In this video, you'll learn about the use of methylene blue and hydroxocobalamin as vasopressors. We'll cover applications, methods for administration, dosing, and the advantages and disadvantages of each agent.
Join our ICU Masterclass: Inotropes and Vasopressors course today!
Providing hemodynamic support for unstable patients can be a daunting process! In our ICU Masterclass: Inotropes and Vasopressors course, you’ll learn a systematic, hands-on approach for using vasopressors and inotropes. You’ll discover why one size does not fit all, as well as the underlying mechanisms of action of these agents so that you can safely and effectively use the appropriate agent for each unique patient.
Methylene blue is a recognized treatment for refractory distributive shock, also known as vasoplegia. It likely works by decreasing nitric oxide production through the inhibition of nitric oxide synthase. This decreases soluble guanylate cyclase production, which ultimately reduces smooth muscle relaxation and vasodilation.
The most notable risk with methylene blue is the development of serotonin syndrome. Although this is rare, the risk is elevated in patients taking other serotonergic medications like serotonin reuptake inhibitors, or monoamine oxidase inhibitors. Patients with a history of glucose-6-phosphate dehydrogenase or G6PD deficiency are at risk for hemolysis.
The typical dose of methylene blue is 1.5 to 2.5 milligrams per kilogram IV, with or without an infusion, at 0.25 to 0.5 milligrams per kilogram per hour, for four to six hours. Hydroxocobalamin or vitamin B12 is available as an injectable dietary supplement. It's approved for the treatment of cyanide poisoning, but also has been shown to improve blood pressure and vesoplegia.
It likely also works through the inhibition of nitric oxide synthase. Although it's considerably more expensive than methylene blue, it does not carry the risk for serotonin syndrome or hemolysis. It should be noted that vitamin B12 may interfere with certain lab tests such as hemoglobin and creatinine, and coagulation studies.
And it interferes with the dialysate sensor and hemodialysis machines. The typical bolus dose for vasoplegia is 5 or 10 grams over 15 minutes which can be repeated.