A 28-year-old farmer from rural Maharashtra presents to the emergency department 4 hours after a snake bite to his left foot while working in the field. On examination, he has local swelling extending up to the knee, with fang marks visible. His vital signs are stable. Blood investigations show: PT 18 seconds (control 12 seconds), aPTT 45 seconds (control 32 seconds), fibrinogen 80 mg/dL (normal 200–400), platelet count 1.2 lakh/μL. 20-minute whole blood clotting test shows no clot formation. What is the most appropriate immediate management?

Explanation

## Clinical Assessment This patient has a **coagulopathic envenomation** (likely from a viper bite, given the local swelling and coagulation derangement) with: - Prolonged PT and aPTT - Hypofibrinogenemia (80 mg/dL) - Thrombocytopenia (1.2 lakh/μL) - **Positive 20-minute whole blood clotting test** (WBCT20) — no clot formation = coagulopathy confirmed **Key Point:** A positive WBCT20 (no clot in 20 minutes) is the gold standard bedside test for venom-induced coagulopathy and mandates immediate ASV administration, regardless of other clinical features. **High-Yield:** The 20-minute whole blood clotting test is the most sensitive and specific bedside test for detecting venom-induced coagulopathy in resource-limited settings. A positive test (no clot) indicates systemic envenomation with coagulation factor consumption. ## Management Algorithm ```mermaid flowchart TD A[Snake bite + local swelling]:::outcome --> B{WBCT20 positive?}:::decision B -->|Yes| C[Coagulopathy confirmed]:::outcome C --> D[Administer ASV IV after sensitivity test]:::action D --> E[Repeat WBCT20 at 30 min, 6 hr, 24 hr]:::action E --> F[Continue ASV if WBCT20 remains positive]:::action B -->|No| G[Observe clinically]:::action G --> H[Repeat WBCT20 at 6 hr]:::action ``` **Clinical Pearl:** ASV should be given **intravenously** for systemic envenomation (coagulopathy, neurological signs, systemic bleeding). Intradermal sensitivity testing (0.05 mL of 1:10 diluted ASV) should precede IV administration to detect anaphylaxis risk. **Mnemonic: WBCT20 POSITIVE = ASV STAT** — Whole Blood Clotting Test at 20 minutes positive indicates immediate ASV administration. ## Why Other Options Are Incorrect | Option | Reason | |--------|--------| | Fresh frozen plasma alone | FFP is supportive only; it does NOT neutralize circulating venom. ASV must be given first to neutralize the venom before supportive transfusion. | | Tranexamic acid | While TXA may be used as adjunctive therapy in severe bleeding, it is NOT a substitute for ASV. The primary goal is venom neutralization, not fibrinolysis inhibition. | | Emergency fasciotomy | There is no evidence of compartment syndrome (no pain out of proportion, no neurovascular compromise). Fasciotomy is reserved for confirmed compartment syndrome with intra-compartmental pressure >30 mmHg. | **Warning:** Do NOT delay ASV waiting for sensitivity test results if the patient is severely envenomated. Sensitivity testing should be done in parallel, and ASV should be given immediately if there is clinical or laboratory evidence of systemic envenomation.