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Purpose: Cerebral autoregulation (CA) is a mechanism that acts to maintain consistent cerebral perfusion across a range of blood pressures, and impaired CA is associated with delirium. Individualized CA-derived blood pressure targets are poorly characterized in critically ill patients and the association with intensive care unit (ICU) delirium is unknown. Our objectives were to characterize optimal mean arterial pressure (MAP opt ) ranges in critically ill adults without brain injury and determine whether deviations from these targets contribute to ICU delirium., Methods: We performed a retrospective cohort analysis of patients with shock of any etiology and/or respiratory failure requiring invasive mechanical ventilation, without a neurologic admitting diagnosis. Patients were screened daily for delirium. Cerebral oximetry and mean arterial pressure data were captured for the first 24 hr from enrolment., Results: Forty-two patients with invasive blood pressure monitoring data were analyzed. Optimal mean arterial pressure targets ranged from 55 to 100 mm Hg. Optimal mean arterial pressure values were not significantly different based on history of hypertension or delirium status, and delirium was not associated with deviations from MAP opt . Nevertheless, the majority (69%) of blood pressure targets exceeded the current 65 mm Hg Surviving Sepsis guidelines., Conclusion: We observed that MAP opt targets across patients were highly variable, but did not observe an association with the incidence of delirium. Studies designed to evaluate the impact on neurologic outcomes are needed to understand the association with individualized mean arterial pressure targets in the ICU., Study Registration: ClinicalTrials.gov (NCT02344043); first submitted 22 January 2015., (© 2023. Canadian Anesthesiologists' Society.)

Delirium is common during critical illness and is associated with morbidity and mortality, but its pathophysiology is unknown. We tested whether dysfunctional cerebral autoregulation (CA) contributes to the development of delirium. Adult patients ( n  = 40) with respiratory failure and/or shock were prospectively enrolled. Continuous recordings of regional cerebral oxygen saturation (rSO 2 ) were obtained by near-infrared spectroscopy (NIRS) during the first 72 h of intensive care unit (ICU) admission. CA function was estimated by the cerebral oximetry index (COx), which is the time-varying correlation between rSO 2 and mean arterial pressure (MAP). Delirium was assessed daily. The median ICU stay was seven days (IQR 4-13). Twenty-four patients (60%) screened positive for delirium on at least one day during their stay. Taking positive COx values to reflect periods of CA dysfunction, we found that the cumulative duration of CA dysfunction during the first one to three days in the ICU was significantly associated with the subsequent development of delirium. Additionally, we assessed two alternative methods for estimating optimal MAP targets in individual patients. In summary, early disturbances in CA may contribute to delirium, and NIRS-derived rSO2 may be used to identify individual perfusion targets in critically ill patients.

Introduction: Survivors of critical illness frequently exhibit acute and chronic neurological complications. The underlying aetiology of this dysfunction remains unknown but may be associated with cerebral ischaemia. This study will use near-infrared spectroscopy to non-invasively quantify regional cerebral oxygenation (rSO 2 ) to assess the association between poor rSO 2 during the first 72 hours of critical illness with delirium severity, as well as long-term sensorimotor and cognitive impairment among intensive care unit (ICU) survivors. Further, the physiological determinants of rSO 2 will be examined., Methods and Analysis: This multicentre prospective observational study will consider adult patients (≥18 years old) eligible for enrolment if within 24 hours of ICU admission, they require mechanical ventilation and/or vasopressor support. For 72 hours, rSO 2 will be continuously recorded, while vital signs (eg, heart rate) and peripheral oxygenation saturation will be concurrently captured with data monitoring software. Arterial and central venous gases will be sampled every 12 hours for the 72 hours recording period and will include: pH, PaO2, PaCO2, and haemoglobin concentration. Participants will be screened daily for delirium with the confusion assessment method (CAM)-ICU, whereas the brief-CAM will be used on the ward. At 3 and 12 months post-ICU discharge, neurological function will be assessed with the Repeatable Battery for the Assessment of Neuropsychological Status and KINARM sensorimotor and cognitive robot-based behavioural tasks., Ethics and Dissemination: The study protocol has been approved in Ontario by a central research ethics board (Clinical Trials Ontario); non-Ontario sites will obtain local ethics approval. The study will be conducted under the guidance of the Canadian Critical Care Trials Group (CCCTG) and the results of this study will be presented at national meetings of the CCCTG for internal peer review. Results will also be presented at national/international scientific conferences. On completion, the study findings will be submitted for publication in peer-reviewed journals., Trial Registration Number: NCT03141619., Competing Interests: Competing interests: JM is the scientific director of the Canadian Frailty Network. SHS is the cofounder of BKIN Technologies, the manufacturer of the KINARM device. IB receives a stipend from the Trillium Gift of Life Network to support his role as a Regional Medical Lead. NO received funding from the Academic Medical Organization of Southwestern Ontario. MS receives a stipend from the Trillium Gift of Life Network to support his role as a Hospital Donation Physician. DG is funded through a Health-Professional Investigator Award from the Michael Smith Foundation for Health Research. JGB receives a stipend from the Trillium Gift of Life Network to support his role as a Regional Medical Lead., (© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: To test the hypothesis that poor brain tissue oxygenation (BtO 2 ) during the first 24h of critical illness correlates with the proportion of time spent delirious. We also sought to define the physiological determinants of BtO 2 ., Materials and Methods: Adult patients admitted to the ICU within the previous 24h were considered eligible for enrollment if they required mechanical ventilation, and/or vasopressor support. BtO 2 was measured using near-infrared spectroscopy, for 24h after enrollment. Hourly vital signs and clinically ordered arterial and central venous blood gases were collected throughout BtO 2 monitoring. Patients were screened daily for delirium with the confusion assessment method for the intensive care unit (CAM-ICU)., Results: BtO 2 and the proportion of time spent delirious did not result in a significant correlation (p=0.168). However, critically ill patients who spent the majority of their ICU stay delirious had significantly lower mean BtO 2 compared to non-delirious patients, (p=0.017). BtO 2 correlated positively with central venous pO 2 (p=0.00003) and hemoglobin concentration (p=0.001). Logistic regression indicated that lower BtO 2 , higher narcotic doses and a history of alcohol abuse were independent risk factors for delirium., Conclusions: Poor cerebral oxygenation during the first 24 hours of critical illness contributes to the development of delirium., Trial Registration: This trial is registered on clinicaltrials.gov (Identifier: NCT02344043), retrospectively registered January 8, 2015., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)