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- 1. SNAKE ENVENOMATION Dr Sujith Chadala Consultant Physician Diabetologist MD General Medicine, IDCCM,PGPC,CCEBDM,FIDM
- 2. EPIDEMIOLOGY • Annual snake bite cases 50,00,000 • Snake envenomations 4,00,000 each year • Snake bite deaths 1,00,000 to 2,00,000
- 3. India • India has the highest snake bite mortality in the world • 83,000/ yr with 11,000 deaths (WHO estimation ) • Majority of bites being lower extremities , children, and males.
- 4. HYDROPHIDAE SEA SNAKES MYOTOXIC VIPERIDAE RUSSELL’S VIPER SAW SCALED VIPER PIT VIPER HEMOTOXIC ELAPIDAE COBRA KRAITS NEUROTOXIC
- 5. SNAKE VENOM • Complex mixture of enzymatic & non- enzymatic polypeptides • Acidic , Sp gravity 1.030-1.070,Water soluble • Lethal dose Russell’s viper 0.15 gm Cobra 0.12 gm Krait 0.06gm
- 6. • Hemorrhagins – Vascular leakage reulting fluid shifts , spontaneous local & systemic bleeding • Proteolytic enzymes – Local tissue necrosis
- 7. • Hyaluronidases – promote spread through connective tissue • Neurotoxins – Act at NMJ to block transmission & cause muscle paralysis
- 8. GENERALISED • Nausea • Vomiting • Malaise • Abdominal pain • Weakness • Drowsiness
- 9. HEMATOLOGICAL • Bleeding from recent wounds ( fang marks , venepunctures ) • Spontaneous systemic bleeding – from gums • Epistaxis , hemoptysis , hemetemesis , malena , hematuria , vaginal bleeding • Skin ( petechia , purpura , ecchymoses )
- 10. LOCAL SYMPTOMS & SIGNS • Fang marks , local bleeding , bruising , blistering , swelling , redness , abscess formation • Necrosis • Local pain , Lymphangitis , Lymph node enlargement.
- 11. NEUROLOGICAL • Drowsiness • Ptosis • Ophthalmoplegia • Facial muscles paralysis
- 12. • Difficulty in opening mouth and swallowing secretions • Aphonia • Respiratory & generalised flaccid paralysis
- 13. CARDIOVASCULAR • Collapse • Hypotension • Cardiac arrhythmias • Pulmonary edema • Cardiac arrest
- 14. RENAL • Hematuria • Hemoglobinuria • Myoglobinuria • Oliguria / Anuria • Uremia
- 15. Snakes Local Tissue damage Coagulation Renal Neurotoxicity Russell’s V + + + + Other V + + + _ Saw scale V + + _ _ Cobra + _ _ + Krait _ _ _ +
- 16. FIELD MANAGEMENT CARRY NO R.I.G.H.T • CARRY – Don’t allow victim to walk even short distance , carry him in any form , specially leg bite • NO – Torniquet Electrotherapy Cutting Pressure Immobilisation
- 17. • R – Reassure patient. 70 % are non venomous ; 50% venomous bites actually envenomate patient • I – Immobilisation Use bandages / cloth to hold splints Don’t block blood supply / apply pressure / tight ligatures
- 18. • GH – Get to Hospital immediately • T- Tell Doctor of any systemic symptoms that manifest on the way to hospital
- 19. HOSPITAL MANAGEMNT • Airway , Breathing , Circulation • Bites on face / neck require early intubation to prevent loss of airway patency caused by rapid soft tissue swelling • Admit victim to ICU even if there is no envenomation evidence , monitor for 24 hrs
- 20. • Bandages / wraps removed once IV access obtained • Release of ligatures may result in hypotension when stagnant acidotic blood with venom released systemically • Venepunture attempts & noncompressible sites ( subclavian ) avoided.
- 21. • Be prepared to handle sudden respiratory distress / hypotension • If torniquet has occluded distal pulse, then blood pressure cuff can be applied to reduce pressure slowly
- 22. • Fluid resuscitation : 20 – 30 ml/g IV isotonic saline & trail of 5% albumin 10-20 ml/kg IV if response is inadequate • Vasopressors if venom induced shock persists even after aggressive volume resuscitation and ASV administration.
