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Acute limb ischemia (ALI)

Evaluation and management

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Acute limb ischemia (ALI)

  2. 2. • Sudden loss of perfusion to the extremity/extremities of less than 14 days duration, resulting in variable ischemic clinical manifestations and the potential risk of limb loss. • Insufficient time for collaterals to compensate for loss of perfusion. • A matter of a few hours can mean the difference between a major amputation,limb salvage or death. INTRODUCTION 2
  3. 3. Depends on: —Degree of obstruction —Site of occlusion —Presence of Collaterals —Affected Tissue • Sluggish circulation distal to occlusion secondary thrombosis occlusion of collaterals. • Different tissue can tolerate ischemia at different rates. PHYSIOLOGY 3
  4. 4. Cont. • Biphasic injury pattern 1. Ischemic injury: Decreased arterial supply to a limb causes ischemic injury by local hypoxemia. 2. Reperfusion injury: Return of arterial blood flow with high oxygen content yields toxic oxygen free radicals, and the • re-circulation of muscle catabolic products and inflammatory mediators. A patient at risk for a fatal systemic reperfusion injury (multiple co-morbidities and/or hemodynamically unstable) should instead undergo an emergent amputation instead of revascularization. 4
  5. 5. ETIOLOGY 1. Embolic • 80% from cardiac source - valve, mural thrombus • 20% non-cardiac source - thrombosed aneurysm, ulcerated atherosclerotic plaque • Decreasing incidence with fewer cases of rheumatic heart disease • Most commonly lodged at: Femoral artery bifurcation, aortoiliac arterial system, brachial artery5
  6. 6. 2. Thrombotic – • Of native or diseased artery • Most commonly located at: Bifurcation, common femoral artery, popliteal artery • Of indwelling bypass graft 6
  7. 7. cont.. 3. Extrinsic compression of arterial lumen Aortic or vascular dissection, creating pseudolumen which compromises true lumen Thoracic outlet syndrome - Condition with scalene muscle scarring and/or a cervical rib causing neurovascular compression in the thoracic outlet, leading to arm pain and paresthesias 4. Trauma 7
  9. 9. cont… • Pain —The severity of the initial symptoms depends on the severity of ischemia and can range from incapacitating pain to the sudden onset of mild claudication. —More severe the ischemia, the faster the patient seeks medical attention. —Irreversible muscle necrosis occurs within 6 to 8 hours if the condition is untreated. 9
  10. 10. Cont… • Pallor —The color of the skin reflects its vascular supply. —Marble white skin is associated with acute total ischemia. —Slow capillary refill is a sign that at least a small degree of distal flow is present and runoff vessels are probably patent. 10
  11. 11. • Pulselessness —Acute ischemia is associated with the loss of peripheral pulses, which also helps define the level of the occlusion. Palpable normal pulses in the contralateral leg points toward embolism as the cause. Cont… 11
  12. 12. Cont… Paresthesisa: Early Light Touch Vibration Proprioception Crude Touch Pressure Late Loss of sensory function, numbness will progress to anesthesia 12
  13. 13. Cont… Paralysis: Loss of motor function indicates limb threatening ischemia Intrinsic foot muscles affected first followed by leg muscles Late irreversible ischemia indicated by loss of muscle turgidity 13
  15. 15. EVALUATION Following clinical assessment and classification, the anatomic location of the arterial occlusion can be diagnosed with a high degree of reliability. • Aortic Occlusion: —Paralysis of the legs is often the presenting feature —patients are unwell, with mottled skin discoloration that often extends above the inguinal ligament onto the lower abdomen —No palpable extremity pulses. —The kidneys are especially at risk, particularly if the aortic occlusion is due to an aortic dissection. —Successful revascularization restores the blood supply to a large muscle mass, but the effects of ischemia-reperfusion may cause further renal damage. 15
  16. 16. • Iliac Occlusion —The femoral pulse is lost on the affected side, and mottling usually extends to the inguinal level. • Femoro-popliteal occlusion —Most Common —Severity depends on involvement of Profunda Femoris Artery. • Popliteal & Infra-popliteal Occlusion —The calf muscles are ischemic with palpable femoral pulse. Cont… 16
  17. 17. INVESTIGATIONS Severity & duration of ischemia at the time of presentation provides narrow margin of time for investigations. 17
  18. 18. cont… • Laboratory • CBC (hemorrhagic risk with anticoagulation) • Basic metabolic panel (nephrotoxic risk of angiography contrast agent) • PT / aPTT • CK (assess for limb myonecrosis; significant risk for post-revascularization compartment syndrome) 18
  19. 19. DUPLEX ULTRASOUND -What are we looking for? -Normal • Triphasic • Pulsatile • regular amplitude 19
