Limb Ischemia Workup
The initial workup for suspected limb ischemia requires immediate bedside clinical assessment using the "6 Ps" (pain, pallor, pulselessness, poikilothermia, paresthesias, paralysis) combined with handheld continuous-wave Doppler examination—imaging is NOT required for initial diagnosis and should never delay anticoagulation or vascular consultation. 1
Immediate Bedside Assessment (Within Minutes)
Start unfractionated heparin immediately unless contraindicated, before any imaging or further workup. 1, 2
Clinical Examination Components
Pulse assessment: Palpate femoral, popliteal, dorsalis pedis, and posterior tibial arteries bilaterally. Absent pulses indicate arterial occlusion. 1, 3
Handheld continuous-wave Doppler: This is more accurate than pulse palpation alone. Loss of arterial Doppler signal means the limb is threatened; absence of both arterial AND venous signals indicates irreversible damage. 1, 3
Neurologic assessment: Check for sensory loss beyond the toes and motor weakness. Any motor deficit indicates Rutherford Class IIb (immediately threatened) requiring revascularization within 4-6 hours. 1, 2
Skin examination: Assess for pallor, mottling, or cyanosis. White or mottled appearance signals advanced ischemia. 3
Temperature: Compare limb temperature bilaterally by palpation. 3
Rutherford Classification (Determines Urgency)
| Category | Sensory Loss | Motor Weakness | Arterial Doppler | Venous Doppler | Action Required |
|---|---|---|---|---|---|
| I (Viable) | None | None | Audible | Audible | Revascularization within 6-24 hours [3] |
| IIa (Marginally threatened) | Minimal (toes only) | None | Inaudible | Audible | Revascularization within 6 hours [1,3,2] |
| IIb (Immediately threatened) | Beyond toes | Mild-moderate | Inaudible | Audible | Emergency revascularization within 4-6 hours [1,2] |
| III (Irreversible) | Profound | Paralysis | Inaudible | Inaudible | Primary amputation; revascularization contraindicated [1] |
Vascular Specialist Consultation
Contact a vascular specialist immediately—before imaging is completed. If local expertise is unavailable, initiate transfer to a capable facility. The more advanced the ischemia, the faster this communication must occur. 1
Imaging Strategy (Based on Rutherford Category)
For Category I or IIa (Viable or Marginally Threatened)
CT angiography (CTA) of the entire lower extremity is the preferred initial imaging test. 1, 3
CTA provides rapid, comprehensive anatomic detail including occlusion level, atherosclerotic burden, and below-knee vessel patency—all essential for revascularization planning. 1, 3
CTA allows immediate diagnosis and treatment planning in a single study. 1, 3
Alternative: Digital subtraction angiography (DSA) can provide simultaneous diagnosis and treatment. 1, 2
For Category IIb or III (Immediately Threatened or Irreversible)
Proceed directly to the operating room or catheter suite WITHOUT prior imaging. Any delay for imaging risks permanent tissue damage or limb loss. 1, 2
What NOT to Order
Ankle-brachial index (ABI): Only confirms occlusion but provides no information about location, cause, or treatment planning. ABI is for screening chronic disease, not acute presentations. 1, 3
Duplex ultrasound: Too time-consuming, operator-dependent, and limited in scope for acute limb ischemia. Cannot provide comprehensive arterial mapping needed for emergency revascularization. 1, 3
MRA: Requires significantly longer acquisition time and may not be readily available in emergency settings. 3
Etiologic Workup (Performed Concurrently, Not Delaying Treatment)
ECG: Obtain immediately to assess for atrial fibrillation or recent myocardial infarction as embolic sources. 1, 2
Echocardiography: Can be performed after stabilization to identify cardiac thrombus, valvular disease, or other embolic sources. This guides long-term anticoagulation but must not delay revascularization. 1, 2
History: Distinguish embolic (sudden onset, normal contralateral pulses, atrial fibrillation) from thrombotic (prior claudication, diminished contralateral pulses, known PAD). 2, 4
Critical Time Constraints
Skeletal muscle tolerates ischemia for only 4-6 hours before irreversible damage occurs. This is the fundamental principle of "time is tissue." 1, 2
Delays beyond 6 hours dramatically increase risk of permanent tissue damage, amputation, and death. 5
Even with rapid revascularization, 1-year mortality remains 10-15% and amputation rate is 10-15% due to coexisting conditions. 1, 6
Common Pitfalls to Avoid
Never delay anticoagulation or vascular consultation to obtain imaging studies. Heparin should be started within minutes of diagnosis. 1, 2
Do not rely on pulse palpation alone. Use handheld Doppler for accurate arterial signal assessment. 3
Do not order ABI as the initial diagnostic test. It wastes time and provides no actionable information for acute management. 1, 3
Do not attempt revascularization in Category III limbs. Reperfusion of irreversibly damaged tissue can cause multiorgan failure from ischemic metabolite circulation. 1
Do not perform comprehensive noninvasive vascular studies in the emergency setting. Initial clinical evaluation can reliably determine limb viability without imaging. 1