❤️ Chapter 44: Cardiogenic Shock

Decreased Cardiac Output · Elevated Filling Pressures · Inotropes · Afterload Reduction · Systolic vs Diastolic Dysfunction · Myocarditis · ECMO

❤️ Cardiogenic Shock: Inability of the Heart to Pump Adequate Blood to Meet Metabolic Demands

📊 Definition & Aetiology
Elevated filling pressures, low cardiac output, hypotension, end-organ hypoperfusion. Common causes: congenital heart disease, myocarditis (most common in children), cardiomyopathy, arrhythmias, post-cardiotomy, ALCAPA, Kawasaki disease, envenomation.
🩸 Pathophysiology
Decreased contractility → compensatory tachycardia and increased SVR (worsens afterload). Ventricular interdependence: RV failure → LV compression → decreased LV output. Systolic vs diastolic dysfunction require different treatments.
🔬 CCF vs Cardiogenic Shock
CCF: chronic, compensated, may have oedema but stable. Cardiogenic shock: acute decompensation, shock signs, requires ICU. Do not confuse — treatment intensity differs.
💊 Inotropes & Vasodilators
• Hypotensive cardiogenic shock → Adrenaline (epinephrine)
• Normotensive/hypotensive with adequate MAP → Dobutamine or Milrinone (inodilators)
• Afterload reduction: Milrinone, nitroprusside, nitroglycerin (add after BP stabilises)
• Diastolic dysfunction → Milrinone (lusitropy), slow filling, avoid tachycardia
📋 Diagnostic Keys
• ECHO: ejection fraction <40%, diastolic dysfunction (E/A ratio reversal), IVC collapsibility
• Lactate, ScvO2 (<65% indicates low CO)
• BNP elevated
• ECG: ischaemia, arrhythmias, ALCAPA findings
⚙️ Mechanical Support
• ECMO (VA-ECMO): bridge to recovery or transplant
• VAD: longer-term support
• IABP: older children (size limitation)
📌 Systolic vs Diastolic Dysfunction: Systolic → decreased contractility, narrow pulse pressure, low EF → treatment: inotropes. Diastolic → stiff non-compliant ventricles, fluid overload, preserved EF → treatment: lusitropy (milrinone), slow filling, avoid tachycardia.

🩺 Step-by-Step: Cardiogenic Shock Management

1
Recognise cardiogenic shock
Look for: tachycardia, narrow pulse pressure, gallop rhythm, hepatomegaly, pulmonary oedema, poor perfusion (cool extremities, delayed CRT, oliguria, altered sensorium). Hypotension is a late sign.
2
Secure airway & breathing
100% O2. Consider early intubation — reduces work of breathing (decreases O2 demand). Use ketamine (avoid etomidate). Intubation may cause hypotension; be prepared with fluids and low-dose adrenaline infusion.
3
Vascular access & cautious fluid trial
IV/IO access. In cardiogenic shock, fluid bolus is risky. Try small aliquot (5-10 mL/kg over 30-60 min) with close monitoring. Stop if CVP rises >3 mmHg or signs of worsening pulmonary oedema.
4
Inotropic support (choose based on BP)
• Hypotensive → Adrenaline (epinephrine) 0.05-0.3 mcg/kg/min
• Normotensive or mild hypotension → Dobutamine 5-15 mcg/kg/min or Milrinone 0.25-0.75 mcg/kg/min (inodilators)
• Avoid pure vasopressors (increase afterload → worsen output)
5
Afterload reduction (once BP stable)
Add milrinone, nitroprusside, or nitroglycerin to decrease SVR and improve stroke volume. Essential for systolic dysfunction. Avoid in fixed outflow obstruction (e.g., critical aortic stenosis).
6
Diastolic dysfunction management
• Use milrinone for lusitropy (diastolic relaxation)
• Avoid tachycardia (causes worse filling)
• Slow fluid administration (colloids preferred)
• Diuretics as infusion (not bolus) for pulmonary oedema
7
Mechanical support & transplant referral
If no improvement with maximal medical therapy → consider VA-ECMO, VAD, or cardiac transplant referral. ECMO is bridge to recovery (myocarditis) or transplant (cardiomyopathy).