A 62-year-old man with a history of smoking presents with acute onset of severe pain in the right foot and calf, with coldness and pallor. On examination, the right foot is pale and mottled, with absent dorsalis pedis and posterior tibial pulses. Sensory loss is present in the foot. The left lower limb pulses are normal. What is the most appropriate immediate next step?

Explanation

## Clinical Diagnosis: Acute Limb Ischaemia This patient has **acute limb ischaemia (ALI)** with the classic "6 Ps" presentation: Pain, Pallor, Pulselessness, Paraesthesia (sensory loss), Poikilothermia (coldness), and Paralysis (threatened). ### Rutherford Classification of Acute Limb Ischaemia | Grade | Viability | Sensory Loss | Muscle Weakness | Doppler | |-------|-----------|--------------|-----------------|--------| | I (Viable) | Not immediately threatened | No | No | Arterial signals present | | IIa (Threatened, salvageable) | Salvageable if revascularized | Mild/moderate | None | Venous signals only | | IIb (Threatened, marginally salvageable) | Salvageable with difficulty | Moderate/severe | Moderate/severe | Venous signals only | | III (Irreversible) | Irreversible tissue loss | Profound | Paralysis | No signals | **Key Point:** This patient has **Grade IIa–IIb acute limb ischaemia** (sensory loss present, mottling, absent pulses). The limb is still potentially salvageable, making immediate anticoagulation and urgent imaging mandatory. ## Why Option A Is the Correct Immediate Next Step **Start IV heparin AND arrange urgent CT angiography** is the most appropriate immediate next step because: 1. **IV Heparin is the cornerstone of immediate management** in ALI. It prevents thrombus propagation, preserves collateral flow, and is universally recommended as the first pharmacological intervention (Rutherford's Vascular Surgery 9e; ESVS 2020 Guidelines). A bolus of 5000–10,000 IU IV heparin should be given immediately upon diagnosis. 2. **CT angiography** provides rapid, non-invasive localisation of the occlusion, assessment of inflow and outflow vessels, and guides the revascularisation strategy (surgical embolectomy vs. catheter-directed thrombolysis vs. endovascular thrombectomy). Modern multi-detector CT angiography is fast and widely available, making it the preferred initial imaging modality in most contemporary vascular centres. 3. The combination of **immediate anticoagulation + urgent imaging** is the standard-of-care first step before any revascularisation procedure. ## Why the Other Options Are Incorrect - **Option B (ABI + duplex ultrasonography):** ABI is unreliable in acute ischaemia and duplex is operator-dependent and time-consuming. These are inappropriate in a vascular emergency where every minute counts. - **Option C (Aspirin 300 mg + angiography with thrombolysis/thrombectomy):** Aspirin is an antiplatelet agent, NOT an anticoagulant. It does NOT prevent thrombus propagation and is NOT the recommended immediate pharmacological intervention in ALI. IV heparin is the correct immediate drug. While angiography with thrombolysis/thrombectomy is a valid revascularisation strategy, the immediate drug should be heparin, not aspirin. - **Option D (Observation + analgesics + elevation):** This is dangerous and inappropriate. ALI is a vascular emergency with a 6–8 hour window for limb salvage. Conservative management alone will result in irreversible ischaemia and amputation. ## Management Algorithm for Acute Limb Ischaemia 1. **Immediate:** IV heparin bolus → prevents propagation 2. **Urgent imaging:** CT angiography → localises occlusion, plans intervention 3. **Revascularisation:** Surgical embolectomy (embolic cause) OR catheter-directed thrombolysis (thrombotic cause, onset <14 days) OR endovascular thrombectomy 4. **Post-revascularisation:** Monitor for compartment syndrome (fasciotomy if needed), rhabdomyolysis (IV fluids, CK monitoring) **Clinical Pearl:** The ESVS 2020 Guidelines and Rutherford's Vascular Surgery both emphasise that **IV heparin must be started immediately** upon clinical diagnosis of ALI, before imaging is completed. Aspirin has no role as the primary immediate agent in ALI. [cite: Rutherford's Vascular Surgery 9e Ch 145; ESVS Clinical Practice Guidelines on the Management of Acute Limb Ischaemia 2020; Harrison's Principles of Internal Medicine 21e Ch 243]