By Binh T. Ly, MD
Gastrointestinal (GI) decontamination is a cornerstone in the general management of poisoned patients. The rationale behind GI decontamination is to prevent absorption of ingested toxins by either eliminating the toxin from the GI tract or binding the toxin within the GI tract. Techniques for GI decontamination can be categorized anatomically according to the organ being decontaminated (Table 1) each with its own advantages, disadvantages, and risks. Gastric emptying techniques have fallen out of favor in the past decade due to a lack scientific evidence demonstrating their efficacy and numerous reports of complications leading to significant morbidity and mortality. Single-dose activated charcoal (AC) has become the most commonly employed method of decontamination due to its applicability to numerous poisoning scenarios and high degree of safety when compared to other methods of GI decontamination (i.e. gastric lavage, syrup of ipecac, cathartics). Activated charcoal has a very large surface area and acts by adsorbing or binding toxins before they can be absorbed into the blood stream. Most, but unfortunately not all, toxins are adequately bound by AC (Table 2). Sustained- or controlled-release (SR) pharmaceutical formulations with their delayed tablet dissolution may be inadequately bound to or unbind (desorb) from AC prior to elimination of the drug from the GI tract. Because SR preparations have delayed dissolution AC may proceed though the GI track more rapidly than through SR preparations. These limitations have prevented activated charcoal from being the universal GI decontamination technique.
Whole bowel irrigation (WBI) was first proposed as a method of GI decontamination in 1982. By administering into the gut large amounts of a bowel preparation solution, the goal of WBI is to “cleanse” the GI tract by physically expelling of all intraluminal contents, including ingested toxin, prior to their absorption into the body.
Gastrointestinal Decontamination Techniques
|Syrup of ipecac||Activated charcoal|
|Whole bowel irrigation|
Toxins Poorly Absorbed by Activated Charcoal
|Inorganic salts (K+)|
|Metals (mercury, arsenic)|
|Glycoles (ethylene glycol)|
|Alkali or acids|
A 24-year-old woman with a history of bipolar disorder is brought to an emergency department by ambulance 2 hours after ingesting several handfuls of her Lithobid (lithium carbonate) and Unisom (doxylamine). Activated charcoal (50 grams) was orally administered during transport. Upon arrival to the emergency department (ED), she does not have any specific complaints but admits to feeling depressed for the past 3 days. Her triage vital signs are as follows: temperature 37.7°C, heart rate (HR) 104 beats per minute, blood pressure (BP) 124/72 mmHg, respiratory rate (RR) 15 breaths per minute. She is awake, alert, and cooperative. On physical examination she is mildly tachycardic and has hypoactive bowel sounds but the examination is otherwise normal. Electrocardiogram shows sinus tachycardia with normal intervals. Serum lithium level is 0.3 mEq/L (therapeutic range 0.6-1.2 mEq/L). Serum acetaminophen level is undetectable. She is closely monitored for 6 hours without any significant change in clinical condition and transferred to an offsite inpatient psychiatric facility for treatment of her depressive episode.
Four hours later (10 hours after ingestion), the charge nurse from the psychiatric ward calls to inform the ED that the patient is now more tachycardic with HR 120/minute and is being sent back to the ED for reevaluation. Upon representation her vitals were temperature 37.5°C, HR 124/minute, BP 132/76, and RR 16/minute. On physical examination she is alert and tachycardic. Her bowel sounds are hypoactive but she now has obvious tremors in both upper extremities. An intravenous catheter is placed for administration of saline and blood is simultaneously obtained and sent to the lab for complete blood count (CBC), serum chemistries, and lithium level. The repeat lithium level is 6.1 mEq/L. Results of serum chemistries and CBC are normal. Electrocardiogram reveals sinus tachycardia and is otherwise normal. Whole bowel irrigation is initiated in the emergency department and the patient is admitted for treatment of lithium toxicity. A nephrology consultation iss also obtained for consideration of hemodialysis.
- Why did the lithium level continue to rise despite receiving AC?
- What factors contributed to this delayed elevation of the lithium level?
- What other diagnostic tests could have been performed in the management of this patient?
- What factors may make WBI difficult to perform in this patient?
Indications for WBI
- Ingestion of large amounts of a toxin that is known to be poorly adsorbed by AC (Table 2)
- Ingestion of massive amounts of drugs where administration of adequate dosages of AC (10:1 ratio of AC to amount of ingested drug) is impractical
- Ingestion of sustained-release or enteric-coated drug preparations (theophylline, calcium channel antagonists, aspirin, etc.)
