01Approach to the Critical Patient/attcp34

Limb-threatening emergency recognition

›Phlegmasia cerulea dolens

›Profound cyanosis with massive unilateral edema

›Severe limb pain with venous gangrene risk

›Compartment syndrome risk requiring urgent vascular surgery consult

›Arterial pulse assessment to exclude superimposed arterial compromise

›Phlegmasia alba dolens

›Pale, massively swollen limb without cyanosis

›Extensive iliofemoral DVT without arterial compromise

›Urgent imaging and hematology consultation required

›Concurrent hemodynamically significant PE

›Hypotension with SBP < 90 mmHg

›Tachycardia > 110 bpm with hypoxia

›Massive PE protocol activation if hemodynamically unstable

Hemodynamic and monitoring targets

›Initial stabilization priorities

›Supplemental oxygen if SpO2 < 94%

›IV access and continuous cardiac monitoring

›12-lead ECG for PE co-detection

›Tachycardia, right heart strain pattern, or S1Q3T3 increases PE suspicion

›Escalation triggers

›Hypotension not responsive to 1 L crystalloid bolus

›Progressive oxygen desaturation below 90%

›Signs of right ventricular failure

›Immediate CT pulmonary angiography or bedside echocardiography

Immediate consults and disposition decisions

›Vascular surgery consultation indications

›Phlegmasia cerulea dolens with limb threat

02History/hx53

Symptom characterization

›Core presenting symptoms

›Unilateral leg swelling in 80% of cases

›Leg pain or tenderness in 80 to 90% of cases

›Erythema of affected limb in approximately 25%

›Warmth and prominent collateral superficial veins in 30%

›Symptom timeline and onset

›Acute onset after immobility, travel, surgery, or hospitalization

›Postpartum period as high-risk trigger

›Gradual onset over days in unprovoked cases

›Concurrent PE symptoms

›New dyspnea, pleuritic chest pain, hemoptysis, or syncope

›30 to 60% of proximal DVT patients have silent PE

Risk factor assessment

›Provoked and transient risk factors

›Major surgery, especially orthopedic hip or knee replacement

›Hospitalization or immobilization greater than 3 days

›Long-distance travel greater than 4 hours

›Trauma and lower extremity fracture

›Pregnancy and postpartum period

›Persistent and chronic risk factors

›Active malignancy — cancer-associated DVT carries high recurrence risk

›Prior VTE — strongest predictor of recurrence

›Known thrombophilia: Factor V Leiden, prothrombin G20210A mutation

›Protein C or S deficiency, antithrombin deficiency

›Antiphospholipid syndrome

›Chronic heart failure or COPD

›Obesity BMI ≥ 30

03Physical Exam/exam32

Vital signs assessment

›Hemodynamic and respiratory stability

›Heart rate — tachycardia above 100 bpm increases PE suspicion

›Blood pressure — hypotension suggests concurrent massive PE

›Respiratory rate — tachypnea with hypoxia increases PE concern

›Oxygen saturation on room air

›Temperature — fever may indicate infected thrombophlebitis or septic emboli

Lower extremity focused exam

›Unilateral swelling assessment

›Calf circumference measured 10 cm below tibial tuberosity

›Difference of 3 cm or more is clinically significant

›Pitting edema confined to symptomatic limb

›Deep venous system tenderness

›Popliteal fossa palpation

›Medial thigh along femoral vein

›Groin and inguinal region

›Skin findings

›Warmth and erythema of affected limb

›Prominent non-varicose collateral superficial veins

›Cyanosis suggesting phlegmasia cerulea dolens

