01Approach to the Critical Patient/attcp55

Immediate stabilization

›Time-critical recognition

›Symptom onset to revascularization window 4 to 6 hours

›Skeletal muscle tolerates ischemia for only 4 to 6 hours

›Beyond 6 hours irreversible damage highly likely

›Emergent vascular surgery consultation for all suspected ALI

›Do not delay consultation for imaging when limb threatened

›Class I recommendation

›Initiate IV unfractionated heparin immediately unless contraindicated

›80 U/kg IV bolus then 18 U/kg/hr infusion

›Class I recommendation to prevent thrombus propagation

›Rutherford category-based urgency

›Category I viable — time for workup and imaging

›Arterial and venous Doppler signals present

›No sensory or motor deficit

›Category IIa marginally threatened — prompt revascularization within hours

›Minimal sensory loss limited to toes

›No motor deficit

›Category IIb immediately threatened — emergent revascularization

›Sensory loss beyond toes

›Mild to moderate motor deficit present

›Category III irreversible — primary amputation

›Profound sensory loss and paralysis

›Loss of both arterial and venous Doppler signals

›Muscle rigidity indicating necrosis

Monitoring and targets

›Hemodynamic and metabolic monitoring

›Continuous cardiac monitoring for AF and arrhythmias

02History/hx70

Onset and symptom characterization

›Temporal pattern

›Sudden thunderclap onset suggests embolic cause

›Atrial fibrillation leading cardiac embolic source

›Cardiac thrombus from recent MI or cardiomyopathy

›Gradual subacute onset over hours to days suggests in situ thrombosis

›Pre-existing PAD with collateralization

›Graft or stent thrombosis on chronic disease

›Symptoms < 2 weeks duration define ALI

›The 6 Ps of acute limb ischemia

›Pain

›Severe unrelenting rest pain typical

›Location and progression pattern

›Pallor

›Skin color change from baseline

›Pulselessness

›Absent distal pulses

›Poikilothermia

›Coolness compared to contralateral limb

›Paresthesias

›Numbness and tingling — sensory loss marker

›Paralysis

›Weakness or inability to move foot or toes — late and ominous sign

›Symptom progression sequence

›Numbness progressing to weakness progressing to paralysis

›Indicates worsening ischemia requiring time-critical intervention

›Painless ischemia in diabetic neuropathy

›Sensory deficit may mask severity

03Physical Exam/exam52

Vital signs and general

›Hemodynamic stability snapshot

›Heart rate and rhythm

›Tachycardia from pain or systemic response

›Irregular rhythm suggesting atrial fibrillation

›Blood pressure bilateral comparison

›Pulse differential between limbs

›Aortic dissection exclusion if significant difference

›Respiratory rate and oxygen saturation

›Systemic deterioration markers

›General assessment

›Level of distress from pain

›Signs of systemic toxicity post-event

›Pale and diaphoretic

›Altered mental status in severe cases

Limb examination

›Temperature and color

›Cool limb compared to contralateral side

›Temperature gradient demarcation line localizes occlusion level

›Pallor at rest

›Blanching skin suggests viable tissue

›Non-blanching mottled skin suggests advanced ischemia

›Cyanosis or dusky discoloration

›Fixed mottling indicating irreversibility

›Pulse examination

›Palpation of femoral, popliteal, dorsalis pedis, posterior tibial bilaterally

›Pulse palpation alone inaccurate in ALI

›Bedside continuous-wave Doppler essential

04Differential Diagnosis/ddx40

Vascular emergencies

›Acute limb ischemia — embolic

›ICD-10 I74.3 embolism and thrombosis of arteries of lower extremities

›Sudden onset without prior claudication

›Cardiac source identified

›Acute limb ischemia — thrombotic

