Cerebral Autoregulation and CO2 Reactivity in Anterior and Posterior Cerebral Circulation During Sevoflurane Anesthesia

Abstract Background: Sevoflurane is one of the most frequently used inhaled anesthetics for general anesthesia. Previously it has been reported that at clinically used doses of sevoflurane, cerebral vasoreactivity is maintained. However, there are no data how sevoflurane influences systemic and cerebral circulation in parallel. The aim of our study was to assess systemic and cerebral hemodynamic changes as well as cerebral CO2-reactivity during sevoflurane anesthesia. Methods: 29 patients undergoing general anesthesia were enrolled. Anesthesia was maintained with 1 MAC sevoflurane in 40% oxygen. Ventilatory settings (respiratory rate and tidal volume) were adjusted to reach and maintain 40, 35 and 30 mmHg EtCO2 for 5 minutes respectively. At the end of each period, transcranial Doppler and hemodynamic parameters using applanation tonometry were recorded. Results: Systemic mean arterial pressure significantly decreased during anesthetic induction and remained unchanged during the entire study period. Central aortic and peripherial pulse pressure and augmentation idex as markers of arterial stiffness significantly increased during the anesthetic induction and remained stable at the time points when target CO2 levels were reached. Both cerebral autoregulation and cerebral CO2-reactivity was maintained at 1 MAC sevoflurane. Discussion: Cerebral autoregulation and CO2-reactivity is preserved at 1 MAC sevoflurane. Cerebrovascular effects of anesthetic compounds have to be assessed together with systemic circulatory effects. The study was registered at http://www.clinicaltrials.gov, identifier: NCT02054143, retrospectively registered.

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Multi-metrics assessment of dynamic cerebral autoregulation in middle and posterior cerebral arteries in young fit women

10.1101/2020.05.25.114447 ◽

2020 ◽

Author(s):

Lawrence Labrecque ◽

Audrey Drapeau ◽

Kevan Rahimaly ◽

Sarah Imhoff ◽

François Billaut ◽

...

Keyword(s):

Cerebral Artery ◽

Cerebral Circulation ◽

Cerebral Autoregulation ◽

Regional Differences ◽

Posterior Cerebral Artery ◽

Blood Velocity ◽

Percent Reduction ◽

Sit To Stand ◽

Posterior Cerebral Circulation ◽

Dynamic Cerebral Autoregulation

AbstractIndividuals with low orthostatic tolerance show greater decrease in posterior cerebral artery mean blood velocity (PCAvmean). Since young fit women often experience presyncopal symptoms, their posterior cerebral circulation may be prone to greater decreases in PCAvmean, probably explained by an attenuated dynamic cerebral autoregulation (dCA). Regional differences in dCA have never been evaluated in young fit women. We compared dCA in the middle cerebral artery (MCA) and posterior cerebral artery (PCA) in 11 young fit women (25 ± 4y; ) in response to a sit-to-stand (5 min sitting followed by 5 min standing) and repeated squat-stand maneuvers performed at 0.05 Hz and 0.10 Hz. The cerebral pressure-flow relationship was characterized using four metrics: 1) percent reduction in blood velocity (BV) per percent reduction in MAP (% BV/% MAP) during initial orthostatic stress (0-15 s after sit-to-stand); 2) onset of the regulatory response (i.e. time delay before an increase in conductance (BV/MAP); 3) rate of regulation (RoR), following sit-to-stand and; 4) transfer function analysis (TFA) of forced MAP oscillations induced by repeated squat-stands. Upon standing, the relative decline in MCAvmean and PCAvmean was similar (−25 ± 9 vs. −30 ± 13%; p=0.29). The onset of the regulatory response (p=0.665), %ΔBV/%ΔMAP (p=0.129) and RoR (p=0.067) were not different between MCA and PCA. In regard to TFA, there was an ANOVA artery effect for gain (p<0.001) and a frequency effect for phase (p<0.001). These findings indicate the absence of regional differences in dCA in young fit women.New findingsWhat is the central question of this study?Are there regional differences in the dynamic cerebral autoregulation in young fit women?What is the main finding and its importance?The key finding of this study is that there are no differences in dynamic cerebral autoregulation between both arteries. These results indicate that dynamic cerebral autoregulation does not seem to be responsible for making the posterior cerebral circulation more vulnerable to transient reduction in blood pressure in young fit women.

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