Methods: Six volunteers each underwent two PET scans; one scan assessed awake-baseline metabolism, and the other assessed metabolism during anesthesia with a propofol infusion titrated to the point of unresponsiveness (mean rate + SD 7.8 + 1.5 mg *symbol* kg1 *symbol* h1). Scans were obtained using the18 fluorodeoxyglucose technique.
Results: Awake whole-brain glucose metabolic rates (GMR) averaged 29 + 8 micro moles *symbol* 100 g1 *symbol* min1 (mean plus/minus SD). Anesthetized whole-brain GMR averaged 13 + 4 micro moles *symbol* 100 g1 *symbol* min1 (paired t test, P < 0.007). GMR decreased in all measured areas during anesthesia. However, the decrease in GMR was not uniform. Cortical metabolism was depressed 58%, whereas subcortical metabolism was depressed 48% (P < 0.001). Marked differences within cortical regions also occurred. In the medial and subcortical regions, the largest percent decreases occurred in the left anterior cingulate and the inferior colliculus. 相似文献
Methods: 15O-labeled water was used to determine rCBF in nine healthy male subjects at baseline and during 1 minimum alveolar concentration (MAC) of xenon (63%). Anesthesia was based solely on xenon. Absolute changes in rCBF were quantified using region-of-interest analysis and voxel-based analysis.
Results: Mean arterial blood pressure and arterial partial pressure for carbon dioxide remained unchanged. The mean (+/- SD) xenon concentration during anesthesia was 65.2 +/- 2.3%. Xenon anesthesia decreased absolute rCBF by 34.7 +/- 9.8% in the cerebellum (P < 0.001), by 22.8 +/- 10.4% in the thalamus (P = 0.001), and by 16.2 +/- 6.2% in the parietal cortex (P < 0.001). On average, xenon anesthesia decreased absolute rCBF by 11.2 +/- 8.6% in the gray matter (P = 0.008). A 22.1 +/- 13.6% increase in rCBF was detected in the white matter (P = 0.001). Whole-brain voxel-based analysis revealed widespread cortical reductions and increases in rCBF in the precentral and postcentral gyri. 相似文献
Methods: Five volunteers each underwent two PET scans; one scan assessed awake-baseline metabolism and the other scan assessed metabolism during isoflurane anesthesia titrated to the point of unresponsiveness (means +/- SD; expired = 0.5 +/- 0.1%). Scans were obtained with a GE2048 scanner (4.5-mm resolution-FWHM) using the18 fluorodeoxyglucose technique.
Results: Awake whole-brain glucose metabolism averaged 6.9 +/- 1.5 mg [center dot] 100 g sup -1 [center dot] min sup -1 (means +/- SD). Isoflurane reduced whole-brain metabolism 46 +/- 11% to 3.6 +/- 0.3 mg [center dot] 100 g sup -1 [center dot] min sup -1 (P less or equal to 0.005). Regional metabolism decreased fairly uniformly throughout the brain, and no evidence of any regional metabolic increases were found in any brain region for any participant. A region-of-interest analysis showed that the pattern of regional metabolism evident during isoflurane anesthesia was not significantly different from that seen when participants were awake. 相似文献
Methods: Using H215O, rCBF was assessed in 16 healthy (American Society of Anesthesiologists [ASA] physical status I) volunteers awake and at three escalating drug concentrations: 1, 1.5, and 2 MAC/EC50, or specifically, at either 2, 3, and 4% end-tidal sevoflurane (n = 8), or 6, 9, and 12 [mu]g/ml plasma concentration of propofol (n = 8). Rocuronium was used for muscle relaxation.
