Prevention and treatment of gastrointestinal complications in patients on mechanical ventilation

There exists a complex, dynamic interaction between mechanical ventilation and the splanchnic vasculature that contributes to a myriad of gastrointestinal tract complications that arise during critical illness. Positive pressure-induced splanchnic hypoperfusion appears to play a pivotal role in the pathogenesis of these complications, the most prevalent of which are stress-related mucosal damage, gastrointestinal hypomotility and diarrhea. Furthermore, characteristics of the splanchnic vasculature make the gastrointestinal tract vulnerable to adverse effects related to positive pressure ventilation. While most of these complications seen in mechanically ventilated patients are reflections of altered gastrointestinal physiology, some may be attributed to medical interventions instituted to treat critical illness. Since maintenance of normal hemodynamics cannot always be achieved, pharmacologic prophylactic therapy has become a mainstay in the prevention of gastrointestinal complications in the intensive care unit. Improved understanding of the systemic effects of mechanical ventilation and greater application of lung-protective ventilatory strategies may potentially minimize positive pressure-induced reductions in splanchnic perfusion, systemic cytokine release and, consequently, reduce the incidence of gastrointestinal complications associated with mechanical ventilation. Herein, we discuss the pathophysiology of gastrointestinal complications associated with mechanical ventilation, summarize the most prevalent complications and focus on preventive strategies and available treatment options for these complications. The most common causes of gastrointestinal hemorrhage in mechanically ventilated patients are bleeding from stress-related mucosal damage and erosive esophagitis. In general, histamine H(2) receptor antagonists and proton pump inhibitors prevent stress-related mucosal disease by raising the gastric fluid pH. Proton pump inhibitors tend to provide more consistent pH control than histamine H(2) receptor antagonists. There is no consensus on the drug of choice for stress ulcer prophylaxis with several meta-analyses providing conflicting results on the superiority of any medication. Prevention of erosive esophagitis include careful use of nasogastric tubes and institution of strategies that improve gastric emptying. Many mechanically ventilated patients have gastrointestinal hypomotility and diarrhea. Treatment options for gastrointestinal motility are limited, thus, preventive measures such as correction of electrolyte abnormalities and avoidance of medications that impair gastrointestinal motility are crucial. Treatment of diarrhea depends on the underlying cause. When associated with Clostridium difficile infection antibacterial therapy should be discontinued, if possible, and treatment with oral metronidazole should be initiated.More studies are warranted to better understand the systemic effects of mechanical ventilation on the gastrointestinal tract and to investigate the impact of lung protective ventilatory strategies on gastrointestinal complications.