Acute blood loss will cause which of the following changes in arterial blood pressure?

Acute blood loss will cause which of the following changes in arterial blood pressure?

• A. Decrease in arterial blood pressure
• B. Increase in arterial blood pressure
• C. No change in blood pressure
• D. Blood pressure becomes unpredictable

Answer: (A)

When acute blood loss occurs, circulating volume drops, which reduces venous return to the heart. With less filling, the heart ejects less blood each beat, so stroke volume falls and cardiac output tends to decrease (even though the heart rate may briefly rise to compensate). Arterial blood pressure is roughly the product of cardiac output and systemic vascular resistance, so a drop in cardiac output tends to lower arterial pressure. The body’s rapid reflexes try to compensate by vasoconstriction and increasing heart rate, but with significant loss the overall pressure still falls. Therefore, the arterial blood pressure decreases.

When acute blood loss occurs, circulating volume drops, which reduces venous return to the heart. With less filling, the heart ejects less blood each beat, so stroke volume falls and cardiac output tends to decrease (even though the heart rate may briefly rise to compensate). Arterial blood pressure is roughly the product of cardiac output and systemic vascular resistance, so a drop in cardiac output tends to lower arterial pressure. The body’s rapid reflexes try to compensate by vasoconstriction and increasing heart rate, but with significant loss the overall pressure still falls. Therefore, the arterial blood pressure decreases.