Propofol and thiopental do not interfere with regional cerebral blood flow response at sedative concentrations.
BACKGROUND
Anesthetics may affect the regional cerebral blood flow (rCBF) response associated with increased brain activity in humans. rCBF was measured as auditory stimulus rate was increased during propofol and thiopental administration.


METHODS
After informed consent, 10 right-handed male volunteer participants (aged 33.5 +/- 10.4 yr, weighing 74.5 +/- 8.4 kg) received thiopental (n = 4) or propofol (n = 6) intravenously at stepwise target concentrations of propofol 1.2 and 2.5-3, or thiopental 4 and 7-9 microg/ml, representing sedative and hypnotic drug concentrations. The latter made volunteers unresponsive to voice or mild stimulation. Quantitative positron emission tomographic brain images were obtained at 0, 20, and 40 auditory words per minute at each drug concentration. Using SPM99 analysis, 10-mm spherical regions of interest were identified by peak covariation of word rate with rCBF across all conditions and drug concentrations. Individual mean rCBF responses in these and primary auditory cortex (Heschl's gyri) were obtained.


RESULTS
Significant increases in rCBF with auditory word rate occurred in temporal lobes bilaterally at baseline (significance, T = 4.95). There was no change in this response during sedation (T = 5.60). During unresponsiveness seven of 10 participants had a diminished response in the left temporal lobe (T = 3.18). Global CBF, corrected for changes in PCO2 (3% .mmHg PCO2), was reduced 15% by sedation and 27% during unresponsiveness.


CONCLUSIONS
The presence of propofol or thiopental does not affect the rCBF response to increasing stimulus rate during consciousness. Thus, changes in rCBF activation patterns with sedative concentrations of these drugs represent effects on brain activity itself. The neuroanatomical targets of drug effect on memory and attention may be revealed by changes in rCBF patterns associated with these cognitive activities.
Veselis
Robert A
RA
Department of Anesthesiology and Critical Care Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA. veselisr@mskcc.org
Feshchenko
Vladimir A
VA
Reinsel
Ruth A
RA
Beattie
Bradley
B
Akhurst
Timothy J
TJ
D000161:Acoustic Stimulation; D000328:Adult; D001519:Behavior / Q000187:drug effects; D002245:Carbon Dioxide / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000187:drug effects; D004569:Electroencephalography / Q000187:drug effects; D007839:Functional Laterality / Q000187:drug effects; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D008279:Magnetic Resonance Imaging; D008297:Male; D010092:Oximetry; D049268:Positron-Emission Tomography; D015742:Propofol / Q000494:pharmacology*; D013874:Thiopental / Q000494:pharmacology*
D006993:Hypnotics and Sedatives; D002245:Carbon Dioxide; D013874:Thiopental; D015742:Propofol