Background: Nitric oxide (NO) production following bacterial infection may play a physiological role in the host defense mechanism due to its antimicrobial activity. However, excess production of NO in severe infection such as sepsis has been implicated in the pathogenesis of septic shock. To determine whether a nitronyl nitroxide NO scavenger compound could prevent the hemodynamic and blood gas alterations in sepsis, bacterial lipopolysaccharide (LPS: 250ng/kg/min) was administered for 2 h in anesthetized dogs with or without infusion of carboxy-2-phenyl-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO: 0.1 mg/kg/min) for 1 h. Control animals received isotonic saline instead of LPS with or without carboxy-PTIO.

      Results:
      Infusion of LPS caused a marked decrease in mean arterial pressure (MAP), metabolic acidosis, and hypoxia. These effects were reversed by co-administration of carboxy-PTIO, without affecting other hemodynamic parameters. In control animals, neither hemodynamic nor blood gas parameters changed with or without carboxy-PTIO.


      Conclusion:
      These results indicate that carboxy-PTIO attenuates LPS-induced hypotension, metabolic acidosis, and hypoxia by scavenging excess NO from the circulation without affecting NO synthase (NOS) activity. An NO scavenger, carboxy-PTIO, may be preferable to non-selective NOS inhibitors for the treatment of human septic shock.