The Cerebral Perfusion Index: Developing a Novel Model of Cerebral Perfusion in the Intensive Care Unit
CCCF ePoster library. J. Gordon Boyd J. 11/13/19; 283440; EP119 Disclosure(s)(s): None
Jasmine Khan & J. Gordon Boyd
Jasmine Khan &  J. Gordon Boyd
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Topic: Retrospective or Prospective Cohort Study or Case Series

Khan, J1; Wood, MD1; Lee KFH2; Maslove, D3,4; Muscedere, J3; English, S5,6; Ball, I7; Slessarev, M6; Boyd, JG1,3,4
1Centre for Neuroscience Studies, Queen's University, Kingston, ON
2School of Medicine, Queen's University, Kingston, ON, Canada
3Dept. of Critical Care Medicine, Queen's University, Kingston, ON
4Dept of Medicine, Queen's University, Kingston, ON
5Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, ON
6Department of Medicine (Critical Care), University of Ottawa, Ottawa ON
7Department of Medicine (Critical Care), Western University of Ontario, London, ON

Background: There is increasing evidence that poor cerebral perfusion may contribute to delirium in the critically ill. Real-time monitoring of cerebral perfusion presents challenges, however, as no non-invasive method exists to directly measure cerebral perfusion.  Researchers have used alternative measures to approximate cerebral perfusion, including near-infrared spectroscopy (NIRS), to capture regional cerebral oxygenation (rSO2).  This technology combined with vital sign analysis to capture disturbances in cerebral autoregulation, a mechanism that regulates perfusion to the brain. Results from studies of reduced cerebral perfusion using alternative measures in critically ill patients have shown that while reduced cerebral perfusion predicted delirium development, there was substantial variation within delirious and non-delirious groups1,2, suggesting that individual metrics approximating cerebral perfusion may not provide an adequate representation of the global changes occurring in the brain3.

Objectives: To determine whether creation of a composite measure of cerebral perfusion, the cerebral perfusion index (CPI), is feasible in a multi-centre prospective observational study. The CPI will capture multiple components of cerebral perfusion, combining rSO2, duration of cerebral autoregulation dysfunction, and time outside of optimal mean arterial pressure (MAPopt) in order to provide a more comprehensive view of cerebral perfusion in ICU patients. Feasibility assessed by completeness of data capture and the ability to acquire/calculate the components of CPI.

Methods: This study was part of a larger feasibility trial, the Cerebral Oxygenation and Neurological Outcomes FOllowing CriticAL Illness-2 (CONFOCAL-2), examining the influence of cerebral perfusion on delirium development and long-term impairment in the intensive care unit (ICU). Briefly, critically ill adults in 4 Ontario ICUs were enrolled if they had shock and/or respiratory failure requiring invasive mechanical ventilation for >24hrs. For the first 72hrs, patients' vital signs, blood gases, and regional cerebral oxygenation (rSO2) levels were monitored. rSO2 was captured using near-infrared spectroscopy (NIRS). Patients were monitored for delirium in the ICU and ward for up to 30 days of their stay.

Results: The capture rate of rSO2 data was 82.7%. Vital sign was lower, at 43.6% for mean arterial pressure (MAP) monitoring. Of the 59 patients enrolled over a one-year period, 30 had sufficient rSO2 and MAP data to calculate CPI.  A mean (± SD) duration of data capture was 3028 (± 1755) minutes.  Mean physiological (± SD) values of the cohort were: rSO2 (70.3 ±7.0%), mean arterial pressure (76.5 ±12.9 mmHg), duration of disturbed autoregulation (291± 276 minutes) and time outside MAPopt (1202±723 minutes).

Conclusions: Screening, enrolment, and data acquisition was deemed feasible. However, calculating the constituents of the CPI was challenging across multiple sites, as MAP data capture was low. Strategies (e.g. close monitoring of first 1-2 enrolled patients) will be implemented to improve data acquisition rates across sites. A composite measure of cerebral perfusion is a potentially useful tool in providing a comprehensive view of perfusion changes that occur in the brain. Future use of CPI will be aimed toward understanding the impact of impaired cerebral perfusion on delirium development and long-term cognitive outcomes in critically ill patients.

1. Wood, M. D., Maslove, D. M., Muscedere, J. G., Day, A. G. & Gordon Boyd, J. Low brain tissue oxygenation contributes to the development of delirium in critically ill patients: A prospective observational study. J. Crit. Care 41, 289–295 (2017).
2. Lee, K. F., Wood, M. D., Maslove, D. M., Muscedere, J. G. & Boyd, J. G. Dysfunctional cerebral autoregulation is associated with delirium in critically ill adults. J. Cereb. Blood Flow Metab. 0, 1–9 (2018).
3. Stocchetti, N. et al. Clinical review: Neuromonitoring - an update. Crit. Care 17, 1–13 (2013).

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