gms | German Medical Science

Introduction: Aneurysmal subarachnoid hemorrhage (aSAH) is hallmarked by rapid increase of intracranial pressure (ICP) and acute hypoperfusion contributing to early brain injury. Non-aneurysmal SAH (naSAH) is assumed to result in less dramatic ICP changes and possibly preserved cerebral perfusion, thereby resulting in a better neurological outcome. The purpose of our study was to develop an experimental model of naSAH by variation of injection velocity in order to determine the role of intracranial pressure variability on acute changes of cerebral perfusion after SAH.

Method: SAH in rats was induced by cisternal injection of 0.5ml arterial blood (AB) or 0.5ml normal saline (NS) in predefined time frames: group AB₁ 0.5ml/1min (n=8), group AB₁₀ 0.5ml/10min (n=11), group AB₃₀ 0.5ml/30min (n=7), group NS1 0.5ml/1 min (n=9); group NS10 0.5ml/10min (n=10). 11 sham-operated animals served as controls without any injection. Regional cortical blood flow (CBF), intracranial pressure (ICP) and mean arterial blood pressure (mABP) were recorded for 6 h after SAH.

Results: Maximum increase of ICP was highest in the rapid injection group (AB₁, p<0.001), but significance was lost after 60 minutes. ICP was significantly higher in the AB groups when compared to the NS groups throughout the observation period (plateau phase >1h post SAH, p<0.001). Maximum increase of mABP was significantly higher in the rapid injection group (AB₁) compared to AB₁₀ and AB₃₀ (p<0.001). With NS injection (NS₁, NS₁₀), no significant difference in mABP was detected pre- and post SAH. CBF decreased significantly in AB₁, AB₁₀ and AB₃₀ compared to baseline pre-SAH (p<0.001, p<0.001, p<0.01 resp.). Maximum decrease was reached at different time points (AB₁ at 1min, AB₁₀ at 12min, AB₃₀ at 70min post SAH). Significant hypoperfusion was observed for 112mins in group AB₁, 165mins in group AB₁₀ and 90mins in group AB₃₀. NS injection led to a transient increase of CBF (p<0.01).

Discussion: Higher velocity of blood injection is associated with a higher increase of ICP, but changes do not extend beyond the hyperacute phase. Acute hypoperfusion is observed at all blood injection velocities, but not with saline injection. Variation of injection velocity may facilitate investigation of different SAH entities (aSAH vs naSAH) and their respective acute and chronic stages.