**7. Gastrointestinal hemorrhage**

Gastrointestinal bleeding is among the most common GIC following cardio-thoracic proce‐ dures. In one study, gastrointestinal bleeding constituted nearly 29% of all GIC-CTS [32]. In general, upper gastrointestinal bleeding occurs more frequently than lower gastrointestinal bleeding, with most hemorrhages (>90%) occurring proximal to the ligament of Treitz [5]. Patients with previous history of peptic ulcer disease may be at higher risk for developing an upper gastrointestinal perforation or hemorrhage following cardiac surgery, although other traditional risk factors such as *H. pylori* infection alone do not seem contributory [39]. Prolonged mechanical ventilation significantly elevates the risk of upper gastrointestinal bleeding [39]. The two most common etiologies of upper gastrointestinal bleeding are duo‐ denal ulceration and gastric erosion. The appearance of gastric erosions following CTS is likely secondary to systemic hypoperfusion with subsequent development of mucosal ische‐ mia and erosion [40].

The initial step in diagnosis of gastrointestinal bleeding is the placement of a nasogastric (NG) tube and lavage of gastric contents. This aids in determining if the gastrointestinal hemorrhage is proximal to the ligament of Treitz. Medical therapy is attempted first, and in‐ cludes the administration of H2-receptor blockers or proton pump inhibitors, red blood cell transfusion, correction of coagulopathy, and temporarily withholding anticoagulation when applicable/possible [41, 42]. If medical management fails, upper endoscopy is the next step in evaluation and treatment of potential bleeding source(s) [43]. Endoscopic attempts aimed at stopping the bleeding by cauterization, vasoconstrictive agent injection, or both are usual‐ ly effective [42, 43]. In one report, approximately half of the patient with upper gastrointesti‐ nal bleeding required upper endoscopy with cauterization to stop the hemorrhage while the other half required surgical intervention to control the bleed [32]. Early surgical intervention if patient fails medical and endoscopic treatment or if significant rebleeding occurs, is rec‐ ommended. In general, the presence of continued hemodynamic instability, or a pre-deter‐ mined transfusion threshold (i.e., >4-6 units of packed red blood cells) are utilized as "surgical triggers". Mortality related to gastrointestinal bleeding, even when requiring an operation has decreased over the past two decades.

Lower gastrointestinal bleeding following cardio-thoracic procedures is usually approached according to established clinical algorithms [44]. The first step in management is hemody‐ namic resuscitation and normalization of coagulation parameters. The bleeding usually stops following these initial maneuvers. If the bleeding does not stop, the next step is the identification of the source of hemorrhage, either endoscopically [45] or by imaging (nuclear scan versus angiography) [46, 47]. In many cases, the bleeding can be controlled endoscopi‐ cally [48, 49]. Select cases can be treated with endovascular embolization [47]. Surgery should be reserved for refractory cases, with the major determinants for surgery being the failure of non-operative therapies, hemodynamic instability and/or the requirement for transfusion (usually 4-6 units of packed red blood cells) [48, 49].