›Pallor suggesting phlegmasia alba dolens

›Homan sign

›Calf pain with dorsiflexion

›Poor sensitivity and specificity — not recommended for clinical decision-making

Limb-threatening findings

›Emergency physical signs

›Tense, massively swollen cyanotic limb — phlegmasia cerulea dolens

›Absent distal pulses suggesting arterial compromise

04Differential Diagnosis/ddx38

Life-threatening conditions to exclude

›Concurrent pulmonary embolism

›ICD-10 I26.9 — pulmonary embolism without acute cor pulmonale

›30 to 60% of proximal DVT have silent concurrent PE

›Differentiating features: dyspnea, pleuritic pain, tachycardia, hypoxia

›Phlegmasia cerulea dolens

›ICD-10 I82.401 — deep thrombosis lower extremity

›Limb-threatening with venous gangrene risk

›Arterial occlusion

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

›Cool pale pulseless limb — 6 Ps: pain, pallor, pulselessness, paresthesia, paralysis, poikilothermia

Common mimics

›Cellulitis

›ICD-10 L03.115 — cellulitis of right lower limb

›Bilateral erythema, fever, leukocytosis, skin breaks or entry points

›DVT and cellulitis can coexist — do not use cellulitis to exclude DVT

›Ruptured Baker cyst

›ICD-10 M71.20 — synovial cyst of popliteal space

›Posterior knee pain radiating to calf, history of knee osteoarthritis

›Ultrasound differentiates — cyst rupture can cause calf swelling

›Superficial thrombophlebitis

›ICD-10 I80.0 — phlebitis and thrombophlebitis of superficial vessels

›Palpable tender cord along superficial vein

›Can coexist with or progress to DVT in 10 to 30%

›Muscle strain or hematoma

›ICD-10 S76.011A — strain of right hip muscle

›History of exertion or direct trauma

›Ultrasound or MRI distinguishes

05Laboratory Tests/lt30

D-dimer testing

›High-sensitivity quantitative D-dimer

›Negative result less than 500 mcg/L combined with low pretest probability safely excludes DVT

›Excludes DVT in approximately 29% of suspected cases when low probability

›High sensitivity but low specificity — elevated in cancer, infection, pregnancy, surgery

›Do not use D-dimer alone without pretest probability assessment

›Age-adjusted D-dimer threshold

›Age multiplied by 10 mcg/L for patients aged 50 years and older

›Improves specificity in older patients without loss of sensitivity

›ACEP Level B recommendation for age-adjusted thresholds in low-probability patients

Hematologic and metabolic baseline

›Complete blood count

›Thrombocytopenia as HIT risk indicator — baseline platelet count before heparin

›Anemia from malignancy or bleeding risk assessment

›Leukocytosis suggesting concurrent infection

›Coagulation studies

›PT/INR as baseline before warfarin initiation

›aPTT as baseline and for unfractionated heparin monitoring

›Renal and hepatic function

›Creatinine and eGFR for DOAC dosing eligibility

›Hepatic panel for coagulopathy and DOAC contraindication assessment

›Pregnancy test

›Reproductive-age patients — changes anticoagulant choice

›DOACs contraindicated in pregnancy — LMWH preferred

Thrombophilia and extended workup

›Thrombophilia testing

›Generally deferred to outpatient setting — rarely changes acute management

›Optimal timing is after anticoagulation completed — not during acute phase

06Diagnostic Tests/dt65

Scoring Systems

›Wells criteria for DVT pretest probability

›Active cancer — 1 point

›Paralysis, paresis, or recent plaster immobilization of lower extremity — 1 point

