Cerebral microcirculation is impaired during sepsis: an experimental study

Introduction: Pathophysiology of brain dysfunction due to sepsis remains poorly understood. Cerebral microcirculatory alterations may play a role; however, experimental data are scarce. This study sought to investigate whether the cerebral microcirculation is altered in a clinically relevant animal model of septic shock. Methods: Fifteen anesthetized, invasively monitored, and mechanically ventilated female sheep were allocated to a sham procedure (n = 5) or sepsis (n = 10), in which peritonitis was induced by intra-abdominal injection of autologous faeces. Animals were observed until spontaneous death or for a maximum of 20 hours. In addition to global hemodynamic assessment, the microcirculation of the cerebral cortex was evaluated using Sidestream Dark-Field (SDF) videomicroscopy at baseline, 6 hours, 12 hours and at shock onset. At least five images of 20 seconds each from separate areas were recorded at each time point and stored under a random number to be analyzed,using a semi-quantitative method, by an investigator blinded to time and condition. Results: All septic animals developed a hyperdynamic state associated with organ dysfunction and, ultimately, septic shock. In the septic animals, there was a progressive decrease in cerebral total perfused vessel density (from 5.9 +/- 0.9 at baseline to 4.8 +/- 0.7 n/mm at shock onset, P = 0.009), functional capillary density (from 2.8 +/- 0.4 to 2.1 +/- 0.7 n/mm, P = 0.049), the proportion of small perfused vessels (from 95 +/- 3 to 85 +/- 8%, P = 0.02), and the total number of perfused capillaries (from 22.7 +/- 2.7 to 17.5 +/- 5.2 n/mm, P = 0.04). There were no significant changes in microcirculatory flow index over time. In sham animals, the cerebral microcirculation was unaltered during the study period. Conclusions: In this model of peritonitis, the cerebral microcirculation was impaired during sepsis, with a significant reduction in perfused small vessels at the onset of septic shock. These alterations may play a role in the pathogenesis of septic encephalopathy.