General Medicine
Envenomation and Poisoning
Envenomation and poisoning for MBBS: venomous snakes and their syndromes, first aid, anti-snake venom, scorpion sting and common poisonings, mapped to NMC codes IM20.1 to IM21.8.
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Envenomation and Poisoning
Envenomation and poisoning for MBBS: venomous snakes and their syndromes, first aid, anti-snake venom, scorpion sting and common poisonings, mapped to NMC codes IM20.1 to IM21.8.
This chapter covers envenomation and poisoning in the Indian setting, from the identification of venomous snakes to the recognition of neurotoxic and haemotoxic syndromes. It emphasises correct first aid, the indications for anti-snake venom, the management of scorpion and bee stings, and the stabilisation and specific treatment of common poisonings.
High-yield: Envenomation and Poisoning
- The four medically important venomous snakes in India are the cobra, common krait, Russell viper and saw-scaled viper.
- Elapid bites from cobra and krait cause neurotoxic envenomation with ptosis and respiratory paralysis.
- Viper bites cause haemotoxic envenomation with local swelling, coagulopathy and bleeding.
- Correct first aid is reassurance, immobilisation of the limb and rapid transport, avoiding tourniquets and incision.
- The 20-minute whole blood clotting test is a simple bedside marker of viper coagulopathy.
- Polyvalent anti-snake venom is indicated when there are signs of systemic envenomation.
- Anaphylactoid reactions to anti-snake venom are managed with adrenaline and supportive care.
- Neostigmine with atropine can reverse neurotoxicity in some elapid, particularly cobra, envenomation.
- Scorpion sting can cause an autonomic storm, and prazosin is used in significant Indian red scorpion envenomation.
- Anaphylaxis from a bee sting is treated with intramuscular adrenaline as the first-line drug.
- The poisoned patient is first stabilised by attention to airway, breathing and circulation.
- Organophosphate poisoning causes a cholinergic crisis treated with atropine and pralidoxime.
- Corrosive ingestion should not be treated by inducing vomiting or attempting neutralisation.
- A poison information centre provides guidance on identification and specific management.
- Haemodialysis enhances elimination of certain dialysable poisons such as methanol and salicylate.
Envenomation and poisoning essentials
- **Snake syndromes:** Neurotoxic (cobra, krait) with paralysis; haemotoxic (vipers) with coagulopathy.
- **First aid:** Reassure, immobilise and transport; avoid tourniquets, incision and suction.
- **Bedside test:** 20-minute whole blood clotting test detects viper coagulopathy.
- **Poisoning:** Stabilise airway, breathing and circulation; organophosphate needs atropine and pralidoxime.
NMC competencies in this chapter
- **IM20.1:** Local venomous snakes and distinguishing features
- **IM20.2:** Correct initial field management of snakebite
- **IM20.7:** Anti-snake venom: indications, dose and reactions
- **IM20.8:** Scorpion envenomation
- **IM20.9:** Bee sting allergy and anaphylaxis
- **IM21.1:** Initial stabilisation of the poisoned patient
- **IM21.4:** Common drug and chemical overdose in India
- **IM21.8:** Dialysis and enhanced elimination in acute poisoning
Frequently Asked Questions
What is the correct first aid for snakebite?
Reassure the patient, immobilise the bitten limb and transport rapidly to hospital, while avoiding tourniquets, incision, suction and attempts to catch the snake.
When is anti-snake venom indicated?
Polyvalent anti-snake venom is given when there are signs of systemic envenomation such as neurotoxicity, coagulopathy on the 20-minute whole blood clotting test, or significant local spread.
How is organophosphate poisoning managed?
It is treated with atropine to counter the cholinergic crisis and pralidoxime to reactivate acetylcholinesterase, alongside airway protection and supportive care.
How does this chapter help for NEET-PG?
Snake envenomation syndromes, the clotting test, anti-snake venom indications and organophosphate management are common exam themes that map directly to questions.
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