Effect of methylene blue on middle cerebral artery flow velocity in a patient with severe sepsis following clipping of a cerebral aneurysm.

INTRODUCTION: The use of methylene blue, an inhibitor of guanylate cyclase, has been described in patients with septic shock who are unresponsive to inotropic agents. However, the effects of methylene blue on the human cerebral circulation are not known. METHODS AND
RESULTS: This article presents a case report of a 58-year old-female with a clinical presentation compatible with severe sepsis and increasing inotropic requirements following clipping of a cerebral aneurysm. Administration of methylene blue (2 milligrams/kilograms) intravenously was undertaken with monitoring of mean arterial pressure and middle cerebral artery flow velocity (FVm). The effect of methylene blue on mean arterial pressure occurred quite rapidly after initiation of the infusion, allowing downward titration of norepinephrine. Initially, FVm increased in association with an increase in mean arterial pressure, reaching its highest value halfway through the infusion. Subsequently, FVm decreased to baseline by the end of the monitoring period. The rise in mean arterial pressure and increase in FVm were accompanied by a reductionin cerebral vascular resistance assuming intracranial pressure, and the diameter of the insonated vessel was unchanged during and immediately after infusion of methylene blue.
CONCLUSION: Methylene blue did not appear to have a major untoward effect on cerebrovascular resistance in this patient. The limited characterization of cerebrovascular effects provided by this article mandates the need for careful monitoring of cerebrovascular behavior and adequacy during use of methylene blue.