Causes and Management of Non-Occlusive Mesenteric Ischemia (NOMI)

Primary Causes

Low flow states or shock, particularly cardiogenic shock, are the most common causes of NOMI, according to the American Heart Association 1, 2
Heart failure with poor cardiac output is a significant risk factor, as stated by the World Journal of Emergency Surgery 3, 4
Hypovolemia leading to reduced splanchnic perfusion is a contributing factor 5
Renal failure, which contributes to altered hemodynamics, is a risk factor 4
Cardiac surgery using cardiopulmonary bypass is a risk factor 4
Post-coarctation repair or after surgical revascularization for intestinal ischemia are risk factors, as reported by the American College of Cardiology 1, 2

Vasoconstrictor medications, including vasopressors (norepinephrine, epinephrine), vasopressin, cocaine, amphetamines, ergot derivatives, and digoxin, can cause mesenteric arterial vasospasm despite patent vessels, as warned by the World Journal of Emergency Surgery 1, 2, 5

Sepsis and multi-organ dysfunction are risk factors for NOMI, according to the World Journal of Emergency Surgery 4, 5
Abdominal compartment syndrome with high intra-abdominal pressure is a risk factor 4
Hemodialysis is a risk factor 4

NOMI occurs due to SMA vasoconstriction associated with reduced splanchnic blood flow, affecting approximately 20-30% of all cases of acute mesenteric ischemia, as reported by the World Journal of Emergency Surgery 3

Critically ill patients in intensive care units are at high risk, as stated by the World Journal of Emergency Surgery 5
Patients with COVID-19 are at risk due to hypercoagulability and fibrinolysis shutdown, according to the World Journal of Emergency Surgery 4

NOMI should be suspected in critically ill patients with abdominal pain or distension requiring vasopressor support, as recommended by the World Journal of Emergency Surgery 5
Early diagnosis is challenging, but right-sided abdominal pain with passage of maroon or bright red blood in stool is highly suggestive of NOMI, as reported by the World Journal of Emergency Surgery 5
Arteriography remains the gold standard for diagnosis, demonstrating characteristic mesenteric arterial vasospasm, as stated by the American College of Cardiology 1, 2

Initial treatment should focus on correcting the underlying shock state and improving cardiac output/peripheral perfusion, as recommended by the American College of Cardiology 1, 2
Transcatheter administration of vasodilator medications (particularly papaverine) into the area of vasospasm is indicated in patients who don't respond to systemic supportive treatment, as suggested by the American College of Cardiology 1, 2
Laparotomy and resection of nonviable bowel is necessary in patients with persistent symptoms despite treatment, as recommended by the American College of Cardiology 1, 2

The American College of Radiology recommends that an ABG should be obtained in patients with suspected mesenteric ischemia to detect metabolic acidosis and elevated lactate levels, which serve as markers of advanced bowel ischemia and tissue hypoperfusion 6
Laboratory findings, including ABG results, are of little value early in the disease course and are insufficient for making the diagnosis of mesenteric ischemia 6
Metabolic acidosis detected on ABG reflects tissue hypoperfusion and anaerobic metabolism from ischemic bowel, indicating that bowel injury has already progressed significantly 6
Elevated lactate levels correlate with the extent of bowel necrosis and are associated with higher mortality rates 6
Normal ABG results do not exclude mesenteric ischemia, as 25% of patients with acute mesenteric ischemia will have normal initial laboratory findings 6

The World Journal of Emergency Surgery suggests that ABG helps assess the severity of illness and degree of systemic compromise in patients with suspected mesenteric ischemia, particularly in critically ill patients requiring vasopressor support 7
CTA of the abdomen and pelvis should be the first-line diagnostic test when mesenteric ischemia is suspected, not laboratory testing, with a sensitivity and specificity of 93-100% for diagnosing mesenteric ischemia 6, 8, 9
A high index of suspicion combined with rapid CTA imaging is necessary for early diagnosis—laboratory tests including ABG should not delay definitive imaging 6