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Snake Bite


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Snake Bite

  1. 1. Snake bite By Dr. Osman Sadig Bukhari
  2. 2. <ul><li>Snake bite is : </li></ul><ul><li>- A major public health problem & an important cause of morbidity and mortality , specially in the tropics </li></ul><ul><li>- In 2002/2003/2004 628 cases were admitted in Gedarif Teaching Hospital with </li></ul><ul><li>8 deaths. </li></ul>
  3. 3. <ul><li>Out of 2700 species 500 belong to three important families :- </li></ul><ul><li>1- Viperidae : vasculotoxic with long erectile fangs. </li></ul><ul><li>2- Elapidae : Neurotoxic with short fangs. </li></ul><ul><li>3- Hydrophidae : Myotoxic with short fangs & flat tail. </li></ul>
  4. 4. A common Sea snake of S E Asia
  5. 5. Thai spitting Cobra
  6. 6. Short front fangs
  7. 7. Very long fangs
  8. 8. <ul><li>Envenomation </li></ul><ul><li>Envenomation is either through: 1- Bites </li></ul><ul><li>2- Spray of venom into the eyes of the aggressor. </li></ul><ul><li>Some bites may be defensive without injecting the venom . </li></ul>
  9. 9. <ul><li>Venom composition </li></ul><ul><li>20 or more components & 90 % of the dry weight is protein . </li></ul><ul><li>1- Polypeptide enzymes : </li></ul><ul><li>a- Proteases : activate blood clotting casc </li></ul><ul><li>b- Phospholipases : cytolytic & produces presynaptic neurotoxin that prevent release of Ach at the N/ muscular junction . </li></ul>
  10. 10. <ul><li>c- Hydrolases : increase vascular permeability and causes edema, blistering, bruises and necrosis. </li></ul><ul><li>d- Hyaluronidases: promote spread of venom through the tissues. </li></ul><ul><li>e- Amino acid oxidases: digestive. </li></ul><ul><li>2- Non- enzymatic polypeptide toxins (Elapidae & Hydrophidae) contains postsynaptic neurotoxins that bind to Ach receptors at the motor end plates and cause paralysis. </li></ul><ul><li>3- Histamines & 5HT contribute to local pain </li></ul>
  11. 11. <ul><li>and permeability at the bite site. </li></ul><ul><li>4- Non- toxic proteins . 5- Non protein ingredients include CHO, lipids, amino acids & amines . </li></ul><ul><li>In conclusion : </li></ul><ul><li>Snake venoms contain a variety of toxins and the variation of its composition from sp. to sp. explains the clinical diversity of snake bites from family to family . </li></ul>
  12. 12. <ul><li>Pathophysiology </li></ul><ul><li>1- Absorption of venom from bite site depends on the tissue binding affinity of the venom components, mol. size and the local effects of za venom on tissue permeability & blood supply. </li></ul><ul><li>2- Local swelling is due to increased vascular permeability leading to swelling, blisters and bruising. Systemic envenomation may cause serous effusions and pulm edema . </li></ul>
  13. 13. Cellulitis of hand
  14. 14. Blisters on za feet
  15. 15. Massive swelling & bulla formation
  16. 16. Pulmonary oedema
  17. 17. <ul><li>3- Local tissue necrosis results from :- a- Direct action of myotoxic and cytolytic factors b- Ischemia due to: - thrombosis - Compression by tight tourniquet - Compression of arteries by swollen muscles within a tight facial compartment </li></ul>
  18. 18. Extensive loss of skin & muscles
  19. 19. <ul><li>4- Hypotension & shock may occur within minutes due to:- </li></ul><ul><li>- Vasodilating amines </li></ul><ul><li>- leak of plasma & blood into bitten </li></ul><ul><li>limb & elsewhere </li></ul><ul><li>- Massive GIT bleeding </li></ul><ul><li>- Direct effects of toxins on the </li></ul><ul><li>myocardium </li></ul>
