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

Abstract

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.

Effects of Traumatic Brain Injury on Regional Cerebral Blood Flow in Rats as Measured with Radiolabeled Microspheres

“…Using the hydrogen clearance method, Lewelt et al (1980) reported that minimal reductions of blood flow to the cau date nucleus occurred at 1 h following midline fluid-percussion brain injury in cats (30.1 ± 1.8 mll min/IOO g in mild injury and 25.7 ± 4.4 mllmin/l00 g in severe injury compared with 34.3 ± 3.2 mll min/IOO g in controls). Using the radioactive mi crosphere technique, DeWitt et al (1986) did not observe any reductions of rCBF up to 1 h following fluid-percussion brain injury in cats (with the ex ception of a transient hyperemia at 1 min post in jury) and suggested that CBF does not change acutely following fluid-percussion brain injury. However, a subsequent microsphere study, using an identical model of fluid-percussion brain injury in the cat, revealed that regional changes in CBF do occur at a later time point (2 h) following injury .…”

“…Using the hydrogen clearance tech nique, Lewelt et al (1980) reported a reduction of blood flow to the caudate nucleus (at 1 h post in jury) that was proportional to the severity of mid line fluid-percussion brain injury in cats. Although DeWitt et al (1986), using radiolabeled micro spheres, found no significant reductions of rCBF up to 1 h following fluid-percussion brain injury in cats, a subsequent study showed that reductions of rCBF occur at 2 h post injury . Recently, new models of fluid-percussion brain injury have been characterized using the rat as an experimental subject (Dixon et al, 1987;McIntosh et al, 1988).…”

Pathophysiology of Cerebral Ischemia and Brain Trauma: Similarities and Differences

“…Acute abnormalities in the vascular endothelium and increased BBB permeability are also documented after TBI (Cortez et al, 1989;DeWitt et al, 1986;Dietrich et al, 1994b;Hekmatpanah and Hekmatpanah, 1985;Povlishock and Kontos, 1985). Increased pinocytotic activity within the endothelial cells, endothelial microvilli projections, large vacuoles and craters are reported (Povlishock and Kontos, 1985).…”

“…Contusions are commonly associated with hemodynamic changes including focal reductions in local cerebral blood flow (lCBF) (DeWitt et al, 1986;. In both clinical and experimental studies, the degree of flow reductions has been reported to correlate with injury severity Graham and Adams, 1971).…”

“…Focal areas of reduced CBF after brain trauma can be surrounded by regions exhibiting milder reductions in flow (DeWitt et al, 1986;Dietrich et al, 1996a). This surrounding area may thus correspond to the penumbral region surrounding an ischemic core (Back, 1998;Hossmann, 1994).…”