Adverse events during endovascular treatment of ruptured aneurysms: A prospective nationwide study on subarachnoid hemorrhage in Sweden.

Introduction: A range of adverse events (AEs) may occur in patients with subarachnoid hemorrhage (SAH). Endovascular treatment is commonly used to prevent aneurysm re-rupture. Research question: The aim of this study was to identify AEs related to endovascular treatment, analyze risk factors for AEs and how AEs affect patient outcome. Material and methods: Patients with aneurysmal SAH admitted to all neurosurgical centers in Sweden during a 3.5-year period (2014-2018) were prospectively registered. AEs related to endovascular aneurysm treatment were thromboembolic events, aneurysm re-rupture, vessel dissection and puncture site hematoma. Potential risk factors for the AEs were analyzed using multivariate logistic regression. Functional outcome was assessed at one year using the extended Glasgow outcome scale. Results: In total, 1037 patients were treated for ruptured aneurysms. Of which, 715 patients were treated with endovascular occlusion. There were 115 AEs reported in 113 patients (16%). Thromboembolic events were noted in 78 patients (11%). Aneurysm re-rupture occurred in 28 (4%), vessel dissection in 4 (0.6%) and puncture site hematoma in 5 (0.7%). Blister type aneurysm, aneurysm smaller than 5 mm and endovascular techniques other than coiling were risk factors for treatment-related AEs. At follow-up, 230 (32%) of the patients had unfavorable outcome. Patients suffering intraprocedural aneurysm re-rupture were more likely to have unfavorable outcome (OR 6.9, 95% CI 2.3-20.9). Discussion and conclusion: Adverse events related to endovascular occlusion of a ruptured aneurysm were seen in 16% of patients. Aneurysm re-rupture during endovascular treatment was associated with increased risk of unfavorable functional outcome.

Adverse events associated with microsurgial treatment for ruptured intracerebral aneurysms: a prospective nationwide study on subarachnoid haemorrhage in Sweden.

BACKGROUND: Adverse events (AEs) or complications may arise secondary to the treatment of aneurysmal subarachnoid haemorrhage (SAH). The aim of this study was to identify AEs associated with microsurgical occlusion of ruptured aneurysms, as well as to analyse their risk factors and impact on functional outcome. METHODS: Patients with aneurysmal SAH admitted to the neurosurgical centres in Sweden were prospectively registered during a 3.5-year period (2014-2018). AEs were categorised as intraoperative or postoperative. A range of variables from patient history and SAH characteristics were explored as potential risk factors for an AE. Functional outcome was assessed approximately 1 year after the bleeding using the extended Glasgow Outcome Scale. RESULTS: In total, 1037 patients were treated for ruptured aneurysms, of which, 322 patients were treated with microsurgery. There were 105 surgical AEs in 97 patients (30%); 94 were intraoperative AEs in 79 patients (25%). Aneurysm rerupture occurred in 43 patients (13%), temporary occlusion of the parent artery >5 min in 26 patients (8%) and adjacent vessel injury in 25 patients (8%). High Fisher grade and brain oedema on CT were related to increased risk of AEs. At follow-up, 38% of patients had unfavourable outcome. Patients suffering AEs were more likely to have unfavourable outcome (OR 2.3, 95% CI 1.10 to 4.69). CONCLUSION: Intraoperative AEs occurred in 25% of patients treated with microsurgery for ruptured intracerebral aneurysm in this nationwide survey. Although most operated patients had favourable outcome, AEs were associated with increased risk of unfavourable outcome.

The impact of previous health on the mortality after aneurysmal subarachnoid hemorrhage: analysis of a prospective Swedish multicenter study.

PURPOSE: There is an an increasing awareness of the importance of health and lifestyle for stroke diseases like spontaneous subarachnoid hemorrhage (SAH). However, the importance of pre-existing medical conditions for clinical course and mortality after SAH has not been studied. The aim of the present study was to identify pre-existing conditions contributing to mortality after SAH. METHODS: Data were extracted from a Swedish national prospective study on patients with SAH. Variables were defined for age, sex, body mass index (BMI), clinical condition at admission, and for 10 pre-existing medical conditions. Models predicting mortality in three time intervals with all possible subsets of these variables were generated, compared and selected using Akaike's information criterion. RESULTS: 1155 patients with ruptured aneurysms were included. The mortality within 1 week was 7.6%, 1 month 14.3%, and 1 year 18.7%. The most common pre-existing medical conditions were smoking (57.6%) and hypertension (38.7%). The model's best predicting mortality within 1 week and from 1 week to 1 month included only the level of consciousness at admission and age, and these two variables were present in all the models among the top 200 in Akaike score for each time period. The most predictive model for mortality between 1 month and 1 year added previous stroke, diabetes, psychiatric disease, and BMI as predictors. CONCLUSION: Mortality within the first month was best predicted simply by initial level of consciousness and age, while mortality within from 1 month to 1 year was significantly influenced by pre-existing medical conditions.

