Which factor would contribute to hypotension?

• A. Decrease in contractility
• B. Increase in blood viscosity
• C. Decrease in respiratory rate
• D. Increase in preload

Answer: (A)

The main idea is that blood pressure is largely set by how much blood the heart pumps each minute, i.e., cardiac output. If the heart’s contractility decreases, each beat ejects less blood (lower stroke volume). With the heart rate unchanged, cardiac output drops, which lowers mean arterial pressure and leads to hypotension. So a decrease in contractility directly reduces the heart’s pumping power, making hypotension more likely.

Increasing blood viscosity raises resistance to flow, which can increase blood pressure rather than lower it. A slower respiratory rate on its own doesn’t directly reduce blood pressure; it may affect gas exchange and overall oxygen delivery, but it doesn’t inherently cause hypotension. Increasing preload typically enhances stroke volume via the Frank-Starling mechanism (up to a point), which tends to raise blood pressure rather than lower it.