Rosen & Barkin's 5-Minute Emergency Medicine Consult (449 page)

• Decreased or occluded blood flow through the mesenteric vessels leading to ischemic or infarcted bowel
  
• Can be from arterial or venous blockage, or low flow states.
  
• 1 in 1,000 of all hospital admissions
  
• 1–2% of all admissions for abdominal pain:
  
  • Most cases occur in patients >50 yr.
    
  • Mortality as high as 60–70%, particularly if diagnosis/presentation delayed >24 hr
    

• Acute mesenteric arterial embolism:
  
  • 50% of cases of acute mesenteric ischemia
    
  • Mean age 70 yr
    
  • Emboli most commonly arise in left atria or ventricle, from a dysrhythmia, valvular lesions, or ventricular thrombus from a prior MI
    
  • Typically lodge 3–10 cm distal to the origin of the superior mesenteric artery (SMA):
    
    • Preserves blood flow to proximal small and large bowel
      
  • Risk factors include dysrhythmia (especially atrial fibrillation), valvular heart disease, prior MI, aortic aneurysm, or dissection.
    
• Mesenteric artery thrombus:
  
  • SMA thrombus in 15% of cases of acute mesenteric ischemia
    
  • Rare in other vessels
    
  • Develops from plaque rupture of mesenteric atherosclerotic disease
    
  • 50–80% may have longstanding intestinal angina (chronic mesenteric ischemia).
    
  • Risk factors include age, atherosclerotic disease, HTN.
    
• Mesenteric venous thrombosis:
  
  • 5–15% of cases of acute mesenteric ischemia
    
  • Subacute/indolent presentation
    
  • 20–40% mortality
    
  • Typically occurs in younger patients with underlying hypercoagulable state
    
  • Risk factors include:
    
    • Hypercoagulable state (lupus, protein C and S deficiency)
      
    • Sickle cell disease
      
    • Antithrombin III deficiency
      
    • Malignancy (particularly portal)
      
    • Pregnancy
      
    • Sepsis
      
    • Renal failure on dialysis
      
    • Estrogen therapy
      
    • Recent trauma or inflammatory conditions
      
• Nonocclusive mesenteric ischemia:
  
  • 20–30% of cases of acute mesenteric ischemia
    
  • Occurs in low cardiac output states with decreased mesenteric blood flow
    
  • Risk factors include CHF, sepsis, hypotension, hypovolemia, diuretic use, recent surgery (especially cardiac), or recent vasopressor requirement.
    
  • Poorer survival rates
    
• Chronic mesenteric ischemia:
  
  • “Intestinal angina”:
    
    • Postprandial, diffuse abdominal pain occurring ∼1 hr after eating, lasts 1–2 hr
      
    • Patients may develop food aversions and eat small meals to avoid pain.
      
• Uncommon causes:
  
  • Spontaneous mesenteric arterial dissection
    
  • Median arcuate ligament syndrome—compression of the celiac axis or SMA by the arcuate ligament of the diaphragm
    
  • Extrinsic compression from tumors
    
  • Medications:
    
    • Digitalis
      
    • Ergotamine
      
    • Cocaine
      
    • Pseudoephedrine
      
    • Vasopressin
      

DIAGNOSIS

• Sudden-onset, severe, diffuse abdominal pain in acute ischemia:
  
  • Pain out of proportion to exam:
    
    • Patients may have relatively benign abdominal exam despite severe pain.
      
• Nausea
  
• Vomiting
  
• Diarrhea
  
• Occult GI bleeding
  
• Elderly patients can have nonspecific symptoms such as altered mental status, tachypnea, or tachycardia.
  
• Late findings:
  
  • Peritoneal signs owing to irreversible bowel ischemia
    
  • Abdominal distention
    
  • Hypoactive bowel sounds
    

Rapidity of onset of pain

Abdominal pain out of proportion to physical exam during the acute phase of illness

Maintain a high index of suspicion in patients >50 yr old with unexplained abdominal pain.

• Often nonspecific and nondiagnostic
  
• CBC:
  
  • Elevated WBC count (90% >15,000)
    
• Chemistry panel:
  
  • Approximately 50% have a metabolic acidosis.
    
• Amylase:
  
  • Elevated amylase found in 50% of cases
    
• Creatine phosphokinase (CPK) may be elevated.
  
