Obstructive shock

• Obstructive shock is caused by mechanical obstruction causing a failure of adequate cardiac output.
• Pulmonary embolism: large PEs (e.g. saddle embolus) can cause right sided heart failure due to elevated pulmonary vascular resistance.
• Tension pneumothorax: elevated pressure in the pleural cavity compresses the heart and great vessels leading to obstruction of venous return and ventricular filling. This results in a failure of cardiac output.
• Cardiac tamponade: this has a number of effects on normal physiology but can be simply thought of as restricting venous return and ventricular filling.
• A characteristic sign of causative conditions like pneumothorax and tamponade may include dilated and engorged neck veins, resulting from the inability of blood to return to the heart