Envenomation
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Snake bites in rural India pose a significant health hazard, with an estimated 50,000 deaths annually, primarily affecting impoverished populations. Various snake families including Elapidae, Viperidae, and Crotalidae contain venomous species, each producing distinct effects such as paralysis, necrosis, and hemorrhagic symptoms. Management of envenomation involves immediate medical attention, use of antivenin, monitoring, and supportive care due to potential severe complications.
Envenomation
- 2. Envenomation in India • Snake bite - major environmental and occupational hazard in rural India and South Asia • There are estimated 50,000 deaths due to snake bite in India every year. • 97% of affected are in rural area • Only 23% of the total snake bite deaths occurred in hospitals
- 3. Snakes • 3500 species – about 375 are poisonous • Important Poisonous species – • Elapidae (Cobras, Kraits, Mambas, Coral snakes)- not in Europe • Viperidae (True vipers) • Crotalidae (Pit vipers and Rattle snakes) • Colubridae – Africa • Hydrophiidae (Sea snakes) – found close to coastline.
- 4. Common in India • Cobras • Indian Cobra • King Cobra • Kraits (small but very poisonous) • Common Krait - கட்டு விரியன் • Banded Krait - yettadi viriyan • Vipers • Pit Viper (pit below eyes) • Russell Viper - கண்ணாடி விரியன் • Saw scaled Viper - சுருட்டைவிரியன்
- 5. Venom • Injected through two fangs in upper jaw– grooved or tubular • Secreted in specialized parotid gland – squeezed through duct to fangs • Constituent : • Toxic proteins and Proteolytic enzymes (Cholinesterases, Phosphatases, Nucleotidases, Hyaluronidase, … etc.
- 6. Effects of Venom • Neurotoxic : • Paralysis – Voluntary muscles Muscles supplied by cr. nerves Brainstem/Medulla • Necrotizing: • Severe inflammation and local necrosis • Hemolytic and Hemorrhagic: • Intravascular hemolysis / severe haemorrhage – depletion of normal clotting factors
- 7. Effects of Venom • Shock: • Severe inflammation and vasodilatation at bitten extremity along with severe hemolysis and haemorrhage • In viperine bites – shock may occur before local features/haemolysis/haemorrhage manifest.
- 8. Effects of Venom • Elapids: • Chiefly neurotoxic • Some degree of hemolysis and local tissue necrosis • Viperidae: • Severe local necrosis, haemolysis • Disturbance in coagulation mechanism • Profuse haemorrhage and Shock
- 9. Points to Note • A bite from poisonous snake does not necessarily cause envenomation. • A bite by any snake P/NP may cause severe fright which may even lead to death. Violent and agitated behaviour may be noticed in them. • P snake bite – 2 fang marks/ NP snake bite – form of inverted ‘U’ • Envenomation serious in children than adult • Pathogens in mouth of PS/NPS Secondary infection • Victim perfectly well/no local inflmtn 6-8hrs after bite Non poisonous.
- 10. Clinical features - Cobra • Local effects: (5 mins) • Bite- Burning pain, Numbness, Red inflamed ring – not as much as viper. • Systemic effects: (10 mins – 2 hrs) • Vomiting, Vertigo, Vision blurring • Circumoral paraesthesia, • Heaviness of eye lids
- 11. Clinical features - Cobra • Weakness and Ataxia – unsteady gait – paralysis of CN supplied muscles • Ptosis – Opthalmoplegia (generally 1st paralytic sign to be observed) • Paralysis of palate, pharynx, tongue – difficult swallowing • Increased salivation – drooling. • Neck weakness – unable to support head • Respiratory muscle paralysis – hypoventilation – hypoxia/hypercapnia • Vital centres of brainstem – hypotension and shock
- 12. Prognosis- Cobra • Generally conscious and helpless till end till paralysis kills him • Death – 4 to 12 hrs (may occur within 1 hour or delayed for 72 hours) • Those surviving >24hrs – may have mild hemolysis and bleeding • If Death doesn’t occur, Paralysis quickly recedes - Recovery
- 13. Clinical features - Krait • Symptoms of Cobra + Severe abdominal pains and cramps.
- 14. Clinical features – Sea snakes • Bite: Painless, May be multiple • First: Headache, sweating, vomiting, thirst, heaviness of tongue • ½ to 4 hrs: Painful stiffness of muscles, Trismus • Followed by Generalized flaccid paralysis • 3 – 8hrs: Rhabdomyolysis Myoglobinuria Renal shutdown • Hyperkalaemia due to release of K+ from damaged cells Cardiac arrest
- 15. Clinical features – Viperine bites • Local effects: • Marked within few minutes of bite • Severe pain, Increasing redness, Oedema, Bullae formation • Necrotizing inflammation – may cause severe creeping gangrene
- 16. Clinical features – Viperine bites Systemic effects: • Acute Circulatory Shock: (May manifest before clinically apparent) • Haemolysis, Pallor, Tachycardia • Extravasation of fluid in affected limb, Sweating, Hypotension • Generalised increase in capillary permeability Restlessness, Oliguria • Haemorrhage
- 17. Clinical features – Viperine bites • Severe Intravascular Haemolysis: • Fall in Hb% • Icterus • Haemoglobinaemia • Haemoglobinuria • Acute tubular necrosis Renal failure • Disturbed Clotting Mechanism with haemorrhage: • Epistaxis, Haematuria, Haemetemesis… • Bleeding from 1 or more sites • Internal bleeding / DIC • Generally in few hrs but may be late than 24 hrs also
- 18. Clinical features – Viperine bites • Fever: • 100oF – 104oF • Leucocytosis (20K – 40K/mm3) • Vomitting/Seizure • Acute Renal Failure: due to • Acute Circulatory Shock • DIC • Acute Intravascular Hemolysis • Acute Tubular Necrosis • Combination Death due to Viperine bites is generally in 12 to 24 hrs
- 19. Management • Avoid tourniquet – • harm>good(30 mins) – Gangrene, Bleeding, Compartment ischaemia, agg local sympts. • Crepe bandaging for immobilization of affected limb (Cobra & Krait only) • Incision over wound to suck poison – wrong decision – secondary infection • Ice packs over wound – no value
- 20. Management • Transport: • Avoid aspiration • Oxygen for Cyanosis • Adrenaline 0.5 ml s/c – autonomic disturbances or hypotension • Prepared for cardiopulmonary resuscitation.