  20. 20. <ul><li>5- Bleeding & clotting disturb are due to: - DIC - Thrombocytopenia - Haemorrhagin which damage vascular endothelium. The combination of defibrination , thrombocytopenia and vessel wall </li></ul><ul><li>damage result in massive bleeding </li></ul><ul><li>specially in Viper bites </li></ul>
  21. 21. Haematuria
  22. 22. <ul><li>6- Intravascular haemolysis : </li></ul><ul><li>Rare, but massive intravascular haemolysis can lead to acute renal failure </li></ul>
  23. 23. <ul><li>7- Renal failure is rare complication of severe envenomation due to:- - ATN from prolonged hypotension - DIC - Direct tubular toxicity - HBuria - Myoglobinuria - Hyperkalaemia .. </li></ul>
  24. 24. <ul><li>8- Neurotoxicity : </li></ul><ul><li>Neurotoxic polypeptie & phospholipases cause paralysis by blocking N/ muscular transmission . Death may follow: </li></ul><ul><li>- Respiratory muscle paralysis +++ </li></ul><ul><li>- Bulbar palsy causing resp obstruction or paralysis. </li></ul>
  25. 25. <ul><li>9 - Rabdomyolysis with release of myoglobin, muscle enzymes & K. Death may follow :- - respiratory paralysis - bulbar palsy, - acute hyperkalaemia - later renal failure . </li></ul><ul><li>10- Venous ophthalmia : Spray from spitting cobras leads to corneal erosions, conjunctivitis, anterior uveitis & secondary infections </li></ul>
  26. 26. <ul><li>Clinical features :- </li></ul><ul><li>1- Most bites are on the FEET 2- Envenomation is not inevitable even in severe bites. Snake bites are unpredictable so keep the pat. in for 24 hrs . </li></ul><ul><li>3- Disease may result from fear, anxiety, local TR or from Envenomation </li></ul><ul><li>4- Nearly 50% of people bitten by snakes </li></ul><ul><li>suffer few or no toxic effects . On the other </li></ul><ul><li>hand mortality without effective TR is high ( up to 15%) </li></ul>
  27. 27. <ul><li>1- Viperidae </li></ul><ul><li>produce more local effects than others . - Early syncope, nausea, vomiting, colics, diarrhea, angioedema & wheeze may occur. - Hypotension & shock may occur early. </li></ul><ul><li>- Local painful swelling and may become massive & spread up za limb in 2-3 days with tender L. nodes. Absence of swelling 2 hrs after bite usually mean no envenomation </li></ul>
  28. 28. <ul><li>- Blistering & bleeding at puncture site are early symptoms. Spreading bruising and blistering suggest a large dose of venom and may proceed to necrosis with secondary infections . </li></ul><ul><li>- Very severe pain & tense swelling may indicate intercompartmental pressure. - Sudden severe pain, absence major of arterial pulses and demarcated cold limb indicate thrombosis of artery. </li></ul>
  29. 29. <ul><li>- Spontaneous systemic bleeding : Gum bleeding, ecchymosis, conjunctival haemorrhage, Hria, GIT bleeding, menorrhg , intra or retroperitoneal bleeding SAH and intracerebral bleeding. Haemoptysis is rare. Incoagulable blood from defibrination may occur. Hage into vital organs may be fatal - Necrosis of za skin, S/C tissue and muscles. 2ry Infection with offensive smell may follow </li></ul>
  30. 30. <ul><li>- Tissue infarction & gangrene may follow vascular thrombosis. </li></ul><ul><li>- Anemia, jaundice & black urine may result from haemolysis . </li></ul><ul><li>- Renal failure may complicate . </li></ul>
  31. 31. <ul><li>2- Elapidae </li></ul><ul><li>- Local tissue swelling is a feature of Asian Cobras & African spitting Cobras. The bite is painful and may be followed by necrosis . </li></ul><ul><li>- Vomiting, hypotension & polymorph leucocytosis suggest systemic envenomation </li></ul><ul><li>- More specific features include ptosis and ophthalmoplegia. B ulbar palsy and resp paralysis and failure in severe cases </li></ul><ul><li>- ECG changes & raised cardiac enzymes . </li></ul>
