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Local changes in venous tone due to bolus injections
1Department of Physiology, University of New England, Armidale, Australia.
Acta Anaesthesiologica Scandinavica
|October 1, 1991
Summary
This study investigated sheep ear vein responses to various solutions and drugs. Most veins showed transient venoconstriction to acidic or alkaline saline and several drugs, though some larger veins were unresponsive.
Area of Science:
- Pharmacology
- Physiology
- Vascular Biology
Background:
- Understanding venous tone regulation is crucial for drug delivery and physiological studies.
- Previous research has explored vascular responses to various stimuli, but specific venous responses require further elucidation.
Purpose of the Study:
- To investigate the effects of infused solutions and drugs on venous tone in anesthetized sheep.
- To characterize the transient venoconstriction response and identify factors influencing it.
Main Methods:
- Solutions and drugs were infused at a constant rate into sheep ear veins.
- Changes in venous tone were measured by monitoring infusion line pressure changes following bolus administration.
- Vein responsiveness was assessed, with unresponsive veins noted and their characteristics analyzed.
Main Results:
- Most veins exhibited transient venoconstriction in response to acidic or alkaline saline and various drugs (e.g., aminophylline, calcium chloride, noradrenaline).
- Approximately one in six veins, typically larger ones, were unresponsive, likely due to significant blood flow causing dilution.
- Responses were generally repeatable and dose-dependent, but unpredictable variations in magnitude were sometimes observed.
Conclusions:
- Sheep ear veins demonstrate a transient venoconstrictive response to a range of chemical stimuli and pharmacological agents.
- Vein size and blood flow rate can influence responsiveness, potentially due to dilution effects.
- Papaverine and nicotinamide were found to typically reduce venous tone.
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