Control of Cerebral Blood Velocity with Furosemide-Induced Hypovolemia and Upright Tilt

Abstract

The purpose of this study was to test the hypothesis that exacerbated reductions of cerebral blood velocity (CBV) during upright tilt with dehydration are associated with impaired cerebrovascular control. Nine healthy men were tilted head-up (HUT) to 70 for 10 min on two occasions separated by 7 days under euhydration (EUH) and dehydration (DEH; 40 mg of furosemide and water restriction) conditions. Beat-by-beat arterial pressures and CBV were measured during a 5-min supine baseline and during the first (T1) and last (T2) 5 min of HUT. Cerebral autoregulation and arterial baroreflex sensitivity were assessed in the frequency domain with cross-spectral techniques. DEH reduced plasma volume by 10% (P = 0.008) and supine mean CBV (CBVmean) by 11% (P = 0.002). Mean arterial pressure (MAP), stroke volume, and baroreflex sensitivity decreased during HUT (P </= 0.002), but absolute reductions were similar between hydration conditions, with the exception of stroke volume, which was lower at T1 during DEH than EUH (P = 0.04). CBVmean during DEH was lower (7 cm/s) over the course of the entire 10 min of HUT (P </= .004) than during EUH. Low-frequency oscillations (0.07-0.2 Hz) of MAP and CBVmean and MAP-CBVmean coherence were higher during DEH than EUH at T1 (P </= 0.02), but not at T2. Our results suggest that increased coherence between arterial pressure and CBV with the combination of DEH and HUT are indicative of altered cerebrovascular control. Increased CBV oscillations with DEH may reflect acute protective mechanisms to ensure adequate cerebral perfusion under conditions of reduced central blood volume.

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Document Details

Document Type
Technical Report
Publication Date
Nov 25, 2010
Accession Number
ADA618938

Entities

People

  • Caroline A Rickards
  • Donovan L. Fogt
  • Gilbert Moralez
  • Kathy L. Ryan
  • Steven A Romero
  • Victor A Convertino
  • William H. Cooke

Organizations

  • United States Army Institute of Surgical Research

Tags

Communities of Interest

  • Biomedical

DTIC Thesaurus Topics

  • Arteries
  • Blood
  • Blood Flow
  • Blood Volume
  • Body Water
  • Cardiovascular Physiological Phenomena
  • Dehydration
  • Frequency
  • Heart Rate
  • Hydration
  • Hypovolemia
  • Magnetic Resonance
  • Measurement
  • Specific Gravity
  • Statistical Analysis
  • Transfer Functions
  • Volume

Fields of Study

  • Medicine

Readers

  • Cardiovascular Physiology
  • Exercise and Sports Science.