Principles Of Gastrointestinal Decontamination


Gastrointestinal (GI) decontamination refers to therapies that may decrease the amount of poison absorbed from the GI tract lumen. The following methods of GI decontamination are available:

Induced Emesis

DONT DO IT

Background

  • Removal of ingested substances by inducing vomiting
  • Mechanism of action (Ipecac)
    • Irritates gastric mucosa
    • Stimulates medullary chemoreceptor trigger zone to induced vomiting

Indications

  • Known ingestion of toxic substance in awake pts
  • Removal of substances not adsorbed by charcoal (hydrocarbons, metals, K, Li) (relative)

Contraindications

  • Ingestions that can cause seizures, decreased consciousness: aspiration risk
  • Any caustics (alkali/acid), body packers (rupture risk), non-toxic ingestions, age <6 mo
  • Any ingestion with antidote available
  • Any fast absorbing liquid ingestion
  • Any pt that can't protect airway

Cautions

  • No longer recommended for inhospital use
  • Persistent vomiting delays administration of activated charcoal
  • Single dose of Ipecac results in vominting in 80-85% of pts

Procedure

  • Contact Poison Control Center to determine if indicated
  • Dosing Syrup of Ipecac
    • 6-12 mo: 10 mL PO
    • 1-5 yo: 15 mL PO
    • >5 yo: 30 mL PO
  • May repeat dose x1 if no vomiting within 30 min

Complications

  • Persistent vomiting, aspiration, aspiration pneumonitis, esophageal injury, increased abd /intracranial pressures, orthostatic hypotension, lethargy

 

Gastric Lavage

TRY NOT TO DO IT

Background

  • Theoretical benefit derived by irrigating/aspirating stomach contents before absorption
    • Does not eliminate toxins in small bowel where absorption occurs
    • Only useful w/in 1 hr post ingestion (contents still in stomach)
      • Delayed gastric emptying may incr effective time period
  • "Gastric lavage should not be employed routinely, if ever, in mgmt of poisoned pts"

Indications

  • Ingestions of significant doses of highly toxic chemicals
  • Theoretical benefit
    • Very recent (<1 hr) ingestion of a significant quantity of a toxic substance
    • Risks should be weighed against sparse evidence of benefit

Contraindications

  • Unprotected airway
    • Pt lost airway reflexes
  • Corrosive substances
    • Strong acid or alkali
  • Hydrocarbon ingestion
  • Anatomic considerations putting a pt at incr risk for hemorrhage or GI perforation
  • Caustics - may injure esophagus, perforation risk
  • Minimally toxic substances, uncooperative pts, substances absorbed by charcoal

Cautions

  • Only consider in extraordinary situations
    • Examine risk-benefit ratio
      • If > 1 hr post ingestion
    • Weigh against use of charcoal alone
      • If drug highly absorbed by charcoal
    • Weigh against observation w/supportive care
    • Weigh against no gastrointestinal decontamination

Procedure

  • Ensure adequate airway protection
    • Intubate if needed beforehand
    • Have suction available
  • Place pt in left lateral decubitus / Trendelenburg position
  • Insert large bore (adults: 36-40 Fr.; peds: 24-28 Fr.) tube in mouth using lubricating jelly
    • Pt maybe asked to swallow w/ water
    • Force should not be used to pass tube
  • Check tube position w/air insufflation and/or by aspiration
    • Insert bite block
  • Flush tube w/ 200-300 mL aliquots fluid (water/saline)
  • Pediatric pts
    • Warm normal saline should be used in 10mL/kg volumes
  • Continue lavage until recovered soln is clear of particulate matter

Complications

  • Aspiration pneumonitis
  • Esophageal perforation
  • Arrhythmias
  • Laryngospasm
  • Hypoxia
  • Fluid and electrolyte imbalances

Activated Charcoal

Background

  • Aqueous charcoal compound
    • Considered first line of treatment in overdose of toxic drugs w/in 1 hr
    • Can be administered quickly in awake pt
    • Effective w/ wide range of substances
      • can use if ingestion unknown
    • Passes through to small intestine at site of absorption
    • Superior efficacy to induced emesis and gastric lavage alone
    • Can be administred w/ an osmotic cathartic
      • 70% sorbitol 1g/kg or 10% sol of Magnesium citrate
      • Allows for decr transit time
  • Mechanism of action
    • High surface area (950-2000 sq. meter/g) that binds toxins and prevents absorption of enough of substance to prevent toxic effects
    • Enhances elimination by establishing a free-drug concentration gradient favoring movement into the GI lumen to enhance elimination
    • Low water soluable and non-dissociated salts most easily adsorbed
    • Small, ionized and water soluble compounds poorly adsorbed
    • Multiple dose, indicated if:
      • substances form bezoars in the GI tract
      • toxins that slow gut function
      • toxins that are released slowly into the gut lumen
      • toxins with enterohepatic circulation