- Removal of ingested packets of illicit drugs (body packers, drug “mules”)
- Ingestion of large amount of drugs that tend to form concretions or bezoars (Table 3)
- Treatment of suspected drug concretion (i.e. continual rise in measurable toxin concentrations despite charcoal administration)
Drugs that Commonly Form Concretions
|Enteric - coated tablets|
|Sustained - release tablets|
Several polyethylene glycol electrolyte solutions (PEG-ES) are available for use (GoLytely, CoLyte). These solutions are isotonic, osmotically balanced, and not absorbed into the body. Originally designed for use as preoperative bowel cleansing preparations, PEG-ES solutions are routinely used for this indication as well as preparing the bowel for endoscopic or radiographic procedures. Their safety is clearly demonstrated in clinical use without any appreciable changes in serum electrolytes or shifts in body fluids. These solutions are also safe for use during pregnancy.
How to perform WBI
Whole bowel irrigation is easily performed with unsophisticated equipment found in any emergency department. However, expecting patients to drink adequate amounts of WBI fluid is unrealistic. Therefore, it may be helpful to place a nasogastric (NG) or small bore cilastin feeding tube to administer the WBI solution. The feeding tube is adequate for administering large quantities of WBI solution and is more comfortable for the patient than the typical stiff NG tube. The WBI solution should be administered by gravity. The infusion pump typically used to administer enteral feeding should not be used, as the typical maximal infusion rate (300 mL/hour) is inadequate. Although no dose-response studies have been performed, Table 4 summarizes the recommended dosing for WBI. The PEG-ES should be started at about 1/10 the goal rate and advanced over 30-60 minutes to achieve the goal rate as tolerated by the patient. Antiemetics should be provided as needed. An agent with promotility effects (such as metoclopromide) is theoretically preferable.
Suggested Goal Rates for WBI Solution
|9 months to 5 years||500 mL/hr|
|6-12 years||1000 mL/hr|
|13 years and older||1500-2000 mL/hr|
Contraindications for WBI
- Unprotected or compromised airway
- Uncontrollable vomiting
- Severe GI hemorrhage
- Bowel obstruction or perforation
- Nausea and vomiting
- Abdominal cramping and bloating
- Pulmonary aspiration
Several methods of GI decontamination are available for use in poisoned patients. The decision to utilize any individual technique should be based on safety and potential benefit with regard to the agent ingested. At present, activated charcoal should remain the mainstay in GI decontamination because of its demonstrated safety and potential benefit in a wide variety of poisoning situation. Whole bowel irrigation should not be routinely used in the management of poisoned patients but there are specific clinical situations in which it can be reasonably recommended particularly when AC is unlikely to be beneficial.
Discussion of case questions
- Lithium is not well adsorbed to AC.
- Several factors likely played a role in the delayed absorption of lithium.
- Lithobid is a sustained-release preparation of lithium carbonate. Sustained-release preparations are designed to slowly release throughout the day. When ingested in massive amounts sustained-release preparations are also more likely to form concretions within the GI tract. These concretions can further delay absorption of drugs and toxicity as in this case.
- Unisom contains doxylamine, which is an antihistaminic drug with antimuscarinic activity. This antimuscarinic activity can slow gastric emptying and decrease intestinal peristalsis. Both of these effects can delay absorption of drugs. The slight tachycardia and hypoactive bowel sounds are clinical clues of doxylamine effect in this case.
- Plain abdominal radiograph and urine pregnancy test.
- Although lithium is not intrinsically opaque, sustained-release preparations are sometimes visualized on a plain abdominal radiograph. In cases where tablets can be seen, serial radiographs may be useful to monitor the progression of tablets through the GI tract. Radiographs may also be used as collaborative data in determining the stopping point for WBI.
- A urine pregnancy test should be performed on all suicidal women of child-bearing potential as treatment, diagnostic tests, or the toxin itself all may have adverse effects on the fetus. The first trimester, when organogenesis is occurring, is a particularly vulnerable period. Urine pregnancy testing should be performed prior to obtaining radiographs in this case.
- Antimuscarinic effects of doxylamine may decrease intestinal motility or cause an ileus, which can impair the ability to administer large amounts of PEG-ELS to adequately expel contents of the GI tract.