Sources: Sabiston Textbook of Surgery (21e), Goldman-Cecil Medicine (International Ed.), Harrison's Principles of Internal Medicine (22e, 2025), Current Surgical Therapy (14e), with supplementary PubMed evidence

---

1. DEFINITION AND OVERVIEW

• Acute Limb Ischemia (ALI) — symptoms present for < 2 weeks, representing a vascular emergency
• Chronic Limb Ischemia (CLI) / Chronic Limb-Threatening Ischemia (CLTI) — symptoms of rest pain or tissue loss present > 2 weeks, with corresponding diagnostic evidence of arterial insufficiency

---

2. ETIOLOGY AND PATHOPHYSIOLOGY

2.1 Acute Limb Ischemia

• Atrial fibrillation (most common)
• Recent myocardial infarction with mural thrombus
• Ventricular aneurysm, cardiomyopathy
• Infective and marantic endocarditis
• Prosthetic heart valves (risk 0.6–2.3%/patient-year; mitral > aortic by 2–3×)
• Atrial myxoma

2.2 Embolism vs. Thrombosis (critical distinction for management)

2.3 Chronic Limb Ischemia / CLTI

• Thromboangiitis obliterans (Buerger's disease)
• Vasculitis
• Thromboembolic disease
• Cystic adventitial disease
• Popliteal artery entrapment
• Hypercoagulable states

---

3. CLINICAL FEATURES

3.1 The "6 Ps" of Acute Limb Ischemia

Pain — Pallor — Pulselessness — Poikilothermia (coolness) — Paresthesia — Paralysis

• Pain: Severe, sudden onset; affects major muscle groups below the occlusion
• Pallor: Early sign; transitions to cyanosis and mottling over time
• Pulselessness: Loss of pulses distal to occlusion; helps localize the level
• Poikilothermia: Coolness of the limb; particularly significant if contralateral limb is warm; transition level correlates with occlusion site
• Paresthesia: Numbness, tingling — indicates sensory nerve ischemia
• Paralysis: Late, grave sign — indicates motor nerve and muscle ischemia; motor deficits progress from distal to proximal (intrinsic foot muscles first → complete paralysis = late/irreversible)

3.2 Chronic Limb Ischemia — Symptom Spectrum

---

4. CLASSIFICATION OF ACUTE LIMB ISCHEMIA

Rutherford Classification of ALI (the gold standard)

---

5. CHRONIC LIMB ISCHEMIA — CLASSIFICATION

Fontaine Classification

WIfI Classification (Society for Vascular Surgery)

• Wound characteristics
• Ischemia (degree of pedal perfusion)
• foot Infection extent

ABI (Ankle-Brachial Index)

• Normal: 1.0–1.4
• Borderline: 0.91–0.99
• Mild PAD: 0.70–0.90
• Moderate PAD: 0.50–0.69
• Severe/CLTI: < 0.50
• Rest pain typically occurs at ABI < 0.40
• Non-compressible (calcified) vessels: ABI > 1.4 (diabetics, elderly)

---

6. INVESTIGATIONS

Bedside/Immediate

• Continuous-wave Doppler: Assess peripheral signals — multiphasic (normal) vs. monophasic/absent. Rutherford classification relies on presence/absence of arterial and venous Doppler signals
• ABI measurement
• ECG: Identify atrial fibrillation, recent MI

Vascular Imaging

Workup for Underlying Etiology (ALI)

• Echocardiogram: Identify wall motion abnormalities, intracardiac thrombus, vegetations, atrial myxoma
• CTA chest/abdomen/pelvis: Aortic atheroma, aneurysm, primary aortic thrombus
• Hypercoagulable panel: If no cardiac or atherosclerotic source identified
• Venous duplex: Rule out paradoxical embolism source (DVT + PFO)

Chronic Ischemia Workup

• Segmental limb pressures — localize level of disease
• Pulse volume recordings (PVR)
• Transcutaneous oxygen (TcPO₂): Predicts wound healing and guides amputation level
• Toe pressures / toe-brachial index (TBI) — more reliable in calcified vessels

---

7. MANAGEMENT

7.1 Acute Limb Ischemia

Immediate General Measures

1. IV heparin immediately upon suspicion: 75–100 units/kg bolus, then 15–18 units/kg/min infusion
   • Prevents thrombus propagation and maintains collateral patency
   • Continue until definitive treatment and transition to oral anticoagulation
   • Alternative in heparin-contraindicated patients: lepirudin (renal metabolism) or argatroban (hepatic metabolism)
2. Analgesia
3. Admit, stabilize medically, assess severity (Rutherford classification)

