The document summarizes key information about snake bites, including that they are a major public health problem causing morbidity and mortality in tropical regions. It describes the three main venomous snake families and the types of toxins they contain. The clinical effects of envenomation are explained for each family, including local tissue damage as well as systemic effects like bleeding, shock, and paralysis. Diagnosis and management of snake bites are also outlined, emphasizing rapid treatment with antivenom as the only specific therapy.

1. Snake bite By Dr. Osman Sadig Bukhari

2. Snake bite is : - A major public health problem & an important cause of morbidity and mortality , specially in the tropics - In 2002/2003/2004 628 cases were admitted in Gedarif Teaching Hospital with 8 deaths.

3. Out of 2700 species 500 belong to three important families :- 1- Viperidae : vasculotoxic with long erectile fangs. 2- Elapidae : Neurotoxic with short fangs. 3- Hydrophidae : Myotoxic with short fangs & flat tail.

4. A common Sea snake of S E Asia

5. Thai spitting Cobra

6. Short front fangs

7. Very long fangs

8. Envenomation Envenomation is either through: 1- Bites 2- Spray of venom into the eyes of the aggressor. Some bites may be defensive without injecting the venom .

9. Venom composition 20 or more components & 90 % of the dry weight is protein . 1- Polypeptide enzymes : a- Proteases : activate blood clotting casc b- Phospholipases : cytolytic & produces presynaptic neurotoxin that prevent release of Ach at the N/ muscular junction .

10. c- Hydrolases : increase vascular permeability and causes edema, blistering, bruises and necrosis. d- Hyaluronidases: promote spread of venom through the tissues. e- Amino acid oxidases: digestive. 2- Non- enzymatic polypeptide toxins (Elapidae & Hydrophidae) contains postsynaptic neurotoxins that bind to Ach receptors at the motor end plates and cause paralysis. 3- Histamines & 5HT contribute to local pain

11. and permeability at the bite site. 4- Non- toxic proteins . 5- Non protein ingredients include CHO, lipids, amino acids & amines . In conclusion : 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 .

12. Pathophysiology 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. 2- Local swelling is due to increased vascular permeability leading to swelling, blisters and bruising. Systemic envenomation may cause serous effusions and pulm edema .

13. Cellulitis of hand

14. Blisters on za feet

15. Massive swelling & bulla formation

16. Pulmonary oedema

17. 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

18. Extensive loss of skin & muscles

19. 4- Hypotension & shock may occur within minutes due to:- - Vasodilating amines - leak of plasma & blood into bitten limb & elsewhere - Massive GIT bleeding - Direct effects of toxins on the myocardium

20. 5- Bleeding & clotting disturb are due to: - DIC - Thrombocytopenia - Haemorrhagin which damage vascular endothelium. The combination of defibrination , thrombocytopenia and vessel wall damage result in massive bleeding specially in Viper bites

21. Haematuria

22. 6- Intravascular haemolysis : Rare, but massive intravascular haemolysis can lead to acute renal failure

23. 7- Renal failure is rare complication of severe envenomation due to:- - ATN from prolonged hypotension - DIC - Direct tubular toxicity - HBuria - Myoglobinuria - Hyperkalaemia ..

24. 8- Neurotoxicity : Neurotoxic polypeptie & phospholipases cause paralysis by blocking N/ muscular transmission . Death may follow: - Respiratory muscle paralysis +++ - Bulbar palsy causing resp obstruction or paralysis.

25. 9 - Rabdomyolysis with release of myoglobin, muscle enzymes & K. Death may follow :- - respiratory paralysis - bulbar palsy, - acute hyperkalaemia - later renal failure . 10- Venous ophthalmia : Spray from spitting cobras leads to corneal erosions, conjunctivitis, anterior uveitis & secondary infections

26. Clinical features :- 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 . 3- Disease may result from fear, anxiety, local TR or from Envenomation 4- Nearly 50% of people bitten by snakes suffer few or no toxic effects . On the other hand mortality without effective TR is high ( up to 15%)

27. 1- Viperidae produce more local effects than others . - Early syncope, nausea, vomiting, colics, diarrhea, angioedema & wheeze may occur. - Hypotension & shock may occur early. - 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

28. - 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 . - 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.

29. - 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

30. - Tissue infarction & gangrene may follow vascular thrombosis. - Anemia, jaundice & black urine may result from haemolysis . - Renal failure may complicate .

