Direct determination of local oxygen consumption of the brain cortex in vivo.

A method is described to determine local oxygen consumption quantitatively in the brain cortex under in vivo conditions. Local oxygen consumption is calculated from the slope of local tissue PO2 decrease during a few seconds of total ischemia of the brain for each second after the stop of circulation. The decrease of tissue PO2 is recorded simultaneously at several measuring sites. To be independent of oxygen chemically bound to hemoglobin, tissue PO2 values are raised above 100 Torr. The calculation of local oxygen consumption for each second during the short period of ischemia showed that the O2 consumption remains constant only for a few seconds ranging from 5 to maximally 15 s at different locations. The O2 consumption decreases continuously although the tissue PO2 values are still above the full saturation of hemoglobin. The rate of local oxygen consumption varies considerably at different measuring sites of the superficial layers of the brain cortex (cat). The mean value amounts to 3 +/- 1.5 ml O2/100 g tissue and minute.