Prospective observational cohort study of cerebrovascular CO2 reactivity in patients with inflammatory CNS diseases

Abstract

The purpose of this study was to evaluate the significance of cerebrovascular CO2 reactivity (CO2 R) in the course and outcome of inflammatory central nervous system (CNS) diseases. Sixty-eight patients with inflammatory CNS diseases and 30 healthy volunteers were included in this prospective observational cohort study. The observational period was between January 2005 and May 2009. The CO2 R was measured by transcranial Doppler (TCD) ultrasound using the breath-holding method. We compared patients with normal CO2 R (breath-holding index [BHIm] ≥ 1.18 = BHIN group) with patients who showed impaired CO2 R (BHIm < 1.18 = BHIR group). We also analyzed the association of impaired CO2 R with the etiology, severity, and outcome of disease. When compared to the BHIN group, the patients from the BHIR group were older, had a heavier consciousness disturbance, experienced more frequent respiratory failure, and, subsequently, had worse outcomes. There were no fatalities among the 28 patients in the BHIN group. The comparison of subjects with bacterial and non-bacterial meningitis revealed no significant differences. The unfavorable outcome of disease (Glasgow Outcome Scale [GOS] score 1–3) was significantly more common in subjects with impaired CO2 R (62.5% vs. 10.7%). Logistic regression analysis was performed in order to establish the prognostic value of BHIm. The outcome variable was unfavorable outcome (GOS 1–3), while the independent variables were age, Glasgow Coma Scale (GCS) score, and BHIm. The age and BHIm showed the strongest influence on disease outcome. A decrease of BHIm for each 0.1 unit increased the risk of unfavorable outcome by 17%. Our study emphasizes the importance of CO2 R assessment in patients with inflammatory CNS diseases.