Real-Time Intraoperative Determination and Reporting of Cerebral Autoregulation State Using Near-Infrared Spectroscopy

Abstract

BACKGROUND: Cerebral blood flow (CBF) is maintained over a range of blood pressures through cerebral autoregulation (CA). Blood pressure outside the range of CA, or impaired autoregulation, is associated with adverse patient outcomes. Regional oxygen saturation (rS o 2 ) derived from near-infrared spectroscopy (NIRS) can be used as a surrogate CBF for determining CA, but existing methods require a long period of time to calculate CA metrics. We have developed a novel method to determine CA using cotrending of mean arterial pressure (MAP) with rS o 2 that aims to provide an indication of CA state within 1 minute. We sought to determine the performance of the cotrending method by comparing its CA metrics to data derived from transcranial Doppler (TCD) methods. METHODS: Retrospective data collected from 69 patients undergoing cardiac surgery with cardiopulmonary bypass were used to develop a reference lower limit of CA. TCD-MAP data were plotted to determine the reference lower limit of CA. The investigated method to evaluate CA state is based on the assessment of the instantaneous cotrending relationship between MAP and rS o 2 signals. The lower limit of autoregulation (LLA) from the cotrending method was compared to the manual reference derived from TCD. Reliability of the cotrending method was assessed as uptime (defined as the percentage of time that the state of autoregulation could be measured) and time to first post. RESULTS: The proposed method demonstrated minimal mean bias (0.22 mmHg) when compared to the TCD reference. The corresponding limits of agreement were found to be 10.79 mmHg (95% confidence interval [CI], 10.09–11.49) and −10.35 mmHg (95% CI, −9.65 to −11.05). Mean uptime was 99.40% (95% CI, 99.34–99.46) and the mean time to first post was 63 seconds (95% CI, 58–71). CONCLUSIONS: The reported cotrending method rapidly provides metrics associated with CA state for patients undergoing cardiac surgery. A major strength of the proposed method is its near real-time feedback on patient CA state, thus allowing for prompt corrective action to be taken by the clinician.

Cerebral Blood Flow Hemispheric Asymmetry in Comatose Adults Receiving Extracorporeal Membrane Oxygenation

“…Previous studies have measured cerebral autoregulation using cross-correlation analysis between continuously measured blood pressure and either invasive (intracranial pressure, brain tissue oximetry) or non-invasive (NIRS-based cerebral oximetry, TCD-based CBF velocity) ( Zweifel et al, 2008 ; Aries et al, 2010 ; Andresen et al, 2018 ; Montgomery et al, 2020 ) neuromonitoring modalities. We did not use this method because MAP variation was low (<5 mmHg) for long periods during monitoring, thus did not yield wide enough MAP ranges to generate full autoregulation curves.…”

Increased interhemispheric asymmetry of cerebral blood flow in comatose adult patients on extracorporeal membrane oxygenation

“…Previous studies have measured cerebral autoregulation using cross-correlation analysis between continuously measured blood pressure and a neuromonitoring modality, invasive (intracranial pressure, brain tissue oximetry) or non-invasive (NIRS-based cerebral oximetry, TCD-based CBF velocity) [35][36][37][38] . We did not use this method because MAP variation was low (<5 mmHg) for long periods during monitoring, thus did not yield wide enough MAP ranges to generate full autoregulation curves each day.…”

Neuromonitoring and Neurocognitive Outcomes in Cardiac Surgery: A Narrative Review

“…Although future directions for cerebral oximetry include entropy and trend analyses, as well as integrated cerebral autoregulatory blood pressure threshold assessments, the most crucial steps toward more clearly establishing its role in cardiac surgery, and in optimizing neurocognitive outcomes, will be the conduct of more high-quality trials, using standardized outcome assessments at homogenized time points, in line with consensus definitions. [92][93][94]…”