8: Techniques Used to Prevent Gastrointestinal Absorption

INTRODUCTION

Gastrointestinal (GI) decontamination is a highly controversial issue in medical toxicology. It can play an essential role in the initial management of orally poisoned patients and frequently is the only treatment available other than routine supportive care. Unfortunately, as is true in most areas of medical toxicology, rigorous studies that demonstrate the effects of GI decontamination on clinically meaningful endpoints are difficult to find. The heterogeneity of poisoned patients demands that very large randomized studies be performed because patients who present to an emergency department (ED) may have an unreliable history and a low-risk exposure.^31,156 These factors, as well as other significant sources of bias, are often hidden in inclusion and exclusion criteria of the available studies. Numerous determinants contribute to the difficulties in designing and completing studies that provide sound evidence for or against a particular therapeutic option. Incontrovertible endpoints, such as complication-specific mortality, also demand exceptionally large studies because the overall morbidity and mortality of poisoned patients are quite low.³¹ Whereas other endpoints, such as the length of stay in the hospital or intensive care unit (ICU), change in xenobiotic concentration, the rate of secondary complications, and the need for specific treatments such as expensive antidotes, must be considered, these surrogate markers are not adequately rigorous and are inadequately precise measures of morbidity. In the science of GI decontamination, we are also faced with the dilemma that randomizing half of a group of potentially ill patients to no decontamination is a significant ethical concern—we rarely omit decontamination unless a minimally toxic exposure has occurred or an effective, safe, readily available, and inexpensive antidote exists. Because acetaminophen (APAP) meets many of these parameters, it has been used both as the xenobiotic of choice in volunteer overdose ­studies^{42,82,94,152,239} and in the evaluation of actually poisoned patients.⁵³ However, despite its widespread use as a model, the applicability of the management approach for APAP poisoning to other ingestions is limited.

As might be suspected, no available study provides adequate guidance for the management of a patient who has definitely ingested an unknown xenobiotic at an unknown time. Fortunately, in most cases, there is some component of the history or clinical presentation, such as vital signs, physical examination, and focused diagnostic studies such as an electrocardiogram and anion gap, that might offer insight into the nature of the ingested xenobiotic (Chap. 3).

For many, the ongoing controversy or debate on GI decontamination culminated in 1997 with the publication of the position statements on activated charcoal, orogastric lavage, syrup of ipecac–induced emesis, and whole-bowel irrigation (WBI) from the American Academy of Clinical Toxicology (AACT) and the European Association of Poisons Centres and Clinical Toxicologists (EAPCCT),^{43,124,208,224,225} and has evolved from very invasive to a less aggressive approach after subsequent revisions.^{44,125,209,...}