The Blood Flow and Oxygen Consumption of the Brain in Patients with Essential Hypertension before and after Adrenalectomy1

Hafkenschiel, Joseph H.; Friedland, Carl K.; Zintel, Harold A.

doi:10.1172/jci102870

Cited by 20 publications

(12 citation statements)

References 10 publications

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“…Mild hypercapnia (5% CO 2 ) allowed for determination of M If mild hypercpania is assumed to not alter CMRO 2 (Chen and Pike, 2010; Hafkenschiel et al, 1954; Jones et al, 2005; Kety and Schmidt, 1948; Kim and Ugurbil, 1997; Kliefoth et al, 1979; Novack et al, 1953; Sicard and Duong, 2005) then the ratio CMRO 2 /CMRO 2o equals one, and the measured CBF and BOLD changes during mild hypercapnia can be combined in equation [1] to calculate M . The derived value of M can then be applied to the functional activation data to calculate stimulus-evoked CMRO 2 /CMRO 2o .…”

Section: Methodsmentioning

confidence: 99%

Test–retest stability of calibrated BOLD-fMRI in HIV− and HIV+ subjects

et al. 2011

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Subject performance, scanner hardware, or biological factors can affect single session neuroimaging measures. Stability studies using calibrated blood oxygenation level dependent functional magnetic resonance imaging (BOLD-fMRI) have been performed in health but not disease. We utilized calibrated BOLD-fMRI to determine the effects of HIV on neurovascular coupling. 6 clinically stable HIV-infected patients (HIV+) and 10 seronegative controls (HIV−) were scanned at two separate sessions approximately 3 months apart. Both mild hypercapnia (5% CO 2 ) exposure and a visual functional activation task were performed. Intra-class correlation coefficients (ICC) and inter-subject variance were determined for calibrated BOLD-fMRI measures (baseline cerebral blood flow (CBF), functional CBF, BOLD, and cerebral metabolic rate of oxygen consumption (CMRO 2 ) changes) for HIV+ and HIV− subjects. The two groups did not differ in age, sex, or education. HIV+ subjects had lower mean baseline CBF (p <0.04, Cohen's d=−1.07) and functional BOLD responses (p< 0.001, Cohen's d=−2.47) and a trend towards a decrease in mean functional CBF responses (p= 0.07, Cohen's d=−0.92) despite similar mean functional CMRO 2 changes (p= 0.71, Cohen's d=0.19). The stability of each calibrated BOLD-fMRI measure, as assessed by ICC, was significantly lower for HIV+ subjects. In addition, HIV+ participants had greater inter-subject variability for baseline CBF (p <0.02), functional BOLD (p< 0.001), CBF (p< 0.001), and CMRO 2 (p< 0.002) responses. Our results demonstrate that calibrated BOLD-fMRI measures have excellent stability within healthy controls. In contrast, these values have greater variability in clinically stable HIV+ subjects and may reflect alterations in coupling between CBF and CMRO 2 with disease.Keywords cerebral blood flow; cerebral metabolic rate of oxygen consumption; stability; functional magnetic resonance imaging; blood oxygenation level dependent imaging

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Section: Methodsmentioning

confidence: 99%

Test–retest stability of calibrated BOLD-fMRI in HIV− and HIV+ subjects

et al. 2011

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“…Lassen (1959) presented a graph of the pressure/flow relationship in man compiled from seven different sources in the literature. This study showed that neither essential nor drug-induced hypertension (Moyer, Miller, Tashnek, Snyder, and Bonman, 1953;Moyer and Morris, 1954;Hafkenschiel, Friedland, and Zintel, 1954;Moyer, Morris, Snyder, and Smith, 1954) nor hypertensive toxaemia of pregnancy caused any significant difference in blood flow when compared with results in control groups of normal young men and normal pregnant women (Kety and Schmidt, 1948;McCall, 1953). Similarly, moderate drug-induced hypotension was not associated with any significant change in blood flow (McCall, 1953).…”

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confidence: 87%

Autoregulation of cerebral blood flow: influence of the arterial blood pressure on the blood flow through the cerebral cortex.

