THE ROLE OF ACID IN UPPER GASTROINTESTINAL HEMORRHAGE DUE TO ULCER AND STRESS-RELATED MUCOSAL DAMAGE

A peptic ulcer is a lesion in which acid and pepsin are essential components of pathogenesis. Regardless of the type of patient or the setting in which the ulcer presents, the basic pathogenetic scheme is the same. The primary event is disruption of mucosal integrity. In the presence of acid and pepsin, such disruption of integrity leads to an ulcer, While rarely sufficient by itself to cause ulceration, the presence of acid is a necessary cofactor. The causes of disruption of mucosal integrity include nonsteroidal anti-inflammatory drugs (NSAIDs), Helicobacter pylori and critical illness. With the latter, tissue ischaemia may be the primary event, leading to back-diffusion of H+ ions through increased membrane permeability. Impaired mucosal buffering then leads to intramural acidosis and cell death. Risk factors for bleeding peptic ulcer in the intensive care unit (ICU) include severe trauma, sepsis, respiratory failure, and coagulopathy. Potential roles for decreasing gastric acidity in the treatment of bleeding peptic ulcer include cessation of active bleeding, prevention of rebleeding in hospital and primary prevention of bleeding. Most published studies dealing with the first two situations suggest no benefit with antisecretory therapy. However, the optimal pH for clot and platelet function may be greater than or equal to 7.0. Can such pH levels be maintained with antisecretory agents such as the proton pump inhibitors! Are the published trials adequate to demonstrate any benefit from antisecretory agents! Primary prevention of bleeding ulcer in the outpatient setting includes avoidance of NSAIDs, use of antisecretory agents and eradication of H. pylori. Antacids, antisecretory therapy and sucralfate have each been shown to reduce the incidence of bleeding ulcer in ICU patients. Which regimens are the most effective? Which are the safest? Does prevention of bleeding improve survival!