Year : 2019 | Volume
: 17 | Issue : 3 | Page : 66--68
Venomous snakebites: Management and anti-snake venom
John Emmanuel Jesudasan, Kundavaram Paul Prabhakar Abhilash
Department of Emergency Medicine, Christian Medical College, Vellore, Tamil Nadu, India
Dr. John Emmanuel Jesudasan
Department of Emergency Medicine, Christian Medical College, Vellore - 632 004, Tamil Nadu
In the Indian subcontinent, the “Big four” snakes of cobra, krait, Russell's viper, and saw-scaled viper are responsible for most of the venomous snakebites. Diagnosing envenomation is a pure clinical skill with no diagnostic kit available yet. Anti-snake venom (ASV) is a precious commodity, and clinicians across the country must be aware of the process of production of ASV so that they may use it judiciously for the treatment of envenomation.
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Jesudasan JE, Abhilash KP. Venomous snakebites: Management and anti-snake venom.Curr Med Issues 2019;17:66-68
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Jesudasan JE, Abhilash KP. Venomous snakebites: Management and anti-snake venom. Curr Med Issues [serial online] 2019 [cited 2022 Jul 3 ];17:66-68
Available from: https://www.cmijournal.org/text.asp?2019/17/3/66/267911
The Indian subcontinent has a rich biodiversity of flora and fauna, with snakes being one of the most dangerous., There are more than 60 species of venomous snakes in India. However, human contact with most of those is rare. The four most common venomous snakes (the “big four” species) with frequent human contact are cobra (Naja naja), krait (Bungarus caeruleus), Russell's viper (Daboia russelii), and saw-scaled viper (Echis carinatus).,,, Fortunately, many bites are “dry bites” with no venom injected into the body.
There are no diagnostic tests or kits available for diagnosing a venomous bite. Hence, one must rely only on clinical skills to diagnose envenomation. If available, positive identification of the snake could help the physician look for specific clinical signs of envenomation. In its absence, awareness of the syndromic toxicity spectrum is a very valuable tool in identifying the “big four” venomous snakes.
Cobra: neurotoxic with significant local reactionKrait: neurotoxic with no local reactionRussell's viper: hemotoxic + neurotoxic with significant local reactionSaw-scaled viper: hemotoxic with mild local reaction.
It is important to look for definite signs of envenomation before administering anti-snake venom (ASV) as it is a very precious commodity.
First aid immediately after a bite is extremely crucial in preventing further spread of venom into the systemic circulation through the lymphatics. Historically, many methods, both invasive and noninvasive, have been tried. The most important step is immobilization of the involved extremity by splinting with whatever means available until hospital transfer.
A broad tourniquet may be applied above the site of the bite, preferably above the joint to occlude the lymphatic flow, pulses should be felt with the tourniquet in place, and one should be able to insinuate a finger under the tourniquet. The traditional teaching of incision and sucking out the venom should be avoided as it is of no benefit and would only increase the risk of secondary infection.
Examination and Investigations
On arrival to the hospital, carefully examine and locate the fang marks to determine if the snake is venomous or not (two fang marks indicate a venomous snake and multiple marks suggest a nonvenomous snake).
Features of neurotoxicity
Difficulty in lifting the neck (suggests neck muscle weakness)PtosisLow single breath count: (normal count is more than 20/min).
Features of hemotoxicity
Bleeding manifestations such as purpura, petechiae, bleeding from gums, hematuria, malena, and hematemesisProlonged whole blood clotting time (WBCT): collect 10 ml of whole blood in a glass tube and leave it by the bedside. Keep examining it every 5 min. Clotting time >10 min suggests hemotoxicity.
The only antidote available for the “big four” snakes is the commercially manufactured ASV. Administer ASV only if there are features of hemotoxicity or neurotoxicity.
Administer analgesics for pain relief. Avoid nonsteroidal anti-inflammatory drugs in patients with hemotoxicity as it can aggravate overt or occult bleedingConsider antibiotic administration for patients with signs of cellulitis and secondary infection at the site of the bite. It is important to cover anaerobic infections. Amoxicillin-clavulanate is a good choiceIt is essential to administer tetanus prophylaxis for all patients who did not receive tetanus toxoid (TT) in the past 5 years. Administer TT 1 ampoule intramuscularly into the deltoid.
