The effects of propofol on cerebral and spinal cord blood flow in rats.

The effects of low and high doses of propofol on global cerebral blood flow (CBF) and spinal cord blood flow (SCBF) as a function of mean arterial blood pressure were investigated. CBF and SCBF during propofol infusion were compared to the levels in rats anesthetized with nitrous oxide (N2O) and fentanyl. Rats in the fentanyl/N2O group (control, n = 13) received 70% N2O in O2 plus fentanyl (bolus: 10 micrograms/kg; infusion: 25 micrograms.kg-1 x h-1). Rats in the low-dose propofol group (n = 10) received 30% O2 in air and propofol infusion (0.5 mg.kg-1 x min-1). Rats in the high-dose propofol group (n = 8) received 30% O2 in air and propofol infusion (2.0 mg.kg-1 x min-1). Blood flow autoregulation was tested by manipulating the mean arterial blood pressure with phenylephrine infusion or trimethaphan infusion and blood withdrawal by measuring CBF and SCBF using radioactive microspheres. Arterial blood gases, pHa, and skull temperature were controlled. Cerebral and spinal cord vasculature showed autoregulation in all treatment groups with a pressure range of 50-140 mm Hg. Within this pressure range, when compared to fentanyl/N2O, propofol decreased cortical CBF 60% (P < 0.001), subcortical CBF 40% (P < 0.001), midbrain blood flow 30% (P < 0.001), and SCBF 20% (P < 0.05). These results indicate that propofol maintains CBF and SCBF autoregulation.