  20. 20. cont… • Advantages: - Noninvasive - Fairly accurate for infrainguinal arterial occlusive disease, especially of bypass grafts in this location • Disadvantages: - Suprainguinal arterial occlusions and distal run-off vessels not well- visualized - Calcifications of arterial walls (in diabetic patients, especially) can create artifacts and obscure visualization. • May be considered as a second-line approach to ALI imaging if angiography is not possible for infrainguinal arterial occlusion. 20
  22. 22. DSA • Advantages: —Level and nature of occlusion —During angiography, may be able to immediately start therapeutic intervention (intra-arterial lysis)without losing time • Disadvantages: —Lack of collaterals and associated spasm limits visualisation of more distal vessels. — incidence of contrast nephrotoxicity — Invasive 22
  23. 23. CT ANGIOGRAPHY Differentiate Embolic & Thrombotic cause if not clear clinically. Conditions of vessels Localizes level of Obstruction. Visualises distal arterial tree and distal cut off. Disadvantages: - Exposure to IV contrast –> If going to angiography after CTA for intra-arterial lysis of clot, patient will now receive a 2nd contrast bolus, increasing the risk of renal failure. 23
  24. 24. MR ANGIOGRAPHY • Advantages: - Less contrast load than angiography - Non ionizing • Disadvantages: - Very time intensive and often unavailable during weekend and night hours -Can be used as an alternative imaging modality for patients at high risk for contrast angiography complications Femoral-popliteal arterial system: sensitivity 92%, specificity 94% Infra-popliteal arterial system: sensitivity 93%, specificity = 71%24
  25. 25. Anticoagulant
  26. 26. INITIAL MANAGEMENT Anticoagulation and Supportive Measures • Unfractionated heparin - To reduce propagation of thrombus and pericatheter thrombosis during angiography - Decreases morbidity and mortality in ALI - Target aPTT of 1.5-2.5 times normal, - Assuming no contraindications (aortic dissection, compartment syndrome, vascular trauma) Initial dose of 100U/kg followed by 1000U/hr infusion 26
  27. 27. cont… • Hydration —Patients are often relatively volume depleted, and careful fluid resuscitation is necessary. —The potential for myoglobinuria due to ischemia- reperfusion, combined with the use of contrast agents during diagnosis and treatment of ALI, increases the risk of acute renal insufficiency. • supplemental oxygen. • intravenous analgesia. 27
  28. 28. ENDOVASCULAR TREATMENT • Catheter Directed Thrombolysis Viable to marginally threatened limb(class I & IIa) Retrograde contralateral femoral approach preferred over Anterograde ipsilateral Femoral Multiple side hole 45/55cm 5F Glidecath catheter is used Low dose Alteplase regimen: 1mg bolus followed by continuous infusion of 0.5mg-1mg/hr for 12 hrs followed by arteriogram High dose Alteplase regimen: 10mg bolus followed by 0.005mg/kg/hr infusion for 6 hrs, max dose 4mg/hr. Unfractioned heparin used 500U/hr to prevent peri sheath thrombosis Monitoring of serum fibrinogen level 4 hrly, stop infusion if fibrinogen drops below 100mg/dl, aPTT. 28
  29. 29. PERCUTANEOUS MECHANICAL THROMBECTOMY Percutaneous mechanical thrombectomy (PMT) devices can be classified as hydrodynamic, rotational, or aspiration throm- bectomy catheters 29
  30. 30. • Resolution of thrombus in 72% - 92% cases • Complications Hemorrhagic complication Compartment syndrome following reperfusion Distal embolisation 30
  31. 31. SURGICAL REVASCULARISATION • ALI class I & II • Baloon catheter thrombectomy/embolectomy • Bypass procedure • Endarterectomy 31
  33. 33. ENDARTERECTOMY • The artery is opened longitudinally at the site of disease. • The plaque is then separated from the artery wall in the direction of the arteriotomy & removed • The arteriotomy can be closed primarily or with a patch. 33
  35. 35. • The reconstruction should be performed with preservation of existing circulation. • End to side anastomosis allows the maintenance of anterograde flow in native vessel at proximal site. • Distal anastomosis is placed in disease free segment distal to obstruction to maintain retrograde flow through patent branches. • Align vessels without kink or twist. • Arteriotomy measuring 1.2 - 2 times graft diameter created. 35
  36. 36. P0ST-OP MANAGEMENT • Monitor distal pulse. • Monitor movement and sensation. • Continue anticoagulant. • Monitor for reperfusion effect. 36
  37. 37. CLINICAL OUTCOME • Mortality- 15%-20% • Major Morbidity 1. Hemorrhage 2. Hematoma 3. Reperfusion Injury 4. Renal insufficiency 37
  38. 38. REPERFUSION INJURY• Local: Compartment Syndrome • Systemic Hypotension ARDS Lactic Acidosis Hyperkalemia Hemoglibinuria Renal Failure 38
  39. 39. IN NUTSHELL 1. A patient with sudden onset of a cold, weak, numb and painful foot has acute limb ischaemia until proven otherwise. 2. The rate of amputation is proportional to the delays in treatment. Peri-operative mortality is influenced by the patient’s medical comorbidities. 3. All patients diagnosed with ALI need to be anticoagulated immediately. 4. Non-viable limbs (Rutherford III) require amputation (usually an above- knee amputation). 5. Rutherford IIb patients need immediate revascularisation, usually employing surgical or hybrid strategies. Percutaneous strategies that require 12 - 24 hours are inappropriate here, e.g. CDT. 39
  40. 40. THANK YOU 40