Cerebral Multimodal Monitoring in Sepsis: An Experimental Study

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Abstract

Acute brain dysfunction is a complication of sepsis and its pathophysiology remains poorly understood. We studied the brain metabolism in a resuscitated animal model of sepsis. Twelve anesthetized, mechanically ventilated and invasively monitored pigs were allocated to a sham procedure (N = 5) or sepsis (N = 7). Sepsis was induced through fecal inoculation in the peritoneum. Fluid resuscitation was maintained during the entire study period. Animals were observed until spontaneous death or for a maximum of 24 hours. In addition to global hemodynamic and laboratory assessment, intracranial pressure and cerebral microdialysis (MD) were evaluated at baseline, 6, 12, 18 and 24 hours after sepsis induction. After euthanasia, the brain was rapidly removed and a fragment from the frontal cortex was analyzed for markers of neuroinflammation, metabolism and neurotransmission. Septic animals developed a hyperdynamic state associated with increased arterial lactate. Cerebral microdialysis showed unchanged levels of lactate/pyruvate ratios and brain glucose between the groups. Brain/serum glucose ratios were increased in the septic animals during the study period despite a progressive decrease in serum glucose. Moreover, extracellular glutamine levels were elevated starting at 6 hours after sepsis. Tissue analysis showed elevated glutamate, glutamine and glutamine synthetase in the sepsis group. However, C-Fos, a marker of neuronal activity, was unchanged between groups. In this animal model of resuscitated sepsis, we found increased oxidative stress and alterations in neuroenergetics characterized by exacerbated activity of the glutamate/glutamine cycle and increased glucose utilization by the brain, however without any evidence of decompensated energy metabolism.

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