← Emergency Medicine Vault • Critical Care Algorithm

Undifferentiated Shock Hemodynamic Matrix

Swan-Ganz Catheter Profiles: PCWP, CVP, CO, SVR, and SvO₂ Across the 4 Shock Etiologies.

Mean Arterial Pressure < 65 Surviving Sepsis 2021
Type I: Volume Depletion Cold & Clammy

Hypovolemic Shock

PCWP (Preload): ↓↓ Markedly Low
CVP: ↓↓ Low (< 4 mmHg)
Cardiac Output (CO): ↓ Decreased
SVR (Afterload): ↑↑ High (Compensatory)
SvO₂ (Venous O₂): ↓ Low (< 65%)
Rx: 30 mL/kg IV Crystalloid bolus; uncrossmatched blood (O-) if hemorrhagic.
Type II: Pump Failure Cold & Wet

Cardiogenic Shock

PCWP (Preload): ↑↑ High (> 18 mmHg)
CVP: ↑↑ Elevated (JVD+)
Cardiac Output (CO): ↓↓ Severely Low
SVR (Afterload): ↑↑ High (Vasoconstriction)
SvO₂ (Venous O₂): ↓ Low (< 60%)
Rx: Inotropes (Dobutamine / Milrinone) + Norepinephrine; emergent cath lab PCI.
Type III: Extracardiac Block Tamponade / PE

Obstructive Shock

PCWP: ↑ in Tamponade / ↓ in PE
CVP: ↑↑ Markedly High
Cardiac Output (CO): ↓ Impaired filling
SVR (Afterload): ↑↑ High
Equalization of Pressures: RA = RV = PCWP (Tamponade)
Rx: Pericardiocentesis (Tamponade); Needle decompression (Pneumothorax); tPA / embolectomy (PE).
Type IV: Vasodilatory Warm & Dry

Distributive (Septic) Shock

PCWP (Preload): ↓ or Normal
CVP: ↓ or Normal
Cardiac Output (CO): ↑↑ High (Hyperdynamic)
SVR (Afterload): ↓↓ LOW (Pathognomonic!)
SvO₂ (Venous O₂): ↑ Elevated (> 70%)
Rx: Norepinephrine (first-line vasopressor) + Vasopressin + Stress-dose hydrocortisone.
Board Rule: The Diagnostic Key to Shock Quick Recall Rule

Look immediately at Systemic Vascular Resistance (SVR): If SVR is DECREASED, the shock is unequivocally DISTRIBUTIVE (Sepsis, Anaphylaxis, or Neurogenic). If SVR is INCREASED, look at PCWP: High PCWP = Cardiogenic; Low PCWP = Hypovolemic; High CVP with low/normal PCWP = Pulmonary Embolism.