Abstract
Background: Ischemic and hyperemic injury have emerged as biologic mechanisms that contribute to cognitive impairment in critically ill patients. Spontaneous deviations in cerebral blood flow (CBF) beyond ischemic and hyperemic thresholds may represent an insult that contributes to this brain injury, especially if they accumulate over time and coincide with impaired autoregulation.Methods: We used transcranial Doppler to measure the proportion of time that CBF velocity (CBFv) deviated beyond previously reported ischemic and hyperemic thresholds in a cohort of critically ill patients with respiratory failure and/or shock within 48 h of ICU admission. We also assessed whether these CBFv deviations were more common during periods of impaired dynamic autoregulation, and whether they are explained by concurrent variations in mean arterial pressure (MAP) and end-tidal PCO2 (PetCO2).Results: We enrolled 12 consecutive patients (three females) who were monitored for a mean duration of 462.6 ± 39.8 min. Across patients, CBFv deviated by more than 20–30% from its baseline for 17–24% of the analysis time. These CBFv deviations occurred equally during periods of preserved and impaired autoregulation, while concurrent variations in MAP and PetCO2 explained only 13–21% of these CBFv deviations.Conclusion: CBFv deviations beyond ischemic and hyperemic thresholds are common in critically ill patients with respiratory failure or shock. These deviations occur irrespective of the state of dynamic autoregulation and are not explained by changes in MAP and CO2. Future studies should explore mechanisms responsible for these CBFv deviations and establish whether their cumulative burden predicts poor neurocognitive outcomes.
Highlights
Ill patients have a high prevalence of acute [1] and long-term cognitive impairment [2, 3]
Spontaneous deviations in cerebral blood flow (CBF) beyond ischemic and hyperemic thresholds earlier in the course of critical illness may represent an insult that contributes to this brain injury, especially if it accumulates over time and occurs during periods of impaired autoregulation
We summarized the data within patients by comparing the cumulative time that cerebral artery blood flow velocity (CBFv) deviated above/below CBF thresholds depending on the state of dynamic autoregulation
Summary
Ill patients have a high prevalence of acute (delirium) [1] and long-term cognitive impairment [2, 3]. Spontaneous deviations in cerebral blood flow (CBF) beyond ischemic and hyperemic thresholds earlier in the course of critical illness may represent an insult that contributes to this brain injury, especially if it accumulates over time and occurs during periods of impaired autoregulation. While spontaneous variation in cerebral blood flow (CBF) are common in both healthy adults [14, 15] and patients with primary brain pathology [16, 17], the proportion of time that CBF deviated beyond ischemic and hyperemic thresholds in critically ill patients without brain injury has not been welldescribed. Spontaneous deviations in cerebral blood flow (CBF) beyond ischemic and hyperemic thresholds may represent an insult that contributes to this brain injury, especially if they accumulate over time and coincide with impaired autoregulation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
