In this episode, I’ll discuss the use of methylene blue for the treatment of refractory anaphylaxis without hypotension.
Methylene blue has some unique uses such as in the treatment of acquired methemoglobinemia and vasoplegia after cardiac surgery. It also appears to have a role in treating patients experiencing anaphylaxis without hypotension, that is not responsive to classical therapy. A case report published in 2013 in the American Journal of Emergency Medicine illustrates the drug’s usefulness for this indication.
A 43-year-old woman with a known history of idiopathic anaphylaxis acutely developed oral papules, urticaria, and dyspnea. Her history included 6 recent episodes of anaphylaxis, all with identical features to the episode discussed in this case.
The patient recognized her symptoms and immediately gave herself epinephrine 0.3 mg via an autoinjector. She developed a choking sensation and gave herself another epinephrine dose 10 minutes after the 1st and called 911. She gave herself a 3rd epinephrine dose 10 minutes after the 2nd.
Paramedics arrived and gave her oxygen, a 4th dose of epinephrine, diphenhydramine and albuterol via nebulizer.
When she reached the emergency department she had a heart rate of 84, blood pressure of 170/90 mm Hg. She also had depressed consciousness, abnormal voice and diffuse wheezing despite the complete absence of urticaria, angioedema, and stridor. She was given methylprednisolone, famotidine, and continuous albuterol via nebulizer but she failed to respond to this therapy.
The physician decided to administer a dose of IV methylene blue 1.5 mg/kg mixed in 100 mL of 5% dextrose over 20 minutes. Six minutes into this infusion she became less dyspneic, and 13 minutes in she was able to speak clearly. By the time the infusion finished her only complaint was mild nausea.
This case was especially notable due to the excellent response to methylene blue despite the lack of hypotension. Methylene blue has been advocated for refractory anaphylaxis with hypotension, presumably, for the same reason it can be used in vasoplegic syndromes. Its mechanism in anaphylaxis without hypotension is proposed to be related to blocking the release of platelet-activating factor, a substance which has been correlated with the severity of anaphylaxis.
The authors suggest that if good clinical response is not achieved from multiple doses of epinephrine and maximal standard therapy that methylene blue 1.5mg/kg IV over 20 minutes be part of the therapy considered in refractory anaphylaxis.
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