How to manage a patient with suspected rodenticide poisoning, presenting with vomiting and stable vital signs?

Management of Acute Rodenticide Poisoning

Immediate Priorities

Contact your regional poison control center immediately (1-800-222-1222 in the US) for expert toxicology guidance, as this is the single most important initial step in managing rodenticide poisoning. 1, 2

Initial Stabilization

• Ensure airway patency, breathing adequacy, and circulatory stability—intubate if there is altered mental status, respiratory depression, or inability to protect the airway 3
• Establish IV access and administer isotonic crystalloid (normal saline 10-20 mL/kg bolus) if hypotensive 4
• Do not delay supportive care while awaiting rodenticide identification—treatment must begin immediately based on clinical presentation 2

Critical Assessment Points

• Determine the type of rodenticide (most commonly long-acting anticoagulants like brodifacoum, bromadiolone, or difenacoum in modern "rat killer" products) 5, 6
• Establish time since ingestion (this patient presented with vomiting, suggesting recent ingestion, but symptoms may be delayed 24-48 hours with anticoagulant rodenticides) 5
• Assess for signs of bleeding: epistaxis, gingival bleeding, hematuria, hematemesis, melena, or ecchymoses 7, 5

Laboratory Evaluation

Obtain baseline coagulation studies immediately, including PT/INR, aPTT, and CBC. 2, 5 However, recognize that:

• INR may be normal initially even after significant ingestion, as anticoagulant effects are delayed 24-48 hours 5
• Repeat INR at 36-48 hours post-exposure is mandatory even if initial values are normal 5
• If INR is normal at 48 hours, no further monitoring or treatment is required 5

Gastrointestinal Decontamination

Do not administer activated charcoal, ipecac, or perform gastric lavage in this patient who presented hours after ingestion with vomiting—these interventions are ineffective once absorption has occurred and may delay definitive care. 1, 2 The 2010 AHA/ARC First Aid Guidelines explicitly state not to administer anything by mouth for poisoning unless advised by poison control 1.

Antiemetic Management

For the acute vomiting:

• Administer ondansetron 4-8 mg IV or metoclopramide 10 mg IV for symptomatic relief 1
• Avoid excessive fluid administration that could complicate potential future bleeding 1

Vitamin K Therapy Decision Algorithm

If INR is Normal and No Bleeding:

• No immediate vitamin K indicated 2, 5
• Mandatory repeat INR at 36-48 hours 5
• Discharge with strict return precautions for any bleeding symptoms

If INR is Elevated (>4.0) Without Active Bleeding:

• Administer phytonadione (vitamin K1) 10 mg IV slowly (over 20-30 minutes to avoid anaphylactoid reactions) 8, 5
• Oral vitamin K1 (10-25 mg PO) is equally effective but slower onset (6-12 hours vs 1-2 hours for IV) 8

If Active Bleeding is Present:

• Immediately administer:
  • Phytonadione 10 mg IV (100 mcg/kg for pediatric patients) 5, 6
  • Prothrombin complex concentrate (PCC) 50 units/kg IV as first-line hemostatic agent 5
  • Fresh frozen plasma 15 mL/kg IV only if PCC unavailable 5
  • Consider recombinant factor VIIa 1.2-4.8 mg IV for life-threatening hemorrhage refractory to PCC 5, 6

Long-Acting Anticoagulant Rodenticide (LAAR) Specific Considerations

Modern rodenticides (brodifacoum, bromadiolone) have half-lives of weeks to months and require prolonged treatment 7, 6:

• Rebound coagulopathy is common after initial correction—patients require ongoing monitoring 6
• If coagulopathy develops, expect to need high-dose vitamin K1 (50-100 mg daily or higher) for an average of 168 days (range 4-12 months) 6
• Weekly INR monitoring is essential during the entire treatment course 6
• The most severe complication is intracranial hemorrhage, which is the leading cause of death 7, 6

Disposition

Admit if:

• Any elevation in INR 5
• Any bleeding manifestations 7, 5
• Intentional ingestion (suicide attempt) requiring psychiatric evaluation 7
• Confirmed large-volume ingestion of LAAR product 6

Discharge if:

• Normal INR at 36-48 hours post-exposure 5
• No bleeding symptoms 5
• Reliable follow-up ensured 5
• Strict return precautions for any bleeding (epistaxis, hematuria, bruising, hematemesis, melena, severe headache) 7, 5

Critical Pitfalls to Avoid

• Never assume safety based on initial normal INR—anticoagulant effects are delayed 24-48 hours 5
• Never give prophylactic vitamin K before documented coagulopathy in asymptomatic patients with minimal exposure 2
• Never use warfarin reversal protocols (which use lower vitamin K doses)—LAARs require much higher and prolonged dosing 6
• Never discharge without confirmed 48-hour INR if any significant ingestion occurred 5
• Never use intramuscular injections in patients with potential coagulopathy 5

For This Specific Patient

Given this 35-year-old man with stable vital signs (pulse 69, BP 132/86) and single episode of vomiting:

1. Contact poison control immediately 1, 2
2. Obtain baseline INR, PT, aPTT, CBC now 5
3. Administer ondansetron 8 mg IV for vomiting 1
4. Do not give activated charcoal 2
5. If INR normal, observe 4-6 hours then discharge with mandatory 48-hour INR recheck 5
6. If INR elevated, admit and initiate vitamin K1 therapy 5, 6