5-ALA fluorescence in randomly selected pediatric brain tumors assessed by spectroscopy and surgical microscope.

PURPOSE: Fluorescence-guided surgery applying 5-aminolevulinic acid (5-ALA) in high-grade gliomas is an established method in adults. In children, results have so far been ambiguous. The aim of this study was to investigate 5-ALA-induced fluorescence in pediatric brain tumors by using the surgical microscope and a spectroscopic hand-held probe. METHODS: Fourteen randomly selected children (age 4-17) with newly MRI-verified brain tumors were included. No selection was based on the suspected diagnosis prior to surgery. All patients received 5-ALA (20 mg /kg) either orally or via a gastric tube prior to surgery. Intratumoral fluorescence was detected with the microscope and the probe. Moreover, fluorescence in the skin of the forearm was measured. Histopathology samples revealed seven low-grade gliomas, four medulloblastomas, one diffuse intrinsic pontine glioma, one glioblastoma and one atypical meningioma. Blood samples were analyzed, and potential clinical side effects were monitored. RESULTS: Microscopically, vague fluorescence was visible in two patients. Intratumoral fluorescence could be detected in five patients with the probe, including the two patients with vague microscopic fluorescence. Three of the oldest children had PpIX fluorescence in the skin. Nine children did not show any fluorescence in the tumor or in the skin. No clinical side effects or laboratory adverse events were observed. CONCLUSION: Fluorescence could not be used to guide surgery in this study, neither with the surgical microscope nor with the hand-held probe. In nine children, no fluorescence was discerned and children with noticeable fluorescence were all older than nine years. 5-ALA was considered safe to apply in children.

Analysis of laser Doppler flowmetry long-term recordings for investigation of cerebral microcirculation during neurointensive care.

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 today's techniques.

Impact of preprocessing methods on the Raman spectra of brain tissue.

Delineating cancer tissue while leaving functional tissue intact is crucial in brain tumor resection. Despite several available aids, surgeons are limited by preoperative or subjective tools. Raman spectroscopy is a label-free optical technique with promising indications for tumor tissue identification. To allow direct comparisons between measurements preprocessing of the Raman signal is required. There are many recognized methods for preprocessing Raman spectra; however, there is no universal standard. In this paper, six different preprocessing methods were tested on Raman spectra (n > 900) from fresh brain tissue samples (n = 34). The sample cohort included both primary brain tumors, such as adult-type diffuse gliomas and meningiomas, as well as metastases of breast cancer. Each tissue sample was classified according to the CNS WHO 2021 guidelines. The six methods include both direct and iterative polynomial fitting, mathematical morphology, signal derivative, commercial software, and a neural network. Data exploration was performed using principal component analysis, t-distributed stochastic neighbor embedding, and k-means clustering. For each of the six methods, the parameter combination that explained the most variance in the data, i.e., resulting in the highest Gap-statistic, was chosen and compared to the other five methods. Depending on the preprocessing method, the resulting clusters varied in number, size, and associated spectral features. The detected features were associated with hemoglobin, neuroglobin, carotenoid, water, and protoporphyrin, as well as proteins and lipids. However, the spectral features seen in the Raman spectra could not be unambiguously assigned to tissue labels, regardless of preprocessing method. We have illustrated that depending on the chosen preprocessing method, the spectral appearance of Raman features from brain tumor tissue can change. Therefore, we argue both for caution in comparing spectral features from different Raman studies, as well as the importance of transparency of methodology and implementation of the preprocessing. As discussed in this study, Raman spectroscopy for in vivo guidance in neurosurgery requires fast and adaptive preprocessing. On this basis, a pre-trained neural network appears to be a promising approach for the operating room.

