Purpose: 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. Materials and Methods: 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. Results: 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. Conclusions: 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.
Keywords: head-down position; laparoscopy complications; robotic prostatectomy.