3.5 Thromboembolic Disease (DVT/PE), Pneumonia, & Pleural Effusions
Key Takeaways
- Pulmonary Embolism (PE) diagnostic workup utilizes the Wells PE Score: low-probability patients require PERC rule or D-dimer to exclude PE, whereas high-probability patients require immediate CT Pulmonary Angiography (CTPA).
- Hemodynamically unstable (massive) PE presents with hypotension (SBP <90 mmHg) or shock and mandates immediate IV systemic thrombolysis (alteplase); stable PE is treated with direct oral anticoagulants (DOACs).
- Community-Acquired Pneumonia (CAP) severity stratification relies on the CURB-65 score (Confusion, Urea >7 mmol/L, RR ≥30, BP <90/60, Age ≥65) to direct outpatient (0-1), ward (2), or ICU (≥3) admission.
- Empiric outpatient CAP treatment in healthy patients without comorbidities is amoxicillin monotherapy; patients with underlying comorbidities require amoxicillin/clavulanate plus a macrolide, or respiratory fluoroquinolone monotherapy.
- Pleural effusions are classified into transudates vs exudates using Light's Criteria; complicated parapneumonic effusions or empyema (pH <7.20, glucose <3.3 mmol/L, positive Gram stain/culture) require mandatory chest tube drainage.
3.5 Thromboembolic Disease (DVT/PE), Pneumonia, & Pleural Effusions
Quick Summary: Diagnostic evaluation of Pulmonary Embolism (PE) relies on Wells criteria: low-risk patients undergo PERC rule or D-dimer testing, while high-risk patients proceed directly to CTPA. Massive PE with shock mandates emergency IV thrombolysis. Pneumonia severity is stratified using CURB-65. Pleural effusions are classified by Light's criteria; empyema or complicated parapneumonic effusions (pH <7.20, glucose <3.3 mmol/L) require prompt chest tube drainage.
Venous Thromboembolism (DVT & PE)
Venous Thromboembolism (VTE) encompasses Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE), driven by Virchow's Triad (venous stasis, endothelial injury, hypercoagulability).
Diagnostic Algorithm for Pulmonary Embolism
- Wells PE Score Parameters: Clinical signs of DVT (+3), PE most likely diagnosis (+3), HR >100 bpm (+1.5), Immobilization/Surgery in past 4 weeks (+1.5), Prior DVT/PE (+1.5), Hemoptysis (+1), Active Malignancy (+1).
- PERC Rule (Pulmonary Embolism Rule-out Criteria): Applied ONLY when PE probability is low (Wells ≤4). If ALL 8 criteria are met (Age <50, HR <100, SpO2 ≥95%, no prior VTE, no recent surgery/trauma, no hemoptysis, no estrogen use, no unilateral leg swelling), PE is excluded without D-dimer testing.
- Age-Adjusted D-Dimer: For patients aged >50 years, the elevated D-dimer cutoff is Age × 10 µg/L (e.g., 70 years = 700 µg/L cutoff).
- Imaging: CT Pulmonary Angiography (CTPA) is the gold standard imaging modality. Ventilation-Perfusion (V/Q) Scan is indicated if CTPA is contraindicated (severe renal impairment eGFR <30 mL/min, contrast allergy, or pregnancy).
Management of VTE
- Hemodynamically Unstable (Massive PE: SBP <90 mmHg or drop ≥40 mmHg for 15 min): Immediate Systemic Thrombolysis (Alteplase 100 mg IV over 2 hours) or catheter-directed/surgical embolectomy.
- Hemodynamically Stable (Submassive / Low-Risk PE): DOACs (Apixaban 10 mg BID x 7 days then 5 mg BID, or Rivaroxaban 15 mg BID x 21 days then 20 mg daily) are first-line anticoagulants over LMWH/Warfarin.
- Duration of Anticoagulation: Provoked by transient risk factor -> 3 months. Unprovoked VTE or active cancer -> Extended / indefinite anticoagulation (DOAC or LMWH for active cancer).
Pneumonia (CAP & HAP)
Community-Acquired Pneumonia (CAP) is an acute infection of the lung parenchyma acquired outside healthcare settings.
Etiology & Severity Stratification (CURB-65)
- Common Pathogens: Streptococcus pneumoniae (most common typical cause), Haemophilus influenzae, Mycoplasma pneumoniae (atypical in young adults), Legionella pneumophila (hyponatremia, diarrhea, air conditioning/water sources), Staphylococcus aureus (post-viral influenza superinfection).
- CURB-65 Criteria (1 Point Each):
- Confusion (new disorientation)
- Urea > 7.0 mmol/L (BUN > 19 mg/dL)
- Respiratory Rate ≥ 30 breaths/min
- Blood Pressure (SBP < 90 mmHg or DBP ≤ 60 mmHg)
- 65 Age ≥ 65 years
- Triage & Disposition: Score 0–1: Outpatient care (Mortality <1.5%). Score 2: Inpatient ward admission (Mortality 9.2%). Score ≥3: Severe CAP, consider ICU admission (Mortality 22%).