Dynamic protein changes in the perihaemorrhagic zone of Surgically Treated Intracerebral Haemorrhage Patients.

The secondary injury cascades exacerbating the initial brain injury following intracerebral haemorrhage (ICH) are incompletely understood. We used dual microdialysis (MD) catheters placed in the perihaemorrhagic zone (PHZ) and in seemingly normal cortex (SNX) at time of surgical ICH evacuation in ten patients (range 26-70 years). Routine interstitial MD markers (including glucose and the lactate/pyruvate ratio) were analysed and remaining microdialysate was analysed by two-dimensional gel electrophoresis (2-DE) and nano-liquid chromatography tandem mass spectrometry (nLC-MS/MS). Two time intervals were analysed; median 2-10 hours post-surgery (time A) and median 68-76 hours post-ICH onset (time B). Using 2-DE, we quantified 232 ± 31 different protein spots. Two proteins differed between the MD catheters at time A, and 12 proteins at time B (p < 0.05). Thirteen proteins were significantly altered between time A and time B in the SNX and seven proteins in the PHZ, respectively. Using nLC-MS/MS ca 800 proteins were identified out of which 76 were present in all samples. At time A one protein was upregulated and two downregulated, and at time B, seven proteins were upregulated, and four downregulated in the PHZ compared to the SNX. Microdialysis-based proteomics is feasible for study of secondary injury mechanisms and discovery of biomarkers after ICH.

Persistent Metabolic Disturbance in the Perihemorrhagic Zone Despite a Normalized Cerebral Blood Flow Following Surgery for Intracerebral Hemorrhage.

BACKGROUND: We hypothesized that reduced cerebral blood flow (CBF) and/or energy metabolic disturbances exist in the tissue surrounding a surgically evacuated intracerebral hemorrhage (ICH). If present, such CBF and/or metabolic impairments may contribute to ongoing tissue injury and the modest clinical efficacy of ICH surgery. OBJECTIVE: To conduct an observational study of CBF and the energy metabolic state in the perihemorrhagic zone (PHZ) tissue and in seemingly normal cortex (SNX) by microdialysis (MD) following surgical ICH evacuation. METHODS: We evaluated 12 patients (median age 64; range 26-71 yr) for changes in CBF and energy metabolism following surgical ICH evacuation using Xenon-enhanced computed tomography (n = 10) or computed tomography perfusion (n = 2) for CBF and dual MD catheters, placed in the PHZ and the SNX at ICH surgery. RESULTS: CBF was evaluated at a mean of 21 and 58 h postsurgery. In the hemisphere ipsilateral to the ICH, CBF improved between the investigations (36.6 ± 20 vs 40.6 ± 20 mL/100 g/min; P < .05). In total, 1026 MD samples were analyzed for energy metabolic alterations including glucose and the lactate/pyruvate ratio (LPR). The LPR was persistently elevated in the PHZ compared to the SNX region (P < .05). LPR elevations in the PHZ were predominately type II (pyruvate normal-high; indicating mitochondrial dysfunction) as opposed to type I (pyruvate low; indicating ischemia) at 4 to 48 h (70% vs 30%) and at 49 to 84 h (79% vs 21%; P < .05) postsurgery. CONCLUSION: Despite normalization of CBF following ICH evacuation, an energy metabolic disturbance suggestive of mitochondrial dysfunction persists in the perihemorrhagic zone.

Meningioma embolization with the pressure cooker technique using Squid 12.

Background Preoperative meningioma embolization may be performed with microparticles or liquid embolic agents. The pressure cooker technique (PCT) has recently been described for the embolization of brain arteriovenous malformations (AVMs). Case We present the case of a 73-year-old woman with a large frontal interhemispheric meningioma that was successfully preoperatively embolized with the PCT using Squid 12, a new ethyl-vinyl alcohol copolymer embolic agent. The PCT presents considerable advantages relative to conventional embolization techniques such as deeper and faster tumor penetration and embolization of tumors with difficult vascular access, and retrograde feeling of pial afferents may be achieved. Conclusions The use of the PCT with Squid 12 may potentially increase the effectiveness of meningioma embolization, increase tumor devascularization and improve outcomes of surgical resection.

The cerebral extracellular release of glycerol, glutamate, and FGF2 is increased in older patients following severe traumatic brain injury.

