Toxicology – GI Decontamination: Whole Bowel Irrigation

Indications

Whole bowel irrigation (WBI) may be considered for selected poisonings in which a substance is expected to remain in the gastrointestinal tract for a prolonged period.

Examples include:

• Large ingestions of sustained-release or enteric-coated medications
• Certain slowly absorbed toxic substances
• Some iron or lead ingestions
• Ingestion of multiple transdermal patches
• Selected sustained-release drugs such as calcium channel blockers, theophylline, venlafaxine, or bupropion

Because evidence and indications vary, WBI should generally be discussed with a medical toxicologist or poison control center.

Mechanism of Action

WBI uses a polyethylene glycol–electrolyte lavage solution (PEG-ELS) to rapidly move gastrointestinal contents through the bowel.

PEG-ELS is designed to be essentially iso-osmotic, allowing large volumes to pass through the intestine with relatively little net fluid or electrolyte absorption.

The goal is to:

• Shorten gastrointestinal transit time
• Reduce continued absorption of substances still present in the bowel
• Promote elimination of intact tablets, drug packets, or poorly absorbed toxic material

Administration

PEG-ELS is given orally or through a nasogastric tube in a monitored setting and continued until bowel output is adequately cleared.

The exact rate and duration depend on factors such as:

• Patient size and age
• Substance involved
• Clinical condition
• Tolerance of the lavage

Important Limitations

WBI is not appropriate for every overdose and may be unsafe in patients with:

• Bowel obstruction or ileus
• Gastrointestinal perforation
• Significant GI bleeding
• Hemodynamic instability
• An unprotected airway or high aspiration risk

Key Points

• WBI is most useful when the toxic substance may remain in the gut for a long time.
• It is conceptually similar to bowel preparation used before colonoscopy, but in toxicology it is used for decontamination.
• Polyethylene glycol (PEG) is completely different from ethylene glycol, the toxic alcohol found in antifreeze.
• WBI should be used selectively and usually with toxicology guidance.