Gastrointestinal Bleeding and Obstruction

Gastrointestinal bleeding and bowel obstruction can both produce tachycardia, hypotension, abdominal discomfort, and worsening weakness, but they threaten the patient through different mechanisms. With significant gastrointestinal bleeding, circulating volume falls. Cardiac output and oxygen delivery then decline, first producing compensatory tachycardia and vasoconstriction and later hypotension, altered mentation, oliguria, and shock. A patient may maintain a seemingly acceptable blood pressure until compensatory reserve is exhausted, so a rising heart rate, cool clammy skin, delayed capillary refill, or new confusion may be an earlier warning than hypotension. With bowel obstruction, fluid and gas collect above the blockage. Vomiting removes fluid externally, while fluid becomes sequestered inside the bowel. Increasing intraluminal pressure can impair venous return and then arterial blood flow to the bowel wall. Ischaemia, bacterial translocation, necrosis, and perforation may follow. The danger is therefore not simply that the bowel is “blocked”; it is that a closed or worsening obstruction can become a source of sepsis, peritonitis, and circulatory collapse. Non-variceal upper gastrointestinal bleeding most commonly arises from peptic ulcer disease, Mallory-Weiss tears, Dieulafoy lesions, or gastric antral vascular ectasia....