- 21. Management • Immediate Priorities on Admission: • Cardiorespiratory and other organ supports • Neutralization of Poison with Antivenin • A Large Peripheral Venous line – later secure a central venous line • 20 mins clotting time test
- 22. Management • Investigations: • CBC, PCV, BT, CT, Coagulation profile • U, C, Sr. Electrolytes • Reticulocyte count, • Tests for hemoglobinaemia/hemoglobinuria • Urine examination • Continuous monitoring: • I/O • CVP • ECG
- 23. Management • Neutralizing the Poison • Using Antivenin • Given as soon as possible • Systemic features (too late) • But efficacy proved even after 24 hrs of bite • Prepared by hyperimmunizing horses against venoms of Cobra, Common Krait, Saw scaled viper and Russell’s viper. • Each ml concentrated serum neutralizes: • 0.6 mg dried venom of Cobra • 0.6 mg dried venom of Russell’s viper • 0.45 mg dried venom of Com. Krait • 0.45 mg dried venom of SS viper
- 24. Management • Using Antivenin: • Reconstitute using distilled water as it is lyophilized. • Sensitivity test Not sensitive inject 5 ml around wound (never in finger or toe) • s/c 0.5 ml of 1:1000 adrenaline & an antihistamine 100 ml of antivenin in 300-500 ml NS over 1-2 hrs (IV preferred) Dose repeated twice or more freq in serious life threatening situations.
- 25. Management • Using Antivenin Contd… • Sensitive patients Under cover of adrenaline, antihistamine, Corticosteroids 0.05ml s/c Increasing dose till 2ml IM Increase dose to 10 ml to 40 ml IM progressively 10 to 20 ml in 500 ml NS over 2 hrs with watch for reactions No reaction
- 26. Management • Using Antivenin Contd… • Small children – • difficult vein – IM allowed • 60 to 100 ml with Hyalace to help absorption (IM) • Or Same dose of adults as infusion over 2 hrs (IV) • Preference: IV>IM
- 27. Management • Effect of Antivenin • Prompt reversal of systemic features • Spontaneous bleeding of viperine bite stops within 1 hr • Coagulation profile reverts within 6-12 hrs. • Systemic envenomation may recur after initial good response • Due to absorption of venom from wound even after bloodstream gets cleared of venom • Repeat dose of antivenin with observation
- 28. Management Adverse reaction of ASV • Seen in 20 % patient Early anaphylactic reaction- • Seen with in 10 min to 3 hrs • Urticaria, diarrhoea, tachycardia, fever, hypotension, etc. Late Serum Sickness • 1-12 days • Fever,nausea,vomiting,diarhoea,arthe ritis,nephrits,myoglobinuria.etc.
- 29. Management Treatment Of Early ASV reaction: • Adrenaline -1:1000 i.m. 0.5 mg in adult 0.01 mg/kg in children can be repeated every 5 min if necessary H1 antihistaminic- i.v. 1 mg of CPM I.V. Hydrocortisone
- 30. Management Treatment Of Late ASV reaction: • 5 days course of oral anti histaminic CPM 2mg/6hour-adult 0.25 mg/kg/day in divided dose Patient who fail to response with in 24 hr Predinisolone- 5mg/6h in adult 0.7 mg/kg/day in divided dose in children
- 31. Management • Cardiorespiratory Support: • Immediate ET Intubation – Cobra/Krait (curare-like paralysis) • Neostigmine 2.5 - 5 mg may be of a little help. Never depend. Not proved helpful. • Inotropes support • Ventilator support • Sufficient Volume load with LV filling pressure 15 mmHg (using Swan-Ganz Cath)
- 32. Management • Other System Supports: • Acute Haemolysis – PRBC transfusions • Severe haemorrhage due to Clotting factors deficiency – FFP 8-10 units or more • Fibrinolysis – Epsilon aminocaproic acid 0.1 gm/kg slow IV infusion • Low fibrinogen level – Cryoprecipitate 8-10 units or more • Renal: Correcting fluid and electrolyte balance/avoid nephrotoxic drugs/temp HD • Metabolic Acidosis: improve tissue perfusion by >O2 transport/NaHCO3 to keep pH>7.30
- 33. Management • Care of Wound: • Wash with KMnO4 • Dress with Antibiotic oint. • Tetenus toxoid • Antibiotics as indicated or as per c/s results • Analgesic for pain management – Avoid morphine in Cobra and Krait bites. • Cryotheraphy – not effective – harm>good
- 34. Management • Use of Corticosteroids: • Good results • Advisable to give Hydrocortisone hemisuccinate 300 mg IV stat 300 mg slow infusion over 24 hrs 100 mg every 8 hrs for 2-3 days
- 35. Bibliography • Principles of Critical Care – 2nd edition – Farokh Erach Udwadia • www.ncbi.nlm.nih.gov • Google Search – articles and ppts