  32. 32. Ptosis & ophthalmoplegia
  33. 33. <ul><li>3- Hydrophidae </li></ul><ul><li>- Early signs similar to Elapidae </li></ul><ul><li>- Specific signs include myalgia and myoglobinuria 3-5 hrs later. </li></ul><ul><li>- Limb paralysis may be followed by resp paralysis & failure which may be delayed for up to 60 hrs. </li></ul><ul><li>- Hyperkalaemia may cause cardiac arrest </li></ul><ul><li>- Acute renal failure may follow. </li></ul>
  34. 34. <ul><li>Course & prognosis:- </li></ul><ul><li>- Local swelling is usually evident within 2 hours, max in za 2 nd or 3 rd day & may take Ws or Ms to resolve. </li></ul><ul><li>- Pats may be totally defibrinated in 1-2 hours after bite by viperidae. </li></ul><ul><li>- Deaths most unusual before ½ hour . </li></ul><ul><li>- Untreated mortality is hard to assess </li></ul><ul><li>as hospital admissions include the mainly severe cases. It can be reduced by TR. </li></ul>
  35. 35. <ul><li>- Interval betw bite & death may be as early as few min. or as long as 6 Ws. - Prognosis is worse in infants & elderly . </li></ul>
  36. 36. <ul><li>Laboratory </li></ul><ul><li>- Neutrophil leucocytosis </li></ul><ul><li>- Decreased haematocrit </li></ul><ul><li>- Thrombocytopenia </li></ul><ul><li>- Increased FDP </li></ul><ul><li>- Prolonged PT </li></ul><ul><li>- Incoagulable blood </li></ul><ul><li>- Increased CPK; AST & ALT </li></ul><ul><li>- Urine ex, BUN & E. </li></ul>
  37. 37. <ul><li>Management of snake bite First aids </li></ul><ul><li>1 - Reassure the victim </li></ul><ul><li>2 - Immobilize the bitten limb using splint and crepe bandage. </li></ul><ul><li>3 - Take za victim quickly to za nearest health facility . </li></ul><ul><li>4 - Avoid harmful time wasting TR: (cauterization, incision & excision, vacuum or mouth suction, local chemicals, cryotherapy & arterial tourniquet ) </li></ul>
  38. 38. <ul><li>5- Take snake to za hospital if killed . </li></ul><ul><li>TR of early symptoms </li></ul><ul><li>1- Paracetamol . Not aspirin. </li></ul><ul><li>2 - IV chlorpromazine for vomiting </li></ul><ul><li>3- IV chlorpheneramine or S/C adr., IV fluids for anaphylaxis and shock </li></ul><ul><li>4- Clear the air way, nurse pat on his side, insert airway & elevate the jaw, artificial ventilation & oxygen for resp distress </li></ul>
  39. 39. <ul><li>C- TR at health facility </li></ul><ul><li>1- Snake bite is a med emergency </li></ul><ul><li>2- Quick clinical assessment: ( site of bite, duration of bite, snake brought vomiting & fainting, fang marks, any bleeding, local signs, look for blood in gingival sulci & recent wounds, look for signs of shock and TR, signs of neurotoxicity, colour and amount of urine) </li></ul>
  40. 40. <ul><li>3- Observe closely pat for 24 hrs even if no signs. Snake bite is unpredictable 4- Anti-venom administration :- </li></ul><ul><li>It is za only specific therapy & should be given in excess of za venom injected as soon as it is indicated </li></ul><ul><li>Whether to give or not ? May produce severe reactions, expensive & in short supply </li></ul>
  41. 41. <ul><li>Indications for administration include </li></ul><ul><li>a- Systemic envenomation : </li></ul><ul><li>1- Haemostatic abnormality:- spontaneous systemic bleeding, incoagulable blood, prolonged PT, FDP and thrombocytop </li></ul><ul><li>2- Acute renal failure:- oliguria/ anuria- biochem </li></ul><ul><li>3- Cardiovascular abn.( hypot, shock, HF </li></ul><ul><li>abn. ECG & pulm edema) </li></ul><ul><li>4 – Neurotoxicity (Ptosis, ophthalmoplegia, paralysis) </li></ul>
