18th Meeting of European Society of Neurosonology and Cerebral Hemodynamics
and 3rd Meeting of Cerebral Autoregulation Network

Porto, Portugal - May24-27, 2013

Abstract Form

Type of presentation  / Oral / X / Poster / Please mark your preference withX
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e-mail / RICKARDS, Caroline A.
Univesity of North Texas Health Science Center
3500 Camp Bowie Boulevard
Fort Worth, Texas 76107, USA
Phone: +1 817-735-2735; Fax: +1 817-735-5084
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Title of the abstract (bold) / Association of cerebral blood flow variability and cerebral tissue oxygenation with tolerance to central hypovolemia
Authors (ex: P. Smith) / C. Rickards1,V. Kay1, M. George2, K. Ryan3, C. Hinojosa-Laborde3, V. Convertino3
Affiliation of all Authors
(Institution/Hospital/Department, City, Country) / 1University of North Texas Health Science Center, Fort Worth, TX, USA; 2ISS, Champaign, IL, USA; 3US Army Institute of Surgical Research, Fort Sam Houston, TX, USA
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Submission deadline: February 24, 2013

Text only – no figures, no formulas. Maximum 300 words.

TEXT:

Background: We have previously shown that high tolerance (HT) to central hypovolemia is associated with an increase in the low frequency (LF) oscillatory power of cerebral blood flow. We hypothesized that this increase in oscillatory cerebral blood flow improves cerebral oxygenation, leading to the delayed onset of presyncopal symptoms, and HT to lower body negative pressure (LBNP). Methods: 20 healthy human subjects were instrumented for measurement of middle cerebral artery velocity (MCAv; via transcranial Doppler ultrasound), non-invasive arterial pressure (AP), end-tidal CO2 (etCO2), and cerebral oxygen saturation (ScO2; via near infra-red spectroscopy), and completed a step-wise LBNP test to presyncope. Subjects were classified as HT if they completed at least the -60 mmHg level of LBNP and low tolerant (LT) if they did not complete this level. Data are presented up to -60 mmHg LBNP, the last common level between tolerance groups. Results: The mean difference in LBNP tolerance time between HT and LT subjects was 482 s (P=0.004). In the HT group (N=12), while mean MCAv and etCO2 fell below baseline levels from -45 mmHg LBNP (P≤0.03), mean MCAv LF power increased above baseline levels at -60 mmHg LBNP (P=0.009), and ScO2 did not fall below baseline (P≥0.26). In contrast, in the LT group (N=8), mean MCAv, etCO2, and ScO2 fell below baseline at -60 mmHg LBNP (P≤0.01), and MCAv LF power did not increase from baseline (P≥0.90). Conclusion: In support of our hypothesis, tolerance to central hypovolemia was associated with protection of cerebral oxygenation and increased oscillatory power of cerebral blood flow, despite early reductions in absolute flow.

Source of Funding: US Army MRMC