›Recently bedridden more than 3 days or major surgery within 12 weeks — 1 point

›Localized tenderness along deep venous system — 1 point

›Entire leg swollen — 1 point

›Calf swelling greater than 3 cm compared with asymptomatic leg — 1 point

›Pitting edema confined to symptomatic leg — 1 point

›Collateral non-varicose superficial veins — 1 point

›Previously documented DVT — 1 point

›Alternative diagnosis as likely or more likely than DVT — minus 2 points

›Wells score interpretation

›Score 2 or higher: DVT likely — approximately 28% prevalence

›Score less than 2: DVT unlikely — approximately 5% prevalence

›DVT unlikely score with negative D-dimer: imaging unnecessary

›DVT unlikely score with positive D-dimer: proceed to compression ultrasound

›DVT likely score: proceed directly to compression ultrasound

›Limitations of Wells score

›Performs poorly in inpatients — AUC of 0.60

›Proceed directly to imaging for inpatients regardless of score

›Validated primarily in outpatient and emergency department populations

MRI

›MR venography indications and technique

›Alternative to CT venography when contrast is contraindicated

›Preferred imaging in pregnancy to avoid ionizing radiation

›Superior soft tissue resolution for pelvic and IVC thrombus

›May Time-of-flight MRV — no contrast required; detects slow or absent flow

›MRI performance characteristics for DVT

›Sensitivity approximately 97% and specificity approximately 95% for pelvic DVT

›Particularly useful for iliac vein and IVC thrombosis not seen on CUS

›Limited availability and longer acquisition time versus ultrasound

›Gadolinium should be avoided in first trimester of pregnancy

CT

›CT venography indications

›Adjunct when compression ultrasound is inconclusive

›Pelvic and IVC thrombus evaluation

›Combined with CT pulmonary angiography for simultaneous PE assessment

›Identifies extrinsic compression causing DVT — pelvic mass, May-Thurner syndrome

›CT pulmonary angiography for concurrent PE

›ACEP Level B recommendation for suspected PE with intermediate to high pretest probability

