Chapter A2: Whole-Bowel Irrigation and Other Intestinal Evacuants

INTRODUCTION

One approach to altering the pharmacokinetics of a xenobiotic is to administer a gastrointestinal (GI) evacuant. Selected patients benefit from minimizing systemic exposure by decreasing GI transit time and increasing rectal evacuation. The most effective process of evacuating the GI tract in poisoned patients is referred to as whole-bowel irrigation (WBI). Whole-bowel irrigation is typically accomplished using polyethylene glycol with a balanced electrolyte lavage solution (PEG-ELS). Unless stated otherwise, WBI will mean WBI with PEG-ELS. A detailed discussion of the merits of WBI in the context of various decontamination strategies is provided in Chap. 5.

HISTORY

In 1625 while endeavoring to recover from the febrile “Hungarian disease,” Johann Glauber drank from a well from which he later isolated sal mirabile, now known as sodium sulfate, Na₂SO₄.⁵⁴ He advocated its use as a purgative and determined a synthetic production method.⁵⁴ In 1675, Nehemiah Grew first observed the presence of the eponymous purgative salt in the springs at Epsom, later determined to be magnesium sulfate.¹²⁵ Phosphate of soda, called “tasteless purging salt,” was found in the urine by Hellot in 1737 and introduced into clinical practice as a purgative by George Pearson some 50 years later.¹¹⁹ In 1882 and 1883, Hay reported a series of experiments that provided the foundational understanding of the mechanism of action of the saline cathartics. He identified the viscus as the main source of bowel fluid, which was secretory in nature, and established the dose–response principle of decreased time to stool as salt concentrations were increased.^50,51 Polyethylene glycol was initially introduced in 1957 as a nonabsorbable marker for the study of human fat, carbohydrate, and protein absorption.²⁰ Experimental studies of intestinal lavage in normal human subjects appeared in 1968.⁸⁹ In 1973, Hewitt and colleagues reported on WBI in clinical practice using their method of “whole-gut irrigation” with a solution of sodium chloride, potassium chloride, and sodium bicarbonate in distilled water to prepare the large bowel for surgery.⁵³ In 1976, WBI was used therapeutically for poisoning in a patient ingesting 300 lead air-gun pellets who was unresponsive to oral magnesium sulfate purgation.¹⁵⁹

PHARMACOLOGY

Nomenclature

Xenobiotics that promote intestinal evacuation are referred to as laxatives, cathartics, purgatives, promotility agents, and evacuants. Depending on the dose, the same xenobiotic might accomplish some or all of these tasks, with differing side effect profiles. Laxatives promote a soft-formed or semifluid stool within 6 hours to 3 days. Cathartics promote a rapid, watery evacuation within 1 to 3 hours.¹³¹ The term purgative relates the force associated with bowel evacuation. Evacuants are commonly used for preprocedural bowel cleansing, with an onset of action of as little as 30 to 60 minutes, but typically require 4 hours for a more complete effect. Promotility xenobiotics stimulate GI motor function ...