Mesenteric Artery Ischemia Treatment & Management

• Nonocclusive mesenteric ischemia is treated medically, while acute and chronic ischemia is correctable with surgery. The first step in treating nonocclusive ischemia is identifying the underlying cause and, once found, correcting it. For instance, if a patient is found to have vasospastic disease, direct injection of papaverine into the SMA may resolve the vasospasm. If resolution with papaverine occurs, start an infusion of 30-60 mg/h.
• Patients with refractory vasospasm may undergo surgery to improve flow to the ischemic bowel.
• In some patients with embolic disease, intra-arterial papaverine has reversed the ischemia and averted operation.
• If hypovolemia is considered likely, fluid resuscitation is required.
• Start all patients with possible bowel ischemia on broad-spectrum antibiotics to cover the possibility of bowel necrosis with contamination.

In cases of acute mesenteric ischemia, the surgeon should decide the location of viable versus nonviable bowel during surgery. Laparotomy reveals that the entire small bowel and proximal colon are affected in patients with SMA thrombosis, reflecting the proximal nature of this disorder. In contrast, patients with SMA embolization have sparing of their proximal jejunum, reflecting the more distal obstruction.

In patients with extensive bowel involvement, make every effort to retain every centimeter of viable bowel. If determining bowel viability is difficult, a second look may be required 24-48 hours later. Patients with emboli are treated with an embolectomy by exposing the SMA below the mesocolon distal to the middle colic artery. A longitudinal arteriotomy is made, and a Fogarty catheter is passed distal to the embolus, is inflated, and is used to extract the embolus. If closure of the arteriotomy is difficult, a patch graft may be used or the patient may require an endarterectomy. Other methods of reperfusion involving prosthetic bypass grafting or autogenous vein grafting have also been performed, and the reader is directed to a surgical technique manual for further discussion.

Kougias et al compared the effectiveness of balloon angioplasty and/or endovascular stenting (48 patients, 58 vessels) with that of open revascularization (96 patients, 157 vessels) in the treatment of chronic mesenteric ischemia.^[4] The investigators found that members of the endovascular group had a shorter hospital stay (3 days) than did patients in the open revascularization group (12 days, P < 0.03) and that the 30-day mortality rate, frequency of inhospital complications, and 3-year cumulative survival rate were the same for both groups.

Three years after the procedures, however, cumulative freedom from recurrent symptoms was found in a higher percentage of open revascularization patients than in members of the endovascular group (66% vs 27%, P < 0.02). The authors suggested that this was because the percentage of patients who underwent a 2-vessel procedure rather than a 1-vessel intervention was higher in the open group than in the endovascular one.

Another study compared the outcomes of patients with chronic mesenteric ischemia who were treated with open mesenteric revascularization before (pre-endo group) and after (post-endo group) the preferential use of endovascular revascularization. The results found that patients treated post-endo presented with higher rates of hypertension, hyperlipidemia, cardiac interventions, and dysrhythmias; higher comorbidity scores; and more extensive mesenteric artery disease. However, similar outcomes for operative mortality, morbidity, length of stay, and immediate symptom improvement were noted in both the pre-endo and post-endo groups. Primary and secondary patency rates and recurrence-free survival rates were 82%, 86%, and 84% in the pre-endo group and 81%, 82%, and 76% in the post-endo group, respectively, at 5 years.^[5]

• Patients with chronic mesenteric ischemia may have nutritional and/or electrolyte imbalances. Correct these deficiencies to prevent intraoperative and postoperative complications.
• If possible, patients undergo bowel preparation the night before surgery and take nothing by mouth after midnight the evening before surgery.
• In patients with acute ischemia, immediate repletion of fluids and correction of any acid-base abnormalities is necessary, followed by operation without delay.
• All patients receive broad-spectrum antibiotic therapy prior to the operation.
• Type and crossmatch 4 units of packed red blood cells.
• If the angiogram shows embolic disease of the SMA, start intra-arterial papaverine.
• A nasogastric tube may help alleviate some of the patient's pain by reducing bowel distention.
• If the surgeon thinks a patient may require extensive resection and that lifelong hyperalimentation will be the only option, this possibility should be thoughtfully discussed with the patient and his or her family to help guide the surgeon during the exploration. These types of issues are best decided beforehand, with educated input from the patient, rather than during surgery, by the surgeon.

