Abstract
IntroductionDynamic cerebral autoregulation (dCA) is frequently altered in patients with sepsis and may be associated with sepsis-associated brain dysfunction. However, the optimal index to quantify dCA in patients with sepsis is currently unknown.ObjectiveTo assess the agreement between two validated dCA indices in patients with sepsis.MethodsRetrospective analysis of prospectively collected data in patients with sepsis; those with acute or chronic intracranial disease, arrhythmias, mechanical cardiac support, or history of supra-aortic vascular disease were excluded. Transcranial Doppler was performed on the right or left middle cerebral artery (MCA) with a 2-MHz probe, and MCA blood flow velocity (FV) and arterial pressure (BP) signals were simultaneously recorded. We calculated two indices of dCA: the mean flow index (Mxa), which is the Pearson correlation coefficient between BP and FV (MATLAB, MathWorks), and the autoregulation index (ARI), which is the transfer function analysis of spontaneous fluctuations in BP and FV (custom-written FORTRAN code). Impaired dCA was defined as Mxa >0.3 or ARI ≤ 4. The agreement between the two indices was assessed by Cohen's kappa coefficient.ResultsWe included 95 patients (age 64 ± 13 years old; male 74%); ARI was 4.38 [2.83–6.04] and Mxa was 0.32 [0.14–0.59], respectively. There was no correlation between ARI and Mxa (r = −0.08; p = 0.39). dCA was altered in 40 (42%) patients according to ARI and in 50 (53%) patients according to Mxa. ARI and Mxa were concordant in classifying 23 (24%) patients as having impaired dCA and 28 (29%) patients as having intact dCA. Cohen's kappa coefficient was 0.08, suggesting poor agreement. ARI was altered more frequently in patients on mechanical ventilation than others (27/52, 52% vs. 13/43, 30%, p = 0.04), whereas Mxa did not differ between those two groups. On the contrary, Mxa was altered more frequently in patients receiving sedatives than others (23/34, 68% vs. 27/61, 44%, p = 0.03), whereas ARI did not differ between these two groups.ConclusionsAgreement between ARI and Mxa in assessing dCA in patients with sepsis was poor. The identification of specific factors influencing the dCA analysis might lead to a better selection of the adequate cerebral autoregulation (CAR) index in critically ill patients with sepsis.
Highlights
Dynamic cerebral autoregulation is frequently altered in patients with sepsis and may be associated with sepsis-associated brain dysfunction
Mechanisms of autoregulation are efficient for a range of mean arterial pressure (MAP), which varies between subject, but is considered to be around 50–150 mmHg; as a consequence, alterations in Cerebral autoregulation (CAR) may result in brain hypoperfusion at MAP levels, which are considered to be adequate in routine practice [5]
Impaired Dynamic cerebral autoregulation (dCA) according to the autoregulation index (ARI) threshold was observed in 40 (42%) patients; impaired dCA according to Mxa threshold was observed in 50 (53%) patients
Summary
Dynamic cerebral autoregulation (dCA) is frequently altered in patients with sepsis and may be associated with sepsis-associated brain dysfunction. Sepsisassociated brain dysfunction (SABD), ranging from delirium to coma, is common during sepsis and can be associated to poor outcomes [2]. Cerebral autoregulation (CAR) is the intrinsic cerebrovascular mechanism that maintains CBF constant within different ranges of cerebral perfusion pressure (CPP); cerebral arterioles can constrict or dilate in response to the elevation or reduction in CPP, the so-called pressure autoregulation, keeping CBF within stable values. Mechanisms of autoregulation are efficient for a range of MAP, which varies between subject, but is considered to be around 50–150 mmHg; as a consequence, alterations in CAR may result in brain hypoperfusion at MAP levels, which are considered to be adequate in routine practice [5]. An impaired CAR has been reported in several studies [5, 7–10]; such disturbances have been associated with increased serum concentrations of brain injury biomarkers [11] and with the occurrence of brain dysfunction [5]
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