Effects of L-arginine and L-nitro-arginine treatment on blood pressure and cardiac output in a rabbit endotoxin shock model

Abstract

To verify the effect of nitric oxide system modification during sepsis, not only in terms of pressure but also in terms of perfusion flow. Experimental, comparative study. Laboratory of a university hospital. Twenty-six New Zealand male rabbits (2 to 2.5 kg body weight) were studied under anesthesia. Nitric oxide pathways were modified during shock-induced hypotension, using L-arginine (600 mg/kg) and L-nitro-arginine (7.5 mg/kg), which were infused 75 mins after endotoxin injection. Mean arterial pressure (MAP) and cardiac output, as well as ascending aortic velocity, were measured and aortic conductance (aortic velocity/MAP in cm/sec/mm Hg) was calculated. Both L-arginine and L-nitro-arginine increased MAP to the pre-endotoxin level, but only L-arginine increased aortic velocity in association with a marked increase in aortic conductance (p < .001). L-nitro-arginine significantly (p < .05) decreased aortic velocity as compared with the control endotoxin group, with an intense vasoconstriction as shown by a significant (p < .001) decrease in aortic conductance. These results, along with the high mortality rate in the L-nitro-arginine treated group, challenge the hypothesis that nitric oxide release inhibition has a beneficial effect in septic shock.