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Assessment of cerebrovascular interactions and control in coronary artery disease patients undergoing anaesthesia
Roberta Saputo1, Riccardo Pernice2, Laura Sparacino1
1Department of Engineering, University of Palermo, Palermo, Italy.
Insights
Propofol anesthesia alters cerebrovascular dynamics, increasing cerebral blood flow dependence on arterial pressure. Frequency-domain analysis reveals subtle changes in regulation overlooked by time-domain methods.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
- Anesthesiology
Background:
- Cerebrovascular regulation maintains adequate cerebral blood flow (CBF) via mechanisms like cerebral autoregulation and Cushing's reflex.
- Disruptions in CBF can precipitate serious neurological pathologies.
- Understanding cerebrovascular dynamics is crucial, especially during surgical interventions and anesthesia.
Purpose of the Study:
- To investigate the causal and self-predictable dynamics of cerebrovascular interactions.
- To assess these dynamics in patients before and after propofol general anesthesia during coronary artery bypass graft surgery.
- To evaluate the pressure-to-flow and flow-to-pressure relationships between mean arterial pressure (MAP) and mean cerebral blood velocity (MCBv).
Main Methods:
- Employed Granger Causality (GC) and Granger Autonomy (GA) in both time-domain and frequency-domain analyses.
- Assessed the links between MAP and MCBv.
- Analyzed data from patients undergoing coronary artery bypass graft surgery before and after propofol anesthesia.
Main Results:
- Time-domain indices of cerebrovascular dynamics remained stable.
- Frequency-domain measures showed significant variations in very-low, low, and high-frequency (HF) bands.
- Increased spectral GC in the HF band correlated with mechanical ventilation; reduced MCBv self-dependency in the HF band indicated weakened regulation post-anesthesia.
Conclusions:
- Propofol anesthesia, through sympathetic suppression and mechanical respiration, enhances the dependence of CBF on MAP within specific frequency bands.
- Frequency-domain analysis is essential for detecting subtle cerebrovascular changes missed by time-domain methods.
- These findings highlight the impact of anesthesia on cerebrovascular regulatory mechanisms.
Abstract:
Cerebrovascular regulation, driven by mechanisms such as cerebral autoregulation and the Cushing's reflex, plays a critical role in maintaining cerebral blood flow (CBF) adequate despite changes in arterial pressure (AP), since a dampening of CBF can lead to serious brain pathologies. This study investigates the causal and self-predictable dynamics of cerebrovascular interactions in patients undergoing coronary artery bypass graft surgery, before and after propofol general anaesthesia. The dynamics of the pressure-to-flow and flow-to-pressure links between mean arterial pressure (MAP) and mean cerebral blood velocity (MCBv) is assessed using time-domain and frequency-domain measures of Granger Causality (GC) and Granger Autonomy (GA). The results indicate that while time-domain indices remain stable, frequency-domain measures reveal variations in the very-low-frequency, low-frequency, and high-frequency (HF) bands. The increased spectral GC in the HF band may be related to the effect of mechanical ventilation during anaesthesia. Additionally, a reduction in self-dependency of MCBv in the HF band reflects weakened internal regulatory mechanisms post-anaesthesia. In conclusion, propofol-induced suppression of sympathetic control and the effects of mechanical respiration increase the dependence of cerebral blood flow on arterial pressure in specific bands of cerebrovascular interest. These findings underscore the importance of frequency-domain analysis in detecting subtle cerebrovascular dynamics that time-domain measures may overlook.
