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Impact of various extents of experimental subarachnoid hemorrhage induced by the endovascular filament model on mortality and changes of cerebral blood flow

Thomas Westermaier, Alina Jauss, Giles H. Vince, Furat Raslan, Joerg Eriskat and Klaus Roosen

Objective: Among various animal models of subarachnoid hemorrhage (SAH), the endovascular filament model has been found particularly suitable to investigate acute pathophysiological changes after experimental SAH. Its major drawback, however, are high mortality and high variability of results. The present studies were carried out to examine the impact of various extents of experimental SAH in rats induced by different filament sizes.

Methods: In study 1, Sprague-Dawley rats were subjected to vessel perforation with a 3-0, 4-0 or 5-0 monofila-ment or served as controls (n = 8). Intracranial pressure (ICP), mean arterial blood pressure (MABP), cerebral perfusion pressure (CPP) and local cortical blood flow (LCBF) were continuously monitored for 6 hours after SAH. 24 hours later, the animals were sacrificed to evaluate subarachnoid blood effusion. In study 2, the ani-mals were subjected to SAH using a 3-0 monofilament or served as controls (n = 8). After 7 days, they were sacrificed for quantification of tissue damage.

Results: With increasing filament size, the decrease of CPP and LCBF and subarachnoid blood effusion were more pronounced. In all SAH-groups, the decline of LCBF after SAH exceeded the decline of CPP. Hippocam-pal damage was moderate but consistent. In both studies, the acute mortality was lower than previously re-ported.

Conclusion: With controlled pre-hemorrhage blood pressure values and longer mechanical ventilation mortality can be kept low even if stronger filaments are used. The impact of subarachnoid vessel perforation on patho-physiological changes and blood effusion can be graded by the use of different filament sizes. The persisting mismatch between CPP and LCBF both in major and minor SAH suggests sustained vasoconstriction occurring independent of the extent of hemorrhage.