December 18, 2014
What is the best treatment for this acute limb ischemia patient?
This issue is complex but approached in a systematic way most patients declare themselves better suited to one form of revascularisation therapy over another (the options being Chemical Versus Mechanical Lysis Versus Surgical Thrombectomy). The decision making and treatment algorithm starts with a thorough history and physical examination. Initially focused on confirming that acute limb ischaemia (ALI) is indeed the culprit pathology, intravenous heparin is commenced to counter the risk of thrombus propagation.
Assessing acute limb ischemia
The physician must be cognizant of the many pathologies that may cause ALI but equally that in the clear majority the cause will result from in situ thrombosis of the native vessel, embolism (usually cardiogenic) or thrombosis of a lower limb bypass graft. Clues may include history of AF/recent AMI, claudication, PAD/previous bypass surgery. The circulatory examination will include all pulses upper and lower limb and their nature, the precordium, abdomen, global neurological function and most importantly lower limbs. Examine the contralateral lower limb for evidence of intact pulses and emboli then focus on the affected limb, once again examining for pulses, color, temperature, old scars, neurological function (motor and sensory), compartmental tension/pain and Doppler signals both arterial and venous. This process allows the physician to determine the Rutherford category of ALI (I, Viable; IIa, Threatened/Marginal; IIb ,Threatened/Immediate; III, Major tissue/Nerve damage Inevitable) which in turn determines the best approach to treatment.
Choosing the right treatment for acute limb ischemia
Stage I can be treated electively after imaging, much as with IC/CLI. Stage III is likely to require amputation or in some cases palliation, unless presentation is very early. Stage IIa can be imaged with angiography/CTA prior to determine the best strategy, whereas IIb requires immediate revascularisation to avoid permanent nerve damage and/or extensive tissue loss. Catheter directed thrombolysis (CDT) has the advantage of being less invasive, as well as facilitating convenient angiographic imaging and supplemental endovascular therapy if required. It is therefore preferred when there is adequate time, the patient is frail or run-off is thrombosed and there are no contraindications to thrombolysis. Surgical thrombo-embolectomy is preferred when timely revascularisation is needed, proximal vessels/bypass grafts are involved with preservation of run-off or the duration of ischemia goes beyond 14 days. There are an array of pharmaco-mechanical thrombectomy methods that offer a timely and less invasive solution for revascularisation. Their advantage over CDT is related to shorter procedural times, non-reliance on ICU and potentially lower rates of bleeding.
Some final thoughts
Finally, one must have a low threshold for performing compartmental fasciotomy following revascularistion. We must identify a source of embolus if that is suspected and provide an anti-coagulation solution both immediately and into the future to prevent recurrent limb threatening events.
