What can you do to treat a deadly snakebite? Learn more about this neglected health hazard through 23 quick FAQs answered in this article by our expert, Dr. Nandini Chatterjee.

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Important facts and salient aspects of snakebite management

Question 1. Are all snakebites venomous?

Answer: Snakebites cause unprecedented panic. There are around 300 species of snakes found in India out of which 52 are venomous. Only 30% of bites are caused by venomous snakes. Sometimes the venom may not even be injected into the bites (50% of the bites). This is a phenomenon called dry bite. 

The most common Indian venomous snakes are Indian Cobra, Indian Krait, Russell's Viper and Saw-scaled viper. So a reassurance to the victim is warranted in most cases, that most snake bites are harmless.

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Question 2. What are the clinical presentations of snakebites?

Answer: It may present as:

• Progressive weakness (neuroparalytic/neurotoxic)
• Bleeding (vasculotoxic/haemotoxic)
• Myotoxic (sea snakes)
• Painful, progressive local swelling

Krait bites are common at night. They generally bite people asleep on the ground. Maximum Viper and Cobra bites occur during the day or dawn while walking barefoot in overgrown grass or crops.

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Question 3. How important are the fang marks? 

Answer: Though we look for obvious evidence after a snakebite such as fang or puncture marks, their patterns give no clue of whether the species was venomous, the amount of venom injected, the severity of systemic poisoning or nature of envenomation – hemotoxic or neurotoxic. Krait bites do not produce fang marks.

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Question 4. What are the markers of envenomation? 

Answer:

1. Local signs: These are very common in Russell’s viper bite but may be present in other viperine bites. Swelling, bleeding, blisters, and necrosis are the hallmarks. It is considered significant when it involves more than half of the bitten limb or there is rapid progression in severity. Pain at the bite site and passive movement with severe swelling along with the absence of peripheral pulses and hypoesthesia helps to diagnose compartment syndrome. Tender enlargement of the local draining lymph nodes may accompany.
2. Systemic signs:
   1. Neuroparalytic features- Ptosis, diplopia, dysphonia, dysarthria, dyspnoea, dysphagia
      1. Ptosis (drooping of eyelids) occurs first while dyspnoea (breathlessness) and dysphagia occur later. This is followed by descending muscular paralysis. Signs of impending respiratory failure are diminished or absent; deep tendon reflexes and head lag due to neck muscle weakness.
      2. Neuroparalytic snakebite patients present within 6 hours in case of Cobra bite and up to 24 hours for Krait bite. However, ptosis in Krait bite has been documented after 36 hours even.
   2. Hematotoxic effects- Visible bleeding from gums or orifices, subconjunctival haemorrhages, continuous bleeding from the bite site. Intra-cranial bleeding with unequal pupils and gastrointestinal or retroperitoneal bleeding with abdominal tenderness should not be missed.
   3. Cardiovascular abnormalities: Hypotension, shock, cardiac arrhythmia, abnormal ECG.

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Question 5. Are all symptoms due to envenomation?

Answer: Sometimes, panic and sympathetic overactivity can manifest as palpitations, sweating, tremulousness, tachycardia, tachypnoea, elevated blood pressure, cold extremities dilated pupils and paraesthesia.

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Question 6. How to identify impending respiratory failure in adults?

• Single breath count– Number of digits counted in one exhalation- >30 is considered normal
• Breath-holding time– Breath held in inspiration- normal >45 seconds
• Completion of a sentence in one breath

First-aid measures: Reassure the patient as around 70% of all snakebites are from non-venomous species.

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Question 7. Is a tourniquet helpful in preventing systemic envenomation?

Answer: No. Tourniquets should not be tied, as blood supply may get obstructed leading to gangrene. Any constricting clothing or jewellery should be removed for the same reason when oedema increases. The limb may be immobilised with bandages or cloth to hold a splint, but not to apply too much pressure.

Care must be taken while removing tight tourniquets as sudden removal can lead to a massive influx of venom leading to paralysis and hypotension due to vasodilatation. Before removal of the tourniquet, the presence of a pulse distal to the tourniquet is felt. If it is occluded, then a blood pressure cuff can be applied to reduce the pressure slowly.

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Question 8. Does sucking/washing/electrocuting the wound from a snakebite prevent envenomation?

Answer: No. The wound is not to be washed or interfered with by any procedures or chemicals as this may lead to infection, bleeding or increased absorption of the venom. Traditional first aid methods and herbal therapy have no role and may do more harm.

Immediately after providing first-aid, the patient is to be transferred to a health facility where anti-snake venom (ASV) is available with provision for close observation, basic laboratory investigation and definite treatment.

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Question 9. How to arrange for transportation of the patient?

Answer: Urgent transportation of the patient to a medical facility by carrying is of utmost importance. Any vehicle, ambulance, boat, bicycle, motorbike, or stretcher is suitable.

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Question 10. Is species identification necessary for treatment?

Answer: No. The clinical manifestations of the patient may not correlate with the species of snake brought – an attempt to kill or catch the snake may be dangerous. Treatment with ASV depends on signs of envenomation and WBCT 20.