›Sensitivity greater than 95% and specificity greater than 96% for PE

›Exposes patient to radiation and iodinated contrast

›Relative contraindication in pregnancy — use V/Q scan or MRI instead

›May-Thurner syndrome detection

›Left iliac vein compression by right iliac artery

›Accounts for left-sided predominance of iliofemoral DVT in young women

›CT venography or MR venography diagnostic

Ultrasound

›Compression ultrasonography as first-line imaging

›Sensitivity greater than 95% and specificity greater than 95% for proximal DVT

›ACEP Level A recommendation for compression ultrasound in suspected DVT

›Non-compressibility of the vein is the diagnostic criterion

›Color Doppler augmentation to assess venous flow

›Proximal two-point compression ultrasound

›Common femoral vein at groin and popliteal vein behind knee

›If negative but suspicion remains, repeat in 1 week or perform whole-leg CUS

›Sensitivity approximately 92% for proximal DVT, lower for isolated distal DVT

›Whole-leg compression ultrasound

›Extends from common femoral to tibial and peroneal veins

›Identifies isolated distal DVT — sensitivity approximately 74%

›Reduces need for repeat testing compared to two-point CUS

›Serial ultrasound strategy

›Repeat proximal CUS at 1 week if initial negative with high clinical suspicion

›Serial strategy detects proximally extending distal clots

›Alternative to whole-leg CUS when distal DVT identification not urgent

›Point-of-care ultrasound in the emergency department

›Adequate for two-point CUS when performed by trained clinician

›Does not replace formal vascular laboratory study for equivocal results

07Disposition/dispo27

Outpatient discharge criteria

›Standard of care outpatient treatment eligibility

›Acute uncomplicated proximal or distal DVT

›Hemodynamically stable without concurrent symptomatic PE requiring admission

›Adequate home support and ability to self-care

›Ability to afford and adhere to DOAC regimen

›Reliable follow-up within 1 to 2 weeks

›No high bleeding risk requiring close inpatient monitoring

Admission indications

›Clinical criteria requiring inpatient admission

›Phlegmasia cerulea dolens or alba dolens — limb-threatening emergency

›Concurrent symptomatic PE with hemodynamic instability

›High bleeding risk requiring close monitoring during anticoagulation initiation

›Massive iliofemoral DVT with severe symptoms

›Inability to tolerate oral medications

›Inadequate home support or inability to arrange reliable follow-up

›Need for catheter-directed therapy or surgical thrombectomy

›Suspected heparin-induced thrombocytopenia requiring parenteral transition

›Active major bleeding while anticoagulated

Observation indications

›Intermediate disposition criteria

›Borderline hemodynamic stability with suspected concurrent PE

›Initiation of warfarin requiring INR monitoring and heparin bridge

›Symptom management of severe limb pain before safe discharge

›Social circumstances preventing same-day outpatient follow-up arrangement

Follow-up planning

›Mandatory follow-up schedule

›1 to 2 weeks post-diagnosis for symptom reassessment and medication adherence

08Treatment/t75

Anticoagulation initiation

›Anticoagulation principles

›Initiate upon diagnosis or high clinical suspicion — do not delay for thrombophilia workup

›DOACs preferred over warfarin for non-cancer DVT — Class I recommendation

›No parenteral bridge needed for apixaban or rivaroxaban

›LMWH required as bridge for dabigatran and edoxaban

DOAC regimens — first-line

›Apixaban

›Initial phase: 10 mg orally twice daily for 7 days

›Maintenance phase: 5 mg orally twice daily

›No parenteral bridge required

›Extended secondary prevention: 2.5 mg twice daily after initial 6 months

›Rivaroxaban

›Initial phase: 15 mg orally twice daily with food for 21 days

›Maintenance phase: 20 mg orally daily with evening meal

›No parenteral bridge required

›Extended secondary prevention: 10 mg daily after initial 6 months

›Dabigatran

›Requires parenteral anticoagulation for 5 to 10 days before initiation

›Maintenance dose: 150 mg orally twice daily

›Renal dose reduction: 110 mg twice daily if eGFR 30 to 50 mL/min

›Edoxaban

›Requires parenteral anticoagulation for 5 to 10 days before initiation

›Maintenance dose: 60 mg orally daily

›Avoid in GI malignancy due to increased GI bleeding risk

Parenteral anticoagulation options

›Low molecular weight heparin — enoxaparin

›1 mg/kg subcutaneously every 12 hours

›Alternative: 1.5 mg/kg subcutaneously daily for uncomplicated DVT

›Preferred in pregnancy, severe renal impairment, antiphospholipid syndrome

›Dose adjust for eGFR less than 30 mL/min — 1 mg/kg daily or UFH preferred

›Unfractionated heparin

›80 units/kg IV bolus followed by 18 units/kg/hour infusion

›Titrate to aPTT 60 to 100 seconds

›Preferred when rapid reversal may be needed or renal failure present

›Monitor platelet count every 2 to 4 days for HIT risk

Warfarin for select indications

›Warfarin therapy initiation

›Overlap with parenteral anticoagulation for minimum 5 days

›Continue overlap until INR 2 to 3 on two occasions 24 hours apart

›Target INR 2 to 3 for standard DVT

›Target INR 3 to 4 for antiphospholipid syndrome with arterial thrombosis

›Warfarin indications over DOACs

›Antiphospholipid syndrome — DOACs inferior, warfarin mandatory

›Significant renal impairment with eGFR below 15 mL/min

›Severe hepatic disease with coagulopathy

›Cost barriers when DOAC access unavailable

Duration of anticoagulation

›Provoked DVT by major transient risk factor

›Surgery, immobilization, or trauma: 3 months then discontinue

›Low recurrence risk after provoked episode with removed trigger

›Provoked DVT by minor or reversible risk factor

›Hormonal contraceptive, minor surgery: 3 to 6 months

›Reconsider trigger and modify risk factors

›Unprovoked proximal DVT

›Consider extended or indefinite anticoagulation

›Recurrence rate 10% at 1 year and 36% at 10 years if anticoagulation stopped

›Weigh bleeding risk versus recurrence risk with validated tools

›Cancer-associated DVT

›Extended anticoagulation for duration of active cancer

›DOACs preferred over LMWH for most cancer-associated DVT

›Exception: avoid edoxaban in GI malignancy — increased GI bleeding risk

Interventional and mechanical therapies

›Catheter-directed thrombolysis

›Reserved for severe symptoms, limb-threatening disease, and low bleeding risk

›Only at experienced centers with multidisciplinary capability

›Reduces postthrombotic syndrome risk in select iliofemoral DVT patients

›IVC filter placement

›Absolute indication: anticoagulation absolutely contraindicated with ongoing VTE risk

