Mesenteric Ischaemia

Abdominal surgical emergncy due to interruption of blood supply to the abdominal viscera, which can be classified by aetiology:

Arterial occlusion causes ~50% of cases, and venous occlusion for ~10%.

Epidemiology and Risk Factors

Risk Factors for Mesenteric Ischaemia
Arterial Occlusion Venous Occlusion Non-Occlusive
  • Embolic disease
    • AF
    • Endocarditis
    • Cardiac surgery
    • LV aneurysm
  • Atherosclerotic disease
    • HTN
    • Dyslipidaemia
    • Chronic mesenteric ischaemia
  • Arterial disease
    • Aneurysm/dissection
    • PVD
  • Recent arterial intervention
    • Angiography
    • VA ECMO
    • IABP
  • Thrombophilia
    • Factor V Leiden
    • Protein C/S deficiency
    • Antiphospholipid syndrome
    • Malignancy
    • OCP use
  • Abdominal inflammation
    • Pancreatitis
  • Inflammatory bowel disease
  • Portal hypertension
  • Abdominal surgery
    • Splenectomy
  • Active shock state
    Particularly non-distributive shock.
  • High-dose vasopressor use

Chronic mesenteric ischaemia occurs to atherosclerotic plaque causing partial occlusion of the mesenteric vessels, leading to a form of ‘intestinal angina’ characterised by:

  • Post-prandial pain
  • Weight loss
  • “Food fear”

Pathophysiology

  • Arterial occlusion results in ischaemia of a single vascular territory
  • Non-occlusive ischaemia results in watershed ischaemia
    • Pancreas, between the coeliac and SMA
    • Splenic flexure, between the SMA and IMA

The SMA is the most vulnerable to embolic ischaemia due to a higher blood flow rate, larger diameter, and low take-off angle from the abdominal aorta. Emboli classically lodge 3-10cm from the origin of the SMA, and spare the proximal jejunum and colon.

Clinical Features

Diagnosis requires a high level of clinical suspicion.

Features are generally non-specific, aetiology is determined on history and investigations:

The exception is that arterial occlusion typically has an abrupt onset, venous occlusion and NOMI have a more subacute onset.

Pain in NOMI classically id more diffuse and associated with a period of low CO.

  • Abdominal pain
    Typically severe and out of proportion to the clinical exam findings.
  • Nausea, vomiting
  • Diarrhoea
  • PR bleeding
  • Peritonism
    Late sign, generally indicates irreversible ischaemia and bowel necrosis.

Diagnostic Approach and DDx

Investigations

Blood:

  • Lactate
    • Metabolic acidosis with ↑ lactate occurs in ~90% of patients
    • Lactataemia is not sufficient for diagnosis, but should prompt consideration for CT

Imaging:

  • CT mesenteric angiogram
    • Bowel ischaemia
      • Portal venous gas
      • Intestinal pneumatosis
SMA Occlusion

Other:

  • Endoscopy
    • Visual identification of ischaemia

Management

  • Treat shock
  • Restore perfusion to ischaemic areas, if possible
  • Urgent resection of non-viable bowel prior to perforation

Resuscitation:

  • C
    • Fluid resuscitation
    • Arterial line
    • Vasopressors should be used to avoid fluid overload
      • Milrinone and dobutamine are preferable
    • Correct underlying shock state
  • G
    • Nasogastric decompression
    • Correct concurrent or underlying shock

Specific therapy:

  • Pharmacological
    • Anticoagulation
      For venous ischaemia.
      • Unfractionated heparin infusion
  • Procedural
    • Laparotomy
      • Mandated for overt peritonitis
      • Resect non-viable regions
      • Damage control surgery is normal and planned re-look laparotomy within 48 hours is usual
    • Restoration of arterial perfusion
      • Endovascular
        • Stenting
        • Catheter-directed thrombolysis or clot retrieval
          Can be available for venous or arterial occlusion.
      • Open repair (including bypass)
  • Physical

Identifying massive gut necrosis should prompt re-evaluation of the appropriateness of curative intent.

Supportive care:

Disposition:

Marginal and Ineffective Therapies

  • Intravenous thrombolysis
    Successful cases are described, but this is precluded by bowel ischaemia or infarction and so if used must be attempted early.

Anaesthetic Considerations

Complications

  • Death
  • G
    • Short bowel syndrome
      After resection.
    • Perforation

Prognosis

Mortality depends intestinal viability, and therefore early diagnosis. In general:

  • Occlusive arterial ischaemia has a good prognosis with early detection and aggressive intervention
  • Occlusive venous ischaemia has a good prognosis, assuming no bowel necrosis
  • The prognosis in NOMI depends on the underlying condition and response to shock

Key Studies

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.
  2. Bala M, Kashuk J, Moore EE, et al. Acute mesenteric ischemia: guidelines of the World Society of Emergency Surgery. World Journal of Emergency Surgery. 2017;12(1):38.