NC, normal cognition (n=114); MCI, mild cognitive impairment (n=196); AD, Alzheimer disease (n=100). cognitive impairment and infection, and no patients were taking central nervous system (CNS)-active medications. These procedures included, as part of their normal care, lumbar drains placed at the time of surgery by the anesthesiologist, in order to a) infuse fluorescein to facilitate leak identification, and b) to maintain low CSF pressures to permit healing of the closure. The drains are typically left in place for 48 to 72h post-operatively, and drained CSF is typically discarded. Exclusion criteria included; age less than 40, known dementias, epilepsy, or any CNS/intracranial process that might influence the CSF results. Lumbar subarachnoid catheters were placed immediately prior to administration of the anesthetic and the surgical procedure. Anesthetic management depended entirely on provider choice and was therefore not randomized. However, the providers for these cases fall neatly into two camps, those that always use inhalational agents for maintenance, mostly sevoflurane, and those that always use total intravenous anesthesia (TIVA), using a combination of propofol and remifentanil. All patients were intubated with the aid of vecuronium, and mechanically ventilated. The first, or baseline, CSF sample of 1-2 mls was taken at the time of lumbar drain placement. Another CSF sample was taken at the end of the procedure (0 time), and then Csta additional samples at 6, 24 and 48h later, or until the catheters were removed. All patients had at least 4 samples (baseline, 0, 6 and 24h) and six had an additional sample at 48h. Samples were collected roughly at the same time of day ( 3h). All samples were aliquoted into 1.5 ml plastic microcentrifuge tubes and immediately frozen at -80C for subsequent batch analysis. Alzheimer Biomarkers Because of well-known inter-laboratory variability, and the effort undertaken to standardize the ADNI laboratories, we submitted aliquots of all our samples to the University of Pennsylvania ADNI biomarker laboratory.17 Briefly, A1-42 , t-tau, and p-tau181p were measured in each of the aliquots using the QS 11 multiplex xMAP Luminex platform (Luminex Corp, Austin, TX) with Innogenetics (INNO-BIA AlzBio3; Ghent, Belgium; for research useConly reagents) immunoassay kitCbased reagents. These kits included well-characterized capture monoclonal antibodies specific for A1-42 (4D7A3), t-tau (AT120), and p-tau181p (AT270), each chemically bonded to unique sets of color-coded beads, and analyte-specific detector antibodies (HT7, 3D6). QS 11 Calibration curves were produced for each biomarker using aqueous buffered solutions that contained the combination of three biomarkers at concentrations ranging from 56 to 1 1,948pg/ml for recombinant tau, 27 to 1 1,574pg/ml for synthetic A1-42 peptide, and 8 to 230pg/ml for a synthetic p-tau peptide phosphorylated at the threonine 181 position. Inflammatory Biomarkers Other aliquots were analyzed for inflammatory biomarkers, also with Luminex xMAP technology18 (Luminex Corp) in the Human Immunology Core of the University of Pennsylvania. Commercial MILLIPLEX MAP kits (Millipore, Billerica, MA) were used in this study to quantify cytokines and neurodegenerative biomarkers in CSF samples, except for S100B, which was quantified with an enzyme-linked immunosorbent assay (ELISA) kit (Abnova, Taipei City, Taiwan, catalog# KA0037). Interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor , and vascular QS 11 endothelial growth factor were simultaneously quantified using Human Cytokines/Chemokines Panel – 5 Plex kit (Millipore, catalog# MPXHCYTO-60K-05). Luminex bead assays were performed according to the manufacturer’s instructions. After thawing, CSF samples were added in duplicate to a 96-well filter-bottom plate and incubated overnight at 4C with antibody-coated beads which were internally coded with fluorescent dyes. After washing, biotinylated detection antibody was added and 1h later, the streptavidin-phycoerythrin conjugate, was added. After washing again, sheath fluid was added and the plate was read on the BioPlex200 instrument (Bio-Rad, Hercules, CA). Standard curves with appropriate background media were run for every plate. Calibration curves were used to convert the median fluorescent intensity readings for each sample to concentrations (pg/ml) using a five-parameter logistic model. Statistical Analysis A repeated measures 1-way analysis of variance (ANOVA) , with the Bonferroni post-hoc test, was used to test statistical differences in the samples out to 24h, for which the n=11 at each time point. The 48h time point (n=6) is demonstrated in the numbers for illustrative purposes. For the stratification by anesthetic technique, a repeated actions 2-way ANOVA design, with the Bonferroni post-hoc test, was used with GraphPad Prism 5.0 software (La Jolla, CA). Results Patients were 536 years old, 8 were ladies and all were American Society of Anesthesiologists status I or II. Six individuals received TIVA, four received sevoflurane for maintenance, and for one it was combined. The methods lasted 6.4 2h, much of the time.