This is due to bite from organisms that inject their toxins (venom). Most of these bites are from snakes; commonest being cobra, krait, Russell viper and saw-scaled viper. The patient may present with history of bite along with swelling, redness, pain, shortness of breath, nausea, vomiting. In severe cases patient may present with respiratory distress or neurological deficit. Bite marks may be visible and often patients or their relatives will be able to describe the type of serpent.
Immediate advice (R.I.G.H.T. approach):
- R = Reassurance – 70% of all snakebites are from non-venomous species. Only 50% of bites by venomous species actually inject venom during bites.
- I = Immobilise the patient and the affected limb completely. Do not apply any compression in the form of tight ligatures.
- G.H. = Get to nearest hospital without delay
- T. = tell the doctor of any systemic symptoms that develop
Tourniquet: It is observed that many snake bite victims reach the emergency with tight tourniquets, however this is not recommended. Care must be taken while removing these as sudden removals can lead to a massive surge of venom, leading to paralysis, hypotension, etc. Before removal of the tourniquet, check for the presence of pulse distal to it. If it is absent, ensure doctors presence before removal who should be able to handle complications such as sudden respiratory distress or hypotension. If the tourniquet has occluded the distal pulse, then blood pressure cuff should be applied, and pressure should be slowly reduced.
Initial Investigation:
- 20 minutes whole blood clotting test (WBCT) – 10 ml blood of victim in plain glass vial is left undisturbed and checked for clotting after 20 minutes. If the blood remains unclotted after 20 mins., there is evidence of coagulopathy and this confirms Viper snake bite. The test should be carried out every 30 minutes from admission for 3 hours and then hourly for next 3 hours. If the blood is still uncoagulable, repeat test every 6 hourly for the requirement for repeat doses of Anti Snake Venom (ASV).
Medication (anti-snake venom):
- Inj. Anti-snake venom (ASV) should be used intravenously only with evidence of systemic envenomation or severe local swelling. Systemic envenomation will be evident from the 20WBCT, signs of spontaneous bleeding or neurological symptoms such as ptosis. Severe local symptoms are defined as swelling rapidly crossing a joint or involving half of the bitten limb. Purely local swelling, even if accompanied by bite mark from an apparently venomous snake, is not an indication for administering ASV.
- The recommended initial dose of anti-snake venom is 10 vials. ASV is reconstituted in isotonic saline or glucose but can be started without any diluent fluid in patients with volume overload. It is administered intravenously over 1 hour without a test dose. No dose adjustments are needed for children, pregnant and elderly patients.
- In case of haemostatic bites – repeat doses based on the 6 hours rule until coagulation has been restored. Liver is unable to replace clotting factors in under 6 hours. Clotting tests and repeat doses of ASV should continue 6-hourly until coagulation is restored or unless a species is identified as one against which polyvalent ASV is not effective.
Supportive treatments:
- For neurotoxic bites – give neostigmine along with atropine.
- Tab. Dolo 650 (Paracetamol 650 mg) – 1 tablet 4 times per day. Aspirin or Nonsteroidal anti-inflammatory drugs (NSAIDs) should be avoided.
- Inj. Tetanus toxoid – 0.5 ml i.m. if patient hasn’t received it over the last 10 years.
- Tab. Moxikind CV 625 (Amoxycillin 500 mg; Clavulanic acid 125 mg) 1 tablet thrice a day for 10 days if additional aerobic infection is suspected.
- Tab. Flagyl 400 (Metronidazole 400 mg) – 1 tablet thrice a day for 10 days if additional non-aerobic infection is suspected.
- Cap. Prowel (Probiotic and prebiotic) – 1 capsule twice a day for gut protection with antibiotics.
Management of adverse reactions to anti-snake venom
- Discontinue anti-snake venom infusion at the first sign of an adverse reaction .
- Give inj. Adrenaline (1:1000) 1 ml intramuscularly. Alternatively, bolus of 1 ml of 1:10,000 intravenously and repeated till blood pressure improves.
- Follow anaphylaxis protocol for further management.
- In elderly when hypotension is corrected, noradrenaline and nitroglycerin infusion can be given to avoid adrenaline induced arrhythmia.
- Once the patient has recovered, the anti-snake venom can be restarted slowly for 10 – 15 minutes, keeping the patient under close observation.
Investigations:
- Complete blood count – Hemolysis and low platelets suggest viper bite. Raised neutrophils suggest systemic absorption of venom. Raised haemoglobin suggests increased capillary leak.
- Serum amylase and creatinine kinase – raised in cases of muscle damage.
- Coagulation screen – raised INR, PT, and aPTT in case of viper bites.
- Urine examination – to identify haematuria, proteinuria, myoglobinuria.
- Renal function test – Raised creatinine is suggestive of viper bite.
- Liver function test – deranged in severe cases.
Referral:
Consider urgent referral to secondary care with ICU facilities if patient is systemically unwell.