Ileus in the critically ill: causes, treatment and prevention

Bowel dysfunction, especially ileus, has been increasingly recognized in critically ill patients. Ileus is commonly associated to constipation, however abnormal motility can also concern the upper digestive tract, therefore impaired gastrointestinal transit (IGT) seems to be a more appropriate term. IGT, especially constipation, is common among patients under mechanical ventilation, occurring in up to 80% of the patients during the first week, and has been associated with worse outcome in intensive care unit (ICU). It is acknowledged that the most relevant definition for constipation in ICU is the absence of stool for the first six days after admission. Concerning the upper digestive intolerance (UDI), the diagnosis should rely only on vomiting and the systematic gastric residual volume (GRV) monitoring should be avoided. IGT results from a complex pathophysiology in which both the critical illness and its specific treatments may have a deleterious role. Both observational and experimental studies have shown the deleterious effect of sepsis, multiorgan failure, sedation (especially opioids) and mechanical ventilation on gut function. To date few studies have reported effect of treatment on IGT and the level of evidence is low. However, cholinesterase inhibitors seem safe and could probably be used in case of constipation but remains poorly prescribed. Prevention with bowel management protocol using osmotic laxatives appears to be safe but did not demonstrate its effectiveness. For patients treated with high posology of opioids during sedation, enteral opioid antagonists may be a promising strategy.