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In addition to immunologic mechanisms, physical (motility), chemical (gastric acidity), and microbiologic (normal colonizing flora) factors normally protect the gastrointestinal tract against infection.
Esophagitis, most commonly caused by Candida albicans or herpes simplex virus, may be underrecognized among patients in the intensive care unit.
Infection with Helicobacter pylori may play a role in the pathogenesis of gastric stress ulceration among critically ill patients.
The epidemiology and microbiology of diarrheal illness is significantly different among patients in the critical care unit than is observed in the community setting. Most infectious diarrhea is hospital acquired and is usually attributable to Clostridium difficile.
A systematic approach to the critically ill patient with diarrhea includes consideration of pathogens that cause noninflammatory, inflammatory, and hemorrhagic diarrhea. Thorough history taking supplements laboratory data in the diagnosis of these patients.
C difficile infection is the single most common cause of gastrointestinal infection among patients in the intensive care unit. The spectrum of disease induced by C difficile infection is broad. Timely diagnosis and treatment is critical both for the management of the infected patient and to prevent the spread of infection through the unit.
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While rarely severe enough to warrant admission to the intensive care unit, gastrointestinal infections account for substantial morbidity and mortality among critically ill patients. Because of severe comorbid disease, impaired immune defenses, and the invasive interventions to which they are subjected, patients in the ICU are especially susceptible to hospital-acquired GI infection. Nevertheless, despite the frequency with which these infections occur, the morbidity and mortality that they cause, and the costs they incur, GI infections can go undetected and untreated in the ICU. While trying to manage patients with deteriorating cardiac function, marginal ventilatory performance, and life-threatening metabolic abnormalities, clinicians in the ICU may fail to recognize the important early signs of GI infection.
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Any discussion of GI infections among critically ill patients must begin with a consideration of the host defenses that normally protect the alimentary tract. As such, the first section of this chapter is devoted to a description of the unique nonimmunologic mechanisms normally active in the GI tract. Particular consideration is given to the means by which these defenses may be compromised in patients in the ICU. Following this introduction, the clinical manifestations of infection affecting each segment of the GI tract are discussed (Table 76-1). In addition to describing the microbiology associated with each syndrome, a rational diagnostic and therapeutic approach is offered, based on the most up-to-date experience reported in the medical literature. The chapter concludes with an expanded discussion of the unique clinical challenges presented by the patient in the ICU with Clostridium difficile infection.
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