Gastrointestinal Decontamination

CHAPTER 202 Gastrointestinal Decontamination

Michael Zeringue, Grant C. Fowler

The overall mortality from acute poisoning is less than 1%; therefore, the challenge to clinicians is to determine which patients face serious complications from poisoning if not treated. If the decision is made to treat, activated charcoal has become the first-line treatment for most ingested toxins, especially for ingestion of a small or moderate amount. Multiple doses of charcoal are recommended by some experts, especially for toxins recycled in the enterohepatic circulation or those with long half-lives. Certain experts also add a laxative or cathartic to charcoal for more rapid elimination and to avoid constipation. Whole-bowel irrigation is a newer treatment; for most toxins, it is usually considered second-line treatment after activated charcoal. Rarely is gastric emptying (by lavage or induced emesis with substances like ipecac) recommended anymore, unless activated charcoal or whole-bowel irrigation is not available or gastric lavage or induced emesis can be performed very rapidly and will not delay administration of activated charcoal. It is rarely indicated for ingestion of corrosives or petroleum distillates because of risk of esophageal injury or aspiration. However, in certain cases, the potential benefit of removal of a highly toxic substance (e.g., benzene, pesticides) may outweigh the risk of complications. Consultation with a medical toxicologist or regional poison control center (1-800-222-1222) may help guide choice of intervention. For the sake of completeness, this chapter continues to cover techniques for gastric emptying.

Mechanisms of Action and Evidence

Charcoal is “activated” by the manufacturer by heating it to approximately 900° C and washing it in a stream of carbon dioxide gas or steam. This increases the surface area from 2 m²/g to greater than 2000 m²/g; consequently, a 50-g dose has the surface area of 10 football fields. When ingested, there is no modification of charcoal’s structure by digestive enzymes as it passes through the stomach and intestines, nor is it absorbed across the intestinal wall. Activated charcoal binds with toxins and then passes through the gastrointestinal tract to be eliminated in the stool as a sticky black substance. As the charcoal absorbs the toxin in the intestine and passes distally, it creates a diffusion gradient. This in turn causes already absorbed toxins to diffuse back across the intestinal membrane and into the lumen; it somewhat dialyzes the intestinal blood. Thus, charcoal decreases systemic absorption of toxins by both its absorptive mechanism and its ability to form a diffusion gradient.

Charcoal has an excellent safety profile; it is even considered safe during pregnancy, in lactating women, and in the pediatric population. Although studies show a better safety profile and a more effective decrease in toxin absorption compared with lavage or ipecac-induced emesis, no significant decrease in mortality, length of hospital stay, or likelihood of clinical deterioration has been demonstrated with use of activated charcoal. In studies using a single dose of at least 50 g of activated charcoal, there was a 47% to 21% reduction in toxin absorption when administered 30 to 180 minutes after toxin ingestion, respectively. Although the clinical benefit of activated charcoal is less clear after 1 hour, “the potential for benefit … cannot be excluded” (Position paper, 2005).

Similarly, although studies have shown statistical significance for multidose charcoal’s effectiveness in removing toxins, it has not been shown to reduce morbidity or mortality. Therefore, multidosing is usually not recommended except for a select list of drugs (see Indications). Although there is no evidence supporting their use, cathartics are added to charcoal by some experts to hasten elimination. This may be especially helpful when large doses of charcoal have been administered, which can be constipating. If cathartics are used, it should be kept in mind that there are general, as well as specific, contraindications to certain agents. In the very young and elderly, cathartics can cause very large stools, dehydration, and electrolyte abnormalities such as hypernatremia. Sorbitol, which is used as a preservative and to decrease the grittiness of charcoal, also enhances the flavor of charcoal by making it slightly sweet. It is not absorbed and therefore encourages water secretion into the lumen, which in turn stimulates bowel peristalsis; however, it can cause severe cramping, hypotension, and vomiting and increase the risk of pulmonary aspiration. Sorbitol dosing in children is not clearly established and, therefore, if premixed with charcoal, may not be appropriate. Magnesium, another cathartic, is contraindicated in patients with hypermagnesemia, myasthenia gravis, renal insufficiency, or cardiac arrhythmias. Sodium-based cathartics should be avoided in patients with severe hypertension, renal failure, or congestive heart failure. Mineral oil– or other oil-based cathartics should not be used because of risk of aspiration.

Whole-bowel irrigation uses the infusion of polyethylene glycol (PEG) electrolyte solution (the same as used for preparation for colonoscopy) at a rate faster than normal for a bowel preparation. PEG infusion works by decreasing enteric transit time, thereby reducing toxin contact time with the intestinal wall and decreasing absorption. Whole-bowel irrigation has an advantage over cathartics in that it does not cause electrolyte disturbances because it does not create an osmotic differential across the intestinal membrane. Whole-bowel irrigation is especially useful for ingestions of toxins not absorbed by charcoal (e.g., iron, lithium, heavy metals), sustained-release or enteric-coated pills (if multidosing charcoal is not indicated), or illegal drug packets. Studies have found whole-bowel irrigation to decrease toxin bioavailability by up to two thirds.

Gastric lavage was at one time the chosen method to decontaminate the intestinal tract. However, in 1997, the American Academy of Clinical Toxicology/European Association of Poisons Centres and Toxicologists made the following statement: “Gastric lavage should not be considered unless a patient has ingested a potentially life-threatening amount of a poison and the procedure can be undertaken within 60 minutes of ingestion. Even then, clinical benefit has not been confirmed in controlled studies.” Despite this knowledge, gastric lavage has not been completely abandoned. Some authorities believe that there are not enough data to direct decisions on all patients with potentially fatal ingestions. They believe that this lack of evidence should not lead to the discontinuance of gastric lavage, a logical, relatively safe, and inexpensive procedure. Gastric lavage can be considered when the substance ingested has high evidence of toxicity or risk of fatality or other supportive modalities are inadequate or unavailable. It is most effective for massive ingestions of solutions or small tablets, and is not as effective for large tablets or mushrooms, which may obstruct the orogastric tube when attempting to aspirate (see Indications and Contraindications). If performed within 5 minutes, 90% of ingestants are recovered, compared with 45% at 10 minutes, 30% at 19 minutes, and 8% at 60 minutes. Gastric lavage can also be used to evaluate gastric contents for poison or to administer charcoal. Specialized lavage (neutralizing) solutions may be indicated (after consultation with a toxicologist or poison control center) for ingested fluoride, formaldehyde, iodine, iron, or oxalic acid.

Syrup of ipecac has two pharmacologically active alkaloids, emetine and cephaeline, which stimulate both the gastric mucosal sensory receptors and the chemoreceptor trigger zone in the brain; given soon after toxin ingestion, ipecac can partially evacuate the gastric contents. However, there is no clear evidence for improved outcomes and its use is associated with the increased risks of pulmonary aspiration and delayed administration of activated charcoal. Therefore, like gastric lavage, induced emesis is no longer routinely recommended in poisoned patients. In fact, American poison centers recommended ipecac in only 0.6% of cases in 2002. That said, it may be considered in an alert patient who has ingested the toxin less than 60 minutes ago and for whom activated charcoal, whole-bowel irrigation, and gastric lavage are not indicated or available. Such may be the case at home or in the prehospital setting.

Indications

Activated Charcoal

• Most toxic substances

• Toxins metabolized by the liver and secreted into the bile

• Toxins that are recycled in the enterohepatic circulation and have long half-lives

Contraindications

Tags: Pfenninger and Fowlers Procedures for Primary Care Expert Consult

May 14, 2017 | Posted by admin in GENERAL & FAMILY MEDICINE | Comments Off

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