title: Measurement of absolute values of hemoglobin oxygenation in the brain of small rodents by near infrared reflection spectrophotometry.
abstract: Reflection near infrared spectroscopy (reNIRS) has been proposed as a novel technique for the measurement of absolute values of total hemoglobin (tHb), oxygenated hemoglobin (oxHb), hemoglobin saturation (SO2), and cytochrome aa3 oxidation status (oxCyt aa3) in living tissue. In this study, we evaluated reNIRS during physiological cerebral blood flow conditions in rats (n=6) and during the induction of global cerebral ischemia in gerbils (n=6). ReNIRS parameters were assessed over the exposed cerebral cortex and compared to regional cerebral blood flow (rCBF) data obtained by laser Doppler flowmetry. Under physiological conditions, reNIRS measurements reflected the large intra- and interindividual variability of oxHb and tHb in the brain. The absolute values obtained by reNIRS for tHb (6.3 +/- 1.7 mg/ml), oxHb (3.7 +/- 1.1 mg/ml), and SO2 (61 +/- 5%) matched expected values. In contrast, measurements of oxCyt aa3 were unstable and results unreliable. reNIRS reliably detected cerebral ischemia, verified by a reduction of rCBF to 11% of baseline. tHb dropped to 74 +/- 7% of baseline (P<0.001), reflecting ischemic microvascular vasoconstriction. oxHb and SO2 dropped to expected near-zero values (2 +/- 4 and 3 +/- 5% of baseline, respectively; P<0.001). We conclude that reNIRS provides reliable and reproducible absolute values for brain tissue tHb, oxHb, and SO2 in small rodents. Determination of physiological values requires measurements at multiple locations, while cerebral ischemia is reliably detected by continuous recordings at a single location.
authors.affiliation: Institute for Surgical Research, Klinikum Grosshadern, Ludwig-Maximilians University, Marchioninistr. 27, 81377, Munich, Germany. plesnila@icf.med.uni-muenchen.de
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Plesnila
authors.forename: Christiane
authors.initials: C
authors.lastname: Putz
authors.forename: Markus
authors.initials: M
authors.lastname: Rinecker
authors.forename: Joachim
authors.initials: J
authors.lastname: Wiezorrek
authors.forename: Ludwig
authors.initials: L
authors.lastname: Schleinkofer
authors.forename: Alwin E
authors.initials: AE
authors.lastname: Goetz
authors.forename: Wolfgang M
authors.initials: WM
authors.lastname: Kuebler
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply / Q000378:metabolism*; D002545:Brain Ischemia / Q000378:metabolism; D005849:Gerbillinae; D006454:Hemoglobins / Q000378:metabolism; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008297:Male; D010108:Oxyhemoglobins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013055:Spectrophotometry, Infrared / Q000379:methods
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins