Effects of fluid-percussion brain injury on regional cerebral blood flow and pial arteriolar diameter.

The effects of two levels of fluid-percussion brain injury on cerebral blood flow (CBF) and pial arteriolar diameter were investigated in cats. Regional CBF was measured using the radioactive microsphere technique. Experimental brain injury resulted in changes in arterial blood pressure, CBF, and pial arteriolar diameter that were related to the severity of the injury. Low-level injury (1.88 +/- 0.11 atm, mean +/- standard error of the mean) resulted in a slight transient increase in CBF which had returned to preinjury levels by 30 minutes. High-level injury (2.68 +/- 0.19 atm) resulted in larger, statistically significant (p less than 0.01) increases in whole-brain CBF, decreases in cerebrovascular resistance, and increases in pial arteriolar diameter 1 minute postinjury. One hour after injury, CBF had returned to preinjury levels while cerebral perfusion pressure was significantly (p less than 0.01) reduced. There was no evidence of reduced CBF in any region studied. Pial arterioles dilated during the posttraumatic hypertensive period and then returned to control diameters within 1 hour after injury. Changes in the diameter of pial arterioles were significantly correlated with posttraumatic changes in CBF.