Real-time Monitoring of Cerebral Blood Flow and Cerebral Oxygenation During Rapid Ventricular Pacing in Neurovascular Surgery: A Pilot Study

Background: Rapid ventricular pacing (RVP) can be used to produce short periods of flow arrest during dissection or rupture of a cerebral aneurysm but carries the risk of inducing cerebral ischemia. This study evaluates the intraoperative effect of RVP on local cerebral blood flow (CBF) and cerebral oxygenation during neurovascular surgery. Materials and Methods: Five patients undergoing elective cerebrovascular surgery were included in a single-center prospective study. RVP was applied in pacing periods of 40 seconds with 30% and 100% FiO2. Regional cerebral oxygenation was monitored using a Foresight near-infrared spectroscopy sensor. A Clark-type electrode and a thermal diffusion microprobe located in the white matter were used to monitor brain tissue pO2 and CBF, respectively. Results: CBF response to RVP closely followed the blood pressure pattern and resulted in a low-flow state. Unlike CBF, brain tissue pO2 and regional cerebral oxygenation showed a delayed response to RVP, decreasing beyond the pacing period and slowly recovering after RVP cessation. We found a correlation between brain tissue pO2 and regional cerebral oxygenation. Increasing the inspired oxygen concentration had a positive impact on absolute regional cerebral oxygenation and brain tissue pO2 values, but the pattern resulting from applying RVP remained unaltered. Conclusions: RVP reduces CBF and cerebral oxygenation. Brain tissue pO2 and regional cerebral oxygenation are correlated but unlike CBF respond to RVP in a delayed manner. Further research is required to evaluate the impact of longer RVP bursts on brain oxygenation.