---

7.2 Interventional Approaches

A. Endovascular Approach (Rutherford I and IIa; thrombotic occlusion; high surgical risk)

• Agents: recombinant tPA, reteplase, tenecteplase
• Most effective for: recent thrombotic occlusion in atherosclerotic vessel, bypass graft, or occluded stent; distal emboli where surgical access is limited
• Ultrasound-emitting catheters improve thrombus permeability
• Disadvantage: longer time to reperfusion; bleeding risk

• Devices using hydrodynamic forces or rotating baskets to fragment/aspirate thrombus
• Reduces infusion time; fewer procedures needed
• Often combined with pharmacologic thrombolysis

• Active bleeding
• Stroke or neurosurgical procedure within 3 months
• Malignant intracranial neoplasm
• History of hemorrhagic stroke
• Recent GI bleed

B. Open Surgical Approach (Rutherford IIb; contraindication to thrombolysis)

• Balloon-tipped catheter passed beyond the thrombus, inflated, then withdrawn to extract clot
• Femoral embolectomy: indicated for absent/water-hammer ipsilateral femoral pulse with normal contralateral pulse
• Bilateral femoral embolectomies: for absence of both femoral pulses (aortic thrombus/saddle embolus)
• Performed in a hybrid OR to allow completion angiography and adjunct endovascular treatment
• After embolectomy in thrombotic disease, underlying stenosis must be treated (angioplasty, endarterectomy, stenting, or bypass) to prevent re-thrombosis

• For extensive thrombotic disease or when embolectomy fails
• Autogenous vein (great saphenous) preferred for infrainguinal bypass (BASIL trial)
• Prosthetic grafts used for suprainguinal or when vein unavailable

C. Primary Amputation (Rutherford III — irreversible ischemia)

• Indicated in: profound paralysis with rigor, anesthetic limb, inaudible arterial AND venous Doppler signals, livedo reticularis
• Revascularizing irreversible ischemia risks multi-organ failure from rhabdomyolysis, hyperkalemia, metabolic acidosis
• Also consider in: poor overall health, devastating tissue loss, non-ambulatory status with poor prognosis

---

7.3 Post-Revascularization: Compartment Syndrome and Reperfusion Injury

• Prophylactically performed in Rutherford IIb ischemia (or if ischemia time > 6 hours)
• Medial incision (2–3 cm posterior to medial tibial border): releases both posterior compartments — superficial posterior, then divide soleus attachments to release deep posterior
• Lateral incision (between anterior crest of tibia and fibula): releases anterior and lateral compartments via parallel fascia incisions; care to avoid superficial peroneal nerve
• Signs of evolving compartment syndrome requiring immediate release:
  • Tense compartments
  • Pain with passive stretch
  • Decreased sensation at dorsal first webspace
  • Motor weakness

• Hemodynamic monitoring and fluid resuscitation
• Correct acidosis and electrolyte imbalance (K⁺ and H⁺ release from damaged cells)
• Serial neurovascular exams
• Continued therapeutic anticoagulation (risk of re-thrombosis up to 30%)

---

7.4 Chronic Limb Ischemia (CLI/CLTI) — Management

A. Risk Factor Modification

• Smoking cessation: Most important modifiable risk factor; counselling + pharmacotherapy (nicotine replacement, varenicline, bupropion)
• Lipid management: High-intensity statin therapy to LDL ≤ 70 mg/dL reduces amputation and death. PCSK9 inhibitors further reduce cardiovascular and major limb events in those already on statin therapy
• Blood pressure control: Target < 130/80 mmHg; β-blockers are NOT contraindicated in PAD
• Diabetes control: Crucial especially with coexisting CLTI
• Exercise prescription: Supervised exercise program preferred

B. Exercise Therapy

• Supervised exercise therapy (SET) is the first-line treatment for intermittent claudication
• Improves walking distance more than unsupervised home exercise
• RCT evidence: supervised exercise > primary stent therapy or home walking + cilostazol for aortoiliac PAD
• Combination of SET + balloon angioplasty superior to SET alone for ABI, walking distance, and quality of life

C. Antiplatelet and Antithrombotic Therapy

• Aspirin 75–325 mg/day: Established role in secondary prevention of MI, stroke, and vascular death in all PAD patients
• Clopidogrel 75 mg/day: Indicated if aspirin not tolerated
• Dual pathway inhibition: Low-dose rivaroxaban 2.5 mg twice daily + aspirin 100 mg daily reduces major cardiovascular events, limb events, and all-cause mortality (at expense of increased bleeding) — COMPASS trial evidence
• Vorapaxar (PAR-1 antagonist): May reduce acute limb ischemia incidence and revascularization need
• Long-term anticoagulation indicated when ALI caused by cardiac thromboembolism

D. Pharmacotherapy for Claudication

• Cilostazol 50–100 mg twice daily (phosphodiesterase inhibitor): Improves maximal walking distance by 40–50% vs. placebo; reduces restenosis after femoral revascularization; contraindicated in heart failure
• Oral vasodilating prostaglandins, vitamin E, chelation therapy with EDTA — not effective

