Which drug shows little change in systemic vascular resistance with mild increases in heart rate and mean arterial pressure?

Which drug shows little change in systemic vascular resistance with mild increases in heart rate and mean arterial pressure?

• A. Dopamine
• B. Dobutamine
• C. Epinephrine
• D. Isoproterenol

Answer: (B)

Dobutamine acts mainly on beta-1 receptors in the heart, boosting contractility and stroke volume (and modestly increasing heart rate) without activating alpha-adrenergic receptors. This sharp focus on the heart increases cardiac output and can raise mean arterial pressure, but since there is little alpha-mediated vasoconstriction and only mild beta-2–driven vasodilation, systemic vascular resistance stays nearly the same. In practice, dobutamine improves perfusion by increasing CO while keeping vascular tone relatively unchanged, which is why it’s the drug that shows little change in systemic vascular resistance with mild increases in heart rate and MAP. Dopamine can raise SVR at higher doses due to alpha-1 effects; epinephrine tends to increase both heart rate and vascular resistance at higher doses because of alpha actions; isoproterenol causes vasodilation via beta-2 receptors and typically lowers SVR.

Dobutamine acts mainly on beta-1 receptors in the heart, boosting contractility and stroke volume (and modestly increasing heart rate) without activating alpha-adrenergic receptors. This sharp focus on the heart increases cardiac output and can raise mean arterial pressure, but since there is little alpha-mediated vasoconstriction and only mild beta-2–driven vasodilation, systemic vascular resistance stays nearly the same. In practice, dobutamine improves perfusion by increasing CO while keeping vascular tone relatively unchanged, which is why it’s the drug that shows little change in systemic vascular resistance with mild increases in heart rate and MAP.

Dopamine can raise SVR at higher doses due to alpha-1 effects; epinephrine tends to increase both heart rate and vascular resistance at higher doses because of alpha actions; isoproterenol causes vasodilation via beta-2 receptors and typically lowers SVR.