Cerebral Blood Flow Affects Dose Requirements of Intracarotid Propofol for Electrocerebral Silence

Background: The authors hypothesized that cerebral blood flow (CBF) changes will affect the dose of intracarotid propofol required to produce electrocerebral silence.

Methods: The authors tested their hypothesis on New Zealand White rabbits. The first group of 9 animals received intracarotid propofol during (1) normoventilation, (2) hyperventilation, and (3) hypoventilation. The second group of 14 animals received intracarotid propofol with or without concurrent intraarterial verapamil, a potent cerebral vasodilator. The third group of 8 animals received bolus injection of propofol during normotension, during severe cerebral hypoperfusion, and after hemodynamic recovery.

Results: In the first group, there was a linear correlation between the dose of intracarotid propofol and percent change (%DELTA]) in CBF from the baseline due to changes in the minute ventilation, Total Dose (y) = 0.17 + 0.012 * %DELTA] CBF (x), n = 27, r = 0.76. In the second group, the dose of propofol was also a function of CBF change after verapamil, Total Dose (y) = 0.98 + 0.1 * %DELTA] CBF (x), n = 14, r = 0.75. In the third group, the duration of electrocerebral silence after intracarotid propofol (3 mg) was significantly increased with concurrent cerebral hypoperfusion compared with prehypoperfusion and posthypoperfusion values (141 +/- 38 vs. 19 +/- 24 and 16 +/- 12 s, respectively, P < 0.0001).