Vasoplegic syndrome--the role of methylene blue.

Vasoplegic syndrome is a recognized complication following cardiac surgery using cardiopulmonary bypass and is associated with increased morbidity and mortality. In several patients profound post-operative vasodilatation does not respond to conventional vasoconstrictor therapy. Methylene blue has been advocated as an adjunct to conventional vasoconstrictors in such situations. There is limited data pertaining to the use of methylene blue and a number of reports have been anecdotal observations. This article reviews the incidence and problems associated with the vasoplegic syndrome, the mechanism of action of methylene blue, its effects and adverse reactions and the literature supporting its intra-operative and post-operative use. In cases where first-line therapy fails, the use of methylene blue seems to be a potent approach to refractory vasoplegia. The early use of methylene blue may halt the progression of low systemic vascular resistance even in patients responsive to norepinephrine and mitigate the need for prolonged vasoconstrictor use. However, dosing regimens and protocols need to be clearly defined before widespread routine use. Whether methylene blue should be the first line of therapy in patients with vasoplegia is a matter of debate, and there is inadequate evidence to support its use as a first line drug. More scientific evidence is needed to define the role of MB in the treatment of catecholamine refractory vasoplegia.