Abstract: Objective To investigate the effect of acute blood loss on postoperative cognitive function of aged spontaneously
hypertensive rats (SHRs). Methods Forty aged male SHRs were randomized into sham hemorrhage group (group A, n=13),
20% hemorrhage group (group B, n=13) and 40% hemorrhage group (group C, n=14). The rats were subjected to acute loss
from the femoral artery and subsequent fluid replacement with lactated Ringer’s Solution (3 folds of the blood loss volume).
All the rats underwent Morris water maze test to assess the visuospatial memory and learning ability, and were then
decapitated to observe the pathological changes of the hippocampus. Results The latency of reference memory in group C was
significantly prolonged after the operation (P=0.002), but the working memory and learning capacity showed no significant
differences between the 3 groups. Immunochemistry did not reveal significant differences in p-CREB expressions in the
hippocampal CA1 region among the groups, but volume reduction of some neurons was noted in the CA1 region in group C.
Conclusion Varying degrees of acute hemorrhage can result in different effect on postoperative cognition in aged SHR. Acute
hemodilutional anemia to 40% of baseline can cause reference memory impairment with cell volume reduction of the neurons
in the hippocampal CA1 region but does not affect the working memory and learning capacity or p-CREB expression.