›ICD-10 I74.3 on background PAD

›Gradual onset with prior claudication history

›Collaterals often present

›Aortic dissection with limb malperfusion

›ICD-10 I71.0

›Back or chest pain concurrent

›Pulse differential between upper limbs

›BP differential > 20 mmHg between arms

Venous and other limb threats

›Phlegmasia cerulea dolens

›ICD-10 I82.49 massive iliofemoral DVT

›Massive venous thrombosis causing limb ischemia

›Distinguished by severe swelling and dusky discoloration rather than pallor

›Preserved venous Doppler signal initially

›Compartment syndrome

›ICD-10 M79.A non-traumatic compartment syndrome

›Trauma related or post-reperfusion

›Tense compartments with pain on passive stretch

›Compartment pressures > 30 mmHg or within 30 mmHg of diastolic BP

Chronic and non-ischemic mimics

›Chronic limb-threatening ischemia

›Symptoms > 2 weeks duration

05Laboratory Tests/lt45

Essential initial labs

›Hematology and coagulation

›Complete blood count

›Baseline hemoglobin and platelet count

›Leukocytosis suggesting systemic inflammation or infection

›Thrombocytopenia raising HIT concern

›PT/INR and aPTT

›Baseline before heparin initiation

›Anticoagulation status assessment

›Type and screen

›Anticipate potential surgical intervention

›Metabolic and renal panel

›Basic metabolic panel

›Creatinine baseline renal function for contrast safety

›Potassium — hyperkalemia risk after reperfusion

›Bicarbonate — metabolic acidosis marker

›Lactate

›Elevated in severe tissue hypoperfusion

›Serial measurement to track response to therapy

Muscle and organ injury markers

›Rhabdomyolysis panel

›Creatine kinase

›Baseline and serial monitoring post-reperfusion

›CK > 5000 U/L predicts 50% risk of acute renal failure

›Trend used to guide hydration intensity

›Urine myoglobin

›Positive indicates rhabdomyolysis

›> 20 mg/dL predictive of renal failure risk

06Diagnostic Tests/dt72

Scoring Systems

›Rutherford classification for ALI severity

›Category I viable limb

›No immediate threat

›Intact sensory and motor function

›Arterial and venous Doppler signals present

›Category IIa marginally threatened

›Minimal sensory loss limited to toes

›No motor deficit

›Audible venous Doppler signal

›Category IIb immediately threatened

›Sensory loss beyond toes

›Mild to moderate motor weakness

›Venous Doppler often inaudible

›Category III irreversible ischemia

›Profound sensory and motor loss

›Both arterial and venous signals absent

›Muscle rigidity indicating necrosis

›Ankle-brachial index

›Ratio < 0.9 defines PAD

›ABI <= 0.60 high risk for ALI in PAD patients

›May be falsely elevated in calcified vessels (diabetics, CKD)

›Not reliable in acute setting — use clinical exam and Doppler

MRI

›MRI angiography role in ALI

›Limited acute utility due to availability and time constraints

›Scan duration incompatible with limb-threatening ischemia timeline

›Motion artifact limitation

›Problem-solving indications when time permits

›Aortic dissection characterization without iodinated contrast

›Complex popliteal aneurysm evaluation

›Contraindications

›Incompatible metallic implants

›Hemodynamically unstable patients

›Claustrophobia limiting scan completion

CT

›CT angiography — first-line imaging modality

›Indications

›All Rutherford I and IIa cases where revascularization planning needed

›Anatomic mapping of occlusion level and extent

›Evaluation of aortoiliac and femoropopliteal anatomy

›Diagnostic performance

›Sensitivity approximately 95% to 100% for arterial occlusion

›Specificity approximately 96% to 100%

›ACR Appropriateness Criteria 2023 supports CTA as first-line for sudden cold painful leg

