Envenomations1
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Envenomations1

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  • 1. Envenomations Prof. Dr. Saad S. Al-Ani MBChB, CABP,IBCLC Senior Pediatric Consultant Khorfakkan hospital
  • 2. Envenomation
    • is the process by which venom is injected into some animal by the bite (or sting) of a venomous animal
  • 3. Envenomation
    • Many kinds of animals , including mammals (e.g., the Northern Short-tailed Shrew , Blarina brevicauda ), reptiles (e.g., the King Cobra ), spiders (e.g., Black widows ), insects (e.g., wasps , honey bees and caterpillars ), employ venom for hunting and for self defense .
    • Most venoms are administered by biting the skin of the victim
  • 4. Envenomations
    • Most bites and stings by:-
    • *Spiders
    • *Snakes
    • *Scorpions, and
    • *Other venomous animals
    • Cause little more than local pain and
    • Do not require medical attention .
  • 5. Common Viper Dice Snake Tessellated Aeskulapian Snake Green Pit Viper Oxus Cobra Big Bend Milk Snake
  • 6. Scorpions
  • 7. Spiders
  • 8. Envenomations
    • Children are at greater risk for severe reactions because of their smaller volume of distribution for a given amount of venom.
  • 9. Envenomations
    • Symptoms of envenomation may be either:
    • 1. IgE-mediated
    • such as anaphylaxis in response
    • to Hymenoptera stings, or
    • 2. Venom-mediated
    • as with the bites of poisonous
    • spiders or snakes or the sting of
    • scorpions
  • 10. Envenomations
    • Species-specific antivenin
    • 1. Ameliorates symptoms and
    • 2. Prevents death from severe venom-
    • mediated reactions,
    • But the use of antivenin carries
    • significant risks.
  • 11. Envenomations
    • Venoms
    • are Species-Specific mixtures of:-
    • 1. Polypeptides
    • 2. Proteolytic enzymes
    • 3. Glycoproteins , and
    • 4. Vasoactive substances .
  • 12. Envenomations
    • All antivenins
    • are animal-derived immunoglobulins
    • that bind and neutralize the proteins
    • in venom.
  • 13. Envenomations
    • The animal origin of antivenins exposes patients to large amounts of foreign proteins that may cause both
    • immediate and
    • delayed hypersensitivity
    • reactions.
  • 14. Envenomations
    • In the United States ,
    • only 4 antivenins are commercially approved by the U.S. Food and Drug Administration (FDA)
  • 15. Envenomations
    • 1 . Pit viper bites
    • - Horse serum-derived Antivenin
    • (Crotalidae) Polyvalent (ACP)
    • - Sheep-derived product ,
    • Crotalidae Polyvalent Immune Fab (Crofab)
    • 2. Coral snake (Micrurus fulvius)
    • Horse serum–produced antivenin
    • 3 . Black widow spider (Latrodectus mactans)
    • Horse serum–produced antivenin
  • 16. Envenomations
    • Immediate hypersensitivity reactions to antivenins may be life-threatening , although the risk varies greatly depending on the product.
  • 17. Hypersensitivity reactions
    • . The incidence of such reactions after administration of
    • * Equine Crotalid antivenin
    • may be as high as 25–40%.
    • * Ovine-produced Crofab antivenin
    • has a much lower rate of acute reaction
    • ( 15% ),
    • * Black widow antivenin
    • * Coral snake antivenin
    • both occur at a rate of about 1%.
  • 18. Hypersensitivity reactions
    • Given the risk of anaphylaxis, antivenin should be given only in a setting in which full resuscitative measures , including:
    • * Oxygen,
    • * Endotracheal intubation,
    • * Intravenous fluid administration, and
    • * Epinephrine,
    • are available .
  • 19. Hypersensitivity reactions
    • Patients should be asked about medication allergies and previous exposure to antivenins.
    • If equine-derived products are to be used, skin testing may be done, but the practice remains controversial.
  • 20. Hypersensitivity reactions
    • Skin testing
    • 1. Delays treatment
    • 2. Has triggered anaphylaxis and
    • serum sickness.
    • 3. Has very high false-positive and
    • false-negative rates of up to 30%.
  • 21. Hypersensitivity reactions
    • The skin test is performed using 0.02 mL
    • of a 1:10 dilution of antivenin.
    • A positive skin test does not preclude the use of antivenin but does alert the clinician to an increased risk of anaphylaxis.
  • 22. Envenomations
    • In such instances, pretreatment with intravenous administration of Diphenhydramine , 1 mg/kg, and Methylprednisolone , 1–2 mg/kg, is required.
