COGNITIVE AND EEG RECOVERY FOLLOWING BOLUS INTRAVENOUS ADMINISTRATIONOF ANESTHETIC AGENTS

Bolus intravenous (IV) administration of commonly used IV anesthetic a gents such as fentanyl and the fentanyl analogues, alfentanil, remifen tanil, and sufentanil, etomidate and propofol, produced anesthesia in rats as measured by the loss of righting (LOR) with calculated ED(150) doses of 0.06, 0.09, 0.037, 0.007, 2.51 and 6.12 mg/kg, respectively. Animals trained in an eight arm radial maze (RAM) were assessed for c ognitive recovery, as measured by response efficiency (percentage of c orrect arm entries within 10 min), immediately, 15 min and 30 min foll owing IV administration of the calculated ED(150) dose of each of thes e agents, and the subsequent return of righting (ROR). Animals adminis tered fentanyl or sufentanil were unable to successfully complete the maze throughout the testing periods. Animals receiving remifentanil sh owed cognitive recovery within the first testing interval (immediately following the return of righting), while animals receiving alfentanil , etomidate or propofol showed recovery at the 15-min testing interval following ROR. In a separate experiment, bolus IV administration of t he ED(150) dose of these agents was evaluated in an acute rat EEG mode l. Following ROR, return to baseline EEG levels occurred at 0.30, 2.88 , 5.06, 16.25, 31.29 and 43.98 min for remifentanil, propofol, alfenta nil, etomidate, fentanyl and sufentanil, respectively. These data show that the return to efficient cognitive functioning corresponds to the return to normal baseline EEG waveforms.