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The order of dilator-constrictor administration affects stenotic hemodynamic responses
K S Li1, F D Ferdinand, T N Tulenko
1Philadelphia Heart Institute, Presbyterian Medical Center, PA 19104.
The American Journal of the Medical Sciences
|June 1, 1993
Summary
In stenotic arteries, the order of administering constrictors and dilators significantly impacts blood flow responses due to intraluminal pressure. This pressure-dependent effect on vasomotor tone is crucial for understanding ischemia.
Area of Science:
- Cardiovascular Physiology
- Pharmacology
Background:
- Intraluminal pressure changes can influence vascular responses to vasoactive agents.
- The order of drug administration may alter hemodynamic outcomes in stenotic arteries.
Purpose of the Study:
- To investigate whether the sequence of administering constrictor (norepinephrine) and dilator (diltiazem, nitroglycerin) agents affects hemodynamic responses in canine carotid arteries with stenosis.
- To determine if intraluminal pressure is a key factor in this pressure-dependent sensitivity.
Main Methods:
- Canine carotid arteries with artificial stenosis were perfused under constant pressure (100 mm Hg).
- Hemodynamic parameters (pressure, flow) were recorded during sequential administration of norepinephrine and either diltiazem or nitroglycerin.
- Responses were compared between administering the dilator before or after the constrictor.
- Control experiments were conducted on isolated arterial rings and normal arteries.
Main Results:
- Administering diltiazem or nitroglycerin before norepinephrine shifted the effective half-maximum dose (ED50) of norepinephrine, indicating altered sensitivity.
- Administering the dilator after norepinephrine-induced constriction required significantly higher concentrations to restore normal pressure and flow.
- These order-dependent effects were not observed in isolated arterial rings or normal arteries, highlighting the role of stenosis and intraluminal pressure.
Conclusions:
- Intraluminal pressure in stenotic arteries significantly influences the hemodynamic response to the sequential administration of constrictors and dilators.
- This pressure-dependent sensitivity of vasomotor tone may play a critical role in the pathophysiology of ischemia.
- The findings underscore the importance of considering the sequence of drug administration in the context of arterial stenosis and pressure dynamics.