Gut Decontamination Methods

Gut Decontamination

• Gut decontamination is the process of removing ingested poisons from the body.

• It is used for orally ingested poisons and is most effective within 4-6 hours of ingestion.

• Methods include:

  • Emesis
  • Gastric Lavage
  • Activated Charcoal
  • Cathartics
  • Whole Bowel Irrigation

Emesis

• Emesis is the induction of vomiting.
• It is indicated for conscious and alert poisoned patients within 4-6 hours of ingestion.
• Syrup of ipecac is the emetic of choice for children over 6 months and adults.
• Ipecac contains two main active ingredients: emetine and cephaeline.
• Mechanism of action:
  • Early vomiting: Local activation of peripheral sensory receptors in the gastrointestinal tract.
  • Late vomiting: Central stimulation of the chemoreceptor trigger zone (CTZ) with subsequent activation of the central vomiting center.
• Dose:
  • Children 6-9 months: 5 ml ipecac syrup + 120 ml water
  • Children 9-12 months: 10 ml ipecac syrup + 120 ml water.
  • Children 1-12 years: 15 ml ipecac syrup + 120 ml water
  • Adults: 30 ml ipecac syrup + 250-350 ml water
  • The dose can be repeated once if emesis has not occurred in 30 minutes.
• If vomiting fails, gastric lavage should be performed immediately.
• Contraindications:
  • Children up to 6 months of age
  • Comatose patients
  • Patients with convulsions
  • Ingestion of hydrocarbons, volatile substances, corrosives, and sharp objects

Gastric Lavage

• Gastric lavage is the process of washing out the stomach contents.

• The patient should be placed on their left lateral decubitus position to prevent passage of the toxicant from the stomach to the intestine.

• Warm water and saline are alternated in small aliquots to avoid hypothermic shock and hyponatremia.

• The stomach contents are removed by suction, with the first aliquot ideally saved for chemical analysis.

• The lavage continues until no further particulate matter is seen.

• It can be performed in comatose patients with concurrent insertion of a cuffed endotracheal tube to protect the airway.

• Contraindications:

  • Relative Contraindications: Patients with unprotected airway, obtunded, comatosed or convulsing patients, poisoning with salicylates or drugs that decrease gastric motility, poisoning for more than 6 hours.
  • Absolute Contraindications: Patients with risk of perforation or hemorrhage, chronic poisoning, poisoning with mineral acids and alkalis corrosives, froth-producing substances.

• Complications:

  • Perforation of the esophagus or stomach
  • Epistaxis
  • Vomiting resulting in pulmonary aspiration of gastric contents

Local Antidotes

• Local antidotes are classified into physical antidotes and chemical antidotes.
• Chemical antidotes are now obsolete.

Physical Antidotes

• These agents interfere with ingested poisons through physical means only, not changing their chemical nature. They include:

  • Demulcents: They coat the gastric mucosa, e.g., milk, egg white, and olive oil.
  • Diluents: They include water, which dilutes some poisons. Dilution and neutralization are contraindicated in acid and alkali corrosives because they may aggravate the chemical burn by heat resulting from the reaction. Powdered ice is preferred.
  • Adsorbents:
    • Activated Charcoal: A highly adsorbent powdered material, made from distillation of organic materials. It is activated through superheating in the presence of oxygen, steam, and acids.
    • It is highly effective in adsorbing most toxins but poorly adsorbs to hydrocarbons, heavy metals, iron, inorganic corrosives, cyanide, alcohols, and lithium.
    • Studies suggest that activated charcoal given alone without prior gastric emptying is as effective as emesis and gastric lavage in reducing drug absorption.

• Indications:

  • Used after toxic ingestion within a reasonable time period after ingestion.
  • Given if other substances have been co-ingested.
  • Repeated doses may be given to enhance elimination of some drugs from the bloodstream.

• Contraindications:

  • Depressed mental status without airway protection
  • Hydrocarbon ingestion
  • Toxins poorly adsorbed by activated charcoal
  • Intestinal obstruction
  • Decreased peristalsis

• Multiple doses activated charcoal (MDAC): Repeated doses of activated charcoal slurry are given along the intestinal tract which allows for a large surface area to adsorb ingested drugs. Dose: 1 gm/Kg/4hr or 0.5 gm/kg/2hr (oral).