Old age is associated with a poor recovery from traumatic brain injury (TBI). In a retrospective study we investigated if the biochemical response following TBI is age dependent. Extracellular fluids were continuously sampled by microdialysis in 69 patients admitted to our NSICU following severe TBI. The concentrations of glycerol, glutamate, lactate, pyruvate, and eight different cytokines (IL-1ß, IL-6, IL-10, IL-8, MIP-1ß, RANTES, FGF2, and VEGF) were determined by fluorescence multiplex bead technology. Patients in the oldest age group (≥65 years) had significantly higher microdialysate concentrations of glycerol and glutamate compared to younger patients: the mean microdialysate concentration of glycerol increased from 55.9 µmol/L (25-44 year) to 252 µmol/L (≥65 years; p<0.0001); similarly glutamate increased from 15.8 mmol/L to 92.2 mmol/L (p<0.0001). The lactate-pyruvate ratio was also significantly higher in the patients ≥65 years of age (63.9) compared with all the other age groups. The patterns of cytokine responses varied. For some cytokines (IL-1b, IL-10, and IL-8) there were no differences between age groups, while for others (MIP-1b, RANTES, VEGF, and IL-6) some differences were observed, but with no clear correlation with increasing age. For FGF2 the mean microdialysate concentration was 43 pg/mL in patients ≥65 years old, significantly higher compared to all other age groups (p<0.0001). Increased concentrations of glycerol and glutamate would indicate more extensive damaging processes in the elderly. An increase in concentration of FGF2 could serve a protective function, but could also be related to a dysregulation of the timing in the cellular response in elderly patients.

A laser Doppler system for monitoring of intracerebral microcirculation.

A two-channel standard laser Doppler perfusion monitor has been adapted for intracerebral measurements. Software developed in Labview makes it possible to present the microvascular perfusion, total light intensity (TLI), heart rate and trend curves in real-time during surgery. A custom-made optical probe was designed in order to enable easy fixation during brain surgery. The constructed brain probe was evaluated and compared to a standard probe. Both probes presented similar feasibility when used for the skin recordings. In addition, evaluation was done in one patient in relation to tumor resection. Stable perfusion and TLI signals were immediately recorded when the probe was positioned in cerebral tissue. Movement artifacts were clearly seen when the probe was moved to a new site. Recordings in cortex and tumor border showed higher perfusion and lower TLI compared to measurements in subcortical white matter. The calculated heart rate estimate agreed well with the noted value from the electrocardiographic patient monitoring system.

Differences in cerebral extracellular response of interleukin-1ß, interleukin-6, and interleukin-10 after subarachnoid hemorrhage or severe head trauma in humans.

BACKGROUND: Microdialysis has become a routine method for biochemical surveillance of patients in neurosurgical intensive care units. OBJECTIVE: To analyze the intracerebral extracellular levels of 3 interleukins (ILs) during the 7 days after major subarachnoid hemorrhage or traumatic brain injury). METHODS: Microdialysate from 145 severely injured neurosurgical intensive care unit patients (88 with subarachnoid hemorrhage, 57 with traumatic brain injury) was collected every 6 hours for 7 days. The concentrations of IL-1ß and IL-6 were determined by fluorescence multiplex bead technology, and IL-10 was determined by enzyme-linked immunosorbent assay. RESULTS: Presented are the response patterns of 3 ILs during the first week after 2 different types of major brain injury. These patterns are different for each IL and also differ with respect to the kind of pathological impact. For both IL-1ß and IL-6, the initial peaks (mean values for all patients at day 2 being 26.9 ± 4.5 and 4399 ± 848 pg/mL, respectively) were followed by a gradual decline, with IL-6 values remaining 100-fold higher compared with IL-1ß. Female patients showed a stronger and more sustained response. The response of IL-10 was different, with mean values less than 23 pg/mL and with no significant variation between any of the postimpact days. For all 3 ILs, the responses were stronger in subarachnoid hemorrhage patients. The study also indicates that under normal conditions, IL-1ß, IL-6, and IL-10 are present only at very low concentrations or not at all in the extracellular space of the human brain. CONCLUSION: This is the first report presenting in some detail the human cerebral response of IL-1ß, IL-6, and IL-10 after subarachnoid hemorrhage and traumatic brain injury. The 3 ILs have different reaction patterns, with the response of IL-1ß and IL-6 being related to the type of cerebral damage sustained, whereas the IL-10 response was less varied.

