Failure of endotoxic shock to elicit superoxide anion production in pig brain

Endotoxin shock in pigs alters cerebral blood flow regulation. This study sought 1) to evaluate global cerebral electrical function using somatosensory evoked potential and 2) to determine if superoxide anion free radical (O₂^-) is generated in brain following endotoxin infusion. Five female pigs received E. coli endotoxin (0.1 mg/kg i.v.) and supplemental fluid to maintain cardiac output at control levels. Somatosensory evoked potential was generated before and after endotoxin infusion, and nitroblue tetrazolium (NBT) precipitation in cranial windows was used to determine O₂^- production by brain. Following endotoxin infusion, mean arterial blood pressure, cerebral perfusion pressure, and systemic vascular resistance fell by 50% and cerebral oxygen extraction increased. The amplitude and the latency of somatosensory evoked potential performed 60 min after endotoxin were unchanged from that generated at control. No precipitation of NBT in cranial windows was observed, indicating that O₂^- was not generated. Since endotoxin shock did not alter cerebral electrical function and O₂^- was not generated by brain, we conclude that alterations in cerebral blood flow regulation observed in fluid-resuscitated endotoxic shock do not result from inadequate cerebral oxygen consumption, nor is the extracellular production of O₂^- involved in the pathogenesis of this disorder.