## Immediate Management of Acute Arsenic Poisoning ### Pathophysiology & Clinical Urgency **Key Point:** Acute arsenic poisoning causes severe gastrointestinal toxicity and hypovolemic shock through direct mucosal damage and fluid losses. The patient is already 6 hours post-ingestion with haemodynamic compromise — supportive care is the priority. ### Stepwise Management Algorithm ```mermaid flowchart TD A[Acute arsenic poisoning suspected]:::outcome --> B{Haemodynamically stable?}:::decision B -->|No - Hypotensive/shock| C[Establish IV access × 2]:::action C --> D[Aggressive IV fluid resuscitation<br/>Normal saline bolus]:::action D --> E[Measure serum/urine arsenic<br/>ECG, electrolytes, renal function]:::action E --> F[Supportive care + monitoring]:::action B -->|Yes| G[Decontamination if < 2 hrs]:::action G --> H[Chelation if indicated<br/>DMSA or DMPS]:::action ``` ### Rationale for Correct Answer **High-Yield:** At 6 hours post-ingestion with ongoing fluid losses and haemodynamic instability, the patient requires: 1. **Immediate vascular access** — Two large-bore IV lines allow rapid fluid administration and blood sampling 2. **Aggressive fluid resuscitation** — Normal saline (not hypotonic solutions) corrects hypovolaemia and maintains renal perfusion; prevents acute kidney injury 3. **Baseline investigations** — Serum and urine arsenic levels confirm diagnosis and guide chelation timing; electrolytes assess hypokalaemia (common in arsenic GI losses) **Clinical Pearl:** Arsenic is radiopaque and may be visible on abdominal X-ray if ingested as a solid. Serum arsenic peaks 1–2 hours post-ingestion; urine arsenic is more reliable for chronic exposure. ### Chelation Timing | Agent | Timing | Indication | Route | |-------|--------|-----------|-------| | **DMSA (succimer)** | Start if serum As > 10 µg/dL or symptomatic | Acute + chronic | Oral | | **DMPS** | Start if serum As > 10 µg/dL | Acute poisoning | IV/IM | | **BAL (dimercaprol)** | ~~Used historically~~ | NOT first-line for arsenic | IM only | **Warning:** BAL is NOT indicated for arsenic poisoning — it is reserved for mercury and lead. DMSA or DMPS are the chelators of choice. ### Decontamination **Key Point:** Activated charcoal does NOT bind arsenic effectively (As³⁺ and As⁵⁺ are not adsorbed). Gastric lavage is indicated only if < 2 hours post-ingestion; at 6 hours, the arsenic has already caused mucosal damage and moved distally — lavage risks perforation. **High-Yield:** Potassium permanganate (1:5000) was historically used to oxidize As³⁺ to As⁵⁺ (less toxic), but this is **no longer recommended** — it causes chemical burns and offers no proven benefit. ### Supportive Care Essentials - Correct electrolyte abnormalities (hypokalaemia, hyponatraemia) - Monitor urine output (target > 0.5 mL/kg/hr) - ECG surveillance (arsenic prolongs QT interval; risk of torsades de pointes) - Treat arrhythmias and maintain blood pressure - Renal function monitoring (risk of acute tubular necrosis) --- ## Why Each Distractor Is Wrong **Option 0 (Activated charcoal):** Arsenic is not adsorbed by activated charcoal. At 6 hours with haemodynamic instability, observation alone is dangerous — the patient needs immediate fluid resuscitation. **Option 2 (BAL immediately):** BAL (dimercaprol) is contraindicated in arsenic poisoning; it is reserved for mercury and lead toxicity. BAL can actually worsen arsenic toxicity by increasing renal excretion of toxic As–BAL complexes. DMSA or DMPS are the correct chelators. **Option 3 (Gastric lavage + succimer):** Gastric lavage at 6 hours is harmful — arsenic has already damaged the mucosa and moved into the small intestine; lavage risks perforation. Succimer (DMSA) is correct as a chelator but should only be started *after* stabilization and confirmation of elevated serum arsenic, not as the first step.
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