Question

Describe how cardiogenic shock would impact cardiac output and mean arterial pressure, then describe how the autonomic nervous system would respond to this.

How could this response be potentially detrimental to both the heart and organs?

Answer 1

Cardiogenic shock reduces cardiac output and the mean arterial pressure.

Cardiogenic shock is a clinical syndrome resulting from decreased blood flow and oxygen delivery to vital organs caused by a sustained reduction in cardiac output. In a condition like cardiogenic shock, blood flow is decreased due to an intrinsic defect in cardiac function or the heart muscles, sometimes the valves are dysfunctional, because of all these the heart cannot pump anymore,The decreased contractility causes a decrease in stroke volume as a result cardiac output decreases. The autonomic nervous system would respond by increasing the sympathetic nervous system, sympathetic nervous system reflexes act within seconds to increase strength of contraction and heart rate and increase mean systemic pressure.The reduction in arterial blood pressure are sensed by the baroreceptors, Rapid decreases in blood pressure, such as in times of cardiogenic shock result in decreased stretching of the artery wall and decreased action potential frequency which ultimately results in increased cardiac output and vasoconstriction resulting in increased blood pressure. The other mechanism is, when blood pressure falls, The renin aldosterone-angiotensinogen mechanism gets activated, as result renin is released which further causes the release of angiotensin, which through various steps act to increase the blood volume as a result blood pressure increases.

The renin-angiotensin-aldosterone system mechansim can increase the blood volume, which leads to ventricular filling pressures increase, The increase in venous pressures can lead to pulmonary and systemic edema. Baroreceptor reflexes not only increase heart rate, but they also increase systemic vascular resistance, particularly in skeletal muscle, gastrointestinal and renal system Vasoconstriction in these organs partially offsets the fall in arterial pressure, and therefore helps to maintain perfusion of the brain and heart circulations; however, blood flow can be profoundly reduced in the constricted organs,  which can accelerate their damage.