Remember that most bites are “dry bites” and do not require ASV., It needs to be given only when there are features of envenomation:
Premedication may be required to decrease the risk of anaphylactic reactions in some patients. It is not required for most patients and is indicated only in with a history of atopy or a previous reaction to equine antiserum. The following is recommended prophylaxis for those requiring it.
Injection chlorpheniramine maleate (Avil) 1–2 ml slow intravenous (IV)Injection adrenaline 0.25 mg Intramuscularly IM (1:1000 dilution) in the anterolateral thigh.
Dose of anti-snake venom
Envenomation with hemotoxicity usually requires 8–10 vials of ASV in 500 ml 5% dextrose over 30 min. Reassess bleeding manifestation and WBCT after 6 h. If hemotoxicity persists, administer a further 4–8 vials depending on the severity of symptomsEnvenomation with neurotoxicity usually requires 8–10 vials of ASV in 500 ml 5% dextrose over 30 min. Reassess after 2 h and if neurotoxicity persists, administer another 4–8 vials depending on the severity of symptoms.
Treatment of early anaphylactic reaction
If a patient has features of anaphylaxis such as itching, urticaria, hypotension, or other systemic features, stop the ASV infusion immediately. Administer injection adrenaline 0.5 mg IM (1:1000 dilution) in the anterolateral thigh. Administer injection adrenaline 0.5 mg IM (1:1000 dilution) in the anterolateral thigh along with injection chlorpheniramine maleate (Avil) 1–2 ml slow IV/IM. After the reaction settles, ASV can be restarted slowly after 30–60 min.
Additional Supportive Care
Respiratory failure: If a patient develops respiratory failure, immediate mechanical ventilation may be required to support the work of breathing till neurotoxicity wears offSignificant bleeding: If a patient develops significant bleeding with a drop in hemoglobin despite giving ASV, blood products may be required. Check fibrinogen levels to assess the severity of disseminated intravascular coagulation. Fresh frozen plasma or cryoprecipitate may be requiredShock: In patients with shock due to myocardial depression, inotropic support after adequate fluid resuscitation may be requiredRenal failure: Hemotoxic and myotoxic snakebites may induce renal failure secondary to rhabdomyolysis or shock. This can be treated with adequate hydration with saline diuresis. Severe renal failure may require hemodialysisPtosis: This initial feature of neurotoxicity may persist for 1–2 weeks and does not warrant more ASV administration. Without other neurological manifestations, there is no indication to continue ASV for just ptosis.
Irulas and the Anti-Snake Venom
All of the venoms used for the production of ASV in India are supplied by the Irulas, who are considered the last “Forest Scientists” of India. Till the passage of the Wildlife Protection Act of 1972, the Irulas main trade was to kill snakes for their skin for export.
The Irulas Snake Catchers Industrial Cooperative Society (ISCICS) was formed by the Irulas from the Chengalpattu area, which under the license from the wildlife department capture the snakes, extract their venom, and then, release them back into their natural habitats. They are currently the only community in India who have the highly perilous job of catching snakes for a living to ensure a constant supply of ASV production for the rest of the country. Without the Irulas, the number of fatalities that may arise from snakebites in the country is unfathomable. Their tracking and digging skills to locate snakes in the wild is internationally renowned. Their expertise was sought by the state of Florida to track and catch the Burmese pesky pythons in the Everglades. Currently, the ISCICS is based at the crocodile park near Chennai, Tamil Nadu.
The venom extracted from these snakes is used to manufacture ASV by hyperimmunizing horses against the venoms of the four common poisonous snakes of India. Plasma obtained from the hyperimmunized horses is enzyme refined, purified, and concentrated. The currently available polyvalent ASV is not effective against king cobra (Ophiophagus hannah) envenomation, which is wildly prevalent in the Western Ghats. Monovalent anti-venom against king cobra is available in some places. In the Million Death Study, the snakebite death was estimated at 45,000 deaths based on verbal autopsy; however, early administration of ASV and good supportive care have shown good outcomes in snakebite; hence, most of the death could have been due to the lack of immediate medical assistance. Awareness about snakebite, its prevention, first aid, and appropriate use of Indian ASV and supportive care could improve the morbidity and mortality.
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Conflicts of interest
There are no conflicts of interest.
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