INTRODUCTION: Recent clinical studies have shown persistent abnormalities in microcirculatory function in patients with vasoactive-dependent circulatory shock are associated with poor outcomes. Nitroglycerin is effective in restoring alterations in microcirculatory blood flow but has failed to improve clinical outcomes in a randomized clinical trial of patients with shock. Our primary aim is to evaluate the application of a topical nitroglycerin solution to identify nitroglycerin responsive patients as well as acutely reversible microcirculatory dysfunction in patients with circulatory shock after cardiac surgery.