Review Question - QID 217648

This patient with a history of atrial fibrillation presents with severe right leg pain, poikilothermia (cold extremity), pallor, and pulselessness, which are indicative of acute limb ischemia secondary to an embolism. After embolectomy, this patient is at an increased risk for a limb reperfusion injury that would present with paresthesias, motor deficits, and decreased pulse.

Reperfusion injuries occur after restoration of blood flow after a period of tissue ischemia. Tissue ischemia results in increased capillary permeability, leading to interstitial edema. During reperfusion, molecular oxygen is re-introduced into formerly ischemic tissue in which oxidative phosphorylation was impaired, resulting in the immediate formation of toxic reactive oxygen species. Inflammatory mediators are also recruited to the affected tissue. This results in more interstitial edema and increases compartment pressures, leading to the risk for acute compartment syndrome. Treatment for preventing reperfusion injury includes regional limb cooling, hypertonic saline, statins, and ethyl pyruvate. These therapies all seek to decrease inflammation in the area of reperfusion.

Kalogeris et al. review the pathophysiology of reperfusion injury. The authors highlight the role of reactive oxygen species and pro-inflammatory neutrophils in tissue damage after reperfusion of ischemic tissue. They recommend that treatment at the time of reperfusion would only be effective in cases where a critical mass of tissue has not yet undergone irreversible ischemia.

Incorrect Answers:
Answer 1: Acute compartment syndrome would present with pain out of proportion to clinical findings, paresthesias, weakness/paralysis, pain with passive motion, and an elevated pressure as measured with a needle manometer (difference between diastolic pressure and compartment pressure <= 30 mmHg; however, this is a clinical diagnosis). Acute compartment syndrome is treated with an emergency fasciotomy to relieve compartment pressures.

Answer 2: Critical limb ischemia is a condition characterized by ischemic limb pain, gangrene, or ulceration in the setting of peripheral arterial disease. It is caused by a atherosclerotic occlusion of an artery, resulting in limb-threatening ischemia. This patient’s acute limb ischemia was most likely caused by an embolism from his atrial fibrillation, not peripheral arterial disease, as his left leg was normal and he does not have ischemic pain at rest (which is required for a diagnosis of critical limb ischemia).

Answer 4: Recurrent arterial embolization could result in a similar constellation of symptoms as the initial presentation due to the development of limb ischemia such as paresthesias and pallor; however, the development of a second emboli that lodges in the exact same location as the first emboli is relatively low. Treatment of recurrent embolization would be embolectomy or bypass.

Answer 5: Sepsis is a potential complication of any surgical procedure due to the introduction of pathogens into surgical wounds. Additionally, post-operative pneumonia or urinary tract infections can also lead to sepsis. Sepsis presents with fever, chills, tachycardia, tachypnea, and leukocytosis. While this patient did undergo a surgical embolectomy, he is at higher risk for limb reperfusion injury given his acute limb ischemia.

Bullet Summary:
Reperfusion injury occurs after a period of limb ischemia, resulting in the generation of toxic reactive oxygen species during reperfusion, causing interstitial edema, increased compartment pressures, and possible compartment syndrome.