Empirical Antimicrobial Regimens
| Setting & Patient Category | Empirical Antibiotic Regimen |
|---|---|
| Outpatient (Healthy, No Comorbidities) | Amoxicillin 1 g PO TID (preferred) OR Doxycycline 100 mg PO BID. (Macrolide monotherapy only if local pneumococcal resistance <25%) |
| Outpatient (With Comorbidities: COPD, DM, CKD, Heart Failure) | Amoxicillin/Clavulanate (875/125 mg PO BID) + Azithromycin (500 mg day 1, then 250 mg daily) OR Respiratory Fluoroquinolone monotherapy (Levofloxacin 750 mg daily or Moxifloxacin 400 mg daily) |
| Inpatient Ward | IV Ceftriaxone (1–2 g daily) + IV/PO Azithromycin (500 mg daily) OR Respiratory Fluoroquinolone IV/PO |
| Inpatient ICU | IV Ceftriaxone (2 g daily) + IV Azithromycin (500 mg daily). Add Vancomycin for MRSA risk; add Piperacillin-Tazobactam for Pseudomonas risk. |
Pleural Effusions & Light's Criteria
A pleural effusion is an abnormal accumulation of fluid in the pleural space. Diagnostic thoracentesis is indicated for any new, unexplained pleural effusion (>1 cm on lateral decubitus X-ray or US), except in obvious bilateral symmetric effusions from CHF.
Light's Criteria (Exudate vs. Transudate)
An effusion is classified as an EXUDATE if AT LEAST ONE of the following three criteria is fulfilled:
- Pleural Fluid Protein / Serum Protein ratio > 0.5
- Pleural Fluid LDH / Serum LDH ratio > 0.6
- Pleural Fluid LDH > 2/3 the upper limit of normal for serum LDH
| Classification | Pathophysiology | Common Etiologies |
|---|---|---|
| Transudate | Increased hydrostatic pressure or decreased plasma oncotic pressure (Intact capillaries) | Congestive Heart Failure (most common), Cirrhosis (hepatic hydrothorax), Nephrotic Syndrome, Hypoalbuminemia |
| Exudate | Increased capillary permeability or impaired lymphatic drainage (Inflammation/Malignancy) | Pneumonia (Parapneumonic effusion), Malignancy (lung, breast, lymphoma), PE, Tuberculosis, Pancreatitis, Autoimmune (RA, SLE) |
Parapneumonic Effusion & Empyema Management
- Uncomplicated Parapneumonic: pH > 7.20, Glucose > 3.3 mmol/L, LDH < 1000 U/L, negative Gram stain/culture -> Antibiotics alone.
- Complicated Parapneumonic / Empyema: pH < 7.20, Glucose < 3.3 mmol/L, LDH > 1000 U/L, positive Gram stain/culture, or frank pus -> Mandatory Chest Tube Drainage (Tube Thoracostomy).
Exam Traps & Special Clinical Scenarios
- Aspiration Pneumonia: Occurs in patients with altered consciousness, dysphagia, or seizure. Involves dependent lung segments: superior segments of lower lobes or posterior segments of upper lobes when supine. Requires anaerobic coverage (e.g., Amoxicillin-clavulanate or Ampicillin-sulbactam).
- Chylothorax: Pleural effusion with milky white fluid, elevated triglycerides (>1.24 mmol/L or 110 mg/dL), caused by thoracic duct disruption (trauma, lymphoma).
- Pseudo-exudate in CHF: Chronic diuretic therapy in CHF concentrates pleural protein, falsely meeting Light's criteria for an exudate. Calculate serum-to-pleural fluid protein gradient; a difference >31 g/L confirms a true transudate.
A 32-year-old female presents to the emergency department with sudden-onset right-sided pleuritic chest pain and dyspnea. She takes oral contraceptive pills. Vital signs: BP 118/76 mmHg, HR 106 bpm, RR 22/min, SpO2 94% on room air. Examination of the lower extremities is unremarkable. Calculation of the Wells PE score yields 4.5 points (PE likely). What is the most appropriate next step in management?
A 74-year-old male with mild vascular dementia is brought from a long-term care facility with a 2-day history of fever, productive cough, and lethargy. On examination: disoriented to time and place, temp 38.6°C, BP 86/54 mmHg, HR 110 bpm, RR 32/min, SpO2 89% on room air. Laboratory testing demonstrates Urea 11.2 mmol/L. Chest X-ray reveals right lower lobe consolidation. What is his CURB-65 score and the recommended triage disposition?
A 65-year-old male hospitalized for left lower lobe pneumococcal pneumonia develops persistent fevers despite 4 days of IV Ceftriaxone. A chest ultrasound reveals a moderate loculated left pleural effusion. Thoracentesis yields cloudy fluid with the following laboratory findings: Pleural Protein 44 g/L (Serum 66 g/L), Pleural LDH 1250 U/L (Serum 220 U/L), Pleural Glucose 1.9 mmol/L, and Pleural pH 7.06. What is the most appropriate next step in management?