Title: Acute Mesenteric Ischemia and Infarction
1Acute Mesenteric Ischemia and Infarction
- foolad Eghbali M.D.
- Vascular surgeon
- Rasool Akram Hosp.
2 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
3- 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.
4- since 1930, many advances have been made that
allow earlier diagnosis and treatment. - Whereas the prognosis remains grave
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7Superior Mesenteric Artery (SMA)
- Largest caliber vessel 45-degree angle makes it
most commonly occluded
Aorta
Celiac Trunk
SMA
IMA
8 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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10Superior Mesenteric Artery (SMA)
- Emboli occlude past the middle colic, causing
small bowel ischemia
Middle Colic
SMA
Jejunal Ileal Arteries
Occlusion Point
Right Colic
Ileocolic
11Pathophysiology
- 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).
12Etiologies 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
13Etiologies of Acute Mesenteric Ischemia (AMI)
- Focal small bowel ischemia - rare
- Partial malrotation, volvulus, mesenteric
hematoma, strangulated hernia - Unknown
- ?Mesenteric small vessel disease
14- 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
15- 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
16- 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)
17- 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
18Epidemiology
- 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
19Prognosis
- 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.
20History 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
21History 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
22History Physical
- Mesenteric Venous Thrombosis
- Fever
- Abdominal distension
- Hemoccult positive stool
23Physical 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.
24- 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.
25Complications
- Bowel necrosis necessitating bowel resection
- Septic shock
- Death
26Diagnostic 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.
27Laboratory Findings
- Anion gap metabolic acidosis
- Elevated arterial/venous lactate
- Leukocytosis
- Hemoconcentration
- Elevated LDH, amylase, AST, and CPK
- Elevated K and Phos are late signs
28Radiology
- 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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33Differential Diagnosis
- Other serious conditions to consider
- Pancreatitis
- Acute Diverticulitis
- Acute Cholecystitis
- Small bowel obstruction
- Perforation of a viscous
- Ruptured aneurysm
34Treatment
- 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,
35- 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
36Surgical 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
37- 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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