VPT 421: Veterinary Toxicology (2+0)

GASTRIC LAVAGE AND OTHER METHODS TO DELAY ABSORPTION

• Gastric lavage

  • If possible a gastric lavage may be given to remove the stomach contents. This can be used in unconscious patients or in sedated patients.
  • For gastric lavage, a rubber tube with a funnel at one end is inserted into the stomach via the mouth.
  • The end of the tube passed into the stomach should not have sharp edges so as to avoid damage to the mucosa.
  • Raising the funnel will allow the liquid to run into the stomach, while, lowering will have an opposite effect.
  • Gastric lavage is not possible in large animals like cattle.
  • Flushing with water is done 10 to 15 times till the aspirate is clear. After flushing with a lavage, precipitants and astringents can be administered.
  • Activated charcoal can be used in lavage as it enhances the effectiveness of washing-out technique.
  • In small animals the head must be lowered to an angle of 30° and 10 ml of lavage fluid (water or normal saline) for every kilogram of body weight must be gently flushed into the stomach.

• When the poison cannot be physically removed, certain agents administered orally can adsorb it and prevent its absorption from the alimentary tract.
• Adsorbants like slurry of activated charcoal, precipitants like tannic acid, oxidizing agents like potassium permanganate, precipitants and demulcents like egg white and butter milk are useful.

• After activated charcoal is introduced into the gastrointestinal lumen, toxins are adsorbed to the charcoal. If the charcoal-toxin complex stays too long in the gastrointestinal lumen, the toxin begins to desorb and is available for absorption into the systemic circulation.
• Milk is also believed to act as the best general antidote. In fact milk promotes the absorption of liposoluble poisons.
• A cardinal rule therefore is not to administer milk.
• Activated charcoal can be administered as a slurry in water at 1g/5ml of water and administered at the rate of 2-5 g of charcoal for every kilogram of body weight.
• Universal antidote containing 10 g activated charcoal, 5g kaolin, 5g tannic acid and 5 g magnesium oxide in the form of a slurry with 200 ml of water can be administered.
• Universal antidote can be used when the specific antidote is not available. This only helps in adsorbing the toxin and prevent further absorption.
• Non-absorbed poisons may be amenable to chemical neutralization if acidic or alkaline in character or to other modes of chemical inactivation e.g. a freshly prepared mixture of ferric hydroxide and magnesium oxide for recently ingested arsenic.
• Changing its physical state may prevent absorption of a poison from the gut.
• A soluble poison may be rendered non available by causing it to be precipitated, by causing it to be complexed or by causing it to be adsorbed. To hasten elimination of the complexed mass as saline purgative may be given.
• In the case of ruminants, emergency rumenotomy can be performed to prevent further absorption.