gms | German Medical Science

Objective: The understanding of the immunological processes in the phase after aneurysmal SAH is still insufficient. In-depth knowledge about alterations of immune cell (sub) populations is largely unexplored. Specific immune cell subpopulations are crucial for the initiation, suppression, and/or maintenance of an inflammatory response.

The aim of the present study is to investigate polarisation of immune cells in systemic circulation after subarachnoid hemorrhage in order to possibly link these changes with the occurrence of particular post SAH complications and clinical outcome.

Methods: All patients with SAH on initial CT imaging with confirmed intracranial aneurysm were enrolled from October 2020 until today. Blood samples (and CSF samples if possible) were taken within 24 hours of admission, as well as at day 4,7, and 11 post bleeding. FACS analysis was performed to quantify different cell populations including T cells (Th1; Th2; Th17; Tregs) and monocytes (classical; intermediate; non-classical). The preliminary statistical analysis was performed using two-way ANOVA followed by Tukey’s multiple comparison test for the comparison between two groups.

Results: At the time of the interim evaluation, the data of 50 included patients were available. The blood samples were analysed. For T cells, there is an overall reduced occurrence after haemorrhage compared to healthy individuals, with only trends for the subpopulations. In contrast, the total monocytes are significantly increased after haemorrhage compared to healthy (mean percentage of cd45 positive monocytes in 1 million blood cells ± SD; Healthy: 2.043±1.458 vs. Day 1: 5.662±2.984 and Day 4: 6.436±2.724 p=0.05; Healthy vs Day 7: 6.436±3.174 p=0.01). There was a non-significant trend with fewer total monocytes in patients with vasospasm compared to patients without vasospasm. Interestingly, patients with vasospasm nevertheless initially had significantly more intermediate monocytes than patients without vasospasm (mean percentage of intermediate monocytes of CD45 positive monocytes in patients without vs with vasospasm ± SD; Day 1: 7.613±6.321 vs 17.629±20.893 and Day 4: 6.077±4.556 vs 16.001±20.653 p=0.05).

Conclusion: SAH patients with vasospasm have significantly more intermediate monocytes in their blood on day 1 and day 4 after haemorrhage than patients without vasospasm. If this correlation is confirmed in a larger number of patients, intermediate monocytes may represent a new therapeutic target in the treatment of SAH complications.