Pulmonology, Critical Care & Shock

Acute Pulmonary Embolism (PE) Stratification

flowchart TD
    Suspicion["Suspected Pulmonary Embolism"] --> Stability{"Hemodynamically Stable? (SBP >= 90 mmHg)"}

    Stability -- No (Massive PE) --> UnstableWorkup["Bedside Echocardiogram (RV strain)"]
    UnstableWorkup --> Thrombolysis["Systemic Thrombolytic Therapy (Alteplase) or Catheter-Directed Embolectomy"]

    Stability -- Yes --> Wells["Calculate Wells Score"]
    Wells -- Wells <= 4 (Unlikely) --> Ddimer["High-Sensitivity D-Dimer"]
    Ddimer -- Negative --> RuleOut["PE Ruled Out (No anticoagulation)"]
    Ddimer -- Positive --> CTPA["CT Pulmonary Angiography"]

    Wells -- Wells > 4 (Likely) --> CTPA
    CTPA -- Confirmed PE --> Anticoag["Therapeutic Anticoagulation (LMWH, Fondaparinux, or DOAC)"]

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Shock Differentiation & Hemodynamic Profiles

Shock Type	Central Venous Pressure (CVP) / Preload	Cardiac Output (CO) / Index	Systemic Vascular Resistance (SVR)	Mixed Venous O2 (ScvO2)	Primary Management
Hypovolemic	↓↓	↓	↑↑	↓	Isotonic Crystalloids (LR or Normal Saline)
Cardiogenic	↑↑	↓↓	↑↑	↓↓	Inotropes (Dobutamine, Milrinone), Revascularization, Diuretics
Distributive (Septic / Anaphylactic)	↓ or ↔	↑ (early) → ↓	↓↓ (Vasodilation)	↑ (Extraction defect)	Norepinephrine, 30 mL/kg IVF, Empiric Antibiotics
Obstructive (Tamponade / Tension PTX)	↑↑	↓↓	↑↑	↓	Relieve obstruction: Pericardiocentesis, Needle Decompression

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Acute Respiratory Distress Syndrome (ARDS)

• Berlin Definition:
  1. Acute onset within 1 week of known clinical insult.
  2. Bilateral opacities on chest imaging not fully explained by effusions, collapse, or nodules.
  3. Respiratory failure not fully explained by cardiac failure or fluid overload (objective assessment like echo required if no risk factor).
  4. Impaired oxygenation: PaO2 / FiO2 ≤ 300 mmHg with PEEP ≥ 5 cm H2O.
• Ventilator Protocol:
  • Low Tidal Volume Ventilation: 4–8 mL/kg of predicted body weight (PBW) to prevent barotrauma and volutrauma.
  • Plateau Pressure Goal: ≤ 30 cm H2O.
  • Permissive Hypercapnia: Tolerated (pH down to 7.20) to avoid excessive ventilation volumes.
  • Prone Positioning: Indicated for severe ARDS (P/F < 150) for ≥ 16 hours/day.