Haemodynamic Shock Quiz

See Section. Distributive shock develops when widespread vasodilation markedly reduces systemic vascular resistance, so A is best. Systemic vascular resistance is the opposition to blood flow through the body’s circulation, much of it controlled by the small arteries. When these vessels relax, arterial pressure can fall despite a heart that is still pumping effectively. Dilated veins can also hold more blood away from the heart, reducing the amount available to fill it, a form of relative hypovolaemia. Sepsis and anaphylaxis may additionally make capillaries leak, so the actual circulating volume need not remain normal. The defining problem is therefore loss of vascular tone and ineffective tissue perfusion, the flow needed to supply organs, rather than a requirement for constant blood volume.

D describes cardiogenic shock, where weak ventricular contraction is the primary pump problem and venous pressures may rise. A true loss of blood or body fluid (B) causes hypovolaemic shock by reducing what is available to fill the heart. C is obstructive shock: tamponade restricts filling, while a large pulmonary embolus limits right ventricular outflow. Chronic arterial-wall thickening from hypertension (E) is a structural adaptation to long-standing pressure, not the abrupt loss of vascular tone causing distributive collapse; these are different processes even if both involve blood vessels.