Chapter 354 - Mesenteric Vascular Insufficiency Flashcards
What is the incidence of mesenteric ischemia?
2-3 people per 100 000.
How can one define the etiology of intestinal ischemia?
“intestinal ischemia is further classified based on etiology, which dictates management: (1) arterioocclusive mesenteric ischemia, (2) nonocclusive mesenteric ischemia, and (3) mesenteric venous thrombosis.”
Which conditions might be associated with arterioocclusive mesenteric ischemia?
“Risk factors for arterioocclusive mesenteric ischemia are generally acute in onset and include atrial fibrillation, recent myocardial infarction, valvular hear disease, and recent cardiac or vascular catheterization, all of which result in embolic clots reaching the mesenteric circulation.”
What are the causes of nonocclusive mesenteric ischemia?
Intestinal angina, cardiogenic or septic shock, high-dose vasopressor infusion and cocaine overdose. It might also complicate cardiovascular surgery.
What is the association between cardiovascular surgery and gastrointestinal ischemia? How frequent is this association?
“Nonocclusive mesenteric ischemia is the most prevalent gastrointestinal disease complicating cardiovascular surgery. The incidence of ischemic colitis following elective aortic repair is 5-9% and the incidence triples in patients following emergent repair.”
Name two colonic points susceptible to ischemia and explain the reason why it is so.
“Collateral vessel within the colon meet at the splenic flexure and descending/sigmoid colon. These areas, which are inherently at risk for decreased blood flow, are known as Griffith’ point and Sudeck’s point, respectively, and are the most common locations for colonic ischemia.”
The splenic flexure might receive more percentage of cardiac output than the kidneys.
True or False?
True.
The splenic flexure can receive up to 30% of the cardiac output, in comparison to 20-25% of renal vascular flow.
What is the most frequent origin of intestinal embolization? Where does it embolize to more frequently?
“Emboli originate from the heart in more than 75% of cases and lodge preferentially in the superior mesenteric artery just distal to the origin of the middle colic artery.”
Even in the early phases of intestinal ischemia, there might be bacteremia due to translocation of bacteria across the intestinal mucosa.
True or False?
True.
How high is the mortality associated with intestinal ischemia?
> 50%
What are the main symptoms of acute intestinal ischemia?
“severe acute, nonremitting abdominal pain strikingly out of proportion to the physical findings. Associated symptoms may include nausea and vomiting, transient diarrhea, anorexia, and bloody stools.”
Which findings might occur in early and late acute intestinal ischemia?
“With the exception of minimal abdominal distension and hypoactive bowel sounds, early abdominal examination is unimpressive. Later findings will demonstrate peritonitis and cardiovascular collapse.”
What would you look for in an abdominal radiography if you suspected of intestinal ischemia?
“A plain abdominal film may show evidence of free intraperitoneal air, indicating a perforated viscs and the need for emergent exploration. Earlier features of intestinal ischemia seen on abdominal radiographs include bowel-wall edema, known as “thumbprinting.” If the ischemia progresses, air can be seen within the bowell wall (pneumatosis intestinalis) and within the portal venous system. Other features include calcifications of the aorta and its tributaries, indicating athersclerotic disease.”
What is the greatest limitation of duplex imaging?
Body habitus (obesity for example).
The key to early diagnosis of arterial embolus as the cause of arterioocclusive mesenteric ischemia is mesenteric angiography.
True or False?
False.
Early laparotomy.
Mesenteric duplex with a high peak velocity of flow in the superior mesenteric artery is associated with an approximately 80% positive predictive value of mesenteric ischemia. This is the significant use of this technique.
True or False?
False.
While the predictive valor is indeed 80%, “More significantly, a negative duplex scan virtually precludes the diagnosis of mesenteric ischemia.”
You have the suspicion that a patient has chronic intestinal ischemia. Mesenteric angiography is not an option since the patient has severe chronic renal insufficiency. Which technique might be useful?
Colonoscopy (evaluation of the splenic flexure).
Which indicators are important in arterioocclusive mesenteric ischemia that require surgical exploration?
“Surgical exploration should not be delayed if suspicion of acute occlusive mesenteric ischemia is high or evidence of clinical deterioration or frank peritonitis is present.”
The small-intestine becomes ischemic while the colon is spared in the occlusion of the superior mesenteric artery.
True or False?
False.
“In the case of superior mesenteric artery occlusion where the embolus usually lies just proximal to the origin of the middle colic artery, the proximal jejunum is often spared while the remainder of the small bowel to the transverse colon will be ischemic.”
Name investigational markers for intestinal ischemia.
D-dimer, glutathione S-transferase, platelet-activating factor and mucosal pH monitoring.
What is the most important intervention to maintain hemodynamics in intestinal ischemia and which one is to be avoided?
Fluid resuscitation and vasoconstricting agents, respectively.
Which ischemic etiology most frequently involves the rectosigmoid region?
Nonocclusive mesenteric ischemia (inferior mesenteric artery).
How does one classify the intestinal ischemia macroscopically (colonoscopy)?
“Ischemia of the colonic mucosa is graded as mild with minimal mucosal erythema or as moderate with pale mucosal ulcerations and evidence of extensions to the muscular layer of the bowel wall. Severe ischemic colitis presents with severe ulcerations resulting in black or green discoloration of the mucosa, consistent with full-thickness bowell-wall necrosis.”
How reversible is ischemia depending on its classification?
Mild ischemia: almost 100% reversible
Moderate ischemia: approximately 50% reversible
Severe ischemia: irreversible