Release of VEGF and FGF in the extracellular space following severe subarachnoidal haemorrhage or traumatic head injury in humans.

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.

Changes in extracellular concentrations of some cytokines, chemokines, and neurotrophic factors after insertion of intracerebral microdialysis catheters in neurosurgical patients.

OBJECTIVE: The extracellular levels of eight different inflammatory agents were analyzed during the initial 36 hours after insertion of microdialysis catheters in patients. METHODS: Cerebral extracellular fluid from 38 patients who were treated in a neurosurgical intensive care unit for severe brain injury was collected every 6 hours for 36 hours. The concentration of interleukin (IL)-1 beta, IL-6, IL-8, macrophage inflammatory protein-1 beta, regulated on activation, normal T-cell expressed and secreted (RANTES), fibroblast growth factor-2, and vascular endothelial growth factor was determined by a multiplex assay, and IL-10 was determined by enzyme-linked immunosorbent assay. RESULTS: This is the first report regarding the presence of IL-10, IL-8, macrophage inflammatory protein-1 beta, regulated on activation, T-cell expressed and secreted, vascular endothelial growth factor, and fibroblast growth factor-2 in the tissue level proper of the living human brain. The study also provides new information regarding the response of IL-1 beta and IL-6 after insertion of a microdialysis catheter. The study confirms that the intriguing patterns of interplay between different components of the inflammatory response studied in laboratory settings are present in the human brain. This was most clearly observed in the variations in response between the three different chemokines investigated, as well as in the rapid and transient response of fibroblast growth factor-2. CONCLUSION: 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.

Variations in the response of interleukins in neurosurgical intensive care patients monitored using intracerebral microdialysis.

OBJECT: The aim of this study was to make a preliminary evaluation of whether microdialysis monitoring of cytokines and other proteins in severely diseased neurosurgical patients has the potential of adding significant information to optimize care, thus broadening the understanding of the function of these molecules in brain injury. METHODS: Paired intracerebral microdialysis catheters with high-cutoff membranes were inserted in 14 comatose patients who had been treated in a neurosurgical intensive care unit following subarachnoidal hemorrhage or traumatic brain injury. Samples were collected every 6 hours (for up to 7 days) and were analyzed at bedside for routine metabolites and later in the laboratory for interleukin (IL)-l and IL-6; in two patients, vascular endothelial growth factor and cathepsin-D were also checked. Aggregated microprobe data gave rough estimations of profound focal cytokine responses related to morphological tissue injury and to anaerobic metabolism that were not evident from the concomitantly collected cerebrospinal fluid data. Data regarding tissue with no macroscopic evidence of injury demonstrated that IL release not only is elicited in severely compromised tissue but also may be a general phenomenon in brains subjected to stress. Macroscopic tissue injury was strongly linked to IL-6 but not IL- lb activation. Furthermore, IL release seems to be stimulated by local ischemia. The basal tissue concentration level of IL-lb was estimated in the range of 10 to 150 pg/ml; for IL-6, the corresponding figure was 1000 to 20,000 pg/ml. CONCLUSIONS: Data in the present study indicate that catheters with high-cutoff membranes have the potential of expanding microdialysis to the study of protein chemistry as a routine bedside method in neurointensive care.

Expression and growth dependency of the insulin-like growth factor I receptor in craniopharyngioma cells: a novel therapeutic approach.

Craniopharyngioma is a rare benign intracranial epithelial tumor that, however, often recurs and sometimes kills the affected patients, one-third of which are children. In many cases, the patients acquire growth hormone deficiency and postoperatively need substitution. Generally, growth hormone promotes local release of insulin-like growth factor I (IGF-I), which in turn activates the IGF-I receptor (IGF-IR) if present. Together, these circumstances raise the question whether IGF-IR may be involved in craniopharyngioma growth. To address this issue, we analyzed phenotypically well-characterized primary low-passage craniopharyngioma cell lines from nine different patients for IGF-IR expression and IGF-I dependency. Two of the cell lines showed no/very low expression of the receptor and was independent on IGF-I, whereas five cell lines exhibited a strong expression and was clearly contingent on IGF-I. The two remaining cell lines had low receptor expression and IGF-I dependency. Upon treatment with an IGF-IR inhibitor, cells with high IGF-IR expression responded promptly with decreased Akt phosphorylation followed by growth arrest. These responses were not seen in cells with no/very low receptor expression. Growth of cell lines with low IGF-IR expression was only slightly affected by IGF-IR inhibition. Taken together, our data suggest that IGF-IR may be involved in the growth of a subset of craniopharyngiomas and points to the possibility of the involvement of IGF-IR inhibitors as a treatment modality to obtain complete tumor-free conditions before growth hormone substitution.

