Microdialysis catheters with high-cutoff membranes can be used in routine clinical practice, allowing for sampling and analysis of cytokines and other macromolecules.
The data presented illustrate the opportunity to monitor biochemical events of possible importance in the human brain and indicate the potential of such monitoring in neurosurgical intensive care. The study also underlines that any analysis of events in the brain involving mechanical invasiveness needs to take into account biochemical changes that are directly related to the manipulation of brain tissue.
This is the first report presenting in some detail the human cerebral response of IL-1β, IL-6, and IL-10 after subarachnoid hemorrhage and traumatic brain injury. The 3 ILs have different reaction patterns, with the response of IL-1β and IL-6 being related to the type of cerebral damage sustained, whereas the IL-10 response was less varied.
Microdialysis allows the study of the local production and temporal resolution of cytokines in living skin. Samples were taken from the normal skin of 10 healthy subjects for 24-28 h after insertion of a concentric microdialysis catheter, and analysed with a Luminex bead-based assay. Interleukin-1 beta (IL1b), IL6 and IL8 were seen in all subjects at all time-points after the first hour. Levels peaked at 5-8 h, equilibrating to lower levels at 24 h. Immunohistological double staining for human leukocyte antigen (HLA)-DR and intracellular cytokines on biopsies taken after catheter removal showed many stained cells in the dermis, in contrast to the few cells stained in the epidermis. This study demonstrates the reactive capability of the dermis when provoked separately from the epidermis. The production of IL1b, IL6 and IL8 occurs invariably in what can be termed an innate, dermal response to "danger"; in this case in the form of sterile needle trauma.
Microdialysate fluid from 145 severely injured NSICU-patients, 88 with subarachnoidal haemorrage (SAH), and 57 with traumatic brain injury (TBI), was collected by microdialysis during the first 7 days following impact, and levels of the neurotrophins fibroblast growth factor-2 (FGF2) and vascular endothelial growth factor (VEGF) were analysed. The study illustrates both similarities and differences in the reaction patterns of the 2 inflammatory proteins. The highest concentrations of both FGF2 and VEGF were measured on Day 2 (mean (+/- SE) values being 47.1 +/- 15.33 and 116.9 +/- 41.85 pg/ml, respectively, in the pooled patient material). The VEGF concentration was significantly higher in TBI-patients, while the FGF2 showed a tendency to be higher in SAH-patients. This is the first report presenting in some detail the human cerebral response of FGF2 and VEGF following SAH and TBI. Apart from increasing the understanding of the post-impact inflammatory response of the human brain, the study identifies potential threshold values for these chemokines that may serve as monitoring indicators in the NSICU.
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