Inclusion Criteria:  Admission to the Neurointensive Care Unit (NICU) at Rigshospitalet Diagnosis of TBI, spontaneous ICH or aneurysmal SAH Initiation of blood sampling possible within 3 days after ictus Expected length of stay in the NICU and/or intermediate care unit of ≥48 hours Closest relatives understand written and spoken Danish  Exclusion Criteria:  Brain death before inclusion Expected death within 24 hours ICH secondary to other causes (e.g., a tumour or arteriovenous malformation) SAH secondary to other causes (e.g., a mycotic aneurysm or arteriovenous malformation)