Acute Mesenteric Ischemia and Infarction

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Acute Mesenteric Ischemia and Infarction

• foolad Eghbali M.D.
• Vascular surgeon
• Rasool Akram Hosp.

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Background

• Acute mesenteric ischemia (AMI) is a syndrome in
  which inadequate blood flow through the
  mesenteric vessels causes ischemia and eventual
  gangrene of the bowel wall.
• Either arterial or venous disease

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• Arterial disease may be subdivided into
  nonocclusive mesenteric ischemia (NOMI)and
  occlusive mesenteric arterial ischemia (OMAI).
• OMAI may be further subdivided into acute
  mesenteric arterial embolus (AMAE) and acute
  mesenteric arterial thrombosis (AMAT). Venous
  disease takes the form of mesenteric venous
  thrombosis (MVT).
• AMI comprises 4 different primary clinical
  entities NOMI, AMAE, AMAT, and MVT.

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• since 1930, many advances have been made that
  allow earlier diagnosis and treatment.
• Whereas the prognosis remains grave

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Superior Mesenteric Artery (SMA)

• Largest caliber vessel 45-degree angle makes it
  most commonly occluded

Aorta
Celiac Trunk
SMA
IMA
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The celiac artery (CA) supplies the foregut,
hepatobiliary system, and spleen the SMA
supplies the midgut (ie, small intestine and
proximal mid colon) and the inferior mesenteric
artery (IMA) supplies the hindgut (ie, distal
colon and rectum). However, multiple anatomic
variants are observed. Venous drainage is through
the superior mesenteric vein (SMV), which joins
the splenic vein to form the portal vein
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Superior Mesenteric Artery (SMA)

• Emboli occlude past the middle colic, causing
  small bowel ischemia

Middle Colic
SMA
Jejunal Ileal Arteries
Occlusion Point
Right Colic
Ileocolic
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Pathophysiology

• Insufficient perfusion of the small bowel and
  colon may result from arterial occlusion by
  embolus or thrombosis (AMAE or AMAT), thrombosis
  of the venous system (MVT), or nonocclusive
  processes such as vasospasm or low cardiac output
  (NOMI).

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Etiologies of Acute Mesenteric Ischemia (AMI)

• SMA Occlusion (at least 60 of cases)
• Embolism MI, Afib, Endocarditis, Valve d.
• Thrombosis Atherosclerosis plaque rupture
• Nonocclusive Mesenteric Ischemia (NOMI)
• Atherosclerosis shock vasopressors
• Mesenteric Venous Thrombosis (MVT)
• Primary clotting disorder

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Etiologies of Acute Mesenteric Ischemia (AMI)

• Focal small bowel ischemia - rare
• Partial malrotation, volvulus, mesenteric
  hematoma, strangulated hernia
• Unknown
• ?Mesenteric small vessel disease

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• Causes of embolic AMI (AMAE) include the
  following
• Cardiac emboli - Mural thrombus after myocardial
  infarction, auricular thrombus associated with
  mitral stenosis and atrial fibrillation, septic
  emboli from valvular endocarditis (less frequent)
  
• Emboli from fragments of proximal aortic thrombus
  due to a ruptured atheromatous plaque
• Atheromatous plaque dislodged by arterial
  catheterization

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• Causes of thrombotic AMI (AMAT) include the
  following
• Atherosclerotic vascular disease (most common)
• Aortic aneurysm
• Aortic dissection
• Arteritis
• Decreased cardiac output from myocardial
  infarction or CHF (thrombotic AMI may cause acute
  decompensation)
• Dehydration from other causes

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• Causes of NOMI include the following
• Hypotension from CHF, myocardial infarction,
  sepsis, aortic insufficiency, severe liver or
  renal disease, or recent major cardiac or
  abdominal surgery
• Vasopressive drugs
• Ergotamines
• Cocaine
• Digitalis (whether digitalis use causes NOMI or
  patients who develop NOMI are older and are more
  likely to have been prescribed digitalis is
  unclear)

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• Causes of MVT include the following (gt80 of
  patients with MVT are found to have predisposing
  conditions)
• Hypercoagulability from protein C and S
  deficiency, antithrombin III deficiency,
  dysfibrinogenemia, abnormal plasminogen,
  polycythemia vera (most common), thrombocytosis,
  sickle cell disease, factor V Leiden mutation,
  pregnancy, and oral contraceptive use
• Tumor causing venous compression or
  hypercoagulability (paraneoplastic syndrome)
• Infection, usually intra-abdominal (eg,
  appendicitis, diverticulitis, or abscess)
• Venous congestion from cirrhosis (portal
  hypertension)
• Venous trauma from accidents or surgery,
  especially portocaval surgery
• Increased intra-abdominal pressure from
  pneumoperitoneum during laparoscopic surgery
• Pancreatitis

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Epidemiology

• Age
• Advanced age is a risk factor due to the
  association with atheroscleosis
• The overall prevalence of AMI is 0.1 of all
  hospital admissions
• No overall sex preference

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Prognosis

• The prognosis of AMI of any type is grave.
  Overall, the mortality rate in the last 15 years
  from all causes of AMI averages 71, with a range
  of 59-93. Once bowel wall infarction has
  occurred, the mortality rate is as high as 90.
  Even with good treatment, up to 50-80 of
  patients die.

