A 32-year-old man from rural Maharashtra presents to the emergency department with acute onset vomiting, profuse watery diarrhoea, and severe abdominal pain 2 hours after consuming contaminated groundwater. On examination, he is hypotensive (BP 90/60 mmHg), tachycardic (HR 120/min), and has signs of dehydration. His wife, who drank the same water, is asymptomatic. Serum electrolytes show hypokalaemia and hyponatraemia. What is the most appropriate immediate next step in management?

Explanation

## Clinical Assessment This is a case of **acute arsenic poisoning** presenting with the classic triad of gastrointestinal symptoms (vomiting, diarrhoea, abdominal pain), haemodynamic instability, and electrolyte derangement. The acute presentation (within 2 hours) and the fact that the wife is asymptomatic (suggesting variable absorption or dose) are key clinical clues. ## Immediate Management Priority **Key Point:** In acute arsenic poisoning with haemodynamic compromise, the FIRST priority is aggressive fluid and electrolyte resuscitation, NOT chelation therapy. The patient is in hypovolaemic shock from massive gastrointestinal losses. The hypotension, tachycardia, and electrolyte derangement indicate severe dehydration and loss of intracellular potassium. ## Management Algorithm ```mermaid flowchart TD A[Acute Arsenic Poisoning]:::outcome --> B{Haemodynamic Status?}:::decision B -->|Shock/Hypotension| C[IV Fluid Resuscitation<br/>Normal Saline + K+ correction]:::action B -->|Stable| D[Supportive Care]:::action C --> E[Monitor UO, BP, Electrolytes]:::action E --> F{Stable after 4-6 hrs?}:::decision F -->|Yes| G[Start Chelation<br/>DMSA or DMPS]:::action F -->|No| H[Repeat Fluids<br/>Consider ICU]:::action G --> I[Continue till Urine As < 50 mcg/L]:::action ``` ## Why This Approach? **High-Yield:** The mortality in acute arsenic poisoning is directly proportional to the degree of dehydration and shock. Fluid resuscitation takes precedence over chelation because: 1. **Restoration of perfusion** prevents multi-organ failure 2. **Electrolyte correction** (especially K^+^) prevents cardiac arrhythmias 3. **Increased urine output** from fluid resuscitation enhances renal excretion of arsenic 4. Chelation agents (DMSA, DMPS) are most effective AFTER haemodynamic stabilization ## Chelation Timing **Clinical Pearl:** Chelation therapy (DMSA or DMPS) should be initiated AFTER: - BP normalizes - Urine output > 0.5 mL/kg/hr - Electrolytes are corrected - Patient is out of acute shock Typically this is 4–6 hours after presentation in severe cases. ## Supportive Measures During Resuscitation - IV normal saline: 1–2 L bolus, then maintenance + ongoing losses - Potassium replacement: Once urine output confirmed, add KCl 20–40 mEq/L to IV fluids - Monitor: Continuous cardiac monitoring, hourly vitals, urine output, serum K^+^ and Na^+^ - Antiemetics: Ondansetron if vomiting persists after fluid repletion [cite:Park 26e Ch 12]