Objective To study the effects of methylene blue(MB), a soluble guanylate cyclase inhibitor , on intestinal perfusion and oxygenation in dogs with septic shock.Methods A septic shock model was established by lipopolysaccharide infusion.After resuscitation with normal saline infusion,2mg/kg MB was infused within 15min in seven dogs.Blood flow of the superior mesenteric artery (SMA) was measured respectively at baseline,post shock for 1h, after resuscitation and 30min after MB injection.Blood gas analysis was done , and oxygenation was calculated.Results Blood flow of the SMA was significantly decreased by 61 8%(P0 0 5 ) ,butO2 extrincreasedby 14 8% .Conclusions Septicshockindogsresultsinadecreaseinintestinalperfusionandanincreasein oxygenextraction ,whichcanbeimprovedbyMBinjection .Theintestinalperfusionispartlyincreasedbyvolumetherapy .