Respi-pulmonary embolism

Question 1

What is Virchow’s triad

Answer 1

Virchow’s Triad - Risk Factors for DVT/PE
1️⃣ Stasis → bed rest, inactivity, CHF, CVA, long air travel
2️⃣ Endothelial Injury → trauma, surgery, prior DVT
3️⃣ Thrombophilia → Factor V Leiden, APS, OCP use
4️⃣ Others → malignancy, thrombosis history

Question 2

What is some clinical presentation of DVT

Answer 2

1. Mild fever (post-op day 5-7)
2. Calf signs: warmth, tenderness, swelling, erythema
3. Phlegmasia Alba Dolens → pitting edema, pallor
4. Phlegmasia Cerulea Dolens → swollen blue leg → venous gangrene
5. Homan’s sign: calf pain on dorsiflexion (<5% sensitivity)

Question 3

What is some clinical presentation of PE

Answer 3

Dyspnea (73%), pleuritic chest pain (66%), cough (37%)
Hemoptysis (13%) (rare due to dual circulation)
Massive PE → syncope, hypotension, PEA, RV failure (↑ JVP, S3)
Intermediate/Low risk PE → markers of RV strain (elevated BNP, RV dilation, troponin elevation)

Question 4

DVT Investigations

Answer 4

1. Duplex ultrasound → 95% sensitivity & specificity for symptomatic DVT
2. D-Dimer <500ng/ml rules out DVT (if low pre-test probability)

Question 5

Diagnostic Investigations for PE

Answer 5

1. CXR → usually normal; rare signs: Hampton’s hump, Westermark sign
2. ECG → T-wave inversion (V1-V4), sinus tachycardia, S1Q3T3 (rare)
3. ABG → hypoxemia, hypocapnia, respiratory alkalosis
4. D-Dimer: Use YEARS criteria to determine need for CTPA
5. CT Pulmonary Angiogram (gold standard)

Question 6

DVT/PE Prophylaxis - Non-Pharmacological

Answer 6

Inflatable calf pumps intra-op
Early ambulation post-op
TED stockings

Question 7

Treatment for PE/DVT

Answer 7

1. Unfractionated Heparin (UFH)

Immediate onset (IV), 30min (SC), ½-life: 1-2 hrs
Monitored via aPTT
Antidote: Protamine sulfate
Risk: HIT (Heparin-Induced Thrombocytopenia)

2. LMWH (Enoxaparin, Clexane)

½-life: 4-5 hrs, renal clearance
Limited reversibility (60% by Protamine)
Preferred in pregnancy

Question 8

DVT/PE Treatment - Oral Anticoagulants

Answer 8

1. Warfarin (VKA)

Vitamin K antagonist, onset: 2-4 days
Goal INR 2-3
Bridging required (with heparin for ≥5 days)
Antidote: Vitamin K, PCC, FFP
2. NOACs (Rivaroxaban, Apixaban, Dabigatran)

Preferred over warfarin (fewer interactions, no INR monitoring)
Dabigatran antidote: Idarucizumab
Factor Xa inhibitors antidote: PCC, Andexanet-alfa

Question 9

When is NOAC contraindiacted?

Answer 9

Mechanical prosthetic valves or moderate-severe mitral stenosis

Question 10

When is Surgical Treatment for PE ie. IVC filter indicated?

Answer 10

• Anticoagulation contraindicated
• Recurrent PE despite anticoagulation
  ❌ Clot location alone is NOT an indication

Question 11

What is the treatment for massive PE

Answer 11

1. Hypotension (SBP <90mmHg)
   Low/mod bleeding risk → Thrombolysis (tPA)
   High bleeding risk / Failed thrombolysis → Embolectomy (surgical/catheter)
2. Non-hypotensive PE → Anticoagulation
3. Subsegmental PE with no proximal DVT
   Low risk → Surveillance
   High risk → Anticoagulation