Abstract
ObjectiveThe amount of extravasated blood is an established surrogate marker for subarachnoid hemorrhage (SAH) severity, which varies in different experimental SAH (eSAH) models. A comprehensive eSAH grading system would allow a more reliable correlation of outcome parameters with SAH severity. The aim of this study was to define a severity score for eSAH related to the Fisher-Score in humans.Material and methodsSAH was induced in 135 male rats using the modified double hemorrhage model. A sham group included 8 rats, in which saline solution instead of blood was injected. Histological analysis with HE(hematoxylin-eosin)-staining for the visualization of blood was performed in all rats on day 5. The amount and distribution of blood within the subarachnoid space and ventricles (IVH) was analyzed.ResultsThe mortality rate was 49.6% (71/143). In all except five SAH rats, blood was visible within the subarachnoid space. As expected, no blood was detected in the sham group. The following eSAH severity score was established (ESAS-score): grade I: no SAH visible; grade II: local or diffuse thin SAH, no IVH; grade III: diffuse / thick layers of blood, no IVH; grade IV: additional IVH. Grade I was seen in five rats (7.9%), grade II in 28.6% (18/63), grade III in 41.3% (26/63) and grade IV in 22.2% (14/63) of the rats with eSAH.ConclusionThe double hemorrhage model allows the induction of a high grade SAH in more than 60% of the rats, making it suitable for the evaluation of outcome parameters in severe SAH.
Highlights
In patients with aneurysmal subarachnoid hemorrhage (SAH), the severity of the bleeding is related to the amount of extravasated blood
We developed a grading system for the distribution and amount of blood within the subarachnoid space and the ventricular system in the double hemorrhage SAH model in rats based on post mortem histological analysis, according to the well-established Fisher score in humans, which is based on the amount of blood in the subarachnoid space and its distribution within the ventricular system on the initial computed tomography scan [21]
With regards to the ESAS-score, we demonstrated that the double hemorrhage experimental SAH (eSAH)-model induces a high-grade eSAH (ESAS III and IV) in more than 60% of all rats, making it especially suitable for the evaluation of outcome parameters in severe SAH
Summary
In patients with aneurysmal subarachnoid hemorrhage (SAH), the severity of the bleeding is related to the amount of extravasated blood. Sugawara et al have described an eSAH grading system, based on a macroscopic semiquantitative evaluation of the amount of subarachnoid blood after sacrificing the animals, 24 hours following the SAH induction using the perforation model in rats [11]. This grading system allows a reliable evaluation of eSAH severity, it is not applicable in experimental studies with an expected duration of more than 24 hours, which are required for all investigations focussing on delayed ischemic complications. We aimed to define an easy to apply eSAH severity grading scale based on post mortem histological analysis five days after SAH induction and evaluated whether the modified double blood injection eSAH-model can reliably induce a severe SAH in rats
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