **absolute indications for hemodialysis**, not observation or supportive care alone. ### Mnemonic: LITHIUM TOXICITY GRADES - **L**ight (mild): <1.5 — GI symptoms, fine tremor → fluids & monitor - **I**ntermediate (moderate): 1.5–2.5 — coarse tremor, confusion → fluids ± dialysis - **T**oxic (severe): >2.5 — ataxia, seizures, arrhythmias → **dialysis mandatory** [cite:Kaplan & Sadock's Synopsis of Psychiatry 12e Ch 31]