[Experimental studies of brain edema by infusion edema model-- biophysical changes of edema fluid in white matter of the brain].
The important changes in the area of brain edema are the accumulation and the spreading of edema fluid through the extracellular space in white matter of the brain. In this study, we described the changes of tissue resistance and compliance as the increment of accumulated volume of fluid produced by the slow infusion of normal saline or plasma into white matter of the cat brain. Adult cats (22) were tracheotomized, paralyzed with Galamine (2 mg/kg) and maintained normocapnic, normotensive under nitrous oxide anesthesia. Normal saline or plasma of their own was infused slowly through 25 gauge needle implanted into left frontal white matter by stereotaxic technique. A low compliance pressure gauge transducer was connected to the line for the measurement of inflow pressure. Tissue resistance and compliance for the movement of infused fluid into white matter were delivered from the changes of inflow pressure by adding the 3 microlitter per minutes on top of the resting steady state pressure. Values of tissue resistance in normal white matter, determined at the accumulated volume of 0.05 ml was very high (normal saline infusion: 6.42 +/- 0.61 X 10(3) mmHg/ml/min, plasma infusion: 5.47 +/- 1.43 X 10(3) mmHg/ml/min). But it decreased rapidly followed by more gradual decrease of tissue resistance became more edematous, reaching a plateau of one sixth of initial value at an infused volume of 0.5 ml. Tissue compliance changed by an opposite pattern of rapid increase and plateau to the changes of tissue resistance.
D000818:Animals; D001794:Blood Pressure; D001921:Brain / Q000378:metabolism*; D001929:Brain Edema / Q000378:metabolism* / Q000503:physiopathology; D002415:Cats; D002560:Cerebrovascular Circulation; D003187:Compliance; D005110:Extracellular Space / Q000378:metabolism