Intra-arterial vasodilator agents to reverse human finger vasoconstriction

Area of Science:

• Cardiovascular Physiology
• Pharmacology

Background:

• Persistent digital vasospasm poses a significant clinical challenge.
• Understanding the mechanisms of digital vasoconstriction is crucial for developing effective treatments.

Purpose of the Study:

• To investigate the efficacy of intra-arterial nitroprusside in reversing humoral and neurogenic digital vasoconstriction.
• To compare the effects of nitroprusside, nitroglycerin, and phentolamine on digital blood flow and capillary flow.

Main Methods:

• Digital blood flow was measured using venous occlusion plethysmography.
• Capillary flow was assessed by the clearance rate of an injected radioisotope.
• Vasoconstriction was induced by intra-arterial norepinephrine or sympathetic nerve stimulation (body cooling).

Main Results:

• Small doses of nitroprusside increased fingertip blood flow in norepinephrine-induced vasoconstriction.
• Large doses of nitroprusside failed to improve blood flow in sympathetically constricted digits.
• Phentolamine significantly increased both fingertip blood flow and capillary flow in sympathetically constricted digits, while nitroglycerin only increased fingertip blood flow.

Conclusions:

• Nitroprusside is effective for humorally mediated digital vasoconstriction.
• Sympathetic digital vasoconstriction is resistant to nitroprusside and less responsive to nitroglycerin compared to phentolamine.
• Phentolamine is the preferred agent for treating sympathetic digital vasoconstriction due to its superior effects on both blood flow and capillary perfusion.