Results: Both drugs decreased the bispectral index and blood pressure dose-dependently. Comparison between adjacent levels showed that sevoflurane initially (0 vs. 1 MAC) reduced absolute rCBF by 36-53% in all areas, then (1 vs. 1.5 MAC) increased rCBF in the frontal cortex, thalamus, and cerebellum (7-16%), and finally (1.5 vs. 2 MAC) caused a dual effect with a 23% frontal reduction and a 38% cerebellar increase. In the propofol group, flow was also initially reduced by 62-70%, with minor further effects. In the SPM analysis of the "awake to 1 MAC/EC50" step, both anesthetic agents reduced relative rCBF in the cuneus, precuneus, posterior limbic system, and the thalamus or midbrain; additionally, propofol reduced relative rCBF in the parietal and frontal cortices. 相似文献
Methods: The regional cerebral metabolic rate of glucose (rcMRGlu) was sequentially assessed in two groups of six volunteers each, using 18F-fluorodeoxyglucose as tracer. In the xenon group, rcMRGlu was determined at baseline and during general anesthesia induced with propofol and maintained with 1 minimum alveolar concentration xenon. In the control group, rcMRGlu was measured using the identical study protocol but without administration of xenon. rcMRGlu was assessed after the plasma concentration of propofol had decreased to subanesthetic levels (< 1.0 [mu]g/ml). rcMRGlu was quantified in 10 cerebral volumes of interest. In addition, voxel-wise changes in rcMRGlu were analyzed using statistical parametric mapping.
Results: Xenon reduced whole-brain metabolic rate of glucose by 26 +/- 7% (from 43 +/- 5 [mu]mol [middle dot] 100 g-1 [middle dot] min-1 to 31 +/- 3 [mu]mol [middle dot] 100 g-1 [middle dot] min-1; P < 0.005) and significantly decreased rcMRGlu in all volumes of interest compared with the control group receiving propofol only. Voxel-based analysis revealed metabolic depression within the orbitofrontal, frontomesial, temporomesial, occipital, dorsolateral frontal, and lateral temporal cortices and thalami. No increases in rcMRGlu were detected during xenon anesthesia. 相似文献
Methods: Sevoflurane was compared to isoflurane in eight studies (N = 2,008) and to propofol in three studies (N = 436). Analysis of variance was applied using least squares method mean values to calculate the pooled mean difference in recovery endpoints between primary anesthetics. The effects of patient age and case duration also were determined.
Results: Sevoflurane resulted in statistically significant shorter times to emergence (-3.3 min), response to command (-3.1 min), orientation (-4.0 min) and first analgesic (-8.9 min) but not time to eligibility for discharge (-1.7 min) compared to isoflurane (mean difference). Times to recovery endpoints increased with increasing case duration with isoflurane but not with sevoflurane (patients receiving isoflurane took 4-5 min more to emerge and respond to commands and 8.6 min more to achieve orientation during cases longer than 3 hr in duration than those receiving sevoflurane). Patients older than 65 yr had longer times to orientation, but within any age group, orientation was always faster after sevoflurane. There were no differences in recovery times between sevoflurane and propofol. 相似文献
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Methods: Ten right-handed male volunteers were included in a 15O-water PET study. Seven underwent three conditions: control (saline), low remifentanil (0.05 [mu]g [middle dot] kg-1 [middle dot] min-1), and moderate remifentanil (0.15 [mu]g [middle dot] kg-1 [middle dot] min-1). The remaining three participated in the low and moderate conditions. A semi-randomized study protocol was used with control and remifentanil conditions 3 or more months apart. The order of low and moderate conditions was randomized. Cardiovascular and respiratory parameters were monitored. Categoric comparisons between the control, low, and moderate conditions and a pixelwise correlation analysis across the three conditions were performed (P < 0.05, corrected for multiple comparisons) using statistical parametric mapping.
