Management of rat killer ingestion
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I now have comprehensive information from both textbooks. Here is a thorough synthesis:
Management of Rat Killer (Rodenticide) Ingestion
Rodenticides are broadly classified as anticoagulant (by far the most common) or non-anticoagulant. Management differs substantially by agent.
1. Anticoagulant Rodenticides (Superwarfarins) — Most Common
Agents
- First-generation: Warfarin (short-acting, ~42-hour half-life)
- Second-generation (superwarfarins): Brodifacoum, difenacoum, bromadiolone, chlorophacinone, diphacinone — long-acting (~150-hour half-life); toxic effects can persist for months
"Most rodenticide exposures will be superwarfarin compounds." — Rosen's Emergency Medicine
Mechanism
Competitive inhibition of Vitamin K → impaired hepatic synthesis of clotting factors II, VII, IX, and X. Also damages capillary walls, worsening bleeding.
Clinical Features
- May be asymptomatic for up to 72 hours, even after large ingestion
- Early: GI irritation (nausea, vomiting) — onset as early as 8 hours
- Late: Bleeding — ecchymosis, epistaxis, gingival bleeding, menorrhagia, hematuria, hemarthrosis
- Life-threatening: Massive GI hemorrhage, intracranial hemorrhage
Diagnostic Workup
| Test | Purpose |
|---|---|
| PT/INR | Key marker; may be normal for up to 48 hours after ingestion |
| aPTT | Assess coagulopathy |
| CBC (Hb/Hct, platelets) | Assess blood loss |
| Type & screen / crossmatch | If actively bleeding |
| Brodifacoum level (reference lab) | <4–10 ng/mL = normal; not routinely needed |
A normal INR at 48 hours essentially excludes significant ingestion.
Management
Decontamination
- Activated charcoal (AC): Give if patient presents within 1 hour of a massive ingestion
- Dose: 10:1 ratio AC:poison; if dose unknown, use 100 g
- Gastric lavage: contraindicated — no clinical benefit and risks inducing GI bleeding with large-bore OGT insertion
- For small accidental exposures (e.g., child tasting 2–3 pellets): no treatment necessary; discharge with outpatient follow-up in 48–72 hours
Antidote — Vitamin K₁ (Phytonadione)
- Vitamin K₁ is the antidote of choice (K₃ and K₄ are ineffective and potentially toxic)
- Do NOT give prophylactically — wait for INR elevation
- Indications: INR >2.0
- Route: Oral preferred for non-emergency cases
- For warfarin rodenticide: suggested total PO daily dose guided by INR
- For superwarfarins: extended courses required (weeks to months) due to the prolonged half-life; patients must be followed closely with serial INR monitoring
Supportive Care / Active Bleeding
- IV fluid resuscitation + transfusion for massive blood loss
- Packed RBCs — replace blood volume
- Fresh Frozen Plasma (FFP) — correct coagulopathy acutely
- Four-factor prothrombin complex concentrate (PCC) — first-line for immediate reversal
- Recombinant activated Factor VIIa — an alternative option
Enhanced Elimination
- No role for enhanced elimination (dialysis, etc.) in superwarfarin toxicity
Disposition
| Scenario | Action |
|---|---|
| Small accidental ingestion (child, 2–3 pellets) | Discharge home; INR recheck at 48–72 hours |
| Large or intentional ingestion | Admit; serial INR monitoring (check at minimum 2 days post-ingestion) |
| Active bleeding or elevated INR | Admit; antidote + blood products |
2. Non-Anticoagulant Rodenticides
Several agents with distinct toxidromes exist (many discontinued but still encountered in stored products):
| Agent | Toxicity / Notes |
|---|---|
| Barium carbonate | Hypokalemia (severe, potentially life-threatening); treat with potassium replacement |
| Zinc phosphide | Releases phosphine gas on contact with stomach acid; GI, pulmonary, and cardiovascular toxicity |
| Vacor (PNU) | Autonomic neuropathy; beta-cell destruction → diabetes mellitus |
| Strychnine | Spinal cord glycine antagonism → generalized rigidity, seizure-like muscle spasms |
| Yellow phosphorus | Hepatic necrosis, "smoking stool" syndrome |
| Thallium | Delayed alopecia, peripheral neuropathy, GI toxicity |
Management of these is largely supportive and symptom-directed; consult Poison Control for specific guidance.
Key Summary Points
- Most rodenticide ingestions are superwarfarin compounds — long-acting anticoagulants.
- INR may be normal for 48 hours — do not rule out toxicity early; always recheck.
- Vitamin K₁ is the antidote; give only when INR is elevated, not prophylactically.
- Superwarfarins require prolonged Vitamin K₁ courses (weeks to months).
- Active bleeding is treated with PCC + FFP ± RBC transfusion.
- No role for gastric lavage or enhanced elimination in anticoagulant rodenticide poisoning.
- Small accidental pediatric exposures are generally benign — observe and follow up.
Sources: Tintinalli's Emergency Medicine: A Comprehensive Study Guide; Rosen's Emergency Medicine: Concepts and Clinical Practice
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