Object. In the treatment of patients with aneurysmal subarachnoid hemorrhage (SAH), early occlusion of the aneurysm is necessary as well as monitoring and treatment of complications following the primary bleeding episode. Monitoring with microdialysis has been studied for its ability to indicate and predict the occurrence of delayed ischemic neurological deficits (DINDs) in patients with SAH. Methods. In 42 patients with aneurysmal SAH microdialysis monitoring of metabolites was performed using a 0.3-µl/minute perfusion flow over several days, and the results were correlated to clinical events and to brain infarction observed on computerized tomography scans. The microdialysis probe was inserted into the territory of the parent artery of the aneurysm. The authors defined an ischemic pattern as increases in the lactate/glucose (L/G) and lactate/pyruvate (L/P) ratios that were greater than 20% followed by a 20% increase in glycerol concentration. This ischemic pattern was found in 17 of 18 patients who experienced a DIND and in three of 24 patients who did not experience a delayed clinical deterioration. The ischemic pattern preceded the occurrence of a DIND by a mean interval of 11 hours. Maximum L/G and L/P ratios did not correlate with the presence of DIND or outcome, and there was no association between the glycerol level and subsequent brain infarction. Conclusions. Microdialysis monitoring of the cerebral metabolism in patients with SAH may predict with high sensitivity and specificity the occurrence of a DIND. Whether an earlier diagnosis results in better treatment of DINDs and, therefore, in overall better outcomes remains to be proven, as it is linked to an efficacious treatment of cerebral vasospasm.

Extracellular vesicles (EVs) are small membrane-enclosed particles released by cells under various conditions specific to cells’ biological states. Hence, mass-spectrometry (MS) based proteome analysis of EVs in plasma has gained much attention as a method to discover novel protein biomarkers. MS analysis of EVs in plasma is challenging and EV isolation is usually necessary. Therefore, we compared differences in abundance, subtypes, and contamination for EVs isolated by high-speed centrifugation, size exclusion chromatography (SEC), and peptide-affinity precipitation (PAP/ME kit) for subsequent MS-based proteome analysis. Successful EV isolation was evaluated by nanoparticle-tracking analysis, immunoblotting, and transmission electron microscopy, while EV abundance, EV subtypes, and contamination was evaluated by label-free tandem MS. High-speed centrifugation and SEC isolates showed high EV abundance at the expense of contamination by non-EV proteins and lipoproteins, respectively. These two methods also resulted in EVs of a similar type, however, with smaller EVs in SEC isolates. PAP isolates had a relatively low EV abundance and high contamination. We consider high-speed centrifugation and SEC suitable as EV isolation for MS biomarker studies, where the choice between the two should depend on the scientific questions and whether the focus is on larger or smaller EVs or a combination of both.

Tissue factor (TF) is the main initiator of coagulation and procoagulant phospholipids (PPL) are key components in promoting coagulation activity in blood. Both TF and PPL may be presented on the surface of extracellular vesicles (EVs), thus contributing to their procoagulant activity. These EVs may constitute a substantial part of pathological hypercoagulability that is responsible for triggering a higher risk of thrombosis in certain patients. The aim of this study was to describe a model system for the isolation of EVs required for investigating their effect on coagulation. Differential ultracentrifugation (DUC) with and without a single washing step was used to isolate and evaluate the procoagulant capacity of EVs from healthy volunteers through analysis of thrombin generation and PPL activity. Ultracentrifugation at 20,000 × g and 100,000 × g resulted in pellets containing larger vesicles and smaller vesicles, respectively. Isolation yield of particle concentration was assessed by nanoparticle tracking analysis. Immunoelectron microscopy and western blotting revealed vesicles positive for the commonly used EV‐marker CD9. Plasma proteins and lipoproteins were co‐isolated with the EVs; however, application of a washing step clearly diminished the amount of contaminants. The isolated EVs were capable of enhancing thrombin generation, mainly due to PPL predominantly present in pellets from 20,000 × g centrifugation, and correlated with the activity measured by a PPL activity assay. Thus, DUC was proficient for the isolation of EVs with minimal contamination from plasma proteins and lipoproteins, and the setup can be used to study EV‐associated procoagulant activity. This may be useful in determining the procoagulant activity of EVs in patients at potentially increased risk of developing thrombosis, e.g. cancer patients.Abbreviations: TF: Tissue factor; PL: Phospholipids; EVs: Extracellular vesicles; FXa: Activated coagulation factor X; TGA: Thrombin generation assay; PPL: Procoagulant phospholipids; DUC: Differential ultracentrifugation; NTA: Nanoparticle tracking analysis; TEM: Transmission electron microscopy; SPP: Standard pool plasma; CTI: Corn trypsin inhibitor; 20K: 20,000 × g; 100K: 100,000 × g; FVIII: Coagulation factor VIII