Indications

  • Can use w/ any OD; sometimes polypharmacy ingestion even if all not adsorbed
  • Substances not significantly adsorbed (PHAILS)
    • Pesticides, Hydrocarbons, Acids/alkali, Iron, Lithium, Solvents
    • Arsenic, boric acid, bromide, potassium, flouride
    • May still be adsorbed enough to reduce toxicity
  • Substances that may benefit from multidosing (enhanced elimination)
    • Aminophylline, theophylline, carbamazepine, chlordecone, cyclosporine, dapsone
    • Valproic acid, salicylates, digoxin/digitoxin, meprobamate, pheobarbital, phenytoin, quinine
    • Sustained release formulations, concretion formation

Contraindications

  • Esophageal or gastric perforation suspected, or emergency endoscopy needed (ex caustic ingestion)
  • Unable to protect the airway due to altered mental status or loss of airway reflexes

Cautions

  • May not be tolerated: requires NGT placement

Procedure

  • Secure airway: intubate if necessary
  • Pre mixed or powder
    • Add water 4:1 - 8:1 to reconstitute (30 g in 240 mL of water)
    • Dose 1-2 g/kg (adults: 50-75 g) PO or NGT (or 10:1 vs. toxin ingested)
    • May add sorbitol 1g/kg as cathartic with first dose (do not use in repeated doses); no clinically proven benefit
    • If vomits: give half original dose
      • May give antiemetics
        • Metoclopramide 1-2 mg/kg IV
        • Ondansteron 4-8 mg (0.15 mg/kg) IV/IM
  • Repeat 0.25 - 0.5g/kg q1-4hr if multidose indicated
    • Sustained release, anticholengergic, concretions
  • Remove via NGT after 4 hr if ileus
    • Prevent gastric distention in multidosing
      • By suctioning prior to next dose

Complications

  • Vomiting, aspiration, intraluminal impaction in pt w/ abnl gut motility, constipation, mechanical obstruction
 

Whole-Bowel Irrigation

Background

  • Whole bowel irrigation (WBI) consists of irrigating entire GI tract w/a polyethylene glycol electrolyte solution (PEG-ES)
    • Examples of PEG-ES are GoLytely and Colyte
  • "Whole bowel irrigation should not be used routinely in the mgmt of poisoned pt"
  • Mechanism of action
    • Direct mechanical movement of intestinal contents before absorbed
    • Does not induce electrolyte/fluid shifts: isoosmolar
    • Not absorbed by GI tract

Indications

  • Substances not absorbed by Activated charcoal
    • Fe, lead, lithium, borates, other heavy metals
  • Enteric coated tablets, sustained release preparations, concretions (bezoars)
  • Body packers/stuffers
    • Used after one dose of activated charcoal
  • Prior to surgical procedures, colonoscopies

Contraindications

  • Ileus, bowel obstruction, perforation
  • Significant GI hemorrhage
  • Intractable vomiting
  • Hemodynamic instability
  • Compromised unprotected airways

Cautions

  • Reduces ability of activated charcoal to absorb
    • Repeat doses of charcoal may be needed

Procedure

  • Ensure adequate airway protection and intubate as needed
  • Insert NGT if patient is unable to tolerate drinking PEG-ES or to prevent aspiration (altered mental status)
    • Intubate if needed
  • GoLytely, Colyte 1.5-2 L/hr PO; total 4-5 L
    • Pediatrics
      • Age 9mo-6yrs: 500 ml
      • 6-12yrs: 1 L
      • >12yrs: 1.5-2 L
  • Slow rate or administer antiemetics if vomiting begins
  • Continue until clear rectal outflow
  • If ingestants/body packers
    • Confirm exit of radiopaque ingestants with pre/post KUB films

Complications

  • Risk of aspiration if unable to protect airway
  • Bloating, cramps, nausea, diarrhea, vomiting