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Difficulty: HardCardiovascular System

A 65-year-old hospitalized patient is evaluated for acute-onset hypotension and signs of poor organ perfusion. The intensive care team places a pulmonary artery (Swan-Ganz) catheter to determine the specific etiology of the shock state. Match each set of central hemodynamic parameters obtained from the catheterization to the most likely underlying clinical condition.

  • RAP: 16 mm Hg (↑), PCWP: 20 mm Hg (↑), CI: 1.6 L/min/m² (↓), SVR: 2200 dynes/sec/cm⁻⁵ (↑)Acute anterior myocardial infarction
  • RAP: 2 mm Hg (↓), PCWP: 4 mm Hg (↓), CI: 1.8 L/min/m² (↓), SVR: 2400 dynes/sec/cm⁻⁵ (↑)Massive upper gastrointestinal hemorrhage
  • RAP: 18 mm Hg (↑), PAP: 60/25 mm Hg (↑), PCWP: 8 mm Hg (↔), CI: 1.7 L/min/m² (↓)Acute saddle pulmonary embolism
  • RAP: 4 mm Hg (↔), PCWP: 6 mm Hg (↔), CI: 4.5 L/min/m² (↑), SVR: 500 dynes/sec/cm⁻⁵ (↓)Septic shock due to severe pneumonia

Answer

The hemodynamic profiles match the four classic forms of shock: cardiogenic shock demonstrates high filling pressures and low output; hypovolemic shock demonstrates low filling pressures and low output; obstructive shock demonstrates high right-sided pressures with normal left-sided filling pressures; and distributive shock demonstrates low systemic vascular resistance with high output.
Right heart catheterization parameters are pivotal for differentiating shock etiologies. Cardiogenic shock presents as primary pump failure leading to backward transmission of volume (elevated RAP and PCWP) and low forward output (decreased CI). Hypovolemic shock originates from volume loss, resulting in critically low filling pressures (decreased RAP and PCWP) and low output. Obstructive shock from a pulmonary embolism acutely blocks the right heart outflow tract, leading to high right-sided pressures (elevated RAP and PAP) but leaves the left heart underfilled (normal PCWP). Finally, distributive shock is primarily a loss of systemic vascular tone (decreased SVR), leading to a compensatory hyperdynamic state with an elevated cardiac index.

Step-by-Step Solution

1
Evaluate Cardiac Index (CI) and Systemic Vascular Resistance (SVR).
Identifies hyperdynamic versus hypodynamic shock states.
Distributive shock is uniquely characterized by a high cardiac index and profoundly low systemic vascular resistance due to widespread vasodilation.
2
Examine Pulmonary Capillary Wedge Pressure (PCWP) in low-output states.
Differentiates cardiogenic shock from hypovolemic and obstructive etiologies.
An elevated PCWP indicates left-sided pump failure with volume backup, whereas a normal or low PCWP indicates an underfilled left heart.
3
Analyze Pulmonary Artery Pressure (PAP) and Right Atrial Pressure (RAP) in the setting of normal/low PCWP.
Identifies isolated right-sided obstructive pathophysiology.
Elevated right-sided pressures (RAP, PAP) combined with normal left-sided filling pressures (PCWP) indicate a barrier in the pulmonary circulation, such as a pulmonary embolism.

Key Concept

Hemodynamic Profiles of Shock
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Topics

Cardiovascular System

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