Diurnal variation in time to presyncope and associated circulatory changes during a controlled orthostatic challenge

Epidemiological data indicate that the risk of neurally mediated syncope is substantially higher in the morning. Syncope is precipitated by cerebral hypoperfusion, yet no chronobiological experiment has been undertaken to examine whether the major circulatory factors, which influence perfusion, show diurnal variation during a controlled orthostatic challenge. Therefore, we examined the diurnal variation in orthostatic tolerance and circulatory function measured at baseline and at presyncope. In a repeated-measures experiment, conducted at 0600 and 1600, 17 normotensive volunteers, aged 26 ± 4 yr (mean ± SD), rested supine at baseline and then underwent a 60° head-up tilt with 5-min incremental stages of lower body negative pressure until standardized symptoms of presyncope were apparent. Pretest hydration status was similar at both times of day. Continuous beat-to-beat measurements of cerebral blood flow velocity, blood pressure, heart rate, stroke volume, cardiac output, and end-tidal Pco2 were obtained. At baseline, mean cerebral blood flow velocity was 9 ± 2 cm/s (15%) lower in the morning than the afternoon ( P < 0.0001). The mean time to presyncope was shorter in the morning than in the afternoon (27.2 ± 10.5 min vs. 33.1 ± 7.9 min; 95% CI: 0.4 to 11.4 min, P = 0.01). All measurements made at presyncope did not show diurnal variation ( P > 0.05), but the changes over time (from baseline to presyncope time) in arterial blood pressure, estimated peripheral vascular resistance, and α-index baroreflex sensitivity were greater during the morning tests ( P < 0.05). These data indicate that tolerance to an incremental orthostatic challenge is markedly reduced in the morning due to diurnal variations in the time-based decline in blood pressure and the initial cerebral blood flow velocity “reserve” rather than the circulatory status at eventual presyncope. Such information may be used to help identify individuals who are particularly prone to orthostatic intolerance in the morning.

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Suctioning and Cerebral Blood Flow

PEDIATRICS ◽

10.1542/peds.73.5.737a ◽

1984 ◽

Vol 73 (5) ◽

pp. 737-737

Author(s):

JEFFREY M. PERLMAN ◽

JOSEPH J. VOLPE

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Intracranial Pressure ◽

Flow Velocity ◽

Arterial Blood Pressure ◽

Blood Flow Velocity ◽

Cerebral Blood Flow Velocity ◽

Base Line ◽

Arterial Blood

In Reply.— Marshall misread a critical piece of information in the text. His interpretation of the data would be correct, if the intracranial pressure, arterial blood pressure, and cerebral blood flow velocity changes occurred simultaneously. However, as we stated in the text (see section on "Temporal Features of Changes with Suctioning"), the intracranial pressure fell to base-line values immediately following suctioning, whereas the changes in arterial blood pressure and cerebral blood flow velocity occurred more slowly over an approximately two-minute period.

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Cerebral blood flow velocity response to induced and spontaneous sudden changes in arterial blood pressure

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2001.280.5.h2162 ◽

2001 ◽

Vol 280 (5) ◽

pp. H2162-H2174 ◽

Cited By ~ 89

Author(s):