Preventing Absorption: Cathartics

• Cathartics are a type of laxative that induces bowel movements. They are used to prevent absorption of poisons.
• Types:
  • Salt: Magnesium Citrate & Sodium Sulphate
  • Saccharide: Sorbitol
• Complications:
  • Abdominal distention and cramps
  • Prolonged diarrhea
  • Electrolyte disturbances
• Contraindications:
  • Magnesium cathartics should be avoided in patients with renal failure and/or CNS problems.
  • Sodium salts should be avoided in patients with renal failure, heart failure, hypertension, pre-existing electrolyte disturbance, intestinal obstruction, GI bleeding, perforation, peritonitis.
  • Poisoning with corrosives

Whole Bowel Irrigation

• It involves the complete irrigation of the bowel with polyethylene glycol (PEG), which is a non-absorbable solution that does not cause electrolyte imbalance. It induces a liquid stool for faster removal of poisons and prevent their absorption.
• PEG is instilled into the stomach through a nasogastric tube over 2-6 hours, resulting in voluminous diarrhea. The patient receives PEG until clear effluent is attained.
• It is particularly valuable for poisons not adsorbed by activated charcoal and in slow-release preparations.

Enhanced Elimination

• Enhancing elimination means increasing the rate of removal of the poison from the blood after absorption.
• This is necessary for:
  • Critically ill patients despite maximal supportive care
  • Patients with impaired normal or usual route of elimination
  • Patients who have ingested a known lethal dose or have a lethal blood level of the drug.

Forced Diuresis

• It involves changing the urinary pH to aid excretion of the poison.
• It is done by altering urine pH according to whether the ingested poison is alkaline or acidic.
• Urine acidification is now obsolete.
• It can enhance elimination of polar drugs by ion trapping.
• Requirements:
  • Low protein binding
  • Low volume of distribution
  • High renal clearance (normal kidney function)

Alkalinization of urine

• Altering urine pH from acidic to alkaline (using sodium bicarbonate). This converts a lipid-soluble acidic drug in the tubular lumen into a charged lipid-insoluble salt, preventing it from easily moving back across the renal epithelium.
• This leads to a marked increase in the excretion of the drug.

Precautions for Alkalinization of urine:

• Check the following:
  • Renal function tests (blood urea nitrogen and serum creatinine should be normal).
  • Urine pH and maintain at 7-8.
  • Urine volume and maintain at 300-500 ml/hour.
  • Blood pH (ensure it is no higher than 7.55 - 7.60) and correct if elevated.
  • Electrolytes and correct any abnormality (e.g. hypokalemia).

Adverse effects of Alkalinization of urine:

• Fluid overload

• Acid-base abnormalities (alkalosis)

• Electrolyte abnormalities (e.g. hypokalemia, hypernatremia).

• Contraindications:

  • The poison is not excreted in urine in active form, has a large volume of distribution, or is highly plasma protein bound.
  • Renal dysfunction.
  • Lack of facilities to monitor pH and electrolyte levels.

Dialysis

• It involves the removal of poisons from the blood through semipermeable membranes.
• The process utilizes either the peritoneum (peritoneal dialysis) or an artificial membrane (hemodialysis).

Hemodialysis

• Blood is taken from a large vein (e.g. femoral vein) with a double-lumen catheter and is pumped through the hemodialysis system.
• The patient must be anticoagulated to prevent clotting of blood in the dialyzer.
• Drugs and toxins flow passively across the semipermeable membrane down a concentration gradient into a dialysate solution.
• Fluid and electrolyte abnormalities can be corrected concurrently.

Requirements for Hemodialysis

• Low volume of distribution
• Low plasma protein binding.
• Drug molecular weight should be less than 500 Dalton.
• High water solubility.
• Heparin should be administered before dialysis to avoid blood coagulation.

Indications for Hemodialysis:

• Severely intoxicated patients who don't respond to early supportive management.

• Renal failure (where forced diuresis can't be applied).

• Prolonged coma.

• If lethal amounts of drug were absorbed despite gut decontamination.

• Complications: Hypotension, Electrolyte disturbances, Bleeding, Thrombocytopenia, Infection.

Hemoperfusion

• Blood is derived from the radial artery and passes through a cartridge coated with activated charcoal, where toxic agents in the blood are adsorbed.
• The blood is then returned to the patient through the radial vein.
• Anticoagulation with heparin is necessary.
• Glucose, calcium, and other electrolytes should be closely monitored as they may be adsorbed to the charcoal.

Indications for Hemoperfusion

• Adsorbed by activated charcoal.
• Low volume of distribution.

Contraindications & Complications for Hemoperfusion:

• The same as hemodialysis.

Exchange Transfusion

• It is infrequently used.
• Involves the removal of a quantity of the patient's blood and replacement with fresh whole blood.

This quiz covers the essential methods of gut decontamination, focusing on the removal of poisons ingested orally. You will explore techniques such as emesis, gastric lavage, and activated charcoal, along with their mechanisms and appropriate cases for use. Test your knowledge on the interventions effective within the critical 4-6 hour window post-ingestion.