    • Some toxicologists recommend pretreatment for all patients receiving antivenin
  • 23. Envenomations
    • If signs of immediate hypersensitivity develop during administration of antivenin, the infusion should be stopped until the patient is stabilized.
  • 24. Envenomations
    • If the severity of envenomation warrants continued infusion of antivenin, it may be:
    • Resumed at a slower rate
    • or
    • Simultaneously with administration
    • of epinephrine.
  • 25. Envenomations
    • Delayed hypersensitivity or serum sickness develops:
    • - In up to 65% of patients who
    • receive equine-derived antivenin
    • and
    • - In 15% of patients who receive
    • ovine-derived products.
  • 26. Envenomations
    • Serum sickness usually develops 5–21 days
    • after exposure and may last for weeks. It is
    • most commonly manifested as
    • 1.Urticaria
    • 2.Pruritus
    • 3.Arthralgia, and malaise,
    • rarely may present as
    • 1. Immune complex glomerulonephritis
    • 2. Neuritis or
    • 3. Myocarditis
  • 27. Envenomations
    • Intradermal skin tests have not been shown to predict the risk of serum sickness accurately.
    • Prophylactic use of antihistamines and corticosteroids may reduce the risk of serum sickness and definitely is of benefit if symptoms develop.
  • 28. SNAKEBITE
    • Of the >3,000 known species of snakes, only 200 are poisonous to humans. Of poisonous snakes, 90% are members of one of three families :
    • 1. the Hydrophidae , or poisonous sea snakes;
    • 2.the Elapidae , which includes the cobras,
    • mambas, and coral snakes; and
    • 3.the Viperidae , or true vipers
  • 29.
    • In the U.S., 95% of poisonous snakebites are inflicted by the Crotalidae, or pit vipers , which are a subfamily of the true vipers. Pit vipers may be identified by their:
    • * Triangular heads
    • * Elliptical eyes , and
    • * Identifiable pit between the eyes and
    • nose
    SNAKEBITE
  • 30. SNAKEBITE
    • Members of the pit viper family in the U.S. include:
    • 1. rattlesnakes
    • 2. cottonmouths , and
    • 3. copperheads .
  • 31. SNAKEBITE
    • Coral snakes , the other poisonous snakes native to the U.S., are found in Texas and the Southeast and are members of the Elapidae family.
    • Coral snakes are small with :
    • * Small, rounded head and
    • * Brightly colored bands of black and red
    • separated by more narrow yellow bands .
  • 32. SNAKEBITE
    • The rhyme “ red on yellow , kill a fellow ; red on black , venom lack ” serves to differentiate the coral snake from the similar-appearing but nonpoisonous scarlet king snake.
  • 33. SNAKEBITE
    • Cobras and kraits
    • are common in parts of Asia
    • whereas vipers , cobras , and adders
    • are common in parts of Africa.
  • 34. Epidemiology
    • The incidence of snakebites is;
    • Higher in
    • - Africa
    • * 5 bites per1000 persons in Nigeria
    • * 23000 snake bites deaths per year
    • in West Africa
    • - Australia
    • 0.6 to 5 bites per 1000
    • - Asia
    • - South America
  • 35. Epidemiology (cont.)
    • In USA ,most snakebites occur in young males and involve alcohol intoxication; often the victim had tried to capture or play with snake.
    • In Africa and Asia most bites occur on lower limbs ,at night ,and provoked by stepping on a snake
  • 36. Epidemiology (cont.)
    • In USA
    • there are only 12 -15 deaths each year
    • In parts of Africa and Asia
    • where as case fatality rates up to 15% are reported among hospitalized victims of snakebites where intensive care and antivenom access are limited
  • 37. Pathogenesis
    • Snake venom is a mixture of;
    • -Polypeptides
    • -Proteolytic enzymes
    • -Toxins (species-specific)
  • 38. Pathogenesis (cont.)
    • Venom of the Elapidae and the Hydrophidae is primarily neurotoxic and has a curare- like effect by blocking neurotransmission at the neuromuscular junction
    • Death results from respiratory depression
  • 39. Pathogenesis (cont.)
    • Crotalidae venom is cytolytic ,causing
    • 1. tissue necrosis
    • 2. vascular leak
    • 3.coagulopathies
    • Death from pit viper bites results from:
    • 1. hemorrhagic shock
    • 2.adult respiratory distress syndrome
    • 3. renal failure
  • 40. Clinical manifestations
    • Pit viper bites
    • -occur usually on the extremities
    • - pain and swelling occur at the site
    • within minutes
    • - as the venom moves proximally , edema
    • and ecchymosis advance
    • - in severe cases , bulla formation and tissue
    • necrosis ensue
  • 41. Clinical manifestations (cont.)
