Cerebrovascular Reactivity Measured by Near-Infrared Spectroscopy Export

@article{citeulike:5087701, abstract = {Background and Purpose-- The pressure reactivity index (PRx) describes cerebral vessel reactivity by correlation of slow waves of intracranial pressure (ICP) and arterial blood pressure. In theory, slow changes in the relative total hemoglobin (rTHb) measured by near-infrared spectroscopy are caused by the same blood volume changes that cause slow waves of ICP. Our objective was to develop a new index of vascular reactivity, the hemoglobin volume index (HVx), which is a low-frequency correlation of arterial blood pressure and rTHb measured with near-infrared spectroscopy. Methods-- Gradual hypotension was induced in piglets while cortical laser-Doppler flux was monitored. ICP was monitored, and rTHb was measured continuously using reflectance near-infrared spectroscopy. The HVx was recorded as a moving linear correlation between slow waves (20 to 300 seconds) of arterial blood pressure and rTHb. Autoregulation curves were constructed by averaging values of the PRx or HVx in 5-mm Hg bins of cerebral perfusion pressure. Results-- The laser-Doppler flux-determined lower limit of autoregulation was 29.4{+/-}6.7 mm Hg ({+/-}SD). Coherence between rTHb and ICP was high at low frequencies. HVx was linearly correlated with PRx. The PRx and HVx both showed higher values below the lower limit of autoregulation and lower values above the lower limit of autoregulation. Areas under the receiver operator characteristic curves were 0.88 and 0.85 for the PRx and HVx, respectively. Conclusions-- Coherence between the rTHb and ICP waveforms at the frequency of slow waves suggests that slow waves of ICP are related to blood volume changes. The HVx has potential for further development as a noninvasive alternative to the PRx. 10.1161/STROKEAHA.108.536094}, author = {Lee, Jennifer K. and Kibler, Kathleen K. and Benni, Paul B. and Easley, R. Blaine and Czosnyka, Marek and Smielewski, Peter and Koehler, Raymond C. and Shaffner, Donald H. and Brady, Ken M.}, citeulike-article-id = {5087701}, citeulike-linkout-0 = {http://dx.doi.org/10.1161/STROKEAHA.108.536094}, citeulike-linkout-1 = {http://stroke.ahajournals.org/cgi/content/abstract/40/5/1820}, citeulike-linkout-2 = {http://view.ncbi.nlm.nih.gov/pubmed/19286593}, citeulike-linkout-3 = {http://www.hubmed.org/display.cgi?uids=19286593}, day = {1}, doi = {10.1161/STROKEAHA.108.536094}, journal = {Stroke}, keywords = {icp, nirs, reactivity, vascular}, month = {May}, number = {5}, pages = {1820--1826}, posted-at = {2009-07-07 16:47:35}, priority = {2}, title = {Cerebrovascular Reactivity Measured by Near-Infrared Spectroscopy}, url = {http://dx.doi.org/10.1161/STROKEAHA.108.536094}, volume = {40}, year = {2009} }

TY - JOUR ID - citeulike:5087701 L3 - citeulike-article-id:5087701 N2 - Background and Purpose-- The pressure reactivity index (PRx) describes cerebral vessel reactivity by correlation of slow waves of intracranial pressure (ICP) and arterial blood pressure. In theory, slow changes in the relative total hemoglobin (rTHb) measured by near-infrared spectroscopy are caused by the same blood volume changes that cause slow waves of ICP. Our objective was to develop a new index of vascular reactivity, the hemoglobin volume index (HVx), which is a low-frequency correlation of arterial blood pressure and rTHb measured with near-infrared spectroscopy. Methods-- Gradual hypotension was induced in piglets while cortical laser-Doppler flux was monitored. ICP was monitored, and rTHb was measured continuously using reflectance near-infrared spectroscopy. The HVx was recorded as a moving linear correlation between slow waves (20 to 300 seconds) of arterial blood pressure and rTHb. Autoregulation curves were constructed by averaging values of the PRx or HVx in 5-mm Hg bins of cerebral perfusion pressure. Results-- The laser-Doppler flux-determined lower limit of autoregulation was 29.4{+/-}6.7 mm Hg ({+/-}SD). Coherence between rTHb and ICP was high at low frequencies. HVx was linearly correlated with PRx. The PRx and HVx both showed higher values below the lower limit of autoregulation and lower values above the lower limit of autoregulation. Areas under the receiver operator characteristic curves were 0.88 and 0.85 for the PRx and HVx, respectively. Conclusions-- Coherence between the rTHb and ICP waveforms at the frequency of slow waves suggests that slow waves of ICP are related to blood volume changes. The HVx has potential for further development as a noninvasive alternative to the PRx. 10.1161/STROKEAHA.108.536094 IS - 5 JF - Stroke EP - 1826 TI - Cerebrovascular Reactivity Measured by Near-Infrared Spectroscopy VL - 40 SP - 1820 KW - icp KW - nirs KW - reactivity KW - vascular AU - Lee, Jennifer AU - Kibler, Kathleen AU - Benni, Paul AU - Easley, Blaine AU - Czosnyka, Marek AU - Smielewski, Peter AU - Koehler, Raymond AU - Shaffner, Donald AU - Brady, Ken PY - 2009/05/01/ UR - http://dx.doi.org/10.1161/STROKEAHA.108.536094 ER -