Causality analysis reveals the link between cerebrovascular control and acute kidney dysfunction after coronary artery bypass grafting

Abstract

Background: Patients undergoing coronary artery bypass graft (CABG) surgery might experience postoperative complications and some of them, such as acute kidney dysfunction (AKD), are the likely consequence of hypoperfusion. We hypothesized that an impaired cerebrovascular control is a hallmark of a vascular damage that might favor AKD after CABG. Objective: Our aim is to characterize cerebrovascular control in CABG patients through the assessment of the relationship between mean arterial pressure (MAP) and mean cerebral blood flow velocity (MCBFV) and to check whether markers describing MCBFV-MAP dynamical interactions could identify subjects at risk to develop postoperative AKD. Approach: MAP and MCBFV beat-to-beat series were extracted from invasive arterial pressure and transcranial Doppler recordings acquired simultaneously in 23 patients just before CABG after the induction of propofol general anesthesia. Subjects were divided into AKD group (n = 9, age: 68 ± 9, 8 males) and noAKD group (n = 14, age: 65 ± 8, 12 males) according to whether they developed postoperative AKD or not after CABG. We computed MAP and MCBFV time-domain and spectral markers as well as MCBFV-MAP cross-spectral indexes in very-low-frequency (VLF, 0.02–0.07 Hz), low-frequency (LF, 0.07–0.15 Hz) and high-frequency (HF, 0.15–0.30 Hz) bands. We also calculated model-based transfer entropy (TE) to quantify the degree of MCBFV dependence on MAP and vice versa. The null hypothesis of MCBFV-MAP uncoupling was tested via a surrogate approach associating MAP and MCBFV in different patients. Main results: Time, spectral and cross-spectral markers had a limited power in separating AKD from noAKD individuals. Conversely, TE from MAP to MCBFV was significantly above the level set by surrogates only in AKD groups and significantly larger than that computed in noAKD. Significance: The reduced cerebrovascular autoregulation in AKD patients suggest a vascular impairment likely making them more at risk of hypoperfusion during CABG and AKD after CABG.

Evaluation of the impact of surgical aortic valve replacement on short-term cardiovascular and cerebrovascular controls through spontaneous variability analysis

“…Markers of cardiac baroreflex and cerebral autoregulation were evaluated via bivariate frequency domain metrics assessing phase and TFM from an input to an output and their degree of association via K 2 [32]. In the case of the assessment of the cardiac baroreflex the input is SAP variability and the output is the RR variability [40,[42][43][44], while in the case of the evaluation of cerebral autoregulation the input is MAP variability and the output is the MCBF variability [18,45,46]. It is well-known that SAVR reduced baroreflex control [26].…”

“…TFM MCBF-MAP (VLF), TFM MCBF-MAP (LF) and TFM MCBF-MAP (HF) were taken as an estimate of the cerebrovascular autoregulation sensitivity [45] and expressed in cm�s -1 �mmHg -1 . While Ph MCBF-MAP (VLF), Ph MCBF-MAP (LF) and Ph MCBF-MAP (HF) were considered markers of the delay/advance of MAPPLOS ONEon MCBF[46] and K2 MCBF-MAP (VLF), K 2 MCBF-MAP (LF) and K 2 MCBF-MAP (HF) were indexes of the MCBF-MAP coupling strength[47].…”

Computation of Mean Cerebral Blood Flow Velocity for the Assessment of Cerebral Autoregulation: Comparison of Different Strategies

“…Some studies proposed to exploit the time at the CBFV minimum (i.e. diastolic time), thus using exclusively the CBFV signal for the computation of MCBFV [9][10][11][12]. Conversely, other research papers detected the diastolic time over the AP signal [13] in correspondence of the AP diastole, thus necessitating the acquisition of AP in addition to CBFV.…”

“…Different strategies were followed to compute MCBFV on a beat-to-beat basis and these strategies depended on the selection of the two fiducial points. While in some studies the diastolic points were detected directly on CBFV signal [9][10][11][12], in other research papers the occurrence of the diastolic events was taken from the AP signal [13]. Some studies exploited the R-wave peak of the electrocardiogram (ECG) to define the temporal limits for the computation of the current MCBFV over CBFV [14].…”

Propofol General Anesthesia Decreases the Coupling Strength Between Mean Arterial Blood Pressure and Mean Cerebral Blood Flow Velocity in Patients Undergoing Coronary Artery Bypass Grafting

“…during general anesthesia or critical care unit), CA is probed using spontaneous variability of MAP and mean CBFV (MCBFV) [1]. CA is known to have a fundamental role in maintaining cerebral perfusion in presence of challenging situations such as during standing [3], it is influenced by sympathetic vascular regulation [4], and it is altered in pathology [5,6].…”