• Lactate:
  
  • Elevated in 90% of patients
    
  • Indicative of advanced tissue damage, may not be elevated early in ischemic course.
    
  • High levels correlate with mortality.
    

• Flat and upright abdominal radiographs:
  
  • Often obtained to rule out acute obstruction or perforation
    
  • Frequently normal
    
  • Late findings:
    
    • Thumbprinting from bowel wall edema and hemorrhage
      
    • Pneumatosis intestinalis: Air in bowel wall from tissue necrosis
      
    • Pneumobilia is a late finding associated with poor outcomes
      
• Abdominal CT scan:
  
  • Can detect bowel wall edema, pneumatosis
    
  • Newer helical and multidetector CT (MDCT) scanners can directly visualize mesenteric vascular anatomy and localize sites of occlusion
    
  • MDCT angiography is more frequently the imaging modality of choice
    
• MRI:
  
  • Excellent images of mesenteric vasculature especially with MR angiography
    
  • Acquisition time and availability limits utility
    
• Angiography:
  
  • Historically the gold standard diagnostic modality, now being replaced by MDCT
    
  • Allows for direct visualization of emboli and administration of vasodilating or fibrinolytic agents
    
  • Invasive, time-consuming, and potentially nephrotoxic
    
• Doppler US:
  
  • Can detect decreased blood flow in SMA but more helpful in chronic mesenteric ischemia
    
  • For optimal results the patient should be NPO for 8 hr, limiting the utility of this study in the ED
    

• Bowel obstruction
  
• Volvulus
  
• GI malignancy
  
• Diverticulitis
  
• Inflammatory bowel disease
  
• Peptic ulcer disease
  
• Perforated viscus
  
• Cholecystitis
  
• Ascending cholangitis
  
• Pancreatitis
  
• Appendicitis
  
• Abdominal aortic aneurysm
  
• MI
  
• Renal stones
  

TREATMENT

Initiate fluid replacement for dehydrated or hypotensive patients.

• Airway, breathing, and circulation management (ABCs) with fluid resuscitation as needed
  
• Caution:
  
  • Early diagnosis and intervention is critical to decrease mortality.
    

• General measures:
  
  • Nasogastric suction to decompress the stomach and bowel
    
  • NPO
    
  • Electrolyte replacement as needed
    
  • Cardiac monitor for dysrhythmia
    
  • Consider invasive cardiac monitoring if patient is unstable
    
  • Monitor urine output
    
  • Analgesics
    
  • Broad-spectrum antibiotics to cover bowel flora (may need to adjust dose if concomitant renal failure):
    
    • Piperacillin/tazobactam
      
    • Ampicillin/sulbactam
      
    • Ticarcillin/clavulanate
      
    • Alternatives include imipenem, meropenem, 3rd-generation cephalosporins + metronidazole
      
  • Anticoagulation with heparin
    
  • Surgical consultation: All patients with peritoneal signs should have exploratory laparotomy.
    
• Specific therapies:
  
  • Papaverine 30–60 mg/h intra-arterial:
    
    • Phosphodiesterase inhibitor causes mesenteric vasodilatation.
      
    • Administered through angiography catheter
      
  • Intra-arterial thrombolytics can be used.
    
  • Surgical revascularization often indicated
    
• Caution:
  
  • Avoid vasoconstrictive medications, which may worsen ischemia:
    
    • If vasopressors are needed, use agents with less impact on mesenteric perfusion—consider dobutamine, low-dose dopamine, milrinone.
      

• Ampicillin/sulbactam: 3 g IV q6h (peds: 100–200 mg/kg/d)
  
• Heparin sulfate: 80 U/kg IV bolus followed by 18 U/kg/h infusion
  
• Metronidazole: 1 g IV bolus followed by 500 mg IV q6h (peds: 12 mg/kg IV bolus, then 7.5 mg/kg IV q6h)
  
• Piperacillin/tazobactam: 3.375 g IV q6h (peds: 240–400 mg/kg/d)
  
• Ticarcillin/clavulanate: 3.1 g IV q4–6h
  

FOLLOW-UP

Admit all patients with mesenteric ischemia.

None

Surgical consultation

• Aggressive pursuit of diagnosis is mandatory.
  
• Mortality rises to 80% when the diagnosis is made >24 hr after symptom onset.
  
• Early surgical evaluation for emergent operative intervention is mandatory.
  

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