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Published on: November 19, 2020
The Relationship Between Pressure Reactivity and Cerebral Oximetry Indexes in Patients with Aneurysmal Subarachnoid
Yunseo Ku1,2,3, Murad Megjhani2,3, Tammam Alalqum2,3
1Department of Biomedical Engineering, College of Medicine, Chungnam National University, Daejeon, Korea.
Background:
Patient differences from optimal mean arterial pressure (MAPOPT) derived by a cerebral oximetry index (COx_a) are associated with outcome, but the validity of COx_a-derived MAPOPT remains in question due to the lack of agreement with pressure reactivity index (PRx)-derived MAPOPT. The study aimed to elucidate the relationship between PRx and COx_a to justify the use of COx_a and COx_a-derived MAPOPT in patients with aneurysmal subarachnoid hemorrhage (aSAH).
Methods:
This was a retrospective single-center study of six patients with aSAH with simultaneous near-infrared spectroscopy, intracranial pressure, and MAP monitoring. Repeated-measures Pearson correlation and Bland-Altman plot analysis were performed to compare PRx and COx_a and to compare PRx-derived MAPOPT and COx_a-derived MAPOPT. Coinciding changes in PRx and COx_a were compared, and the ability of COx_a to detect PRx-based autoregulation impairment was assessed over different time windows.
Results:
Repeated-measures Pearson correlation analysis showed no correlation between PRx and COx_a (r = 0.06, p < 0.01). The correlation between PRx- and COx_a-derived MAPOPT over 388 h was r = 0.50 (p < 0.01). The bias and upper and lower limits of agreement were - 1.60, + 20.24, and - 23.43 mm Hg, respectively. The shift in the overall distribution of moving correlation to higher values as the time-window length increased was more pronounced for COx_a than PRx (COx_a: 0.09-0.41, PRx: 0.00-0.15). When using a typical PRx threshold of 0.3, COx_a was found to be ineffective in identifying impaired autoregulation across all time windows (area under the receiver operating characteristic curve: 0.494-0.527).
Conclusions:
The threshold applied to PRx should not be applied to COx_a. It is suggested to consider higher thresholds for COx_a than PRx in deriving the range for MAPOPT calculations for continuous cerebral autoregulation assessment in aSAH. Further research is needed to optimize the MAPOPT derived from PRx and COx_a based on specific monitoring targets.
