Snake Bite PDF

Snake bite Snake Bite Only 5% to 10% of snake bites involve venomous snakes. In Egypt, venomous snakes belong either to the family, Elapidae as cobra which inject neuro...

Snake bite Snake Bite Only 5% to 10% of snake bites involve venomous snakes. In Egypt, venomous snakes belong either to the family, Elapidae as cobra which inject neurotoxic venom, and Viperidae which inject a vasculotoxic venom, and Hydrophidae which inject myotoxic venom. v Toxic action: § Neurotoxic venom: o It is secreted by Elapidae. o It has a curare-like action causing paralysis of motor nerve endings in voluntary muscles. § Vasculotoxic venom: o It is secreted by Viperidae. o It contains phospholipase enzyme. o It produces destruction of RBCs leading to extra and intravascular haemolysis. o This action is manifested as coagulative disorders and Thrombocytopenia with bleeding tendency from external orifices of the body and site of the bite. § Myotoxic venom: o It secreted by Hydrophidae. o It simulates the neurotoxic as it produces generalized muscular pain and weakness followed by degeneration of the muscles and myoglobinuria ending in respiratory and renal failure in fatal cases. v Clinical picture: Neurotoxic Manifestations: Elapid snake bite: Local effects: - Mild or minimal swelling and inflammation around the fang marks. Systemic effects: - Dropping of Eye lid: Ptosis (1st neurological sign) & squint and paralysis of extraocular muscles. - Dysphonia & Nasal tonation - Dysartheria: Difficulty in speaking - Dysphagia: Difficulty in swallowing. - Descending paralysis, muscular weakness & staggering gait. 1 of 5  Snake bite Slow, labored breathing, ending in a respiratory failure, followed by cardiac arrest. - Dizziness, Confusion, Giddiness & Lethargy. - Nausea, vomiting and Salivation. Ophthalmic effects: (If the 'spat' venom enters the eyes) Snake (cobra) venom ophthalmia. - Pain: There is immediate and intense burning & stinging pain. - Followed by Inflammatory Signs: profuse watering of the eyes with production of whitish discharge, congested conjunctiva, swelling of the eyelids, photophobia and clouding of vision. - Infectious Signs: Secondary infection may lead to panophthalmitis and BLINDENESS. Vasculotoxic Manifestations: Viper snake bite: Local effects - Severe local pain, erythema, progressive swelling, petechiae, ecchymosis, and hemorrhagic blebs may develop over the next several hours. Systemic effects - Nausea, vomiting. - Weakness, muscle fasciculations, diaphoresis & paresthesia. - Hypovolemic shock: Collapse with cold clammy skin, rapid weak pulse, dilated pupils and loss of consciousness. - Local compartment syndrome: It may occur secondary to fluid and blood sequestration in injured areas. - Petechial haemorrhage and bleeding from body orifices followed by haemoglobinurea. - Death results from circulatory collapse. Mayotoxic Manifestations: Local effects - Mild or minimal local swelling around the fang marks. Systemic effects - Stiffness of the neck, followed by generalized muscle weakness. - Respiratory distress. 2 of 5  Snake bite - Brown colour of urine (myoglobinuria). - Hyperkalemia. v Treatment: I. First aid measures: The first 30-45 minutes are very important, and it is necessary to: 1) Allaying anxiety and fright. 2) Preventing the venom spread. 3) Removing as much as possible of the venom from the wound. 1) Allaying anxiety and fright: } Reassurance of the victim to prevent death from shock due to severe fright. 2) Prevention of venom spread: } Immobilization: prevent the movement of the bitten part to reduce venom spread through lymphatic circulation. } Lymphatic constricting band (tourniquet). Tourniquet characters: It is applied 2.5-10 cm above the bite or the first proximal joint. It should be tight enough to occlude the superficial venous and lymphatic return without impeding the arterial blood flow. It must be released for 1-2 minutes every half an hour to allow the blood flow and prevent ischemia. It should be removed as soon as the antivenin is given. Dangers of severe tight tourniquet or other occlusive methods: Ischaemia and gangrene. Damage to superficial nerves. Intensification of local effects of venom in the occluded limb. 3) Removing as much as possible of the venom from the wound: } Incisions: Characters Superficial cut incisions are made parallel to the long axis of the limb through the fang marks. They should not be: deep (just through the skin) or cross cut incisions. Dangers 3 of 5  Snake bite Aggravate bleeding especially with vipers. Damage nerves and tendons. Introduce infection and delay healing. } Suction: Applied with suction cup. Oral suction should be avoided since absorption from injured oral mucosa is possible II. Medical treatment: Monitor the patient closely for at least 12-24 hours for local and systemic manifestation. 1- Provide local wound care. 2- Symptomatic treatment of systemic effects 3- Specific drug and antidote. 1- Provide local wound care: - Monitor local swelling at least hourly. - Consult surgeon for management of serious wound complication. - Provide tetanus prophylaxis if needed. - Administer broad spectrum antibiotics if there are signs of infection. 2- Symptomatic treatment of systemic effects: - Monitor for respiratory muscle weakness. - Maintain airway and assist ventilation if necessary. - Treat severe coagulopathy with fresh frozen plasma. - Hypotension: IV crystalloids. - Rhabdomyolysis: Sodium bicarbonate. 3- Specific drugs and antidotes (antivenin): Dosage and method of administration: 1.Initial dose is based on severity of symptoms, not on body weight (Table 1). 2.Children may require doses larger than those of adults. 3.The end point of antivenin therapy is the reversal of systemic manifestation (e.g., shock, coagulopathy and parethesias), halting of progressive oedema and pain. 4.Treat all patients in an intensive care unit. 5.Before skin test or antivenin administration, insert at least one and preferably two secure IV lines. 4 of 5  Snake bite 6.Perform skin test for horse serum sensitivity only when signs of envenomation are present and imminent antivenin therapy is anticipated, using 1:10 dilution of antivenin. 7.Do not abandon antivenin therapy if skin test is positive. 8.Even if skin test is negative, anaphylaxis may still occur unpredictably. 9.If antivenin is used in a patient with a positive skin test pre-treat with IV diphenhydramine, 1mg/kg slowly and have ready at the bedside a preloaded syringe containing epinephrine (1/10,000 for IV use) in case of anaphylaxis. 10. Dilute the antivenin to 1:10 and give each vial over a long period as tolerated. Table (1): Dose of antivenin. Severity of envenomation Dose None or minimal None Mild (local pain and swelling). 5 Moderate (proximal progression of swelling, ecchymosis and mild systemic 10 symptoms). Severe (hypotension, rapidly progressive swelling, ecchymosis and 15-20 coagulopathy). 5 of 5