Endotoxemia reduces cerebral perfusion but enhances dynamic cerebrovascular autoregulation at reduced arterial carbon dioxide tension*

Patrice Brassard, Yu-Sok Kim, Johannes van Lieshout, Niels H Secher, Jaya B Rosenmeier

    24 Citations (Scopus)

    Abstract

    OBJECTIVE:: The administration of endotoxin to healthy humans reduces cerebral blood flow but its influence on dynamic cerebral autoregulation remains unknown. We considered that a reduction in arterial carbon dioxide tension would attenuate cerebral perfusion and improve dynamic cerebral autoregulation in healthy subjects exposed to endotoxemia. DESIGN:: Prospective descriptive study. SETTING:: Hospital research laboratory. SUBJECTS:: Ten healthy young subjects (age: 32 ± 8 yrs [mean ± SD]; weight: 84 ± 10 kg; weight: 184 ± 5 cm; body mass index: 25 ± 2 kg/m) participated in the study. INTERVENTIONS:: Systemic hemodynamics, middle cerebral artery mean flow velocity, and dynamic cerebral autoregulation evaluated by transfer function analysis in the very low (0.15 Hz) frequency ranges were monitored in these volunteers before and after an endotoxin bolus (2 ng/kg; Escherichia coli). MEASUREMENTS AND MAIN RESULTS:: Endotoxin increased body temperature of the subjects from 36.8 ± 0.4°C to 38.6 ± 0.5°C (p <.001) and plasma tumor necrosis factor-α from 5.6 (2.8-6.7) pg/mL to 392 (128-2258) pg/mL (p <.02). Endotoxemia had no influence on mean arterial pressure (95 [74-103] mm Hg vs. 92 [78-104] mm Hg; p = .75), but increased cardiac output (8.3 [6.1-9.5] L·min vs. 6.0 [4.5-8.2] L·min; p = .02) through an elevation in heart rate (82 ± 9 beats·min vs. 63 ± 10 beats·min; p <.001), whereas arterial carbon dioxide tension (37 ± 5 mm Hg vs. 41 ± 2 mm Hg; p <.05) and middle cerebral artery mean flow velocity (37 ± 9 cm·sec vs. 47 ± 10 cm·sec; p <.01) were reduced. In regard to dynamic cerebral autoregulation, endotoxemia was associated with lower middle cerebral artery mean flow velocity variability (1.0 ± 1.0 [cm·sec] Hz vs. 2.8 ± 1.5 [cm·sec] Hz; p <.001), reduced gain (0.52 ± 0.11 cm·sec.mm Hg vs. 0.74 ± 0.17 cm·sec.mm Hg; p <.05), normalized gain (0.22 ± 0.05 vs. 0.40 ± 0.17%·%; p <.05), and higher mean arterial pressure-to-middle cerebral artery mean flow velocity phase difference (p <.05) in the low frequency range (0.07-0.15 Hz). CONCLUSIONS:: These data support that the reduction in arterial carbon dioxide tension explains the improved dynamic cerebral autoregulation and the reduced cerebral perfusion encountered in healthy subjects during endotoxemia.
    Original languageEnglish
    JournalThe Open Critical Care Medicine Journal
    Volume40
    Issue number6
    Pages (from-to)1873-1878
    Number of pages6
    ISSN1874-8287
    DOIs
    Publication statusPublished - 2012

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