title: Brain microdialysis as a tool to explore the ionic profile of the brain extracellular space in neurocritical patients: a methodological approach and feasibility study.
abstract: Our aim is to determine whether the ionic concentration in brain microdialysate enables calculations of the actual Na(+), K(+), and Cl(-) concentrations in vitro and whether this method can be applied to determine the ionic concentrations in the brain extracellular fluid. We designed an experiment using CMA-71 probes (M Dialysis, Stockholm, Sweden) and the standard conditions used in a clinical setting. Nine CMA-71 probes were inserted in different matrices and perfused with mock cerebrospinal fluid containing 3% albumin at the standard infusion rate used in the clinical setting (0.3 μL/min). Microvials were replaced every 12 h, and the ionic concentrations, both in the dialysate and the matrix, were analyzed. For each ion, scatter plots were built, with [Na(+)], [K(+)], and [Cl(-)] in the dialysate as the predictor variables and the matrix concentrations as the outcome variables. A linear regression model allowed us to calculate the true ionic concentrations in the matrix. To demonstrate the feasibility of the method, we present the calculated ionic profile of one patient with a malignant infarction and a second with a severe traumatic brain injury. Our results confirm that the ionic concentration in microdialysate can be used to calculate the true concentrations of ions in a matrix and the actual concentrations in the extracellular fluid. Microdialysis offers the unique possibility of monitoring the dynamic changes of ions in the brain over time and opens a new avenue to explore the brain's ionic profile, its changes in brain edema, and how this profile can be modified with different therapies.
authors.affiliation: 1 Neurotraumatology and Neurosurgery Research Unit (UNINN), Vall d'Hebron University Hospital , Universidad Autònoma de Barcelona, Barcelona, Spain .
authors.forename: Tamara
authors.initials: T
authors.lastname: Martínez-Valverde
authors.forename: Marian
authors.initials: M
authors.lastname: Vidal-Jorge
authors.forename: Noelia
authors.initials: N
authors.lastname: Montoya
authors.forename: Angela
authors.initials: A
authors.lastname: Sánchez-Guerrero
authors.forename: Susana
authors.initials: S
authors.lastname: Manrique
authors.forename: Francisca
authors.initials: F
authors.lastname: Munar
authors.forename: Maria-Dolors
authors.initials: MD
authors.lastname: Pellegri
authors.forename: Maria-Antonia
authors.initials: MA
authors.lastname: Poca
authors.forename: Juan
authors.initials: J
authors.lastname: Sahuquillo
mesh_terms: D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D001929:Brain Edema / Q000378:metabolism*; D001930:Brain Injuries / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D005240:Feasibility Studies; D006801:Humans; D017551:Microdialysis / Q000379:methods*
keywords: brain edema; brain microdialysis; ionic profile; potassium; relative recovery