A 35-year-old woman from Madhya Pradesh is brought to the hospital 6 hours after a cobra bite to her right hand. She has local swelling up to the elbow, but her vital signs are stable and she is fully conscious. Neurological examination is normal. Investigations: PT 14 seconds (control 12 seconds), aPTT 36 seconds (control 32 seconds), fibrinogen 250 mg/dL, platelet count 2.5 lakh/μL. 20-minute whole blood clotting test shows normal clot formation. What is the most appropriate next step in management?

Explanation

## Clinical Assessment This patient has **local envenomation only** — no systemic manifestations are present: - Local swelling confined to hand and forearm (below elbow) - Stable vital signs; fully conscious; **normal neurological examination** - **Negative 20-minute whole blood clotting test (WBCT20)** — normal clot formation - Coagulation profile: PT 14 s (control 12 s), aPTT 36 s (control 32 s) — **minimally prolonged, NOT clinically significant coagulopathy**; fibrinogen and platelets are entirely normal - Presentation is **6 hours post-bite** — within the window for delayed systemic manifestations **Key Point:** The WBCT20 is the single most important bedside test for viper-induced coagulopathy. A **negative WBCT20** (clot forms and holds at 20 minutes) effectively rules out significant consumptive coagulopathy. The mildly prolonged PT/aPTT here does NOT constitute coagulopathy warranting ASV — it is within the range of normal biological variation and does not meet the threshold for systemic envenomation. ## Why Option B is Correct Per WHO/SEARO and Indian National Snakebite Protocol guidelines, **ASV is indicated only when systemic envenomation is confirmed**, not as prophylaxis. The correct approach for local-only envenomation with negative WBCT20 is: 1. **Admit for 24-hour observation** 2. **Repeat WBCT20 at 12 and 24 hours** (or sooner if clinical deterioration) 3. **Administer ASV immediately if systemic signs develop** (neurotoxicity, coagulopathy, cardiovascular compromise) ## Why Option A is Inferior to Option B Option A states "administer ASV only if the patient develops neurological symptoms **or** coagulopathy." While this sounds similar to Option B, it is subtly inferior because: - It does not specify the need for **active observation and repeat testing** — a passive "wait for symptoms" approach risks missing insidious neurotoxicity - It conflates neurological symptoms and coagulopathy as equivalent, parallel triggers without acknowledging that **coagulopathy is best detected by repeat WBCT20** (not just clinical signs) - Option B explicitly incorporates the structured monitoring protocol (repeat investigations at 12 hours), which is the standard of care **Clinical Pearl:** Cobra (elapid) bites can cause **delayed neurotoxicity** — ptosis, ophthalmoplegia, and respiratory paralysis — appearing 12–24 hours after the bite. Continuous in-hospital observation with serial neurological checks every 2–4 hours is mandatory. This is why discharge (Option D) is absolutely contraindicated. **High-Yield Decision Algorithm:** | Finding | Action | |---|---| | Positive WBCT20 | Give ASV immediately | | Systemic signs (neuro/cardiovascular/hemorrhagic) | Give ASV immediately | | Local swelling only + negative WBCT20 + mildly abnormal labs | Observe 24 hrs; repeat WBCT20 at 12 hr; give ASV if systemic signs develop | | No envenomation signs at 24 hrs | Discharge with follow-up | ## Supportive Care During Observation - **Local measures:** Limb elevation, analgesics, tetanus prophylaxis if indicated - **Monitoring:** Vital signs and neurological examination every 2–4 hours; repeat WBCT20 at 12 and 24 hours - **ASV:** NOT given prophylactically; reserved for confirmed systemic envenomation *Reference: WHO Guidelines for the Management of Snake-bites in South-East Asia (2016); Harrison's Principles of Internal Medicine, 21st ed., Chapter on Envenomations.*