There is no gold standard to measure/monitor GI function in critically ill patients.
Monitoring of GI dysfunction is based on complex evaluation of abdominal and GI signs and symptoms.
Presence of several signs and symptoms concomitantly is independently associated with increased mortality.
Impairment of GI and gall bladder motility is common in critically ill patients.
Treatment with prokinetics is effective to reduce enteral feeding intolerance, whereas its effect on patient-relevant outcomes is not clear.
Mechanical GI and biliary obstructions are rare in patients admitted to the ICU but lead to adverse outcomes if not timely detected and interventionally managed.
DEFINITION OF GI DYSFUNCTION IN THE ICU
Despite the recognition of the role of the intestinal tract in multiple organ dysfunction,1,2 there are still several problems with defining gastrointestinal (GI) dysfunction in critically ill patients.3,4 Acute gastrointestinal injury (similar to acute kidney injury and acute lung injury) has been proposed to specifically describe GI dysfunction as a part of Multiple Organ Dysfunction Syndrome (MODS).5 It is most difficult to identify the presence of normal GI function in patients managed in the intensive care unit (ICU) with no gold standard to measure GI function.
Assessment of GI dysfunction in the ICU is currently based on clinical assessment of GI signs and symptoms; it is therefore unavoidably associated with subjective components in assessment and is mainly based on evaluation of GI dysmotility.4
Biliary and pancreatic dysfunction as important aspects of maldigestion and malabsorption are not clearly represented in the abovementioned assessment approach addressing dysmotility of GI tract. Biomarkers for assessment of malabsorption are warranted to achieve further progress in the field with a broader, more robust, and reproducible approach for GI dysfunction in critical illness. Moreover, barrier dysfunction as a key contributor to GI dysfunction promoting MODS needs attention and ideally should be included in such an assessment.
Conceptually, GI dysfunction in critically ill patients should be defined as functional impairment of the GI tract that may include disturbances in motility, absorption, mucosal integrity, perfusion, and microbiome.4 Importantly, also, mechanical issues commonly needing interventions by surgeons or gastroenterologists lead to disturbed barrier function and similarly may result in MODS (Fig. 107-1).
Pathophysiological mechanisms leading to systemic consequences of GI dysfunction.
In this chapter we address both functional and mechanical mechanisms of GI dysfunction.
IMPAIRED GASTRIC AND BOWEL FUNCTION
Pathophysiology, Diagnosis, and Monitoring
The GI system has multiple functions (energy intake, and hormonal, immunological, and barrier function) and impairment in all these functions in critically ill patients has been described.4
Current clinical practice in critical care focuses on symptoms of GI dysmotility limiting ...