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History Physical

• Classic Presentation
• Rapid onset of severe, unrelenting periumbilical
  pain
• Pain out of proportion to findings on physical
  examination.
• Nausea and vomiting
• Forceful/urgent bowel evacuation
• Risk factors for acute mesenteric ischemia

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History Physical

• SMA Thrombosis
• Prodrome of postprandial pain/nausea and weight
  loss
• Presentation with classic symptoms
• Non-occlusive Mesenteric Ischemia
• Unexplained decline in clinical status or failure
  to follow expected recovery

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History Physical

• Mesenteric Venous Thrombosis
• Fever
• Abdominal distension
• Hemoccult positive stool

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Physical Examination

• The different etiologies notwithstanding,
  physical examination findings are generally
  similar in patients with AMI. The main
  distinction is between early and late
  presentation. Early in the course of the disease,
  in the absence of peritonitis, physical signs are
  few and nonspecific. Tenderness is minimal to
  nonexistent. Stool may be guaiac positive.

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• Peritoneal signs develop late, when infarction
  with necrosis or perforation occurs. Tenderness
  becomes severe and may indicate the location of
  the infarcted bowel segment. A palpable tender
  mass may be present. Bowel sounds range from
  hyperactive to absent. Voluntary and involuntary
  guarding appears. Fever, hypotension,
  tachycardia, tachypnea, and altered mental status
  are observed. Foul breath may be noted with bowel
  infarction, from the putrefaction of undigested
  alimentary material accumulated proximal to the
  pathologic site
• Signs reflecting risk factors for AMI may be
  noted.

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Complications

• Bowel necrosis necessitating bowel resection
• Septic shock
• Death

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Diagnostic Considerations

• Because acute mesenteric ischemia (AMI) is a
  condition with an unclear initial presentation,
  serious morbidity, and a high mortality rate
  without proper treatment, clinical suspicion
  should remain high. Obtain early angiography if
  any suspicion of AMI exists. Subsequent treatment
  should be initiated as rapidly as possible. No
  patient in whom AMI is suspected should be
  discharged unless AMI can be ruled out.

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Laboratory Findings

• Anion gap metabolic acidosis
• Elevated arterial/venous lactate
• Leukocytosis
• Hemoconcentration
• Elevated LDH, amylase, AST, and CPK
• Elevated K and Phos are late signs

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Radiology

• Plain films thumbprinting, thickened bowel
  (lt40 sensitivity)
• CT thickened/dilated bowel, intramural
  hematoma, pneumatosis (64 sensitivity)
• MRI promising but untested to date
• Mesenteric angiography test of choice can
  identify the type of AMI

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Differential Diagnosis

• Other serious conditions to consider
• Pancreatitis
• Acute Diverticulitis
• Acute Cholecystitis
• Small bowel obstruction
• Perforation of a viscous
• Ruptured aneurysm

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Treatment

• Resuscitation with fluids/blood products
• Anticoagulation, Administer heparin as a bolus of
  80 U/kg, and then as an infusion at 18 U/kg/h
  until full conversion to oral warfarin
• Infusion of a vasodilator
• Glucagon systemically OR
• Papaverine through a catheter, Start an infusion
  of 30-60 mg/h after angiography,

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• Inpatient medications include the following
• Papaverine - For patients with arterial occlusive
  AMI or nonocclusive mesenteric ischemia (NOMI)
• Heparin - For patients who have mesenteric venous
  thrombosis (MVT) or have undergone
  revascularization
• Warfarin - For long-term treatment of patients
  with MVT or atrial fibrillation
• Broad-spectrum antibiotics and pain medications -
  For all patients
• Thrombolytics - For selected patients with
  embolic AMI
• Some experience with percutaneous endovascular
  interventions has been accumulated. In select
  cases, especially in isolated spontaneous
  dissection of the SMA, stent placement may offer
  the best option

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Surgical Care

• Before operative management of AMI, stabilize
  patients by means of intravenous (IV) fluid
  administration, antibiotic prophylaxis covering
  the colonic flora, nasogastric tube
  decompression, and bladder catheterization, with
  heparin or papaverine administered as indicated.
  Blood should be available

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• In all types of AMI, resection of necrotic bowel
  may be required if signs of peritonitis develop.
  Differentiation of nonviable from viable bowel
  can be enhanced by intraoperative fluorescein
  administration

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• Thank you