›Protocol considerations

›Multi-phase CTA from aorta to foot

›Renal function assessment before contrast administration

›Allergy premedication if prior contrast reaction

›CT findings

›Abrupt arterial cutoff at occlusion site

›Collateral vessel mapping

›Popliteal aneurysm identification

›Aortic dissection flap if present

Ultrasound

›Bedside continuous-wave Doppler — most important initial tool

›Assess femoral, popliteal, dorsalis pedis, posterior tibial bilaterally

›Loss of arterial signal indicates threatened limb

›Loss of both arterial and venous signals indicates likely irreversibility

›Triphasic to biphasic to monophasic waveform degradation with severity

›No ionizing radiation and immediately available

›Duplex ultrasound

›Confirms occlusion level and length

›B-mode thrombus visualization

›Color Doppler flow mapping

›Graft surveillance in post-revascularization patients

›Velocity ratios and peak systolic velocity

›Operator-dependent limitation

›ACR Appropriateness Criteria 2023 rates duplex as appropriate initial modality

›Point-of-care cardiac ultrasound

›Left ventricular thrombus detection

›Apical thrombus in dilated cardiomyopathy or post-MI

›LV function and wall motion assessment

›Embolic source identification

›Pericardial effusion screen

›IVC assessment for fluid status guidance

07Disposition/dispo34

Admission criteria

›All ALI patients require admission

›No safe outpatient management for acute limb ischemia

›All Rutherford categories require inpatient management

›Risk of rapid progression to irreversible ischemia

›Minimum monitored bed with telemetry

›Post-revascularization metabolic monitoring

›Serial neurovascular examinations every 1 to 2 hours

Level of care selection

›ICU indications

›Rutherford IIb or III with systemic toxicity

›Metabolic acidosis and hyperkalemia

›Hemodynamic instability

›Post-revascularization reperfusion syndrome

›Myoglobinuria and rhabdomyolysis management

›Arrhythmia from hyperkalemia

›Fasciotomy requirement

›Airway and hemodynamic management

›Concurrent cardiac event

›ACS or decompensated heart failure

›Vascular surgery floor

›Rutherford I and IIa after successful revascularization

›Stable neurovascular exam

›No metabolic derangement

Transfer criteria

›Emergent transfer if local facility lacks vascular capability

›No on-site vascular surgery or interventional capability

›More advanced ischemia requires more urgent transfer

08Treatment/t96

Immediate ED interventions

›Anticoagulation — initiate immediately

›Unfractionated heparin IV

›80 U/kg IV bolus

›18 U/kg/hr continuous infusion

›Target aPTT 60 to 100 seconds

›Class I recommendation to prevent thrombus propagation

›If HIT suspected — use alternative anticoagulant

›Argatroban 2 mcg/kg/min IV — adjust for hepatic impairment

›Bivalirudin 0.15 to 0.2 mg/kg/hr IV — preferred in renal impairment

›Analgesia

›IV opioids for severe ischemic pain

›Morphine 2 to 4 mg IV titrated to effect

›Hydromorphone 0.5 to 1 mg IV alternative

›Multimodal adjuncts as tolerated

›Acetaminophen 1 g IV every 6 hours

›Limb positioning and protection

›Dependent positioning below heart level to maximize perfusion

›Class I recommendation

›Avoid warming devices — thermal injury to ischemic tissue

›Protect from pressure injury

Revascularization by Rutherford category

›Category I — viable limb

›Diagnostic imaging and planning phase

›CTA for anatomy mapping

›Duplex ultrasound consideration

›Heparin bridge while planning definitive approach

›Category IIa — marginally threatened

›Catheter-directed thrombolysis first-line for native artery occlusion

›Alteplase (tPA) 0.05 mg/kg/hr intra-arterial up to maximum 2 mg/hr

›Urokinase 240,000 IU/hr for first 4 hours then 120,000 IU/hr

›Duration typically 12 to 24 hours with re-imaging

›Continue systemic heparin at sub-therapeutic dose during lysis

›Percutaneous mechanical thrombectomy as adjunct

›Aspiration thrombectomy devices

›Rheolytic thrombectomy adjunct option

›Category IIb — immediately threatened

›Open surgical thromboembolectomy preferred for rapid revascularization

›Fogarty balloon catheter embolectomy

›Groin cutdown for femoral access

›Hybrid endovascular-surgical approach for complex anatomy

›Concurrent heparinization maintained throughout

›Category III — irreversible

›No revascularization — primary amputation

›Revascularization contraindicated due to lethal reperfusion syndrome risk

›Hyperkalemia, acidosis, myonecrosis toxins released systemically

›Amputation level determined by tissue viability

Post-revascularization management

›Fasciotomy

›Perform for clinical compartment syndrome

›Pain on passive stretch

›Compartment pressure > 30 mmHg or within 30 mmHg of diastolic BP

›Consider prophylactic fasciotomy

›Rutherford IIa or IIb revascularization

›Ischemia duration > 6 hours

›Class IIa recommendation

›Four-compartment lower leg fasciotomy standard approach

›Rhabdomyolysis prevention and management

›Aggressive IV hydration

›Normal saline or lactated Ringer at 1 to 2 mL/kg/hr minimum

›Target urine output >= 200 mL/hr during active myoglobinuria

›Urine alkalinization

›IV sodium bicarbonate 1 to 2 mEq/kg bolus then infusion

›Target urine pH > 6.5 to prevent myoglobin precipitation in renal tubules

