In acute arsenic poisoning, which organ system is primarily affected in the first 24 hours?

Explanation

## Acute Arsenic Poisoning: Organ System Involvement **Key Point:** The gastrointestinal tract is the primary target organ in acute arsenic poisoning, with hemorrhagic gastroenteritis occurring within the first 24 hours of exposure. ### Timeline of Acute Arsenic Toxicity | Phase | Timeframe | Primary Manifestations | Mechanism | |-------|-----------|------------------------|----------| | **Gastrointestinal** | 0–24 hours | Burning in mouth/throat, vomiting, abdominal pain, hemorrhagic diarrhea | Direct corrosive effect on mucosa; inhibition of Na⁺-K⁺-ATPase | | **Cardiovascular** | 24–72 hours | Hypotension, shock, arrhythmias, QT prolongation | Myocardial depression; fluid/electrolyte loss | | **Renal** | 24–72 hours | Oliguria, acute kidney injury, hematuria | Hypovolemia; direct tubular toxicity | | **Neurological** | Days 3–7 | Peripheral neuropathy, encephalopathy (rare in acute) | Axonal degeneration; metabolic derangement | **High-Yield:** Hemorrhagic gastroenteritis with "rice water" or "bloody" stools is the hallmark of acute arsenic poisoning and occurs within hours of ingestion. This is the most common cause of death in the acute phase (from hypovolemic shock). ### Pathophysiology 1. **Direct corrosive effect** on the gastric and intestinal mucosa 2. **Inhibition of cellular respiration** via interference with pyruvate dehydrogenase and other SH-dependent enzymes 3. **Massive fluid loss** from the GI tract → hypovolemic shock 4. **Electrolyte derangement** (hypocalcemia, hypokalemia) → cardiac arrhythmias **Clinical Pearl:** The classic presentation is a patient with severe vomiting and bloody diarrhea within 1–2 hours of arsenic ingestion. Death in the acute phase is usually from hypovolemic shock and electrolyte imbalance, NOT from direct organ failure. **Mnemonic:** **"GI FIRST"** — Gastrointestinal involvement is the FIRST and most prominent feature in acute arsenic poisoning. **Warning:** Do NOT confuse acute arsenic poisoning (GI-dominant, hours) with chronic arsenic poisoning (skin changes, neuropathy, weeks to months).