Cerebral blood flow is monitored in the neurointensive care unit (NICU) to avoid further brain damage caused by secondary insults following subarachnoid hemorrhage and brain trauma. Current techniques are mainly snap-shot based and focus on larger vessels. However, continuous monitoring of the smaller vessels may help detect the onset of secondary insults at an earlier stage. In this study, long-term measurements of brain microcirculation with laser Doppler flowmetry (LDF) were performed and evaluated. The aim was to identify and describe physiological signal variations and separate these from movement artifacts. Fiberoptic probes for subcortical LDF recordings of perfusion and total light intensity (TLI) were implanted in three patients with subarachnoid hemorrhage. Data were successfully collected and visualized in real-time over 4 days, resulting in 34, 12, and 8.5 h per patient. Visual observation, wavelet transforms, moving medians, and peak envelopes were used to identify and describe movement artifacts and physiological changes. Artifacts occurred in <5% of the total recording time and could be identified through signal processing. Identified physiological signal patterns included a slowly increasing perfusion trend over hours, vasomotion mainly at 2 cycles/min both in the perfusion and the TLI, and rapid, synchronized changes in the TLI and the perfusion on 38 occasions. Continuous LDF recordings indicating changes in the microvascular blood flow can increase the understanding of the microcirculation in the injured brain. In the long run, this may become a complement for the detection of secondary insults at an earlier stage than possible with todays techniques.

Purpose: Multimodal monitoring is used in the neurointensive care unit (NICU) to avoid further brain injury in patients with subarachnoid haemorrhage (SAH). The aims were to investigate cerebral microcirculation in patients with SAH using laser Doppler flowmetry (LDF), and to compare LDF data with intracranial pressure (ICP) and mean arterial pressure (MAP). Methods: An LDF system with an in-house developed two-channel fibre optical probe and software was used for bedside monitoring of microvascular CBF (Perf) in seven patients. Analyses of mean, peak-to-peak amplitude and frequency variations were performed on selected data based on protocol information. Analysis of frequency variations focused on vasomotion. Data comparisons were evaluated on longer timescales using Pearson correlation and on shorter timescales using a moving correlation index. Results: Microvascular data were successfully recorded for up to 10 days, resulting in 274 h of artefact-free data. The average perfusion ranged from 91 +/- 29 a.u. to 424 +/- 242 a.u. across patients and channels. Vasomotion was observed in 7-37 % and 4-44 % in the Perf and ICP data, respectively, with spatial, temporal, and interpersonal variations. Occasional positive and negative correlations between Perf and clinically monitored data were found on shorter timescales. Conclusion: Correlations varied daily among all individuals, confirming the need for moving indices to track correlation over time. Combining vasomotion analysis and correlations with clinical data can increase the knowledge about the underlying mechanisms of blood flow regulation in the injured brain in SAH patients.

BackgroundSubarachnoid haemorrhage (SAH) is one of the most severe forms of stroke in which delayed cerebral ischemia is one of the major complications. Neurointensive care aims at preventing and treating such complications and identification of biomarkers of early signs of ischemia might therefore be helpful.MethodsWe aimed at describing proteome profile in cerebral microdialysate in four patients with aneurysmal SAH using two dimensional gel electrophoresis in combination with mass spectrometry in search for new biomarkers for delayed cerebral ischemia and to investigate if there were temporal fluctuations in those biomarkers over time after aneurysmal bleed.ResultsThe results showed transthyretin in nine different proteoforms (1001, 1102, 2101, 3101, 4101, 4102, 5001, 5101, 6101) in cerebral microdialysate samples from four patients having sustained SAH. Several proteoforms show highly differing levels and pooled analysis of all samples showed varying optical density related to time from aneurysmal bleed, indicating a temporal evolution.ConclusionsTransthyretin proteoforms have not earlier been shown in cerebral microdialysate after SAH and we describe differing levels based on proteoform as well as time from subarachnoid bleed. Transthyretin is well known to be synthetized in choroid plexus, whilst intraparenchymal synthesis remains controversial. The results need to be confirmed in larger studies in order to further describe transthyretin.