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Question 11. What is the differential diagnosis of snakebite like krait?

Answer: Early morning symptoms of acute pain in the abdomen without neuroparalysis can be mistaken for acute abdomen due to appendicitis, cholecystitis pancreatitis etc. If neuroparalysis is present, stroke, GB syndrome, myasthenia gravis and hysteria are the differentials. Neurotoxicity leads to descending paralysis in contrast to GB syndrome where it is ascending.

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Question 12. Is ASV effective against all venomous snakes?

Answer: In India only polyvalent ASV is available; it is effective against all 4 common species: Russell's viper, Common Cobra, Common Krait and Saw Scaled Viper.

It is documented that known species such as the Hump-nosed pitviper, Malabar pit viper, also Sochurek's Saw Scaled Viper in Rajasthan, and Kalach in West Bengal polyvalent ASV is not very effective.

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Question 13. What is the protocol on admission?

Answer: All victims of snakebite confirmed or suspected are to be kept under observation for 24 hours. Observation for signs of envenomation and consumptive coagulopathy are detectable by 20 minutes Whole Blood clotting test (20 WBCT). ASV therapy is to be instituted where there is evidence of envenomation. One should not apply or inject antisnake venom (ASV) locally.

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Question 14. How to monitor the patient?

Answer: Check for the following:

• Pulse rate
• Respiratory rate
• Blood pressure
• 20 WBCT hourly for initial 3 hours and every 4 hours for the remaining 24 hours

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Question 15. How to perform a 20 WBCT test?

Answer: 2 ml of freshly drawn venous blood is to be put in a glass test tube and observed after 20 minutes. Then, gently tilt to see if the blood has clotted or not. If the patient has hypofibrinogenemia due to venom-induced consumptive coagulopathy there will be no clot.

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Question 16. What are the other tests to be done?

Answer:

• Urine dipstick test or microscopic examination
• Prothrombin time
• Platelet count
• Liver function test
• Renal function test
• Blood sugar
• ECG
• Abdominal ultrasound
• Arterial blood gases

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Question 17. What should be the total dose of ASV?

Answer: Antisnake venom treatment is the only specific treatment and should be given as soon as it is indicated. It may be effective even if infused after several days.

Dose of ASV for neuroparalytic snakebite:10 vials of ASV is to be infused stat over 30 minutes. If no improvement is observed within 1 another 10 vials are to be given (total 20 vials).

Hemototoxic bite: 10-30 vials with first 10 vials stat as the infusion over 30 minutes is to be repeated every 6 hours till correction of 20WBCT.

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Question 18. Is an ASV test dose necessary?

Answer: Skin/conjunctival hypersensitivity testing is not recommended. These reactions cannot predict future adverse events. They activate complement to pre-sensitize the patient. They may predispose to future hypersensitivity events.

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Question 19. What is the dosage of ASV in children and pregnant women?

Answer: ASV dosage is identical for children, pregnant women and adults. As snakes inject a similar quantity of venom into adults and children, the neutralising dose is the same.

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Question 20. What are the reactions to ASV administration?

Answer: Patients may develop severe life-threatening anaphylaxis rarely with ASV but 20-60% of patients suffer either early or late mild reactions after the infusion is started.

• Early anaphylactic reactions by 10–180 minutes
• Pyrogenic reactions (fever) by 1–2 hours
• Late (serum sickness–type) reactions develop 1–12 (mean 7) days later

New clinical features noticed after the onset of ASV infusion should be considered a reaction to ASV.

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Question 21. What is the treatment of neuroparalytic envenomation?

Answer: Combination of Atropine 0.6 mg followed by neostigmine (1.5mg) (AN) to be given IV stat, thereafter neostigmine 0.5 mg with atropine is to be given every 30 minutes for 5 doses. The next doses are to be given at 1, 2, 6 and 12 hours.

Recovery of the ptosis by 50% or more in one hour is the marker of improvement, usually achieved by 5 doses. In Common Krait bite paralysis is due to presynaptic blockage, ASV and Neostigmine dose. Beyond 3 doses should not be given as natural regeneration takes 4-5 days. Both ASV and AN injection may be terminated with an improvement of pharyngeal muscle palsy.

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Question 22. What are the supportive therapies?

Answer:

• IV fluids/ionotropes for hypotension
• Dialysis- haemodialysis preferable
• NIV/mechanical ventilation where indicated
• Antibiotics for sepsis
• FFP for coagulopathy
• Surgical debridement/fasciotomy if required

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Question 23. What are the complications of snakebite?

Answer:

• Acute renal injury
• Respiratory failure
• ARDS
• Haemorrhage
• Shock
• Cardiac arrhythmia
• Severe sepsis
• Compartment syndrome
• Late complication– hypopituitarism due to pituitary haemorrhage

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Conclusion

Snakebite is a life-threatening health hazard that needs public awareness and prompt intervention in a healthcare facility. If properly managed without prejudice, morbidity and mortality can be significantly reduced.

Dr. Nandini Chatterjee is a professor of medicine from Kolkata.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.