A microdialysis technique for routine measurement of macromolecules in the injured human brain.

OBJECTIVE: To evaluate a new intracerebral microdialysis catheter with a high-cutoff membrane and its potential for the study of macromolecules in the human brain. METHODS: Paired intracerebral microdialysis catheters were inserted in 10 patients who became comatose after subarachnoid hemorrhage or traumatic brain injury and were then treated in our neurosurgical unit. The only differences from the routine use of microdialysis in our clinic were the length (20 mm) and cutoff properties of the catheter membranes (100 kD) and the perfusion fluids used (standard perfusion fluid, 3.5% albumin, or Ringer-dextran 60). Samples were weighed (for net fluid fluxes) and analyzed at bedside (for routine metabolites) and later in the laboratory (for total protein and interleukin-6). The in vitro recovery of glucose, glutamate, and glycerol were also investigated under different conditions. RESULTS: Even brief perfusion with standard perfusion fluid resulted in a significant loss of volume from the microdialysis system. For albumin and Ringer-dextran 60 fluid, recovery was comparable to standard settings. Interleukin-6 (highest value close to 25,000 pg/ml) was sampled from all catheters, and total protein was analyzed from catheters perfused with Ringer-dextran 60 (average concentration, 234 mug protein/ml). There were detectable patterns of variations in the concentration of interleukin-6, seemingly related to concomitant variations in intracerebral conditions. In the present study, no direct comparison was made with the standard CMA 70 catheter (CMA Microdialysis, Stockholm, Sweden), but in vivo, the measured mean concentrations of glucose, glycerol, lactate, and pyruvate were comparable to those previously reported from standard catheters. In vitro, the recovery of metabolites was better when using Ringer-dextran 60 compared with albumin. CONCLUSION: Microdialysis catheters with high-cutoff membranes can be used in routine clinical practice, allowing for sampling and analysis of cytokines and other macromolecules.

Human neuroblastoma (SH-SY5Y) cells are highly sensitive to the lysosomotropic aldehyde 3-aminopropanal.

3-Aminopropanal (3-AP), a degradation product of polyamines such as spermine, spermidine and putrescine, is a lysosomotropic small aldehyde that causes apoptosis or necrosis of most cells in culture, apparently by inducing moderate or extensive lysosomal rupture, respectively, and secondary mitochondrial changes. Here, using the human neuroblastoma SH-SY5Y cell line, we found simultaneous occurrence of apoptotic and necrotic cell death when cultures were exposed to 3-AP in concentrations that usually are either nontoxic, or only cause apoptosis. At 30 mM, but not at 10 mM, the lysosomotropic base and proton acceptor NH3 completely blocked the toxic effect of 3-AP, proving that 3-AP is lysosomotropic and suggesting that the lysosomal membrane proton pump of neuroblastoma cells is highly effective, creating a lower than normal lysosomal pH and, thus, extensive intralysosomal accumulation of lysosomotropic drugs. A wave of internal oxidative stress, secondary to changes in mitochondrial membrane potential, followed and gave rise to further lysosomal rupture. The preincubation of cells for 24 h with a chain-breaking free radical-scavenger, alpha-tocopherol, before exposure to 3-AP, significantly delayed both the wave of oxidative stress and the secondary lysosomal rupture, while it did not interfere with the early 3-AP-mediated phase of lysosomal break. Obviously, the reported oxidative stress and apoptosis/necrosis are consequences of lysosomal rupture with ensuing release of lysosomal enzymes resulting in direct/indirect effects on mitochondrial permeability, membrane potential, and electron transport. The induced oxidative stress seems to act as an amplifying loop causing further lysosomal break that can be partially prevented by alpha-tocopherol. Perhaps secondary brain damage during a critical post injury period can be prevented by the use of drugs that temporarily raise lysosomal pH, inactivate intralysosomal 3-AP, or stabilize lysosomal membranes against oxidative stress.