🚫 Chapter 45: Obstructive Shock

Impaired Diastolic Filling or Excessive Afterload · Tamponade · Tension Pneumothorax · Pulmonary Embolism · Duct-Dependent Systemic Lesions · PGE1

🚫 Obstructive Shock: Obstruction to Blood Flow in the Cardiovascular Circuit

📊 Definition & Aetiology
Obstruction to flow into or out of the heart → decreased cardiac output. Types: extrinsic (tamponade, tension pneumothorax, PE) vs intrinsic (duct-dependent systemic lesions: HLHS, critical AS, coarctation).
🩸 Pathophysiology
Impaired diastolic filling (tamponade) or excessive afterload (PE, tension pneumothorax) → decreased CO → shock. Raised JVP/CVP is hallmark. Ventricular interdependence worsens LV filling.
🫀 Pericardial Tamponade
Beck's triad: hypotension, muffled heart sounds, raised JVP. Pulsus paradoxus (>10 mmHg inspiratory fall). ECHO: diastolic RA/RV collapse. Treatment: pericardiocentesis.
🫁 Tension Pneumothorax
Unilateral absent breath sounds, hyperresonance, tracheal deviation, hypotension. Treatment: needle decompression (2nd ICS MCL) → chest tube.
🩸 Massive Pulmonary Embolism
Sudden dyspnoea, hypoxia, hypotension, RV strain on ECHO. High-risk PE: thrombolysis or embolectomy.
❤️ Duct-Dependent Systemic Circulation
Neonates present with shock within days of birth as PDA closes (HLHS, critical AS, coarctation). Treatment: PGE1 infusion 0.05-0.1 mcg/kg/min to reopen PDA.
⚠️ Critical Pearl: Obstructive shock is a surgical/ procedural emergency. Tamponade, tension pneumothorax, and duct-dependent lesions will NOT respond to fluids or inotropes alone — you must relieve the obstruction!

🩺 Step-by-Step: Obstructive Shock Management

1
Recognise obstructive shock pattern
Shock + raised JVP/CVP + ± pulsus paradoxus + ± muffled heart sounds + ± absent breath sounds + ± cyanosis. Consider diagnosis BEFORE imaging if unstable.
2
Perform rapid bedside assessment
• Tension pneumothorax: absent breath sounds, hyperresonance, tracheal deviation
• Tamponade: muffled heart sounds, pulsus paradoxus, large heart on CXR
• PE: sudden hypoxia, RV strain on ECHO
• Neonatal: differential cyanosis/pulses → suspect duct-dependent lesion
3
Tension pneumothorax — immediate needle decompression
14-16G needle in 2nd intercostal space, midclavicular line. Listen for rush of air. Follow with chest tube. Do NOT wait for X-ray if clinical suspicion high.
4
Pericardial tamponade — pericardiocentesis
ECHO-guided pericardiocentesis. Give small fluid bolus (5-10 mL/kg) while preparing for tap. Avoid positive pressure ventilation (worsens preload).
5
Massive pulmonary embolism — thrombolysis
If hypotensive with RV strain → thrombolysis (rtPA). Surgical embolectomy if contraindication. Anticoagulate with heparin.
6
Neonatal duct-dependent systemic lesion — PGE1
Start PGE1 0.05-0.1 mcg/kg/min IV. May cause apnoea → prepare to intubate. Reopens ductus within 30 min-2 hours. Consult cardiology immediately.
7
Fluids & inotropes are secondary
Obstructive shock does NOT respond to fluids or inotropes until obstruction relieved. Fluids may help transiently in tamponade but can worsen PE. Inotropes may increase RV afterload in PE/tamponade.