    • Pit viper bites (cont.)
    • - systemic symptoms include ;
    • * nausea, vomiting
    • * diaphoresis
    • * weakness
    • * tingling around the face
    • * muscle fasciculation
    • Gold BS,Dart RC, Barish RA: bites of venomous snakes, N Engl J Med 2002;347:347-356
  • 42. Clinical manifestations (cont.)
    • Pit viper bites (cont.)
    • * Rarely .may present with :
    • # generalized edema
    • # cardiac arrhythmias
    • # complex clotting abnormalities
    • Gold BS,Dart RC, Barish RA: bites of venomous snakes, N Engl J Med 2002;347:347-356
  • 43. Clinical manifestations (cont.)
    • The coral snakes bites
    • Bites of most Elapidae, including the coral snakes
    • are minimally painful because the venom has no cytotoxin
    • Lack of immediate symptoms should not be mistaken for the absence of serious envenomation
    • -
    • Gold BS, Dart RC, Barish RA: bites of venomous snakes, N Engl J Med 2002;347:347-356
  • 44. Clinical manifestations (cont.)
    • The venom of the coral snake is primarily neurotoxic , and symptoms can progress rapidly in a few hours
    • from
    • mild drowsiness
    • to
    • cranial nerve palsies
    • weakness
    • and
    • death from respiratory failure
    • Gold BS, Dart RC, Barish RA: bites of venomous snakes, N Engl J Med 2002;347:347-356
  • 45. Treatment
    • First: determine whether the bite was by a poisonous snake and if envenomation occurred
    • Immediate care is to immobilize the bitten extremity and transport the patient quickly to the nearest hospital If the bite is determined to be from a venomous snake
    • Gold BS, Dart RC, Barish RA: bites of venomous snakes, N Engl J Med 2002;347:347-356
  • 46. Treatment
    • Avoid applying of ice to the bite site or using excision and suction as it is believed to cause more tissue damage than benefit
    • Many experts now eschew any constricting bands because of the risk of ischemia
    • Gold BS, Dart RC, Barish RA: bites of venomous snakes, N Engl J Med 2002;347:347-356
  • 47. Treatment
    • On arrival at the emergency department
    • 1. a large-bore i.v line should be inserted
    • 2. initial blood tests should include;
    • i. type and cross match’
    • ii. Complete blood cell and platelets counts
    • iii. Prothrombine and partial thromboplastin times
    • iv. Fibrinogen and fibrin degradation products’
    • v. Blood urea nitrogen ,creatinine, and creatine phosphokinase level
    • these investigations must be repeated at intervals depending on severity of envenomation
    • Gold BS, Dart RC, Barish RA: bites of venomous snakes, N Engl J Med 2002;347:347-356
  • 48. Treatment
    • baseline vital signs and measurement of circumference of the bitten extremity should be obtained and demarcation of 3eccyhmosis and swelling should be marked on the limb
    • The wound should be cleansed and tetanus toxoid given if appropriate
    • Gold BS, Dart RC, Barish RA: bites of venomous snakes, N Engl J Med 2002;347:347-356
  • 49. Treatment
    • Usage of antivenin
    • It depends on the severity and progression of symptoms
    • Rattlesnake envenomation requires antivenin
    • Copperhead bites do not
    • Cottonmouth bites fall between these extremes
    • Gold BS, Dart RC, Barish RA: bites of venomous snakes, N Engl J Med 2002;347:347-356
  • 50. The severity of envenomation is commonly graded on a 4 –point scale Minimal envenomation (local swelling and pain without progression) Grade 1 No envenomation Grade 0 Features Grade
  • 51. The severity of envenomation (Cont,) Severe envenomation (marked local response ,severe systemic findings and significant alteration in laboratory findings Grade 3 Moderate envenomation (swelling ,pain , or ecchymosis progress beyond the site of injury Mild systemic or laboratory manifestations) Grade 2 Features Grade
  • 52. Antivenin
    • Is most effective if delivered within 4 hr of the bite
    • Is of little value if administration is delayed beyond 12 hr
    • Poses a small ,but significant risk of an immediate hypersensitivity reaction
  • 53. Antivenin
    • Antivenin (Crotalidae) Polyvalent
    • - is administered in increments of 5 vials and repeated every 2hr as needed to neutralize circulating venom, as measured by;
    • - normalization of clotting parameters
    • - A halt in the progression of swelling of the affected limb
    • - children often require more antivenin than a similarly envenomated adult because of their small volume-to venom ratio
  • 54.
    • Thank you