E. Revascularization for Chronic Ischemia

• Lifestyle-limiting claudication unresponsive to exercise + pharmacotherapy
• Rest pain
• Tissue loss (ulcer/gangrene) — CLTI

• Endovascular first preferred for amenable lesions (lower peri-procedural mortality/morbidity)
  • Angioplasty with or without stenting
  • Drug-eluting stents (DES) and drug-coated balloons (DCB) provide superior, more durable benefit for femoropopliteal disease vs. angioplasty alone (equivalent to each other)
  • Angioplasty more cost-effective than surgery if expected 5-year patency ≥ 30%
• Open surgical bypass preferred for:
  • Extensive multi-segment disease not amenable to endovascular treatment
  • Failed endovascular approach
  • BASIL trial: bypass vs. angioplasty — similar mortality, amputation, and patency at 4 years in femoropopliteal disease
  • BASIL-2 trial (2023): In CLTI requiring infrapopliteal intervention — vein bypass vs. best endovascular treatment first; vein bypass showed improved outcomes in patients with suitable vein
  • BEST-CLI trial (2022): Surgery or endovascular therapy — surgery superior in patients with single-segment great saphenous vein available
• Hybrid procedures: Combine open and endovascular in same setting

---

8. ATHEROEMBOLISM (Special Variant)

• Multiple small deposits of fibrin, platelets, and cholesterol debris from proximal atherosclerotic lesions/aneurysms lodge in distal small vessels
• Distal pulses remain palpable (unlike classic ALI)
• Presentations: "Blue toe syndrome," petechiae, splinter hemorrhages, livedo reticularis, localized tenderness
• Skin/muscle biopsy: cholesterol crystals (pathognomonic)
• May follow intraarterial procedures
• Difficult to treat: Local foot care ± amputation; analgesics; statins + antiplatelet therapy for cardiovascular risk; thrombolysis and surgical revascularization are NOT helpful due to multiplicity and distal location
• Endovascular/surgical exclusion of the source vessel/aneurysm may be needed for recurrent atheroembolism

---

9. COMPLICATIONS OF LIMB ISCHEMIA

---

10. PROGNOSIS

• ALI: Perioperative mortality 20–40%; limb loss 12–50% for lower extremity ALI
• CLTI untreated: Major amputation rate ~22% at 1 year
• Below-knee amputation: 30-day mortality ~8.9%
• Above-knee amputation: 30-day mortality ~27.7%
• Quality of life is profoundly impaired in CLTI; significant improvement follows successful revascularization
• Patients with PAD carry high systemic cardiovascular risk: MI, stroke, and vascular death are the primary causes of death

---

11. RECENT EVIDENCE (PubMed, 2023–2026)

---

SUMMARY MNEMONICS

Pain, Pallor, Pulselessness, Poikilothermia, Paresthesia, Paralysis

Viable → Marginally threatened → Immediately threatened → Irreversible

Heparin immediately → Assess Rutherford → Image (CTA/angio) → Revascularize (endovascular IIa, open IIb) or Amputate (III)

Embolus = sudden, no PAD, cardiac source, Fogarty Thrombosis = background PAD, Thrombolysis or bypass

---

1. Definition & Overview — ALI vs. CLI definitions, incidence, mortality figures
2. Etiology & Pathophysiology — Embolism vs. thrombosis distinction (clinically critical), cardiac/non-cardiac sources, atherosclerotic mechanisms, inflammatory role in CLTI
3. Clinical Features — The 6 Ps (Pain, Pallor, Pulselessness, Poikilothermia, Paresthesia, Paralysis); claudication spectrum; differential diagnosis table
4. Rutherford Classification — Full table with Doppler findings and prognosis for each grade (I, IIa, IIb, III)
5. Chronic Ischemia Classification — Fontaine stages, WIfI system, ABI thresholds
6. Investigations — Bedside Doppler, ABI, duplex, CTA, MRA, arteriography, echocardiography
7. Management of ALI — Immediate heparin, Fogarty embolectomy, catheter-directed thrombolysis, mechanical thrombectomy, bypass, primary amputation; contraindications to thrombolysis; treatment algorithm image
8. Compartment Syndrome & Reperfusion Injury — Four-compartment fasciotomy technique and indications
9. Chronic Limb Ischemia Management — Risk factor modification, supervised exercise, cilostazol, aspirin/rivaroxaban dual pathway, endovascular vs. bypass (BASIL, BEST-CLI, BASIL-2 trial evidence)
10. Atheroembolism — Blue toe syndrome, special management considerations
11. Complications, Prognosis, Recent Evidence
12. Mnemonics for quick revision