Anti-Snake Venom (ASV) administration for snake bites
M3 India Newsdesk May 10, 2019
After a venomous snakebite, first aid to retard the progression of envenoming should be made the priority. Rapid access to a health facility and anti-snake venom (ASV) therapy with optimal supportive care greatly decrease the chances of death and long term complications.
The recognition of snakebite as a “ neglected tropical disease” by the World Health Organization, led to efforts and research to combat this highly neglected topic. India in particular is considered to have a high occurrence of snakebites and associated deaths; the lack of systematic preventive measures at community and national levels are held responsible for the same.
Even though there are well-formulated snakebite treatment protocols for low resource settings, these are poorly implemented. The existing protocols are not standardised and numerous conflicting versions exist with differing indications for antivenom administration and dosing.
Discussed here are the various steps to be followed for effective ASV administration as per specific snake species.
Management of Krait Bite Victims
Beta bungarotoxin toxins in the Krait venom release acetylcholine at the nerve endings at the neuromuscular junction and then subsequently damage it. The damaged receptors prevent the release of acetylcholine and lead to resistance to anti-cholinesterase.
- On arrival, 100 ml (10 vials) of anti-snake venom (ASV) should be added to 200 ml of normal saline and should be run over 30 to 50 minutes
- Repeat dose of ASV can be administered within 30 minutes after the initial dose, if there is no improvement of neurological manifestations; however, no more than 20 vials of ASV should be used
Other measures to take
- First aid should be provided immediately; the surface-deposited venom should be removed and cleaned with cloth or cotton. Crepe bandage should be used from the distal end of the bite site with the right amount of pressure.
- The bitten part should be kept below heart level and the victim should not be allowed to walk. In an emergency, mouth-to-mouth ventilation should be started.
- Initial clinical signs such as bulbar palsy, muscle power, tendon reflexes, respiratory rate, oxygen saturation, one-minute counting, pooling of saliva, broken neck sign should be noted in detail.
- Blood pressure and ECG changes should be monitored. Serum electrolytes and renal profiling should be done every few hours till clinical improvement is seen.
- One should sit by the side of the victim for early diagnosis and treatment of anaphylaxis. Ventilation may be required in patients unable to lift the neck from the pillow and in cases with salivary pooling, respiratory failure, abdominal-thoracic respiration and decline in oxygen saturation.
- Endrotracheal intubation can be performed in cases of suffocation and cerebral hypoxia. If not feasible, a laryngeal mask may be used and ambu bag ventilation can be initiated. Anticholinesterase inhibitor (AChI) may be administered if there is a slight improvement in ptosis.
- Nitroglycerine drip and non-invasive ventilation are recommended for dealing with severe uncontrolled hypertension.
Management of Cobra Bite Victims
Due to its smaller molecular size, Cobra venom is rapidly absorbed into the circulation, where it attaches reversibly to postsynaptic receptors.
ASV protocol: Anti-snake venom of 100 ml (10 vials) should be administered by intravenous route; a maximum of 20-25 vials can be used.
Other measures to take
- The affected part should be kept below heart level and the victim should not be allowed to walk or run.
- No time should be wasted in using tourniquets. Mouth-to-mouth ventilation and chest compression should be initiated in an unconscious patient with no respiration.
- Artificial ventilation should be initiated by ambu bag or ventilator
- Neostigmine 50 μg/kg should be administered over the first hour; the dose should be halved to 25 μg/kg for the next couple of hours. Atropine should be used before neostigmine to counter the muscarinic action.
- Intravenous antibiotic, daily dressing and plastic surgery are recommended if required.
Management of Russell’s Viper Bite Victims
Viper venom exhibits both anti-coagulant and coagulant effects on blood clotting mechanism and results in defibrination syndrome or disseminated intravascular fibrin-coagulopathy. Acute bleeding is caused by hypofibrinogenaemia which occurs due to massive consumption of fibrinogen and fibrinolysis of blood clots.
- Take 2 to 3 ml of blood in a dry detergent-free glass test tube; keep it undisturbed for 20 minutes and then tip it off if blood did not clot, to confirm hypofibrinogenaemia which indicates the presence of circulating venom and hence confirms the requirement for ASV
- ASV- 200 ml (20 vials) diluted in 200 ml of 5% dextrose should be run over 30 minutes by the intravenous route
- Repeat dose of 50 ml of ASV may be administered if external bleeding does not stop within 20 to 30 minutes
- Subsequent doses of ASV are decided by assessing the 20 min whole blood clotting time (20MWBCT), which is a simple, rapid and reliable test of coagulopathy
Other measures to follow
- The use tourniquet may damage more local tissue and hence should be avoided. The bitten part should be kept below heart level if active bleeding occurs; temporary compression may help prevent massive loss of blood
- Thrombocytopenic, abnormal and crenated RBCs represent disseminated intravascular coagulation (DIC).
- In addition to ASV, plasma products and whole blood transfusion can be used, however, they are rarely required if the adequate dose of ASV is administered in time.
- Hypotension can be managed with fluid and inotropic agents. Severe hypotension may require the administration of heavy doses of intravenous methyl-prednisolone and correction of electrolytes.
- The edematous limb can be elevated once the clotting mechanism is reversed (20MWBCT). Glycerin Magsulf dressing, aspiration of tense blebs by sterile needle and debridement of dead tissues should be performed.
- Surgical decompression should be avoided unless absolutely essential. Before intervention by a surgeon, one should be sure that the blood is coagulable.
- Intravenous antibiotics can be given to overcome infection. One should always rule out diabetes mellitus.
Management of Green Pit Viper and Bamboo Pit Viper Bite Victims
Pit Viper bites are characterised by local oedema and rarely systemic bleeding disorder. Coagulopathy and renal failure may also be observed.
- No antivenom for these two vipers is available in India; empirical treatment with polyvalent venom can be initiated to alleviate the envenoming
- Antivenom should be administered as soon as signs of systemic or severe local swelling are seen
- The patient should be closely observed daily for minimum 3 to 4 days before discharge
Management of Carpet or Saw-Scaled viper (Echis Carinatus) Bite Bictims
A protein in the Echis carinatus (absent in snakes of Bengal and Kashmir) has the unique effect of enhancing fibrinolysis by plasminogen activation by urokinase. Rapid bleeding in the brain, lungs, kidney, heart and GI tract is caused due to haemorrhagins -1, 2 and metalloendopeptidase.
ASV protocol: Anti-snake venom requirement in Maharashtra is 30 to 50 ml; in Jammu and Puducherry, ASV requirement is >100 ml.
Management protocol is same as that followed for Russell’s viper bite.
The effects of a sea snake bite are both myotoxic and neurotoxic. Myoglobin and potassium released from damaged skeletal muscle can cause renal failure, while the hyperkalemia thus produced may lead to cardiac arrest.
The initial critical steps include
- Stabilization with airway control
- Pressure immobilization of the bitten extremity
- Prompt transport to a facility capable of providing advanced medical care (including ASV administration)
- Intravenous polyvalent ASV 100 mL should be administered in patient with signs of envenomation
- The patients treated with antivenom should be monitored for allergic reactions
Other measures to take
- Ventilator should be prepared for respiratory failure.
- Aggressive hydration with diuresis can help promote renal myoglobin clearance. Urine alkalinization may be of some benefit in cases of myoglobinuria.
- Insulin glucose drip should be started. Salbutamol may be provided to prevent bronchospasm.
- Sea snake neurotoxin is of low enough molecular weight to be dialyzable. Dialysis may be lifesaving in cases of severe hyperkalaemia.
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