Harper¹

1966

Journal of Neurology, Neurosurgery & Psychiatry

426

134

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Until fairly recently it 'was believed that cerebral blood flow followed more or less passively the mean arterial blood pressure, and the stability of the cerebral circulation under physiological conditions reflected only the relative constancy of the arterial pressure maintained by the homeostatic pressor reflex mechanism ' (Sokoloff, 1959). That there might also be an intrinsic regulation of cerebrovascular tone was suggested by Fog (1934Fog ( , 1938 and by Forbes, Nason, and Wortman (1937). These workers observed that the blood vessels of the pia mater constricted in response to a rise in arterial blood pressure and dilated in response to a fall in pressure.Although more recent studies in man (summarized by Lassen, 1959) seem to refute the idea of a passive pressure/flow relationship for the cerebral circulation, there is still conflict on the precise role of the arterial blood pressure in the control of the cerebral blood flow.The experiments reported in this paper were undertaken to measure the effect of gradual reduction of the mean arterial blood pressure on the blood flow through the cerebral cortex under 'normal' respiratory conditions (that is a PaCO2 of 40 mm. Hg) and under conditions of hypercapnia (CO2 being added to the respiratory mixture). METHODOne hundred and seventeen measurements of blood flow through the cerebral cortex were made on 12 unselected mongrel dogs. The animals were anaesthetized with thiopentone. A cuffed endotracheal tube was inserted and connected to a Starling respiratory pump, through which a 4:1 mixture of N20 and oxygen was delivered in open circuit. Suxamethonium chloride was administered at intervals. Repeated small doses of thiopentone were given during the actual operation. A cannula was inserted into the femoral artery and connected to a damped mercury manometer for the measurement of the systemic blood pressure. This cannula was also used for the withdrawal of arterial blood samples.The thyroid branch of the common carotid artery was cannulated centripetally, the distal end being tied. The temporal muscle was excised and a trephine hole made over the perietal bone. A cruciate incision was made in the dura and the exposed brain cortex was covered with a plastic membrane (Melinex) 6p in thickness. A thin lead shield was placed over the surrounding dura and bone, leaving exposed only the area of cortex covered by the membrane. An end window Geiger counter, mounted 1 mm. above the exposed cortex, was connected to a ratemeter and.a direct writing recorder. After the operation was completed, thiopentone administration was discontinued and the preparation remained undisturbed for one hour before the first measurements of blood flow were made. Plasma substitute (Dextran), saturated with 85 Krypton, was injected, rapidly at first and then more slowly, into the carotid artery over two to three minutes. The blood flow through the cerebral cortex was calculated from the half-life of the initial slope of a semi-logarithmic plot of the clearance curve using the formula of Ingvar (...

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“…This calibrated-BOLD approach exploits the fact that the BOLD signal depends on changes in CBF and CMRO 2 , while the arterial spin labeling (ASL) signal [Williams et al, 1992] depends only on CBF changes. With the assumption that mild hypercapnia does not alter CMRO 2 [Hafkenschiel et al, 1954; Jones et al, 2005; Kastrup et al, 1999; Kety and Schmidt, 1948; Kim and Ugurbil, 1997; Kliefoth et al, 1979; Novack et al, 1953; Sicard and Duong, 2005], the hypercapnic response allows for the determination of the scaling parameter M that defines the maximal possible BOLD response for a brain region from that defined baseline state and for the particular image acquisition parameters. As has been recently demonstrated by Chiarelli and colleagues, accurate determination of M , rather than the use of assumed values, is critical for subsequently calculating fractional changes in CMRO 2 [Chiarelli et al, 2007a,b] using the relatively simple mathematical model that has been proposed by Davis et al [1998].…”

Section: Introductionmentioning

confidence: 99%

Effects of aging on cerebral blood flow, oxygen metabolism, and blood oxygenation level dependent responses to visual stimulation

Ances¹,

Liang²,

Leontiev³

et al. 2008

Human Brain Mapping

200

182

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Calibrated functional magnetic resonance imaging (fMRI) provides a noninvasive technique to assess functional metabolic changes associated with normal aging. We simultaneously measured both the magnitude of the blood oxygenation level dependent (BOLD) and cerebral blood flow (CBF) responses in the visual cortex for separate conditions of mild hypercapnia (5% CO 2 ) and a simple checkerboard stimulus in healthy younger (n = 10, mean: 28-years-old) and older (n = 10, mean: 53-years-old) adults. From these data we derived baseline CBF, the BOLD scaling parameter M, the fractional change in the cerebral metabolic rate of oxygen consumption (CMRO 2 ) with activation, and the coupling ratio n of the fractional changes in CBF and CMRO 2 . For the functional activation paradigm, the magnitude of the BOLD response was significantly lower for the older group (0.57 ± 0.07%) compared to the younger group (0.95 ± 0.14%), despite the finding that the fractional CBF and CMRO 2 changes were similar for both groups. The weaker BOLD response for the older group was due to a reduction in the parameter M, which was significantly lower for older (4.6 ± 0.4%) than younger subjects (6.5 ± 0.8%), most likely reflecting a reduction in baseline CBF for older (41.7 ± 4.8 mL/100 mL/min) compared to younger (59.6 ± 9.1 mL/100 mL/min) subjects. In addition to these primary responses, for both groups the BOLD response exhibited a post-stimulus undershoot with no significant difference in this magnitude. However, the post-undershoot period of the CBF response was significantly greater for older compared to younger subjects. We conclude that when comparing two populations, the BOLD response can provide misleading reflections of underlying physiological changes. A calibrated approach provides a more quantitative reflection of underlying metabolic changes than the BOLD response alone. Keywordsaging; functional magnetic resonance imaging (fMRI); blood oxygen level dependent (BOLD) effect; cerebral blood flow (CBF); cerebral metabolic rate of oxygen (CMRO 2 ); visual cortex

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The Blood Flow and Oxygen Consumption of the Brain in Patients with Essential Hypertension before and after Adrenalectomy1

Cited by 20 publications

References 10 publications

Test–retest stability of calibrated BOLD-fMRI in HIV− and HIV+ subjects

Test–retest stability of calibrated BOLD-fMRI in HIV− and HIV+ subjects

Autoregulation of cerebral blood flow: influence of the arterial blood pressure on the blood flow through the cerebral cortex.

Effects of aging on cerebral blood flow, oxygen metabolism, and blood oxygenation level dependent responses to visual stimulation

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