- 23. • Platelet count • Peripheral smear • PT / aPTT / Fibrinogen / D Dimer • RFT • ECG • ABG • Urine for proteinuria / hemoglobinuria / myoglobinuria
- 24. 20 WBCT • Most reliable bed side test of coagulation • Few ml of fresh venous blood should be placed in fresh clean & dry tube , left undisturbed for 20 minutes. • Gently tilted to detect whether blood is in coagulable.
- 25. • Should be carried every 30 min from admission and then hourly. • If blood is incoagable , 6 th hourly cycle to be opted to test for requirement for repeat doses of ASV • Limb circumference measured every 15 min until local effects have been stabilised
- 26. ASV • Main stay of treatment • Immunoglobulins purified from plasma of horse / mule / donkey / sheep that has been immunised with venoms of one or more species of snake.
- 27. ASV FORMS • ASV available in Liquid & Lyoplilised forms • Liquid ASV requires reliable cold chain & 2 yr shelf life • Lyophilised ASV has 5 yr shelf life & requires only to be kept cool
- 29. ASV TYPES • Monovalent : directed against particular snake species • Polyvalent : covering several species in a geographic region
- 30. • If ASV doesn’t contain antibodies to that snake venom components , provides no benefit • ASV bind & deactivate circulating venom components • Established renal failure & paralysis improve with supportive therapies only
- 31. ASV INDICATIONS • Hemotoxicity Clinically significant bleeding / abnormal coagulation studies • Local toxicity Progressive soft tissue swelling Severe , local swelling involving > half of the bitten limb , extensive blistering / bruising
- 32. • Neurotoxicity Any evidence of CN abnormalities & progressing to descending paralysis including diaphragm • Hemodynamic / Respiratory instability Hypotension , respiratory distress
- 33. ASV TEST DOSE • No ASV test dose must be administered • Test doses have no predictive in detecting anaphylactic / late serum reactions.
- 34. TIMING OF ASV • Best effects of ASV observed within 4 hrs of bite • Effective in symptomatic pts even 48 hrs after bite • Efficacious even 6-7 days after bite in Vipers.
- 35. INITIAL ASV DOSE • Recommended dose is amount of ASV required to neutralize average venom yield when captive snakes are milked of their venom. • In practice , choice of initial dose of ASV is usually empirical. • Each vial is 10 ml of reconstituted ASV.
- 36. Average yield of venom per bite R viper – 63 mg , Saw scaled – 13 mg Cobra – 60 mg , Krait – 20 mg 1ml ASV neutralises 0.6 mg Russel & Cobra , 0.45 mg Saw scaled & Krait
- 38. • Dilute reconstitued vials in 250 ml of saline & start at 20-50 ml/hr for first 10 min • Increase rate to 250 ml/hr ( if no allergic reactions ) • Some evidence supporting routine pretreatment with low dose Epinephrine ( 0.25 mg of 1:1000 SC ) to prevent anaphylactic reactions after ASV
- 39. ASV ROUTE Two methods of administration are recommended 1. IV push injection : Reconstituted freeze dried ASV is given by slow IV inj ( not >2ml/min). 2. IV infusion : Diluted in appx. 5-10 ml isotonic fluid /kg & infused at constant rate over 1 hr.
- 40. RESPONSE TO ASV A. Spontaneous systemic bleeding usually stops in 15 – 30 min. B. Blood coagulability ( 20min WBCT ) usually restored in 3-9 hrs. C. Active hemolysis may cease within few hrs and urine returns to its normal color
- 41. RESPONSE TO ASV D. BP may increase within first 30-60 min and arrhthymias may resolve. E. Neurotoxicity may begin to improve as early as 30 min after ASV but usually takes several hours. F. General symptoms Nausea, headache & generalized aches may disappear quickly.
