What is the appropriate emergency department workup and initial management for a patient who has ingested rat poison?

Emergency Department Workup for Rat Poison Ingestion

For patients presenting with rat poison ingestion, immediately assess for signs of bleeding or coagulopathy, obtain baseline coagulation studies (PT/INR), and determine the specific rodenticide type and dose—most modern rat poisons contain long-acting anticoagulant rodenticides (LAARs) requiring a 48-72 hour repeat PT/INR for asymptomatic patients who ingested ≥1 mg of active ingredient 1.

Initial Assessment and Triage

Immediate ED Referral Required For:

• Any intentional ingestion (self-harm, abuse, or malicious administration) regardless of reported dose 1
• Symptomatic patients with bleeding, bruising, or any signs of coagulopathy 1
• Chronic/repeated ingestions to evaluate intent and coagulopathy 1
• Patients on therapeutic anticoagulation who require baseline PT and 48-72 hour follow-up 1

Can Be Observed at Home:

• Unintentional ingestions <1 mg active ingredient (includes virtually all pediatric unintentional exposures in children <6 years) 1
• These patients require no laboratory monitoring 1

Critical Workup Components

History Taking - Specific Details to Obtain:

• Exact product name and concentration (most contain 0.005% brodifacoum, difenacoum, or bromadiolone)
• Estimated dose ingested (1 mg threshold determines monitoring need)
• Timing of ingestion (coagulopathy typically develops 24-72 hours post-exposure)
• Intent (intentional vs unintentional dramatically changes management)
• Concurrent anticoagulant use (warfarin, DOACs, aspirin)
• Symptoms: bleeding (any site), bruising, hematuria, hematemesis, melena, epistaxis

Physical Examination - Key Findings:

• Signs of bleeding: petechiae, ecchymoses, gingival bleeding, conjunctival hemorrhage
• Vital signs: hypotension/tachycardia suggesting significant hemorrhage
• Abdominal examination: hepatomegaly, tenderness (hepatotoxicity with yellow phosphorus-containing products) 2
• Neurological status: altered mental status from intracranial hemorrhage

Laboratory Workup:

Baseline (at presentation):

• PT/INR (primary test for LAAR toxicity)
• Complete blood count (assess for anemia from bleeding)
• Type and screen (if bleeding present)
• Comprehensive metabolic panel (if yellow phosphorus suspected) 2

Follow-up at 48-72 hours:

• Repeat PT/INR for all patients with ≥1 mg ingestion 1
• This timing captures peak anticoagulant effect of LAARs

Management Algorithm

Decontamination:

• Do NOT use ipecac or gastric lavage 1
• Do NOT delay ED transport for activated charcoal 1
• Dermal exposures: wash with mild soap and water 1

Antidote Administration:

• Do NOT give vitamin K prophylactically before documented coagulopathy 1
• Vitamin K1 is indicated only after confirmed coagulopathy (elevated PT/INR)
• Dosing for confirmed poisoning: typically high-dose oral vitamin K1 (25-50 mg daily), potentially for weeks to months with LAARs 3, 4

Supportive Care Priority:

As emphasized in general poisoning management, supportive care takes precedence over antidote administration 5. This includes:

• Airway management if altered mental status
• Hemodynamic support if active bleeding
• Blood product replacement (fresh frozen plasma, packed red blood cells) for severe coagulopathy with bleeding

Common Pitfalls to Avoid

1. Premature discharge: LAARs have delayed onset (24-72 hours). Asymptomatic patients at presentation may develop severe coagulopathy days later 1

2. Inadequate follow-up: Patients with ≥1 mg ingestion MUST have 48-72 hour PT/INR checked, even if asymptomatic 1

3. Assuming negative initial coagulation studies rule out toxicity: Initial PT/INR is often normal; the 48-72 hour repeat is critical 1

4. Prophylactic vitamin K administration: This obscures diagnosis and is not recommended 1

5. Inadequate testing sensitivity: If clinical suspicion is high but initial brodifacoum assay is negative, send to a reference laboratory with more sensitive testing 3

6. Overlooking non-anticoagulant rodenticides: Yellow phosphorus-containing products cause hepatotoxicity, not coagulopathy 2

Special Populations

Pregnant patients: Unintentional exposures <1 mg can be managed outpatient with obstetric follow-up; no immediate ED evaluation required 1

Patients on therapeutic anticoagulation: Require baseline and 48-72 hour PT/INR regardless of dose 1. Consider DOAC interactions if resuming anticoagulation during prolonged vitamin K therapy 4

Consultation

Contact your regional poison center (1-800-222-1222 in US) for specific guidance, as board-certified toxicologists can provide expert treatment recommendations for complex cases 5.