Cerebral autoregulation derived blood pressure targets in elective neurosurgery

Poor postoperative outcomes may be associated with cerebral ischaemia or hyperaemia, caused by episodes of arterial blood pressure (ABP) being outside the range of cerebral autoregulation (CA). Monitoring CA using COx (correlation between slow changes in mean ABP and regional cerebral O-2 saturation-rSO(2)) could allow to individualise the management of ABP to preserve CA. We aimed to explore a continuous automated assessment of ABP(OPT) (ABP where CA is best preserved) and ABP at the lower limit of autoregulation (LLA) in elective neurosurgery patients. Retrospective analysis of prospectively collected data of 85 patients [median age 60 (IQR 51-68)] undergoing elective neurosurgery. ABP(BASELINE) was the mean of 3 pre-operative non-invasive measurements. ABP and rSO(2) waveforms were processed to estimate COx-derived ABP(OPT) and LLA trend-lines. We assessed: availability (number of patients where ABP(OPT)/LLA were available); time required to achieve first values; differences between ABP(OPT)/LLA and ABP. ABP(OPT) and LLA availability was 86 and 89%. Median (IQR) time to achieve the first value was 97 (80-155) and 93 (78-122) min for ABP(OPT) and LLA respectively. Median ABP(OPT) [75 (69-84)] was lower than ABP(BASELINE) [90 (84-95)] (p < 0.001, Mann-U test). Patients spent 72 (56-86) % of recorded time with ABP above or below ABP(OPT) +/- 5 mmHg. ABP(OPT) and ABP time trends and variability were not related to each other within patients. 37.6% of patients had at least 1 hypotensive insult (ABP < LLA) during the monitoring time. It seems possible to assess individualised automated ABP targets during elective neurosurgery.