IM21.4-6 | Snake Bite Clinical Evaluation and Testing — Summary & Reflection

KEY TAKEAWAYS

The clinical evaluation of snakebite integrates a structured 7-domain history (time/circumstances, species ID, local evolution, haematotoxic symptoms, neurotoxic symptoms, pre-hospital interventions, background history) with a systematic examination (vitals, local wound, cardiovascular, and the 5-element serial neurological exam for elapid bites) and targeted investigations.

20WBCT is the cornerstone bedside test for haematotoxic envenomation: 2–3 mL blood in a clean dry GLASS tube, undisturbed 20 minutes; no clot = VICC = antivenom indicated. Must be in glass — plastic gives false negatives. Repeat every 30–60 min for first 6 hours; repeat at 6 h post-antivenom to confirm response.

Haematotoxic lab panel: PT/INR, aPTT, fibrinogen, D-dimer, platelet count, CBC, creatinine, electrolytes, CK, urine dipstick (myoglobinuria = red-brown urine, blood on dipstick, no red cells on microscopy = rhabdomyolysis → aggressive IV fluids).

Neurotoxic monitoring: No blood test — serial clinical exam every 30 min: ptosis, ophthalmoplegia, bulbar function, neck flexion (grade 3/5 = danger), count test (<20 = impending respiratory failure), SpO2. Neostigmine test (1.5 mg IV + atropine 0.6 mg) for post-synaptic (cobra) block — no response confirms pre-synaptic (krait) or irreversible block. Intubation threshold: SpO2 <95%, count <10, neck flexion grade ≤3.

REFLECT

Reflect on the two patients in the opening hook. The first (farmer with visible wound, haematotoxic) is alarming in appearance and you are instinctively drawn to the dramatic local injury. The second (woman with ptosis and failing count test) is quiet, her wound is invisible, but she is minutes from respiratory arrest. In emergency medicine, the quietest patient can be the sickest. Think about how the structured evaluation approach — serial count tests, meticulous neurological examination every 30 minutes — protects against the cognitive bias of anchoring on the dramatic and missing the silent deterioration. How would you communicate the plan for serial 30-minute neurotoxic evaluations to a junior nurse on the ward who has not previously managed a snakebite case? What would be on your handover note?