›Not indicated as adjunct to anticoagulation — does not reduce PE mortality

›Retrievable filters preferred when temporary contraindication anticipated

›Surgical thrombectomy

›Reserved for catheter-directed therapy failures or massive iliofemoral DVT

›Vascular surgery consultation required

Supportive measures

›Limb elevation and ambulation

›Elevate affected limb above heart level for edema reduction

›Early ambulation is encouraged — does not increase PE risk

›Compression therapy

›Compression stockings for symptom management during acute phase

›Routine compression for postthrombotic syndrome prevention not strongly supported

›SOX trial showed no significant PTS reduction with routine elastic stockings

09Special Populations/sp54

Pregnancy

›Diagnostic approach in pregnancy

›Compression ultrasonography first-line — safe, no ionizing radiation

›MR venography if CUS inconclusive — avoid gadolinium in first trimester

›D-dimer elevated physiologically in pregnancy — specificity very low

›Do not use D-dimer alone to exclude DVT in pregnancy

›VTE risk in pregnancy

›DVT rate 114 per 100,000 in third trimester

›VTE rate 421 per 100,000 in first 3 weeks postpartum — highest risk period

›Pregnancy is a prothrombotic state — hemodilution, venous stasis, hypercoagulability

›Anticoagulation in pregnancy

›LMWH is treatment of choice throughout pregnancy — Class I recommendation

›Enoxaparin 1 mg/kg subcutaneously twice daily — weight-based throughout pregnancy

›DOACs contraindicated in pregnancy — cross placenta and teratogenic

›Warfarin contraindicated in first trimester — fetal warfarin syndrome risk

›Warfarin may be used postpartum and is safe during breastfeeding

›Delivery management

›Hold LMWH 24 hours before planned delivery or regional anesthesia

›Resume LMWH 6 to 12 hours postpartum if hemostasis achieved

›Minimum 6 weeks of anticoagulation postpartum regardless of antepartum duration

Geriatric

›Increased DVT risk and atypical presentation

›Age above 55 is an independent DVT risk factor

›Atypical or minimal symptoms more common — lower threshold for imaging

›Comorbidities complicate anticoagulation eligibility and safety

›Pharmacologic considerations

›Renal function decline — creatinine clearance calculated before DOAC dosing

›Apixaban 2.5 mg twice daily dose reduction criteria: 2 of 3 criteria met

10Background/b54

Epidemiology

›Incidence and prevalence

›Annual DVT incidence approximately 1 to 2 per 1,000 in the general population

›Incidence doubles approximately every decade after age 40

›DVT and PE together — VTE — affect approximately 900,000 Americans annually

›Annual mortality from PE approximately 100,000 in the United States

›Risk distribution

›Left leg more commonly affected — likely due to May-Thurner anatomy

›20% of DVT patients have bilateral involvement even with unilateral symptoms

›Cancer patients have 4 to 7 times higher VTE risk than general population

›Recurrence risk

›Unprovoked DVT — recurrence 10% at 1 year and 36% at 10 years if anticoagulation stopped

›Provoked by major surgery — low recurrence after 3 months anticoagulation

›Provoked by minor risk factor — intermediate recurrence risk

›Long-term complications

›Postthrombotic syndrome develops in 30 to 50% within 2 years

›PTS manifestations: chronic pain, edema, stasis changes, venous ulceration

›Chronic thromboembolic pulmonary hypertension — rare but serious long-term complication

