Cardiogenic shock management

Pathophysiology & Diagnosis - The Failing Pump

• Vicious Cycle: A primary cardiac insult (e.g., large MI) drastically reduces contractility, leading to a sharp ↓ in Cardiac Output (CO) and subsequent hypotension.
• Maladaptive Compensation: The body's response-↑ sympathetic tone and ↑ Systemic Vascular Resistance (SVR)-paradoxically increases cardiac afterload and myocardial oxygen demand, which further impairs pump function and worsens ischemia.

• Diagnosis: Based on clinical signs of hypoperfusion (cool, clammy skin; altered mental status; oliguria) and congestion (JVD, rales).
  • Hemodynamic Criteria (Invasive Monitoring):
    • Systolic BP < 90 mmHg
    • Pulmonary Capillary Wedge Pressure (PCWP) > 18 mmHg
    • Cardiac Index (CI) < 2.2 L/min/m²

⭐ The classic hemodynamic signature is a low Cardiac Index (< 2.2) with a high PCWP (> 18), differentiating it from hypovolemic or distributive shock.

Initial Management - First-Response ABCs

• A - Airway: Assess patency. Low threshold for endotracheal intubation in patients with altered mental status or impending respiratory collapse to reduce the work of breathing.
• B - Breathing:
  • Administer supplemental O₂ to maintain SpO₂ > 90%.
  • Consider Non-Invasive Positive Pressure Ventilation (NIPPV) for acute pulmonary edema if the patient is alert and hemodynamically stable.
  • Proceed to mechanical ventilation if NIPPV fails or is contraindicated.
• C - Circulation:
  • Secure 2 large-bore peripheral IVs.
  • Treat unstable arrhythmias (tachycardia/bradycardia) per ACLS.
  • ⚠️ Judicious fluid challenge: 250-500 mL isotonic crystalloid only if no signs of fluid overload (e.g., pulmonary rales).

⭐ Unlike other shock types, large-volume fluid resuscitation is harmful in cardiogenic shock as it exacerbates pulmonary edema and cardiac strain.

Pharmacotherapy - Potent Potion Push

• Goal: Improve cardiac output (CO) & maintain mean arterial pressure (MAP) > 65 mmHg.

• First-line therapy depends on blood pressure.

• Key Agents:

  • Norepinephrine: α1 > β1 agonist. ↑SVR, ↑MAP. First choice in hypotension.
  • Dobutamine: β1 > β2 agonist. ↑CO, ↓SVR. Can cause hypotension. Use when BP is stable or with a pressor.
  • Milrinone: PDE-3 inhibitor. Inodilator (↑CO, ↓SVR). Useful if patient is on beta-blockers.
  • Diuretics (Furosemide): Use cautiously for pulmonary congestion if BP allows.

⭐ In cardiogenic shock with profound hypotension, norepinephrine is the initial vasopressor of choice. Dobutamine can be added once MAP is stabilized (>65 mmHg) to specifically improve cardiac contractility and output.

Mechanical Support - The Big Guns

• Intra-Aortic Balloon Pump (IABP):
  • Mechanism: Counter-pulsation. Inflates in diastole (↑coronary perfusion), deflates in systole (↓afterload).
  • Provides modest hemodynamic support.
  • ⚠️ CI: Significant aortic regurgitation, aortic dissection.
• Percutaneous VADs (e.g., Impella):
  • Mechanism: Axial flow pump actively pulls blood from the left ventricle to the aorta.
  • Directly unloads the LV, providing superior support to IABP.
• VA-ECMO (Veno-Arterial ECMO):
  • Provides full cardiopulmonary support; highest level of support.

  ⭐ VA-ECMO increases LV afterload, which can worsen pulmonary edema. May require LV venting (e.g., with an Impella).

High‑Yield Points - ⚡ Biggest Takeaways

• Cardiogenic shock is defined by low cardiac output and high PCWP (>18 mmHg).
• Initial stabilization may require inotropes (dobutamine) and vasopressors (norepinephrine).
• Use IV fluids cautiously or not at all, as they can worsen pulmonary edema.
• Definitive treatment targets the underlying cause, most commonly urgent revascularization for acute MI.
• Intra-aortic balloon pump (IABP) can serve as a bridge to definitive therapy.
• Avoid beta-blockers and nitrates during the acute hypotensive phase.