Ronney B. Panerai ◽

Suzanne L. Dawson ◽

Penelope J. Eames ◽

John F. Potter

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Flow Velocity ◽

Arterial Blood Pressure ◽

Blood Flow Velocity ◽

Cerebral Blood Flow Velocity ◽

Step Response ◽

Arterial Blood ◽

Step Responses

The influence of different types of maneuvers that can induce sudden changes of arterial blood pressure (ABP) on the cerebral blood flow velocity (CBFV) response was studied in 56 normal subjects (mean age 62 yr, range 23–80). ABP was recorded in the finger with a Finapres device, and bilateral recordings of CBFV were performed with Doppler ultrasound of the middle cerebral arteries. Recordings were performed at rest (baseline) and during the thigh cuff test, lower body negative pressure, cold pressor test, hand grip, and Valsalva maneuver. From baseline recordings, positive and negative spontaneous transients were also selected. Stability of Pco 2 was monitored with transcutaneous measurements. Dynamic autoregulatory index (ARI), impulse, and step responses were obtained for 1-min segments of data for the eight conditions by fitting a mathematical model to the ABP-CBFV baseline and transient data (Aaslid's model) and by the Wiener-Laguerre moving-average method. Impulse responses were similar for the right- and left-side recordings, and their temporal pattern was not influenced by type of maneuver. Step responses showed a sudden rise at time 0 and then started to fall back to their original level, indicating an active autoregulation. ARI was also independent of the type of maneuver, giving an overall mean of 4.7 ± 2.9 ( n = 602 recordings). Amplitudes of the impulse and step responses, however, were significantly influenced by type of maneuver and were highly correlated with the resistance-area product before the sudden change in ABP ( r = −0.93, P < 0.0004). These results suggest that amplitude of the CBFV step response is sensitive to the point of operation of the instantaneous ABP-CBFV relationship, which can be shifted by different maneuvers. Various degrees of sympathetic nervous system activation resulting from different ABP-stimulating maneuvers were not reflected by CBFV dynamic autoregulatory responses within the physiological range of ABP.

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An investigation of simultaneous variations in cerebral blood flow velocity and arterial blood pressure during Sleep Apnea

2012 Annual International Conference of the IEEE Engineering in Medicine and Biology Society ◽

10.1109/embc.2012.6347272 ◽

2012 ◽

Cited By ~ 2

Author(s):

R. Alex ◽

G. Bhave ◽

M. A. Al-Abed ◽

A. Bashaboyina ◽

S. Iyer ◽

...

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Sleep Apnea ◽

Flow Velocity ◽

Arterial Blood Pressure ◽

Blood Flow Velocity ◽

Cerebral Blood Flow Velocity ◽

Arterial Blood

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Complexity of cerebral blood flow velocity and arterial blood pressure in subarachnoid hemorrhage using time-frequency analysis

2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) ◽

10.1109/embc.2015.7320176 ◽

2015 ◽

Cited By ~ 2

Author(s):

Michal M. Placek ◽

Pawel Wachel ◽

Marek Czosnyka ◽

Martin Soehle ◽

Peter Smielewski ◽

...

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Subarachnoid Hemorrhage ◽

Flow Velocity ◽

Frequency Analysis ◽

Blood Flow Velocity ◽

Cerebral Blood Flow Velocity ◽

Time Frequency ◽

Arterial Blood

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A model of cerebral blood flow velocity as a function of mean arterial blood pressure using Kalman filter estimation techniques

Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and Biology ◽

10.1109/iembs.2002.1106417 ◽

2003 ◽

Cited By ~ 1

Author(s):

F. Karnangar ◽

M.A. Masnadi-Shirazi ◽

K. Behbehani ◽

R. Zhang ◽

N. Nazeran ◽

...

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Kalman Filter ◽

Flow Velocity ◽

Arterial Blood Pressure ◽

Mean Arterial Blood Pressure ◽

Blood Flow Velocity ◽

Cerebral Blood Flow Velocity ◽

Arterial Blood

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Suctioning in the Preterm Infant: Effects on Cerebral Blood Flow Velocity, Intracranial Pressure, and Arterial Blood Pressure

PEDIATRICS ◽

10.1542/peds.72.3.329 ◽

1983 ◽

Vol 72 (3) ◽

pp. 329-334 ◽

Cited By ~ 4

Author(s):

Jeffrey M. Perlman ◽

Joseph J. Volpe

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Intracranial Pressure ◽

Preterm Infant ◽

Flow Velocity ◽

Blood Flow Velocity ◽

Cerebral Blood Flow Velocity ◽

Systemic Hemodynamic ◽

Arterial Blood

The relationship of suctioning to changes in the cerebral circulation was studied in 35 premature newborn infants. The objectives of the study were to determine whether important alterations occur in cerebral hemodynamics with suctioning and whether such alterations relate to systemic hemodynamic events. A transcutaneous Doppler technique was used to measure blood flow velocity in the anterior cerebral arteries. A prominent increase in cerebral blood flow velocity was documented in nearly all patients. Accompanying the increase in cerebral flow velocity was a marked increase in blood pressure; thus, the increased cerebral flow velocity appeared to reflect directly changes in systemic hemodynamic events. Also accompanying the increase in cerebral flow velocity was a marked increase in intracranial pressure. These data suggest potentially deleterious effects of suctioning in the preterm infant at risk for the occurrence of intraventricular hemorrhage and raise questions regarding the advisability of routine suctioning of such infants.

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