What is the optimal vasodilator for preventing spasm in the left internal mammary artery during coronary arterial bypass grafting?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was which (if any) vasodilator prevents spasm of the internal mammary artery in patients undergoing coronary artery bypass grafting. Two hundred papers were found using the reported search, of which 13 represented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses were tabulated. We conclude that mammary arteries often have low flow initially, but invariably will double their flow after 15-20 min even with no treatment. The strongest evidence for safe prevention of spasm is for papaverine given topically and periarterially, however many studies have also shown no benefit and thus no treatment at all is an entirely acceptable strategy.