• During direct visualization of the bowel, establish viability. If the first part of the jejunum is not involved, an embolus may be present and immediate embolectomy may be indicated. Look for peristalsis, and observe the color of the bowel (pink and healthy vs red and edematous). A gross specimen is depicted in the image below. Following reconstitution of arterial flow, the viability of the bowel is reassessed. This is based on clinical findings, including the color of the bowel and the presence or absence of palpable pulses. Gross specimen showing hemorrhagic dead bowel.
• Intraoperative Doppler scans of the bowel can provide valuable information on the patency of the vessels. One gram of intravenous fluorescein followed by bowel examination under a Wood lamp can help delineate poorly perfused bowel. Institute intraoperative anticoagulation therapy with intravenous heparin.
• The most reliable method of determining bowel viability is a second-look laparotomy. The decision to perform a second look is made during the initial exploration. If a second look is deemed necessary, the surgeon should not change his or her mind, regardless of the patient's clinical progress.

• Monitor blood pressure and hemoglobin parameters to evaluate for sepsis or hemorrhage.
• Continue heparin anticoagulation postoperatively to reduce thrombotic events, and papaverine may be administered to reduce vasospasm.
• Perform a 12-lead ECG to evaluate for myocardial dysfunction.
• Consider an echocardiogram to evaluate for valvular vegetations.
• A patient can be expected to have a postoperative ileus because of bowel reperfusion.
• Continuation of antibiotics postoperatively is required to prevent any septic events.

• Because of the high likelihood of concomitant vascular disease in the rest of the arterial tree, patients must be closely monitored.
• Any laboratory or radiologic examinations not previously performed in the hospital are performed in an outpatient setting.
• The patient should have frequent visits to monitor the prothrombin time, activated partial thromboplastin time, and international normalized ratio to assure proper anticoagulation.

Because of the high prevalence of atherosclerosis, one of the most common complications involves MI. Prevent postoperative MI by identifying correctable coronary artery disease before the patient enters the operating room, if possible. During the perioperative period, use a Swan-Ganz catheter to monitor fluid and cardiac function. Finally, when cross-clamping the supraceliac aorta, notify the anesthesiologist, who can use myocardial protective maneuvers and afterload reduction to maximize cardiac output.

Acute renal failure in the immediate postoperative period can be prevented by keeping the patient well hydrated and administering mannitol before the aorta is cross-clamped.

Other possible complications include bleeding, infection, bowel infarction, prolonged ileus, and graft infection.

Because of the delay in diagnosis, mesenteric artery ischemia is typically a lethal disease, with a mortality rate of 45-65%. When more than half the bowel is removed, mortality rates of up to 80% have been reported. A review of 45 studies demonstrated that the prognosis for patients with acute mesenteric ischemia differs when one looks at the etiology. Mortality rates are highest for patients with arterial thrombosis (70-87%), followed by nonocclusive mesenteric ischemia (70-80%), arterial embolism (66-71%), and venous thrombosis (44%). Mortality rates have been improving over the last 4 decades.

Over the past 20 years, diagnosis and treatment of mesenteric ischemia has advanced only minimally.

• In a review of 57 cases, only 18% of patients were properly diagnosed with mesenteric ischemia before operation or death. Of the 57 patients in this review, 46 died.
• Some advances in diagnosis include magnetic resonance imaging and laser Doppler flowmetry.^[6] Preliminary results for these modalities are encouraging.
• Percutaneous transluminal angioplasty with stenting has proven valuable as a treatment option in selected patients.^{[7, 8, 9, 10, 11]} A study demonstrated that, at 6 months, patency was equivalent between stenting and open revascularization; however, freedom from symptoms was less in the stented group.
• As previously mentioned, similar results were found in a study by Kougias et al, in which the effectiveness of balloon angioplasty and/or endovascular stenting (48 patients, 58 vessels) was compared with that of open revascularization (96 patients, 157 vessels) in the treatment of chronic mesenteric ischemia.^[4] The investigators determined that members of the endovascular group had a shorter hospital stay (3 days) than did patients in the open revascularization group (12 days, P < 0.03) and that the 30-day mortality rate, frequency of inhospital complications, and 3-year cumulative survival rate were the same for both groups.
• Three years after the procedures, however, cumulative freedom from recurrent symptoms was found in a higher percentage of open revascularization patients than in members of the endovascular group (66% vs 27%, P < 0.02). The authors suggested that this was because the percentage of patients who underwent a 2-vessel procedure rather than a 1-vessel intervention was higher in the open group than in the endovascular one.
• Some authors recommend a trial of thrombolytic therapy if patients can be treated within 8 hours of presentation and do not have signs of bowel necrosis or peritonitis.^[12] If no evidence of improvement is noted within 4 hours, patients should undergo exploration.
• Local tissue plasminogen activator may reduce the amount of bowel requiring resection.