  42. 42. <ul><li>5- Generalized rhabdomyolysis and intravascular haemolysis b- Local envenomation : 1- Signs of local envenomation + (neutrophil leucocytosis, high CPK, AST and ALT, haemococ and hypoxaemia) </li></ul><ul><li>2- Severe local swelling extending more than ½ of za bitten limb or blistering or bruising) at any stage specially in pats showing biochemical abnormalities in 1. </li></ul><ul><li>C- impaired consciousness </li></ul>
  43. 43. <ul><li>D- Administration of anti-venom </li></ul><ul><li>- Preliminary testing is not necessary </li></ul><ul><li>and delays TR. </li></ul><ul><li>- Multival anti- venom is given as soon </li></ul><ul><li>as it is indicated & it is never late e.g </li></ul><ul><li>for 2/52 or more in persisting </li></ul><ul><li>haemostatic abnormalities. Local effects of the venom are probably not reversible if anti- venom is delayed more than 2 hours - Slow IV infusion diluted in 250-500 ml </li></ul><ul><li>NS or DNS over ½ hr. Rarely slow IV </li></ul><ul><li>injection at 2 ml/min. </li></ul>
  44. 44. <ul><li>- No absolute contraindication Dose = amount of antivenom required to neutralize the venom injected. In practice it is empirical. 2-10 amp, but it should be based on studies. Dose can be repeated. 2 nd dose if cardio-resp or neurotoxic symptoms persist for > 30 min or in incoagulable blood > 6 hrs after initial dose. - Same dose for children. </li></ul><ul><li>- The response to anti-venom is quick </li></ul><ul><li>if sufficient dose is given </li></ul>
  45. 45. <ul><li>E- Reaction to anti-venom develop 10-180 min after administration & treated by adr, hydrocortisone & antihistamine. In severe envenomation continue infusion despite reaction with S/C and adr as necessary </li></ul><ul><li>- Anaphylactoid </li></ul><ul><li>- Pyrogenic </li></ul><ul><li>- Serum sickness F- Anti-cholinesterase for neurotoxicity </li></ul><ul><li>G- Supportive TR </li></ul><ul><li>- Artificial ventilation for neurotoxic bites. </li></ul><ul><li>Anticholinesterases should always be tried </li></ul><ul><li>- Plasma expander & dopamine for shock. </li></ul>
  46. 46. <ul><li>- conservative management or dialysis for renal failure </li></ul><ul><li>- Antibiotic +/- ATS for local infection </li></ul><ul><li>- Incision for intercompartmental synr </li></ul><ul><li>- Strict bed rest, fresh blood, fresh frozen plasma or specific clotting factors & vit K for haemostatic abn. Avoid IM & repeated venepuncture. Use IV canulae. Heparin and anti- fibrinolytic agents ? </li></ul><ul><li>H- Local tissue debridement & skin graft . </li></ul>
  47. 47. <ul><li>Prevention of snake bite (precautions) </li></ul><ul><li>- Snakes should never unnecessarily be disturbed, handled or attacked even if they are thought to be harmless or dead </li></ul><ul><li>- Avoid venomous sp. as pets </li></ul><ul><li>- Protective clothings, boots, socks & long trousers should be worn by persons at risk. </li></ul><ul><li>- Carry light at night sp. for farmers, harvesters, fire wood collectors & for those removing debris likely to conceal snakes </li></ul><ul><li>- Immunization with venom toxoid to those at risk. </li></ul>
  48. 48. <ul><li>Snake bite is : </li></ul><ul><li>- A major public health problem and an important cause of morbidity and mortality , specially in the tropics </li></ul><ul><li>- It is important occupational disease </li></ul><ul><li>- Goverments, academic institutions, pharmaceut </li></ul><ul><li>agricultural bodies should encourage & sponsor </li></ul><ul><li>clinical studies in all aspects of snake bite. - Education & training on snake bite should be </li></ul><ul><li>included in the curriculum of medical schools. </li></ul><ul><li>- Community education on snake bites ,first </li></ul><ul><li>aid methods and preventive measures is </li></ul><ul><li>recommended. </li></ul>