Experimental study on the correlation between the cerebral energy metabolism and cerebral blood flow changes in rats with subarachnoid hemorrhage-induced delayed cerebral vasospasm

Objective: To explore the changes of the cerebral energy metabolism in rats with experimental subarachnoid hemorrhage (SAH)-induced delayed cerebral vasospasm, and the correlation with cerebral blood flow (CRF) changes. Methods: Male Sprague-Dawley rats (n = 50) were randomly divided into five groups: control group and 1 d, 3 d, 5 d and 7 d SAH group. The animal model was prepared by two injections of nonheparinized autologous arterial blood into the cisterna magna. Another 5 rats were used to observe intracranial blood distribution. Microdialysis (MD) was applied to monitor the levels of glucose (Glu), lactic acid (Lac), pyruvic acid (Pyr) in the cerebral extracellular fluid (ECF) in each group, and calculated the ratio of Lac and Pyr. The cortical CBF was measured by Laser Doppler Flowmetry (LDF). Histopathological changes of the basilar artery wall were observed by light microscope and transmission electron microscope. Results: 1) In 5 rats for observing intracranial blood distribution, the blood of 4 SAH models was distributed mainly in basal cistern, interpeduncular cistern and the basis of frontal lobe. The mixture of methylene blue and blood was mainly deposited at the base of skull, and blood was distributed in cerebral ventricules and longitudinal fissure cistern. In the rest one as a control which was injected with artificial cerebrospinal fluid, no intracranial hemorrhage and blood deposition were seen. It indicated that SAH model was successively prepared. 2) In comparison with the control group, levels of Glu and Pyr decreased significantly (P < 0.01) and Lac/Pyr ratio increased significantly (P < 0.01) in SAH rats while the increase of Lac/Pyr ratio was most remarkable in 5 d group and 7 d group (P < 0.01). The increase of Lac level was also significant in 5 d group (P < 0.01). 3) In the monitor of LDF, the CBF reduction rates in SAH groups were higher than that in control group (P < 0.05), and the reduction in 5 d group was most significant in comparison with other subgroups (P < 0.05). The changes in CRF was positively correlated with Lac/Pyr ratio and Lac level (r = 0.721, 0.477; P < 0.01, for all), but was negatively correlated with Glu level and Pyr level (r = -0.447, -0.579; P < 0.01, for all). Conclusion: MD indexes are consistant with CBF changes. It can be used as a dynamic monitor to indicate the biochemical index of cerebral interstitial fluid in SAH, and can be also used for predicting the onset of delayed cerebral vasospasm.