Changes of Cerebral Blood Volume During Robot-Assisted Laparoscopic Radical Prostatectomy: Observational Prospective...

Robot-assisted laparoscopic radical prostatectomy (RARP) requires a steep head-down tilt and pneumoperitoneum, which may cause an increase in cerebral blood volume (CBV). With a new near-infrared time-resolved spectroscopy device, the tNIRS-1, we can measure the absolute value of the cerebral hemoglobin concentration and hence calculate CBV and cerebral oxygen saturation (rSO₂). Using this device, we evaluated the time course of CBV during surgery and also evaluated the changes in rSO₂ simultaneously. We performed a prospective observational study of 21 patients scheduled for RARP. We evaluated CBV and rSO₂ by using the tNIRS-1 at 10 time points during surgery. The CBV was 2.92 ± 0.38 mL ·100 g^-1 after the end of anesthetic preparation. It significantly increased to 3.05 ± 0.44 mL ·100 g^-1 after the head-down tilt and was around 3.1 mL ·100 g^-1 until 120 minutes after the head-down tilt. However, just before the return to the horizontal position, it decreased to 2.93 ± 0.46 mL ·100 g^-1 and then decreased more after the return to the horizontal position. Changes in rSO₂ over time were within only 3%, and no significant differences from the control value were observed. The increase in CBV was <10% despite the steep head-down tilt and pneumoperitoneum, and it was compensated for at around the end of surgery. Clinically significant changes in rSO₂ were not observed during the surgery.