How are types of shock differentiated via a hemodynamics chart?

Hemodynamic Differentiation of Shock Types

The most effective way to differentiate types of shock is through hemodynamic parameters including cardiac index, systemic vascular resistance, and pulmonary capillary wedge pressure, which provide distinct patterns for cardiogenic, hypovolemic, distributive, and obstructive shock. 1, 2

Key Hemodynamic Parameters for Shock Classification

• Cardiac Index (CI): Normal range 2.2-4.0 L/min/m²; reduced in cardiogenic and hypovolemic shock, normal or elevated in distributive shock 1, 2
• Systemic Vascular Resistance (SVR): Elevated in cardiogenic shock, decreased in distributive shock 1
• Pulmonary Capillary Wedge Pressure (PCWP): Elevated (>15 mmHg) in cardiogenic shock, decreased in hypovolemic shock 1
• Central Venous Pressure (CVP): Elevated in cardiogenic and obstructive shock, decreased in hypovolemic shock 1

Hemodynamic Patterns in Different Shock Types

Cardiogenic Shock

• CI: Decreased (<2.2 L/min/m²) 1
• SVR: Increased (compensatory mechanism) 1
• PCWP: Elevated (>15 mmHg) 1
• Clinical presentation: Hypotension (SBP <90 mmHg), signs of hypoperfusion, pulmonary congestion 1
• Additional hemodynamic markers: Cardiac power output ([CO × MAP]/451) <0.6 W, shock index (HR/systolic BP) >1.0 1

Hypovolemic Shock

• CI: Decreased 3
• SVR: Increased (compensatory) 3
• PCWP: Decreased 1
• CVP: Decreased 1
• Clinical presentation: Hypotension, tachycardia, poor peripheral perfusion, decreased urine output 4

Distributive Shock (including Septic Shock)

• CI: Normal or increased 1
• SVR: Decreased 1
• PCWP: Normal or decreased 1
• Clinical presentation: Hypotension, warm extremities (early), increased lactate 1

Obstructive Shock

• CI: Decreased 3
• SVR: Increased 3
• CVP: Elevated 3
• Right ventricular parameters: In right ventricular shock, pulmonary artery pulse index [(PASP-PADP)/CVP] <1.0, CVP >15 mmHg, CVP-PCW >0.6 1
• Clinical presentation: Hypotension, signs of specific obstruction (e.g., tension pneumothorax, cardiac tamponade) 3

SCAI Classification for Cardiogenic Shock

The Society for Cardiovascular Angiography and Interventions (SCAI) classification provides a standardized staging system for cardiogenic shock 1:

• Stage A (At risk): Normal hemodynamics, normotensive, clear lungs, normal perfusion 1
• Stage B (Beginning shock): Hypotension (SBP <90 mmHg), normal perfusion, preserved renal function 1
• Stage C (Classic shock): Hypotension, hypoperfusion, altered mental status, decreased urine output, respiratory distress 1
• Stage D (Deteriorating): Worsening of Stage C parameters despite interventions 1
• Stage E (Extremis): Cardiac arrest, refractory hypotension/hypoperfusion, requiring CPR 1

Practical Application of Hemodynamic Monitoring

• Initial assessment: Evaluate blood pressure, heart rate, peripheral perfusion, urine output, mental status, and lactate levels 2
• Non-invasive monitoring: Echocardiography provides rapid assessment of cardiac function, volume status, and potential obstructive causes 5
• Invasive monitoring: Arterial line for continuous blood pressure, pulmonary artery catheter or other advanced hemodynamic monitoring for CI, SVR, and filling pressures when shock is refractory to initial treatment 1, 6

Clinical Pitfalls in Hemodynamic Assessment

• Mixed shock states: Patients may present with features of multiple shock types, particularly in septic shock with myocardial depression 7
• Dynamic changes: Hemodynamic parameters can change rapidly as shock progresses or responds to treatment 1
• Misinterpretation of isolated parameters: Single measurements should not be used in isolation; trends and clinical context are essential 8
• Delayed recognition: Relying solely on blood pressure can delay recognition of shock; tissue perfusion markers should be evaluated concurrently 6

Hemodynamic-Guided Treatment Approach

• Cardiogenic shock: Inotropic support (dobutamine, milrinone) for low CI with normal BP; vasopressors (norepinephrine) for hypotension; mechanical circulatory support for refractory cases 1, 2
• Hypovolemic shock: Fluid resuscitation with balanced crystalloids 3
• Distributive shock: Combination of vasopressors and fluid replacement 3
• Obstructive shock: Immediate intervention to relieve obstruction (e.g., pericardiocentesis for tamponade) 3

By systematically evaluating these hemodynamic parameters, clinicians can rapidly identify the type of shock and initiate appropriate treatment strategies to improve outcomes.