The effect of brain compression under venous circulatory impairment.

It is well known that surgical obliteration of the cerebral veins with additional brain compression by retractors is dangerous. To evaluate the mechanism, we studied the change in cerebral microcirculation and parenchymal damage following brain compression with venous circulatory impairment using a rat model. The animals were divided into the following four groups (each n = 5) (1) a sham-operated control; (2) group A, one cortical vein occlusion; (3) group B, a 30 mmHg compression pressure; and (4) group C, one cortical vein occlusion with 30 mmHg compression. The cortical vein was occluded photochemically. Local cerebral blood flow (l-CBF) in the compressed area was measured by stationary laser-Doppler (LD) flowmetry and regional CBF (r-CBF) in the surrounding area was also measured by LD scanning technique for 120 min. l-CBF in the compressed area decreased significantly in groups B and C. A gradual and significant increase in group B and decrease in group C in r-CBF of the surrounding area were observed. Histologically, more extensive damage was observed in group C than in group A and B. The degree of hypoperfusion of the affected brain correlated well with the subsequent brain damage in the experiments. We demonstrated that, compared with vein occlusion or brain compression alone, the accumulated episode caused severe ischemia, then increased the vulnerability of the rat brain to tissue damage.