The ICP-lowering effect of 10 degrees reverse Trendelenburg position during craniotomy is stable during a 10-minute period.

Recently we studied the effect of 10 degrees reverse Trendelenburg position on subdural pressure and cerebral perfusion pressure (CPP) during craniotomy. Within 1 minute we found a significant decrease in subdural pressure while CPP was unchanged. A longer time span, however, is necessary to exclude a temporary effect. In the present investigation we studied subdural pressure, CPP, and jugular bulb pressure (JBP) before and during a 10-minute period after change in position. Fifteen patients with supratentorial cerebral tumors were anesthetized with propofol/fentanyl in the supine position. Mean arterial blood pressure and JBP were measured invasively, and subdural pressure was measured after removal of the bone flap. End-tidal CO2, PaCO2, PaO2, heart rate, jugular venous oxygen saturation (SjO2), and arteriovenous oxygen difference (AVDO2) were also measured. Dural tension was estimated by the surgeon. The measurements were performed with the patients in a neutral position and during a 10-minute period after positioning the patient in a 10 degrees reverse Trendelenburg position. After 1 minute in the reverse Trendelenburg position, the mean value of subdural pressure decreased from 10.9 +/- 5.7 to 7.3 +/- 5.2 mm Hg (P<0.05) and remained unchanged for the following 9 minutes. Correspondingly, dural tension was lessened significantly. Jugular pressure and mean arterial blood pressure decreased significantly as well (P<0.05), but the CPP was unaffected. No significant changes in PaCO2, PaO2, end-tidal CO2, heart rate, SjO2, or AVDO2 were disclosed. During craniotomy 10 degrees reverse Trendelenburg position reduces subdural pressure and dural tension within 1 minute without reducing CPP. During the following 9 minutes the levels of subdural pressure and CPP are unchanged.