**10. Embolic phenomena**

mucosal sloughing, gangrenous changes of the bowel wall, and perforation. Mortality may exceed 65% for patients with acute mesenteric ischemia [8]. Early recognition of signs and symptoms of bowel ischemia and early intervention are integral to successful outcomes and lower mortality rates [50]. One of the earliest signs of mesenteric ischemia is abdominal pain out of proportion to physical examination findings [51]. However, this can be quite difficult to elicit in postoperative CTS patients as many are mechanically ventilated and sedated fol‐ lowing surgery. In the setting of high clinical suspicion, sigmoidoscopy or colonoscopy can aid in diagnosis of colonic ischemia [52]. The subsequent sections will discuss post-CTS mes‐ enteric ischemia as divided into two major pathophysiologic types: (a) "low flow state" sec‐

**Figure 3.** Abdominal CT scan of a patient who developed peritonitis several days after undergoing coronary artery bypass grafting. The study shows diffuse portal venous gas (left) and pneumatosis of the bowel and the mesentery (right). The patient underwent laparotomy with segmental resection of necrotic small bowel. A planned "second-look"

Patients with poor cardiac functional status are at risk for splanchnic hypoperfusion secon‐ dary to a number of pre-operative (i.e., pre-existing mesenteric arterial disease), intra-opera‐ tive (i.e., hypotension/tissue hypoperfusion), and post-operative (i.e., low cardiac output) risk factors. Preoperative presence of conditions such as low left ventricular ejection fraction and peripheral vascular disease have been shown to be significant risks for developing post‐

Intraoperatively, hypovolemia and use of vasoconstrictors can contribute to splanchnic hypo‐ perfusion [53]. Additionally, patients requiring longer cardiopulmonary bypass times may be at greater risk for developing intestinal hypoperfusion [53]. This may be due to the non-pulsa‐ tile cardiopulmonary bypass flow characteristics, in conjunction with other factors such as the

laparotomy showed no further bowel necrosis and primary small bowel anastomosis was performed.

**9. Ischemia secondary to low flow state**

operative gastrointestinal ischemia [32].

ondary to systemic hypoperfusion; or (b) thrombo-embolic events.

360 Principles and Practice of Cardiothoracic Surgery

Mesenteric ischemia following cardiac surgery results from embolic disease secondary to macrovascular embolism or thrombosis, such as SMA embolus, or microvascular emboli, such as embolic cholesterol "showering" secondary to aortic manipulation. Septic emboliza‐ tion with occlusive phenomena has also been reported in cases of endocarditis following open heart surgery [56]. The size of the embolus may be an important prognostic factor. For example, patients with large vessel emboli may have better outcomes when compared to pa‐ tients with microvascular or "distal" emboli [8]. High index of suspicion is critical to optimal patient outcomes. If recognized promptly, occlusive emboli to the mesenteric circulation can be treated via either endovascular and/or open surgical approaches, with acceptable success rates [51]. Patients with hypotension, cardiogenic shock, and/or pump failure requiring in‐ tra-aortic balloon pump not only are at risk of significant intestinal hypoperfusion, but are also at risk secondary to embolization and thrombus formation which may further exacer‐ bate the original insult to the intestinal tract. Surgical therapy is indicated if the patient de‐ velops peritonitis, perforation, sepsis, and/or end-organ failure in the setting of elevated clinical suspicion [57]. Planned or "second look" surgery is warranted if ischemic (but nonnecrotic) bowel segments are noted at the conclusion of the initial procedure [58, 59]. Open abdominal approaches using temporary abdominal coverage with negative pressure wound therapy have been described in such situations [27].

**12. Acute cholecystitis**

laparoscopic cholecystectomy.

**immunosuppression**

Acute cholecystitis is another commonly seen gastrointestinal complication following CTS (Figure 5). In one study, incidence of acute cholecystitis was approximately 8% among all postoperative gastrointestinal complications [5]. Many cases of acute cholecystitis associated with CTS are termed "acalculous cholecystitis" and are secondary to biliary stasis as a result of multiple factors such as lack of enteral feeding and gallbladder wall ischemia secondary to a "low flow" state. Mortality rates associated with acalculous cholecystitis are significant (>50%) which may reflect the overall poor general health status of patients at risk for this complication [62, 63]. Typical symptoms include right upper quadrant pain and tenderness on examination. However, diagnosis is often delayed secondary to the presence of mechani‐ cal ventilation and sedation in significant proportion of patients with acalculous cholecysti‐ tis. Patients with acute cholecystitis, diagnosed most often on right upper quadrant ultrasound or cholescintigraphy scan, require surgical intervention or percutaneous chole‐ cystostomy tube placement for treatment of cholecystitis. For poor surgical candidates, per‐ cutaneous cholecystostomy can serve as "bridging" therapy that facilitates the patient's

Gastrointestinal Complications in Cardiothoracic Surgery: A Synopsis

http://dx.doi.org/10.5772/54348

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**Figure 5.** Elderly male patient developed cerebral infarction 2 days after undergoing aortic valve replacement. His re‐ covery was further complicated by acute cholecystitis, as demonstrated by right upper quadrant ultrasound showing distended gallbladder with wall thickening, sludge and pericholecystic fluid (left). His operative risk for cholecystecto‐ my was prohibitive at that time, prompting the placement of percutaneous cholecystostomy (right). Following good functional recovery and hospital discharge, the percutaneous drain was removed and the patient underwent elective

**13. Gastrointestinal complications unique to transplant recipients and**

Immunosuppressive regimens administered to transplant recipients predispose this patient population to elevated risk for bacterial, fungal, parasitic, and viral infections [65]. Within

recovery until he or she is ready to undergo cholecystectomy [64].