›Serial CK and urine myoglobin monitoring

›Every 6 hours until CK trending down

›Hyperkalemia treatment

›Calcium gluconate 1 to 2 g IV for membrane stabilization

›Repeat every 5 minutes if ECG changes persist

›Insulin 10 units IV plus dextrose 50% 50 mL IV

›Shift potassium intracellularly

›Sodium bicarbonate 50 to 100 mEq IV

›Alkalosis drives potassium into cells

›Dialysis if refractory or anuric

›Continuous renal replacement therapy for hemodynamically unstable patients

Long-term antithrombotic therapy

›Cardioembolic etiology — atrial fibrillation or LV thrombus

›Therapeutic-dose direct oral anticoagulant

›Rivaroxaban 20 mg daily with evening meal

›Apixaban 5 mg twice daily

›Warfarin target INR 2.0 to 3.0 if DOAC contraindicated

›PAD-related thrombosis

›Short-course dual antiplatelet therapy then long-term aspirin

›Aspirin 81 mg daily plus clopidogrel 75 mg daily for 1 to 4 weeks

›COMPASS/VOYAGER regimen for PAD

›Low-dose rivaroxaban 2.5 mg twice daily plus aspirin 81 mg daily

›Shown to reduce MACE and MALE in symptomatic PAD patients

›Statin therapy for all patients

›High-intensity statin regardless of LDL

›Atorvastatin 40 to 80 mg daily

›Rosuvastatin 20 to 40 mg daily

Thrombolysis contraindications

›Absolute contraindications to catheter-directed thrombolysis

›Active internal bleeding excluding menses

›Stroke within prior 2 months

›Intracranial neoplasm

›Relative contraindications

›Major surgery or trauma within 10 days

›Uncontrolled hypertension > 180/110 mmHg

›Recent GI bleed within 10 days

›Hepatic failure with coagulopathy

09Special Populations/sp58

Pregnancy

›Pregnancy-specific considerations

›Hypercoagulable state of pregnancy increases thrombotic risk

›Protein S deficiency physiologic in pregnancy

›Antiphospholipid syndrome exacerbated by pregnancy

›Heparin is safe in all trimesters

›Unfractionated heparin does not cross placenta

›Low molecular weight heparin alternative for maintenance

›Avoid DOACs — teratogenic and fetal bleeding risk

›Warfarin teratogenic in first trimester — avoid

›Thrombolytic therapy high risk in pregnancy

›Risk of placental abruption and fetal loss

›Use only in life or limb-threatening situations

›Surgical revascularization generally preferred over thrombolysis

›Multidisciplinary decision with maternal-fetal medicine

›Imaging with CTA — fetal radiation exposure acceptable for limb-threatening emergency

›Abdominal shielding where possible

›Benefit clearly outweighs risk when limb viability threatened

›Fetal monitoring throughout procedure if viable gestation

Geriatric

›Older adult features

›Higher prevalence of PAD and AF — increased baseline risk

›ALI incidence peaks in sixth to eighth decade

›Prior revascularization history more likely

›Atypical presentations common

›Reduced pain sensitivity from neuropathy may mask severity

›Weakness interpreted as deconditioning delaying diagnosis

›Polypharmacy considerations

10Background/b64

Epidemiology

›Incidence and burden

›Incidence approximately 1.5 per 10,000 persons per year

›Higher rates in patients with established PAD (0.8% to 1.7% per year)

›Incidence increasing with aging population and PAD prevalence

›Mortality and amputation

›30-day mortality 10% to 15%

›Amputation rates up to 15% even with treatment

›Combined mortality/major amputation rate up to 30% at 30 days

›Sex distribution

›Embolic ALI slight female predominance (AF association)

›Thrombotic ALI slight male predominance (PAD burden)

›Geographic and socioeconomic factors

›Higher rates in low- and middle-income countries

›Limited access to vascular intervention worsens outcomes

Pathophysiology

›Mechanisms of arterial occlusion

›Embolic — 70% to 80% of cases historically

›Cardiac origin most common — AF, LV thrombus, valvular disease

›Arterial origin — aortic or peripheral aneurysm

›Paradoxical embolism through patent foramen ovale (rare)

›Thrombotic — in situ

›Plaque rupture on pre-existing PAD

›Graft or stent thrombosis

›Hypercoagulable state-driven thrombosis

›Less common mechanisms

›Aortic dissection with limb malperfusion

›Popliteal artery entrapment

›Trauma-related arterial injury

›Ischemia-reperfusion injury cascade

›Ischemic phase

›ATP depletion leads to calcium influx and cell swelling

›Xanthine oxidase accumulation

›Anaerobic metabolism with lactate production

›Reperfusion phase

›Reactive oxygen species burst on blood return

›Endothelial activation and neutrophil adhesion

›Microvascular no-reflow phenomenon

›Systemic consequences

›Myoglobin release from muscle necrosis causes tubular renal injury

›Potassium release causes hyperkalemia with cardiac toxicity

›Metabolic acidosis from lactate and potassium

›ARDS from systemic inflammatory response

Therapeutic Considerations

›Anticoagulation rationale

›Heparin prevents thrombus propagation — does not lyse existing clot

›Immediate initiation reduces limb loss even before revascularization

›Time to adequate anticoagulation matters — do not delay for imaging

›Alternative anticoagulation when heparin contraindicated

›HIT — argatroban or bivalirudin

›Fondaparinux not recommended in acute thrombectomy setting

›Revascularization strategy principles

›Open versus endovascular — determined by Rutherford category, anatomy, and center expertise