Pathophysiology

›Virchow triad

›Endothelial injury — surgery, trauma, central venous catheter, infection

›Venous stasis — immobility, heart failure, venous insufficiency, compression

›Hypercoagulability — malignancy, thrombophilia, pregnancy, hormonal therapy

›Clot propagation

›Thrombus initiates at venous valve pockets with low flow

›Proximal propagation from distal to proximal veins in lower extremity

›Proximal DVT carries significantly higher PE risk than isolated distal DVT

›Distal DVT isolated to calf veins: PE risk approximately 1 to 3%

11Patient Discharge Instructions/pdi37

copy discharge instructions

›What is deep vein thrombosis

›A blood clot that has formed in one of the deep veins of your leg

›The clot can break off and travel to your lungs — this is called a pulmonary embolism and is a medical emergency

›Most patients with DVT are treated safely at home with blood thinners

›Your blood thinner medication

›Take your medication exactly as prescribed — do not skip doses

›Missed doses increase your risk of clot growing or new clot forming

›Do not stop your blood thinner without speaking to your doctor first

›Carry a list of your medications and a medical alert card noting you are on anticoagulation

›Activity instructions

›You may walk and move around — early activity does not cause the clot to travel to your lungs

›Avoid prolonged sitting or standing in one position

›Elevate your leg above heart level when resting to reduce swelling

›Calf exercises: pump your feet up and down for 5 minutes every hour during travel

›Dietary considerations

›If you are on warfarin, maintain consistent intake of green leafy vegetables

›Avoid sudden large changes in vitamin K intake which can affect your INR

›Stay well hydrated — especially during travel or hot weather

›Return to emergency department immediately for

›New or worsening shortness of breath or difficulty breathing

›Chest pain, especially pain that worsens with breathing

›Coughing up blood

›Fainting or near-fainting

›Worsening leg swelling, increasing pain, or the leg turning blue or very pale

›Unusual or excessive bleeding: blood in urine or stool, black tarry stools, prolonged bleeding from cuts

›Severe headache or vomiting blood

›Sudden weakness, confusion, speech difficulty, or vision changes

12References/r29

Guidelines and key sources

›ACEP Clinical Policy — Wolf SJ et al., Annals of Emergency Medicine 2018

›Critical issues in evaluation and management of adult ED patients with suspected acute VTE

›Supports D-dimer with clinical prediction rules and compression ultrasound

›American College of Chest Physicians — Bates SM et al., Chest 2012

›Antithrombotic therapy and prevention of thrombosis, 9th edition

›Foundational guideline for DVT diagnosis and treatment algorithms

›JAMA Review — Chopard R, Albertsen IE, Piazza G. JAMA 2020

›Diagnosis and treatment of lower extremity venous thromboembolism

›Evidence-based overview of DVT workup and management pathway

›Lancet Review — Khan F, Tritschler T, Kahn SR, Rodger MA. Lancet 2021

›Venous thromboembolism — comprehensive review of epidemiology, pathophysiology, and treatment

›Lancet Review — Di Nisio M, van Es N, Buller HR. Lancet 2016

›Deep vein thrombosis and pulmonary embolism

›JAMA — Tritschler T et al. JAMA 2018

›Venous thromboembolism: advances in diagnosis and treatment

›JAMA 2026 — Le Gal G et al.

›Age-adjusted D-dimer cutoff levels to rule out deep vein thrombosis

›Cochrane Review — Wang X et al. 2023

›Oral direct thrombin inhibitors or oral factor Xa inhibitors versus conventional anticoagulants for DVT treatment

›Cochrane Review — Flumignan CD et al. 2022

›Antiplatelet agents for the treatment of deep venous thrombosis

›American Family Physician — Nasir M, Brumbaugh S, Wile K. AFP 2025

›Venous thromboembolism: diagnosis and treatment

›NEJM — Skeith L, Bates SM. 2026

›Sex hormone influences on venous thrombotic and cardiovascular risk

›Journal of Thrombosis and Haemostasis — Cox C, Roberts LN. 2025

›Basics of diagnosis and treatment of venous thromboembolism

Evidence & Review

Evidence & Review