From the Guidelines
Methylene blue can act as a pressor in certain clinical situations, particularly in vasoplegic shock that is refractory to conventional vasopressors. It works by inhibiting nitric oxide synthase and guanylate cyclase, which reduces vasodilation and helps maintain blood pressure. Methylene blue is typically administered intravenously at doses of 1-2 mg/kg as a loading dose, followed by continuous infusion of 1 mg/kg/hour if needed, as indicated in the 2023 American Heart Association guidelines 1. Some key points to consider when using methylene blue as a pressor include:
- Monitoring for potential side effects including blue discoloration of skin and body fluids, hemolytic anemia (particularly in G6PD-deficient patients), and serotonin syndrome if combined with serotonergic medications.
- Using methylene blue cautiously in patients with renal impairment as it is primarily excreted by the kidneys.
- Being aware that its vasopressor effect is generally temporary, lasting about 1-2 hours after administration, which may necessitate continuous infusion in some cases. Additionally, it's essential to consider the recommendations for vasopressor therapy in septic shock, as outlined in the Surviving Sepsis Campaign guidelines 1, which suggest norepinephrine as the first-choice vasopressor, and to use methylene blue as an alternative or adjunct therapy when necessary. It's also crucial to be aware of the potential risks and complications associated with methylene blue administration, such as hemolytic anemia in G6PD-deficient patients, as highlighted in the American Journal of Hematology study 1.
From the Research
Methylene Blue as a Pressor Agent
- Methylene blue has been considered as a potential alternative to standard therapy for refractory hypotension in the intensive care unit 2.
- Studies have shown that methylene blue can be effective in treating refractory hypotension, including cases where patients are unresponsive to other treatments such as fluids, vasoactive agents, and epinephrine 3, 4, 5.
- The mechanism of action of methylene blue is thought to be related to its inhibition of the enzyme nitric oxide synthase, which prevents smooth muscle dilation and ultimately leads to increased blood pressure 4.
- Methylene blue has also been shown to be effective in combination with epinephrine for the treatment of anaphylactic shock, with the two agents having a synergistic effect on hemodynamic variables and prevention of brain ischemia 6.
Clinical Evidence
- A case report published in 2017 described a patient with refractory hypotension due to losartan overdose, who responded to treatment with methylene blue with an increase in systolic blood pressure from 60 mmHg to 100 mmHg within 30 minutes 3.
- Another case report published in 2008 described a patient with anaphylaxis and refractory hypotension, who was treated with methylene blue and showed improvement in hemodynamic stability and a decrease in the need for vasoactive agents 4.
- A more recent case report published in 2025 described a patient with polysubstance overdose and refractory hypotension, who responded to treatment with methylene blue with an improvement in blood pressure 5.