Über die Beziehung zwischen O2-Aufnahme des Gehirns und O2-Druck im Sinusblut des Gehirns bei uneingeschränkter und eingeschränkter Durchblutung

Quantitative evaluation of optical reflection spectra of blood-free perfused guinea pig brain using a nonlinear multicomponent analysis

After developing a blood-free perfused preparation of the guinea pig brain a nonlinear multicomponent analysis (NLMCA) of the reflection spectra of the brain surface was worked out by which the redox state of cytochrome aa3, c, and b could be evaluated quantitatively and almost continuously. The NLMCA allowed to simulate the tissue reflection spectra in such a way that only a small statistical error remained between the recorded and the computed spectra. Using redox states of cytochrome aa3 and c as an intracellular oxygen probe it was found that in order to supply the guinea brain with sufficient oxygen by a saline medium equilibrated with 95% oxygen and 5% CO2 the temperature had to be reduced to 18-20 degrees C. At this temperature cytochrome aa3 was 95% oxidized.

Effects of severe arterial hypocapnia on regional blood flow regulation, tissue PO2 and metabolism in the brain cortex of cats

The effect of a stepwise decrease in PaCO2 from 3.9-1.6 kPa on rCBF, rCMRO2, tissue PO2 and concentrations of glucose, lactate, pyruvate, ATP, ADP, AMP and phosphocreatine in the brain cortex was studied in cats lightly anaesthetized with sodium pentobarbital. 1. Moderate lowering of PaCO2 to 2.5 kPa induced in all animals a homogeneous decrease of rCBF in corresponding areas of the right and left hemisphere. Mean rCBF fell from 129.2 to 103.1 ml X 100 g-1 X min-1, while rCMRO2 remained unchanged (12.7-12.9 ml X 100 g-1 X min-1). The tissue PO2 frequency histograms showed a shift to lower values without indicating the presence of brain tissue hypoxia. 2. Severe arterial hypocapnia (PaCO2 = 1.6 kPa) caused an inhomogeneous blood flow reaction. Both further decreased as well as increased rCBF values were measured simultaneously in the brain cortex of individual animals (mean rCBF = 97.6 ml X 100 g-1 X min-1). At the same time tissue PO2 measurements and metabolite assays indicated the presence of pronounced brain tissue hypoxia. The tissue concentrations of lactate and pyruvate and the lactate/pyruvate ratio were significantly increased, while the phosphocreatine concentration was significantly reduced. In addition, rCMRO2 decreased to 11.3 ml X 100 g-1 X min-1. The results provide conclusive evidence that severe arterial hypocapnia leads to an insufficient O2 supply of the brain cortex, which in turn seems to counteract the influence of hypocapnia on cortical blood flow regulation.

A cat head model with isolated perfusion by the animal's own blood

A model consisting of a cat head perfused in isolation with the animal's own blood is described. The use of endogenous blood allows the organ to function under physiological conditions for several hours. The blood is taken from the abdominal aorta of the anaesthetized animal and passed to the carotid arteries via an extracorporeal circulation system. The perfusion pressure can be varied at will and is regulated electronically. The volume of blood in the extracorporeal circulation system is only 6 ml. The tests performed on this model were designed to study the behaviour of the cortical EEG and the cortical micro flow. Neither of these parameters underwent any change after institution of the artificial perfusion, and the blood gases also remained fairly stable. The model is suitable for studying both physiological and pharmacological problems.