›Endovascular preferred for Category I and IIa — lower procedural risk

›Open surgical preferred for Category IIb requiring rapid restoration

›Catheter-directed thrombolysis evidence

›Cochrane review 2021 — thrombolysis comparable to surgery for limb salvage in IIa

›Higher stroke and bleeding risk with systemic thrombolysis versus catheter-directed

›STILE trial and TOPAS trial evidence

›Thrombolysis superior for occluded grafts < 14 days

›Surgery superior for native artery occlusions requiring rapid revascularization

›Etiology-based secondary prevention

›AF-related ALI — long-term oral anticoagulation reduces recurrence

›PAD-related thrombosis — COMPASS regimen rivaroxaban 2.5 mg BID plus aspirin 81 mg

›15% relative risk reduction in MALE in VOYAGER PAD trial

›Smoking cessation as most impactful modifiable risk reduction

›Statin therapy — reduces cardiovascular events and may stabilize plaque

11Patient Discharge Instructions/pdi32

copy discharge instructions

›Acute limb ischemia discharge information

›Medications as prescribed — do not skip or stop blood thinners

›Take anticoagulant exactly as directed — same time each day

›Never stop without calling your doctor first

›Activity restrictions

›No prolonged sitting or standing in first weeks

›Elevate legs when resting to reduce swelling

›Gradual walking program as directed by vascular surgeon

›Wound care for surgical access or fasciotomy sites

›Keep clean and dry as instructed

›Return if redness, swelling, or discharge develops

›Return to emergency immediately for

›Return of pain, numbness, weakness, color change, or coolness in the treated limb

›Dark or tea-colored urine (possible kidney warning sign)

›Decreased urine output

›Chest pain or palpitations

›Shortness of breath

›Signs of bleeding — unusual bruising, blood in stool or urine (blood thinner side effects)

›Swelling, redness, or pus at any wound or catheter site

›Follow up appointments

›Vascular surgery within 1 to 2 weeks

›Cardiology if heart rhythm problem identified

›Duplex ultrasound surveillance of treated vessel or graft as scheduled

›Lifestyle and risk factor modification

›Smoking cessation — single most important action

›Heart-healthy Mediterranean diet

›Control of blood pressure, blood sugar, and cholesterol

12References/r22

Guidelines and key sources

›Primary guidelines

›2024 ACC/AHA/SCAI/SVS Guideline for Management of Lower Extremity Peripheral Artery Disease

›Gornik HL et al. Journal of the American College of Cardiology. 2024

›Comprehensive evidence-based management of PAD including ALI

›JACC Scientific Statement on Antithrombotic Strategies for PAD

›Bonaca MP et al. Journal of the American College of Cardiology. 2024

›COMPASS and VOYAGER PAD regimen guidance

›TASC II Inter-Society Consensus for Management of Peripheral Arterial Disease

›Norgren L et al. Journal of Vascular Surgery. 2007

›Key clinical references

›Creager MA, Kaufman JA, Conte MS. Acute Limb Ischemia. NEJM 2012

›Rutherford classification system and management algorithm

›Arnold J, Koyfman A, Long B. High Risk and Low Prevalence Diseases — Acute Limb Ischemia. American Journal of Emergency Medicine. 2023

›Emergency medicine focused review

›Broderick C, Patel JV. Infusion Techniques for Peripheral Arterial Thrombolysis. Cochrane Database 2021

›Systematic review comparing CDT techniques

›ACR Appropriateness Criteria — Sudden Onset of Cold Painful Leg. 2023 Update

›Browne WF et al. Journal of the American College of Radiology. 2023

›Coding references

›ICD-10 I74.3 embolism and thrombosis of arteries of lower extremities

›ICD-10 I75.02 atheroembolism of lower extremity

›ICD-10 I82.49 acute venous embolism and thrombosis — phlegmasia cerulea dolens differential

Evidence & Review

Evidence & Review