- 42. ASV REPEAT DOSES • Criteria for giving more ASV 1.Persistence / recurrence of incoagulability after 6 hrs ( 20 WBCT ) / of bleeding after 1-2 hrs 2.Deteriorating neurotoxic / cardiovascular signs after 1-2 hrs of ASV.
- 43. • Viperid bites ASV administration continued till victim shows definite improvement ( reduced pain , stabilised vital signs , restored coagulation ) • Neurotoxicity difficult to reverse with ASV once established & intubated , further doses unlikely beneficial
- 44. HEMOTOXIC ENVENOMATION • Once initial dose is administered ,no further ASV for 6 hrs. • Dose should be repeated if blood remains incoagulable ( 20 WBCT ) after 6hrs (time taken for liver to restore coagulabe levels of Fibrinogen & other clotting factors is 3-9 hrs )
- 45. NEUROTOXIC ENVENOMATION • ASV alone cant be relied upon to save life of pt with bulbar palsy and respiratory paralysis. • Pt should be electively intubated & mechanically ventilated if there is loss of gag reflex , respiratory distress , pooling of secretions , failure of cough reflex
- 46. NEOSTIGMINE TEST • Trail of NEOSTIGMINE should be performed in every neurotoxic envenomation. • Neostigmine 0.02mg/kg IV given & observe for 30 min • If objective improvement , Neostigmine 0.5mg/IV every hr ( as needed )
- 47. • Not a substitute for ASV administration • Promote neurologic improvement with post synaptic neurotoxins
- 48. ASV REACTIONS • 20 % pts usually develop ASV reactions • Types A. Early : within 10-180 min B. Late : develop within 1- 12 days ( mean 7 )
- 49. Early Tachycardia Hypotension Laryngeal Edema Bronchospasm Rigors , vomiting Late Fever , chills Myalgias Arthralgias
- 50. ASV REACTIONS MANAGEMANT • ASV should be stopped. • Adrenaline 0.5 mg (1 in 1000) IM , can be given 3 times if needed. • IV hydrocortisone ( Adults 100mg , children 2mg/kg ) prevent recurrent anaphylaxis
- 51. • Fluids , Inotropes along with Adrenaline ( in circulator collapse ). • Once recovered , ASV may be further diluted in larger volumes & restarted slowly for 10-15 min • Then normal drip should be resumed.
- 52. • Late reactions managed with oral prednisolone 1-2mg/kg daily untill all symptoms have resolved , with subsequent taper over 1-2 wks • Antihistamines & analgesics provide additional relief of symptoms
- 53. ASV IN CHILDREN & PREGNANT • Children & Pregnant women should be given exactly same dose of ASV as adults. • Pregnant women should be assessed of any impact on fetus
- 54. SUPPORTIVE MANAGENT • Prophylactic antibiotics are unnecessary unless prehospital care included incision / mouth suction • Tetanus immunisation • Pain managed with paracetamol / opioids as needed.
- 55. LOCAL TISSUE CARE • Intact serum filled vesicles / hemorrhagic blebs left undisturbed • Debridement is conservative ( because muscle may recover to significcant degree after ASV • Aseptic debridement of clearly necrotic tissue once coagulopathy is fully reversed
- 56. BLOOD PRODUCTS • Rarely needed • If required should be given only after ASV administration ( to avoid fueling ongoing consumptive coaguopathy )
- 57. HEMODIALYSIS • ATN usually d/t persistent hypotension recovers by few weeks with help of occasional dialysis. • Cortical necrosis requires MHD on long term basis. • Hypermetabolic Hyperkalemia in envenomation respond to Calcium gluconate , Glucose & Insulin ineffectively warranting HD
- 58. COMPARTMENT SYNDROME • Severe pain , increasing swelling , altered sensation , cyanosis , pulselesness. • Managed by • Extremity elevation , • IV Mannitol to reduce muscle edema , • Compartmental decompression to preserve neurologic function.
- 59. DISCHARGE • Warn pt of possible recurrent coagulopathy ( first 2-3 wks ) • Symptoms/ signs of late ASV reactions & wound infection • Avoid elective Sx /activeties of high risk of trauma • Outpatient analgesics , wound management & physical therapy should be provided.