Toshiyuki Oda

Does the redox state of cytochrome aa3 reflect brain energy level during hypoxia? Simultaneous measurements by near infrared spectrophotometry and 31P nuclear magnetic resonance spectroscopy.

We studied cerebral oxygen metabolism during hypoxia to demonstrate whether the redox state of cytochrome aa3 (cyt.aa3), as measured by near infrared spectrophotometry (NIRS), reflects brain energy level. Rats (n = 6) subjected to hypoxia were simultaneously monitored by NIRS and31 P nuclear magnetic resonance spectroscopy (NMRS). Brain function was evaluated using the electroencephalogram (EEG). After a reduction of the fraction of inspired oxygen (FIO2) from 0.21 to 0.15, we observed a significant increase in reduced cyt.aa3 (from 16.5% +/- 2.1% to 41.2% +/- 2.8%; P < 0.01), without significant changes in phosphocreatine (PCr) and beta-adenosine triphosphate (beta-ATP) levels. The PCr decreased significantly at a FIO2 of 0.10 (53.8% +/- 6.4% as compared with 97.7% +/- 10.9% at a FIO (2) of 0.21; P < 0.05), and reached a minimum at a FIO2 of 0.04. beta-ATP did not change significantly at a FIO2 of 0.10 or 0.08. With a FIO2 of less than 0.08, cyt.aa3 was almost totally reduced. EEG activity slowed at a FIO2 of 0.08 and became isoelectric at 0.04. Significant correlations were found between the levels of cyt.aa3 and PCr (P < 0.001, r = 0.83) as well as between cyt.aa3 and beta-ATP (P < 0.001, r = 0.73) by using the overall values at FIO (2) levels from 0 to 1.0. However, no significant correlations were observed among these variables when the FIO2 was less than 0.10. These findings suggest that the increase in reduced cyt.aa3 reflects brain energy depletion; however, the redox state of cyt.aa3 will not indicate brain energy depletion during extreme hypoxia because cyt.aa3 is reduced totally during hypoxia insufficient to deplete intracellular ATP. (Anesth Analg 1996;83:513-8)

Comparison between sevoflurane and isoflurane anesthesia in pig hepatic ischemia-reperfusion injury

AbstractPurpose. Sevoflurane and isoflurane have been reported to exert protective effects against ischemia-reperfusion injury (IRI) in various organs. To compare the effect of sevoflurane anesthesia on liver IRI with that of isoflurane anesthesia, we performed the present study in pigs. Methods. Nineteen pigs were assigned to either the sevoflurane (n = 9) or the isoflurane group (n = 10). Hepatic warm ischemia was produced by 30-min hepatic artery and portal vein clamping beginning 90 min after the start of the inhalation anesthesia; this was followed by a 240-min reperfusion. To extend our evaluation, we evaluated the degree of IRI using various parameters (plasma α-glutathione-S-transferase [α-GST], lipid peroxide, and lactate concentrations), in addition to the conventionally used liver damage markers. Results. The lactate level was significantly higher under isoflurane than under sevoflurane at 120 min after reperfusion (4.0 ± 0.4 mmol·l−1vs 2.5 ± 0.3 mmol·l−1; P < 0.05). How-ever, this difference had disappeared after 240 min of reperfusion. No significant differences between the two groups were observed in values for α-GST, lipid peroxides, aspartate aminotransferase, alanine aminotransferase, or lactic dehydrogenase. Conclusion. The extent of the hepatic IRI seen under sevoflurane anesthesia in pigs did not differ significantly from that seen under isoflurane, as judged from measurements of a number of parameters over a 240-min reperfusion period.

Continuous, noninvasive measurement of cytochrome oxidase in cerebral cortex by near-infrared spectrophotometry during aortic arch surgery.

The incidence of neurological dysfunction after cardiac surgery or thoracic aortic surgery with cardiopulmonary bypass (CPB) is much higher than after general surgery [1,2]. To prevent neurological complications, it is important to detect any deterioration in cerebral function and oxygenation as early as possible in the perioperative period. Accordingly, we noninvasively and continuously monitored changes in hemoglobin oxygenation and in the redox state of cytochrome oxidase (Cyt.aa3) in the cerebral cortex by near-infrared spectrophotometry (NIRS) during aortic arch surgery, and evaluated whether or not the level of reduced Cyt.aa3 could be used as a real-time indicator of any neurological prognosis.