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SELECTED ARTICLES FROM THE RECENT LITERATURE 2007
November 2, 2007
Statins and a long-term decline in lung function
Summary
This article is an excellent review of the role that nitric oxide plays in the production of hypotension in anaphylaxis. It has long been known that nitric oxide could have potentially beneficial as well as detrimental effects in anaphylaxis. For example, it can be a bronchodilator, thus potentially relieving the bronchospasm that occurs in asthmatics experiencing an anaphylactic event. However, it also causes vasodilatation and can therefore play a role in shock. It appears as if the overall effect of nitric oxide is detrimental, and that this mediator can play an important role in hypotensive reactions occurring during anaphylactic events. The authors discussed the internal mechanism responsible for the adverse effect of nitric oxide in this regard. Nitric oxide can inhibit the release and the effects of catecholamines, thus preventing the exogenous compensatory response to hypotension consisting of the release of norepinephrine from terminal nerve endings and epinephrine from the adrenal gland. Its vasodilatory effect is through activation of guanylyl cyclase. Such activation reduces smooth muscle relaxation by increasing the concentration of cyclic guanosine monophosphate.
Until fairly recently, the only treatment for the vasodilatation was vasopressors and fluids. However, recently, methylene blue has shown to reverse the vasodilatory effect induced by nitric oxide by inhibiting guanylyl cyclase. The authors discussed the animal models dealing with this phenomenon, and also reviewed the 11 case reports in which methylene blue was used to treat hypotension not responding to standard therapy.
The dose of methylene blue used varied in these studies. Most employed a bolus infusion of 1.5 to 2 mg/kg followed by an infusion of 1.5 to 2 mg/kg.
Editor's Comments
This review discusses what appears to be an effective therapy for hypotension occurring during an anaphylactic event that is unresponsive to epinephrine and fluids.
Reference
Evora P and Simon M. Role of nitric oxide production in anaphylaxis and its relevance for the treatment of anaphylactic hypotension with methylene blue. Annals of Allergy, Asthma, and Immunology 2007; 99(4):306-313.
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