31. 2- Elapidae - Local tissue swelling is a feature of Asian Cobras & African spitting Cobras. The bite is painful and may be followed by necrosis . - Vomiting, hypotension & polymorph leucocytosis suggest systemic envenomation - More specific features include ptosis and ophthalmoplegia. B ulbar palsy and resp paralysis and failure in severe cases - ECG changes & raised cardiac enzymes .

32. Ptosis & ophthalmoplegia

33. 3- Hydrophidae - Early signs similar to Elapidae - Specific signs include myalgia and myoglobinuria 3-5 hrs later. - Limb paralysis may be followed by resp paralysis & failure which may be delayed for up to 60 hrs. - Hyperkalaemia may cause cardiac arrest - Acute renal failure may follow.

34. Course & prognosis:- - Local swelling is usually evident within 2 hours, max in za 2 nd or 3 rd day & may take Ws or Ms to resolve. - Pats may be totally defibrinated in 1-2 hours after bite by viperidae. - Deaths most unusual before ½ hour . - Untreated mortality is hard to assess as hospital admissions include the mainly severe cases. It can be reduced by TR.

35. - Interval betw bite & death may be as early as few min. or as long as 6 Ws. - Prognosis is worse in infants & elderly .

36. Laboratory - Neutrophil leucocytosis - Decreased haematocrit - Thrombocytopenia - Increased FDP - Prolonged PT - Incoagulable blood - Increased CPK; AST & ALT - Urine ex, BUN & E.

37. Management of snake bite First aids 1 - Reassure the victim 2 - Immobilize the bitten limb using splint and crepe bandage. 3 - Take za victim quickly to za nearest health facility . 4 - Avoid harmful time wasting TR: (cauterization, incision & excision, vacuum or mouth suction, local chemicals, cryotherapy & arterial tourniquet )

38. 5- Take snake to za hospital if killed . TR of early symptoms 1- Paracetamol . Not aspirin. 2 - IV chlorpromazine for vomiting 3- IV chlorpheneramine or S/C adr., IV fluids for anaphylaxis and shock 4- Clear the air way, nurse pat on his side, insert airway & elevate the jaw, artificial ventilation & oxygen for resp distress

39. C- TR at health facility 1- Snake bite is a med emergency 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)

40. 3- Observe closely pat for 24 hrs even if no signs. Snake bite is unpredictable 4- Anti-venom administration :- It is za only specific therapy & should be given in excess of za venom injected as soon as it is indicated Whether to give or not ? May produce severe reactions, expensive & in short supply

41. Indications for administration include a- Systemic envenomation : 1- Haemostatic abnormality:- spontaneous systemic bleeding, incoagulable blood, prolonged PT, FDP and thrombocytop 2- Acute renal failure:- oliguria/ anuria- biochem 3- Cardiovascular abn.( hypot, shock, HF abn. ECG & pulm edema) 4 – Neurotoxicity (Ptosis, ophthalmoplegia, paralysis)

42. 5- Generalized rhabdomyolysis and intravascular haemolysis b- Local envenomation : 1- Signs of local envenomation + (neutrophil leucocytosis, high CPK, AST and ALT, haemococ and hypoxaemia) 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. C- impaired consciousness

43. D- Administration of anti-venom - Preliminary testing is not necessary and delays TR. - Multival anti- venom is given as soon as it is indicated & it is never late e.g for 2/52 or more in persisting 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 NS or DNS over ½ hr. Rarely slow IV injection at 2 ml/min.

44. - 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. - The response to anti-venom is quick if sufficient dose is given

45. 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 - Anaphylactoid - Pyrogenic - Serum sickness F- Anti-cholinesterase for neurotoxicity G- Supportive TR - Artificial ventilation for neurotoxic bites. Anticholinesterases should always be tried - Plasma expander & dopamine for shock.

46. - conservative management or dialysis for renal failure - Antibiotic +/- ATS for local infection - Incision for intercompartmental synr - 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 ? H- Local tissue debridement & skin graft .

47. Prevention of snake bite (precautions) - Snakes should never unnecessarily be disturbed, handled or attacked even if they are thought to be harmless or dead - Avoid venomous sp. as pets - Protective clothings, boots, socks & long trousers should be worn by persons at risk. - Carry light at night sp. for farmers, harvesters, fire wood collectors & for those removing debris likely to conceal snakes - Immunization with venom toxoid to those at risk.

48. Snake bite is : - A major public health problem and an important cause of morbidity and mortality , specially in the tropics - It is important occupational disease - Goverments, academic institutions, pharmaceut agricultural bodies should encourage & sponsor clinical studies in all aspects of snake bite. - Education & training on snake bite should be included in the curriculum of medical schools. - Community education on snake bites ,first aid methods and preventive measures is recommended.