Results: Cardiorespiratory parameters were maintained constant over time. At the low remifentanil dose, significant increases in relative rCBF were noted in the lateral prefrontal cortices, inferior parietal cortices, and supplementary motor area. Relative rCBF decreases were observed in the basal mediofrontal cortex, cerebellum, superior temporal lobe, and midbrain gray matter. Moderate doses further increased rCBF in mediofrontal and anterior cingulate cortices, occipital lobe transition, and caudal periventricular grey. Significant decreases were detected in the inferior parietal lobes. These dose-dependent effects of remifentanil on rCBF were confirmed by a correlation analysis. 相似文献
Methods: The authors analyzed 4,112 samples of 270 individuals (150 men, 120 women, aged 2-88 yr, weighing 12-100 kg). Population pharmacokinetic modeling was performed using NONMEM (NONMEM Project Group, University of California, San Francisco, CA). Inter- and intraindividual variability was estimated for clearances and volumes. The effects of age, weight, type of administration and sampling site were investigated.
Results: The pharmacokinetics of propofol were best described by a three-compartment model. Weight was found to be a significant covariate for elimination clearance, the two intercompartmental clearances, and the volumes of the central compartment, the shallow peripheral compartment, and the deep peripheral compartment; power functions with exponents smaller than 1 yielded the best results. The estimates of these parameters for a 70-kg adult were 1.44 l/min, 2.25 l/min, 0.92 l/min, 9.3 l, 44.2 l, and 266 l, respectively. For patients older than 60 yr the elimination clearance decreased linearly. The volume of the central compartment decreased with age. For children, all parameters were increased when normalized to body weight. Venous data showed a decreased elimination clearance; bolus data were characterized by increases in the volumes of the central and shallow peripheral compartments and in the rapid distribution clearance (Cl2) and a decrease in the slow distribution clearance (Cl3). 相似文献
Methods: Positron emission tomography measurements were performed with injection of 7 mCi 15O-water during nonpainful heat and painful heat stimulation of the volar forearm. Three experimental conditions were used during both sensory stimuli: saline, 0.05 [mu]g [middle dot] kg-1 [middle dot] min-1 remifentanil, and 0.15 [mu]g [middle dot] kg-1 [middle dot] min-1 remifentanil. Cardiovascular and respiratory parameters were monitored noninvasively. Across the three conditions, dose-dependent effects of remifentanil on regional cerebral blood flow were analyzed on a pixel-wise basis using a statistical parametric mapping approach.
Results: During saline infusion, regional cerebral blood flow increased in response to noxious thermal stimulation in a number of brain regions as previously reported. There was a reduction in pain-related activations with increasing doses of remifentanil in the thalamus, insula, and anterior and posterior cingulate cortex. Increasing activation occurred in the cingulofrontal cortex (including the perigenual anterior cingulate cortex) and the periaqueductal gray. 相似文献
Methods: In 10 healthy volunteers, the end-tidal carbon dioxide concentration was varied according to a multifrequency binary sequence that involved 13 steps into and 13 steps out of hypercapnia (total duration, 1,408 s). In each subject, two control studies, two studies at a plasma target propofol concentration of 0.75 [mu]g/ml (Plow), and two studies at a target propofol concentration of 1.5 [mu]g/ml (Phigh) were performed. The ventilatory responses were separated into a fast peripheral component and a slow central component, characterized by a time constant, carbon dioxide sensitivity, and apneic threshold. Values are mean +/- SD.
Results: Plasma propofol concentrations were approximately 0.5 [mu]g/ml for Plow and approximately 1.3 mg/ml for Phigh. Propofol reduced the central carbon dioxide sensitivity from 1.5 +/- 0.4 to 1.2 +/- 0.3 (Plow;P < 0.01 vs. control) and 0.9 +/- 0.1 l [middle dot] min-1 [middle dot] mmHg-1 (Phigh;P < 0.001 vs. control). The peripheral carbon dioxide sensitivity remained unaffected by propofol (control, 0.5 +/- 0.3; Plow, 0.5 +/- 0.2; Phigh, 0.5 +/- 0.2 l [middle dot] min-1 [middle dot] mmHg-1). The apneic threshold was reduced from 36.3 +/- 2.7 (control) to 35.0 +/- 2.1 (Plow;P < 0.01 vs. control) and to 34.6 +/- 1.9 mmHg (Phigh;P < 0.01 vs. control). 相似文献