Snake Physiology and Venom Quiz

Corrosive Poisons

• Inorganic Acids:
  • Examples: concentrated sulfuric acid, nitric acid, hydrochloric acid
  • Action: local corrosion only
  • Fatal oral dose: 4 ml
  • Poisoning methods: accidental skin contamination, ingestion, inhalation of fumes, or homicidal attacks
• Corrosive Burns:
  • Visible physical damage to skin
• Clinical Signs:
  • Local corrosion on skin
  • Severe oral burning pain from mouth to stomach
  • Severe colic and bloody vomitus with pieces of gastric mucosa; vomitus highly acidic
  • Dark vomitus due to acid haemation
  • Black charring in sulfuric acid; yellow in nitric acid
  • Dehydration with thirst
• Additional Clinical Signs:
  • Oliguria and constipation
  • Shock with weak rapid pulse and hypotension
  • Evidence of corrosion on lips and mouth
  • Oedema of the glottis and stridor and cyanosis
  • Death: few hours from shock and dehydration or days from perforation and peritonitis
  • Possible esophageal stricture and dysphagia in survivors
• Inhalation of Acid Fumes:
  • Burning pain in the chest
  • Severe cough and dyspnea
  • Oedema of the glottis and stridor
  • Pulmonary oedema
  • Cyanosis and death from asphyxia
  • Bronchopneumonia may occur

Corrosive Alkalies (K+ and Na+ Hydroxide)

• Potassium hydroxide (caustic potash) and sodium hydroxide are common in household cleaning products
• Accidental poisoning frequently occurs in children
• Fatal dose: 3-5 grams of the solid or the corresponding amount of solution
• Picture:
  • Mouth mucosa is white
  • Vomit is whitish, slimy, alkaline, and contains blood
  • Diarrhea may occur
  • Stomach perforation is delayed
  • Esophageal strictures are common

Organic acids: Acetic Acid

• Glacial acetic acid is a strong corrosive acid when ingested or inhaled as fumes.
• Presents with similar findings to other corrosives, with the added smell of vinegar
• Treatment: same as corrosive acids

Carbolic Acid (Phenol)

• Forms white crystals with a strong characteristic smell
• Crude form is used as a toilet disinfectant
• Lysol, cresol, and dettol have similar effects
• Action:
  • Local: coagulative necrosis with thickening of the tissue; superficial ulcers with local anesthetic effects on sensory nerve endings; gangrene of skin with prolonged exposure
  • After absorption: CNS and respiratory depression; acute toxic glomerulonephritis
• Fatal Dose: 2-4 gm of the solid phenol or the corresponding amount of the crude acid
• Poisoning:
  • Mostly accidental ingestion or skin contamination in children
  • Used suicidally due to its availability and painlessness
• Picture:
  • Temporary burning pain from mouth to stomach
  • Colic and vomiting
  • Whitish buccal mucosa and brownish carbolic eschars on lips and chin that turn darker with oxidation
  • Drowsiness, then coma due to CNS depression
  • Slow, difficult respiration; cyanosis; pulmonary edema; death from asphyxia after a few hours
• Further signs:
  • Pupils constrict, then dilate before death
  • Smell of phenol from breath
  • Acute toxic glomerulonephritis with oliguria, albuminuria, haematuria, and casts
  • Urine turns green from oxidation of hydroquinone and pyrocatecn
  • Delayed death from anemia can occur in 7-10 days

Treatment (general)

• Emetics and gastric lavage are contraindicated due to fear of perforation; use bicarbonates and carbonates to avoid causing gastric distension and rupture
• Give water orally to dilute the acid
• Neutralize with weak alkalis such as magnesium oxide, lime water (Ca hydroxide), or soap solution
• Milk, egg albumin, olive oil, or butter are also good, but important not to use heat
• Morphine (8-15 mg IV) to relieve pain and treat shock and pulmonary edema
• IV fluids for dehydration; tracheostomy for glottis edema; pulmonary edema treatment; treat with antibiotics and corticosteroids to prevent strictures; surgical treatment
• Contaminated skin: wash with soap and water, and then treat surgically
• Gastric lavage is performed, using magnesium sulphate (15-30 gm in a glass of water) to precipitate the poison; if this isn't available, 10% ethanol or glycerin for dissolving the poison as an antidote but needs to be rewashed
• General measures for care of coma, and respiration; Atropine (1 mg IV) measures for controlling pulmonary edema; treat impaired renal function through 1.26% sodium bicarbonate IV or dialysis

Snake Bites

• Introduction:
  • Over 3,000 snake species globally, 15% are venomous
  • Venomous snakes found on all continents except Antarctica
  • 45,000 venomous snake bite incidents annually in the US
  • 7,000-8,000 incidents involve venomous snakes
  • 10 people die annually from snake bites
• Snake Venom:
  • Toxin (Hemotoxin, Neurotoxin, Cytotoxin)
  • Excreted through a modified parotid salivary gland located behind eye on skull
  • Combination of proteins and enzymes
  • Venom flows through pumping mechanism in alveolar sac storage, proceeds through channel to tubular fang
  • Not inhaled, therefore not classified as a poison
• Benefits:
  • Control animal populations
  • Farmers: save up to $75 USD annually from removing rodents and insects that carry diseases
  • Medicinal uses: oils extracted from snakes are used for pain relievers, such as rheumatoid arthritis, thought to contain Eicosapentaenoic acid (EPA) for inflammation reduction, pain relief, and may cure diseases.
• Venom Composition:
  • Primarily protein (90%) with enzymes and non-enzymatic toxins
  • Carbohydrates (CHO), Metals, Lipids, and Free amino acids
• Enzymes:
  • Activate mammalian blood clotting cascade
  • Phospholipase (A2), damaging mitochondria, RBCs, leucocytes, and skeletal muscles, and vascular endothelium
  • Hydrolases: increase vascular permeability; cause edema, blistering, bruising, and necrosis
  • Neurotoxins: interfere with acetylcholine release at neuromuscular junctions
  • Histamine and 5-HT (5-hydroxy tryptamine): induce edema and local pain at the bite site
• Mechanism of Action:
  • Toxic effects of snake venom can be isolated for beneficial purposes, including antivenom production for multiple sclerosis treatment, and reduced cancer growth and metastasis
• Side Effects:
  • Respiratory paralysis, fever, rapid pulse, increased thirst, dizziness, local tissue damage, blurred vision, nausea/vomiting, diarrhea, coma, and death
• Case Study #1:
  • 41-year-old male bitten on left third finger by a Gaboon Viper
  • Necrosis and blanching of the finger/hand
  • Numbness and edema
  • Prothrombin time (PT) 15.53 (normal range 11.0-13.0)
  • International Normalized Ratio (INR) 1.2
  • Moderate leucocytosis and normal platelets
  • Treated with antibiotics, diphenhydramine, hydrocortisone, and SAIMR antivenom
  • Developed lymphangitis of the left arm
  • Required amputation of the left third finger
• Antivenin production.
  • Made by injecting horses with snake toxins and monitor for survival
  • After immunity, process and extract blood into antivenin
• African Snake Species:
  • Echis carinatus: scaled or carpet viper
  • Bitis arietans: puff adder
  • Naja nigricicolis: black-necked spitting cobra
  • Naja haje: Egyptian cobra
  • Dendroaspis: mambas
  • Snake bites are common in farming areas in Africa