A 52-year-old woman with bipolar disorder has been on lithium 900 mg daily for 3 years with good mood stabilization. She presents to the emergency department with severe nausea, vomiting, coarse tremor, confusion, and ataxia that started 6 hours ago. Her serum lithium level is 2.8 mEq/L (normal therapeutic range 0.6–1.2 mEq/L). On examination, she is disoriented to time and place, has hyperreflexia, and clonus is elicited. Her renal function is normal (creatinine 0.9 mg/dL), and she denies recent NSAIDs or diuretic use. What is the most appropriate immediate management?

Explanation

## Acute Lithium Toxicity Management **Key Point:** Severe lithium toxicity (serum level >2.5 mEq/L with neurological signs) requires aggressive removal via haemodialysis, not conservative management. ### Clinical Presentation Recognition This patient exhibits **severe (late) lithium toxicity** with: - Neurological: confusion, ataxia, clonus, hyperreflexia - GI: nausea, vomiting - Serum level: 2.8 mEq/L (markedly elevated) ### Pathophysiology Lithium is a small ion that crosses cell membranes slowly. At high serum concentrations, it accumulates intracellularly, particularly in the CNS, causing: 1. Displacement of Na^+^ from Na^+^/K^+^-ATPase 2. Impaired cellular excitability and neurotransmitter release 3. Polyuria and nephrogenic diabetes insipidus (chronic effect) ### Management Algorithm ```mermaid flowchart TD A[Lithium Toxicity Suspected]:::outcome --> B{Serum Level & Symptoms?}:::decision B -->|Mild: <1.5 mEq/L, GI only| C[Stop lithium, IV fluids, monitor]:::action B -->|Moderate: 1.5-2.5 mEq/L, neuro signs| D[IV saline, consider haemodialysis]:::action B -->|Severe: >2.5 mEq/L, CNS signs| E[URGENT: IV saline + haemodialysis]:::urgent C --> F[Recheck level in 4-6 hrs]:::action D --> G{Improving?}:::decision G -->|Yes| H[Continue IV fluids, repeat level]:::action G -->|No| E E --> I[Haemodialysis immediately]:::action I --> J[Lithium clearance 3-4x higher than GFR]:::outcome ``` ### Why IV Saline + Haemodialysis? | Intervention | Rationale | |---|---| | **IV Normal Saline** | Expands ECF volume, increases glomerular filtration of lithium; Na^+^ competes with Li^+^ at renal tubule reabsorption site | | **Haemodialysis** | Lithium clearance via dialysis (40–50 mL/min) >> renal clearance (~20 mL/min); indicated when serum level >2.5 mEq/L OR neurological toxicity regardless of level | | **Fluid restriction** | CONTRAINDICATED — worsens toxicity by promoting renal reabsorption of lithium | **High-Yield:** Lithium is NOT absorbed by activated charcoal (it is an ion, not an organic molecule). **Clinical Pearl:** Haemodialysis may need to be repeated because lithium redistributes from intracellular to serum compartment after initial dialysis, causing a "rebound" rise in serum level. ### Why NOT the Other Options? - **Activated charcoal:** Ineffective for ionic substances; lithium is not protein-bound - **Dose reduction alone:** Too slow for severe toxicity with CNS signs; patient needs immediate removal - **Sodium bicarbonate:** Increases urine pH but does NOT significantly enhance lithium excretion; not indicated [cite:Kaplan & Sadock 11e Ch 31]