Methylene Blue and Microcirculation in Septic Shock

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The mortality rate of patients with septic shock remains very high. Arterial hypotension, related to arteriolar vasodilation and myocardial depression are the mainstays of septic shock pathology. At the level of the micro-circulation, there is insufficient delivery of oxygen to organs and tissues wh...

The mortality rate of patients with septic shock remains very high. Arterial hypotension, related to arteriolar vasodilation and myocardial depression are the mainstays of septic shock pathology. At the level of the micro-circulation, there is insufficient delivery of oxygen to organs and tissues which results in organ dysfunction and potential organ necrosis.One key factor leading to vascular dysfunction is the inappropriately increased production of nitric oxide within the blood vessel endothelium. Elevated levels of nitric oxide results in the blood vessel endothelium receiving direct vasodilator input, as well as the inability to respond to norepinephrine-mediated vasoconstriction. Nitric oxide activates the soluble isoform of the enzyme guanylatecyclase, which in turn increases production of cyclic guanosine monophosphate. Nitric oxide has other beneficial effects which are mediated via other pathways than guanylatecyclase; therefore, administration of a guanylate cyclase inhibitor such as methylene blue could be a safer therapeutic option than the inhibition of nitric oxide production. These effects of methylene blue could be related to vasoconstriction and positive inotropic effects as well to an increase in blood volume, itself related to a decrease in vascular permeability. The use of methylene blue has been recently advocated as a potential adjunct in the treatment of shock states. However, the effect of MB at the level of the capillary bed, where vital exchange of oxygen and nutrients occurs, is unknown. Thus in this study, the investigators will investigate the effect of methylene blue in combination with NE at the microvascular level in septic shock.

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