Which haemodynamic pattern is characteristic of intravenous isoproterenol infusion?

• A Increased systolic pressure with reflex bradycardia
• B No change in heart rate with increased mean arterial pressure
• C Increased diastolic pressure with decreased pulse pressure
• D Decreased diastolic pressure with marked tachycardia ✓

Explanation

Isoproterenol is a pure beta agonist with no alpha activity. Beta-2 mediated vasodilation in skeletal muscle beds lowers diastolic pressure and mean arterial pressure, while beta-1 stimulation raises heart rate and contractility directly, with no reflex slowing because mean pressure falls. Alpha-1 agonists such as phenylephrine produce the opposite pattern with reflex bradycardia, which distinguishes option A clearly.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

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