Determination of Cerebral Autoregulation at the Bedside: A Narrative Review

OBJECTIVES: To summarize the current evidence on cerebral autoregulation (CAR) monitoring techniques in critical care settings, highlighting their advantages, limitations, and practical applications at the bedside to inform understanding and clinical decision-making for various acute brain injuries and systemic illnesses. DATA SOURCES: Articles were retrieved using Ovid MEDLINE, PubMed, and Cochrane library using a comprehensive combination of subject headings and key words including "cerebral autoregulation," "transcranial Doppler," "near-infrared spectroscopy," and "intracranial pressure." See Supplemental Appendix A ( https://links.lww.com/CCM/H763 ) for complete list of search terms. Relevant articles as well as those discovered through the review process (e.g., references in selected articles) were incorporated into the article. STUDY SELECTION: Original research, review articles, commentaries, and guidelines focusing on bedside CAR monitoring methodologies, their validation, and applications in critically ill patients were included. The review encompassed both acute brain injury and systemic critical illness conditions. DATA EXTRACTION: Data from included publications were evaluated and synthesized into a comprehensive narrative review examining CAR monitoring methods and clinical applications. DATA SYNTHESIS: Three commonly used bedside approaches for assessing CAR were identified. Transcranial Doppler ultrasound measures vessel flow velocity response to blood pressure changes, either through vasopressor administration or monitoring spontaneous fluctuations. Near-infrared spectroscopy evaluates regional cerebral oxygenation changes in response to hemodynamic alterations through continuous, noninvasive forehead sensors. Intracranial pressure monitoring enables assessment of pressure reactivity index through analyzing the correlation between intracranial and arterial blood pressure. CAR impairment is common across critical illness, from acute brain injury to systemic conditions like sepsis, cardiac surgery, and hepatic failure, where dysregulation can lead to secondary brain injury and worse outcomes. While each technique offers unique insights into CAR status, they vary in invasiveness, continuous monitoring capability, and technical requirements. Evidence suggests these methods can help to detect impaired CAR, identify optimal perfusion targets, and may guide individualized management strategies. CONCLUSIONS: Bedside CAR monitoring represents a promising approach for personalizing hemodynamic management in critically ill patients. While current evidence supports its role in prognostication and management decisions, further research is needed to standardize assessment methods and validate CAR-guided therapy across different critical care conditions. Multimodal monitoring approaches may provide complementary information to optimize patient care.