Continuous Optical Monitoring of Cerebral Hemodynamics During Head-of-Bed Manipulation in Brain-Injured Adults
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Head-of-bed manipulation is commonly performed in the neurocritical care unit to optimize cerebral blood flow (CBF), but its effects on CBF are rarely measured. This pilot study employs a novel, non-invasive instrument combining two techniques, diffuse correlation spectroscopy (DCS) for measurement of CBF and near-infrared spectroscopy (NIRS) for measurement of cerebral oxy- and deoxy-hemoglobin concentrations, to monitor patients during head-of-bed lowering.
Ten brain-injured patients and ten control subjects were monitored continuously with DCS and NIRS while the head-of-bed was positioned first at 30° and then at 0°. Relative CBF (rCBF) and concurrent changes in oxy- (ΔHbO2), deoxy- (ΔHb), and total-hemoglobin concentrations (ΔTHC) from left/right frontal cortices were monitored for 5 min at each position. Patient and control response differences were assessed.
rCBF, ΔHbO2, and ΔTHC responses to head lowering differed significantly between brain-injured patients and healthy controls (P < 0.02). For patients, rCBF changes were heterogeneous, with no net change observed in the group average (0.3 ± 28.2 %, P = 0.938). rCBF increased in controls (18.6 ± 9.4 %, P < 0.001). ΔHbO2, ΔHb, and ΔTHC increased with head lowering in both groups, but to a larger degree in brain-injured patients. rCBF correlated moderately with changes in cerebral perfusion pressure (R = 0.40, P < 0.001), but not intracranial pressure.
DCS/NIRS detected differences in CBF and oxygenation responses of brain-injured patients versus controls during head-of-bed manipulation. This pilot study supports the feasibility of continuous bedside measurement of cerebrovascular hemodynamics with DCS/NIRS and provides the rationale for further investigation in larger cohorts.
KeywordsDiffuse correlation spectroscopy Near-infrared spectroscopy Diffuse optical spectroscopy Head-of-bed Cerebral blood flow Neurocritical care Cerebral hemodynamics
We are grateful for the contributions of Mark Burnett who initiated the earliest protocols in the neurointensive care unit that led to this study. We also thank Dalton Hance, Justin Plaum, and neurointensive care unit nurses and radiology staff at the Hospital of the University of Pennsylvania for technical assistance. Finally, we acknowledge the Center for Cognitive Neuroscience at the University of Pennsylvania for assistance with control subject recruitment.
Sources of Support (if applicable): Name(s) of Grantor(s), Grant or contract numbers, name of author who received the funding, and specific material support given: National Institute of Heath: NS-054575 (JAD), NS-060653 (AGY), NS-045839 (JAD), HL077699 (AGY), RR-02305 (AGY, JAD), R25-NS065743 (BLE). TD gratefully acknowledged partial support by Fundacio Cellex Barcelona, Marie Curie IRG (FP7, RPTAMON), Institute de Salud Carlos III (DOMMON, FIS), Ministerio de Ciencia e Innovación (MICINN), Ministerio de Economía y Comepetitividad, Institució CERCA (DOCNEURO, PROVAT-002-11), Generalitat de Catalunya, European Regional Development Fund (FEDER/ERDF) and LASERLAB (FP7) and Photonics4Life (FP7) consortia. University of Pennsylvania Research Foundation (JHG). Financial Disclosure AGY, JAD, JHG, TD are co-inventors on patents related to the optical technology. However, they do not receive any income or royalties from those patents.
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