Effects of hemorrhagic hypotension on the cerebral circulation. I. Cerebral blood flow and pial arteriolar caliber.

MacKenzie, Eric T.; Farrar, J. K.; Fitch, W.; Graham, David I.; Gregory, P. C.; Harper, A. M.

doi:10.1161/01.str.10.6.711

Cited by 168 publications

(73 citation statements)

References 37 publications

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“…In Fig. 4, model predictions are compared with several sets of experimental data (7,12,21,22). When all three mechanisms are included, the autoregulation predicted by the model is consistent with that seen experimentally.…”

Section: Resultssupporting

confidence: 56%

“…The contribution of the metabolic response to autoregulation has not been previously evaluated. Including the metabolic response with both the myogenic and shear-dependent responses produces a level of autoregulation close to that which is observed in cerebral (7,12,21), mesenteric (14), and renal (30,31) tissue. The current model shows that the combined effects of the myogenic and metabolic responses are necessary and sufficient to generate autoregulatory behavior, despite the contrary effect of the shear-dependent response.…”

Section: Discussionmentioning

confidence: 57%

“…Oxygen demand is 8.28 cm 3 O2 ⅐ 100 cm Ϫ3 ⅐ min Ϫ1 , which is within the 6.3-8.3 cm 3 O2 ⅐ 100 cm Ϫ3 ⅐ min Ϫ1 range of oxygen consumption rates in rat cortex (28). Analysis using this level of oxygen demand is appropriate since the model results are compared with experimental data also from cerebral tissue (7,21). A list of all model variables and parameters is provided in Table 2.…”

Section: Methodsmentioning

confidence: 99%

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Theoretical model of blood flow autoregulation: roles of myogenic, shear-dependent, and metabolic responses

Carlson¹,

Arciero²,

Secomb³

2008

American Journal of Physiology-Heart and Circulatory Physiology

153

160

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Carlson BE, Arciero JC, Secomb TW. Theoretical model of blood flow autoregulation: roles of myogenic, shear-dependent, and metabolic responses. Am J Physiol Heart Circ Physiol 295: H1572-H1579, 2008. First published August 22, 2008; doi:10.1152/ajpheart.00262.2008The autoregulation of blood flow, the maintenance of almost constant blood flow in the face of variations in arterial pressure, is characteristic of many tissue types. Here, contributions to the autoregulation of pressure-dependent, shear stress-dependent, and metabolic vasoactive responses are analyzed using a theoretical model. Seven segments, connected in series, represent classes of vessels: arteries, large arterioles, small arterioles, capillaries, small venules, large venules, and veins. The large and small arterioles respond actively to local changes in pressure and wall shear stress and to the downstream metabolic state communicated via conducted responses. All other segments are considered fixed resistances. The myogenic, shear-dependent, and metabolic responses of the arteriolar segments are represented by a theoretical model based on experimental data from isolated vessels. To assess autoregulation, the predicted flow at an arterial pressure of 130 mmHg is compared with that at 80 mmHg. If the degree of vascular smooth muscle activation is held constant at 0.5, there is a fivefold increase in blood flow. When myogenic variation of tone is included, flow increases by a factor of 1.66 over the same pressure range, indicating weak autoregulation. The inclusion of both myogenic and shear-dependent responses results in an increase in flow by a factor of 2.43. A further addition of the metabolic response produces strong autoregulation with flow increasing by a factor of 1.18 and gives results consistent with experimental observation. The model results indicate that the combined effects of myogenic and metabolic regulation overcome the vasodilatory effect of the shear response and lead to the autoregulation of blood flow. conducted response; microcirculation; blood flow regulation; vascular smooth muscle; vascular tone THE ABILITY OF VASCULAR BEDS to maintain a relatively constant blood flow over a large range of arterial pressures is known as vascular autoregulation. With increasing arterial pressure, the degree of vascular smooth muscle (VSM) activation, VSM tone, increases in arterioles, resulting in decreased vessel diameter and increased flow resistance. Several mechanisms contribute to changes in vascular tone, including responses to intraluminal pressure (myogenic response), shear stress on the endothelial lining of vessels (shear-dependent response), metabolite concentrations in vessels and/or tissue (metabolic response), and neural stimuli. The cerebral and renal vasculature show the most stable flow over a wide range of arterial pressures (2, 25), whereas in other beds, such as those in the mesentery, autoregulation is less effective.Several theoretical models for the autoregulation of blood flow have been developed using a multicompartmen...

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Section: Resultssupporting

confidence: 56%

Section: Discussionmentioning

confidence: 57%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Theoretical model of blood flow autoregulation: roles of myogenic, shear-dependent, and metabolic responses

Carlson¹,

Arciero²,

Secomb³

2008

American Journal of Physiology-Heart and Circulatory Physiology

153

160

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“…No differences in baseline CBF, ASL CVR, OEF, or CMRO 2 were found. This may have been caused by the large intersubject variability in CBF, OEF, and CMRO 2 38,39 measurements and our relatively small sample size. For instance, the study performed by Coles et al 38 showed intersubject coefficients of variation of 13.5%, 7.3%, and 12.8% for CBF, OEF, and CMRO 2 , respectively, and Parkes et al 39 found an intersubject variation of up to 100% perfusion difference.…”

Section: Patients Versus Controlsmentioning

confidence: 94%

Calibrated MRI to Evaluate Cerebral Hemodynamics in Patients with an Internal Carotid Artery Occlusion

Vis

Petersen

Bhogal

et al. 2015

J Cereb Blood Flow Metab

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The purpose of this study was to assess whether calibrated magnetic resonance imaging (MRI) can identify regional variances in cerebral hemodynamics caused by vascular disease. For this, arterial spin labeling (ASL)/blood oxygen level-dependent (BOLD) MRI was performed in 11 patients (65 ± 7 years) and 14 controls (66 ± 4 years). Cerebral blood flow (CBF), ASL cerebrovascular reactivity (CVR), BOLD CVR, oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO 2 ) were evaluated. The CBF was 34 ± 5 and 36 ± 11 mL/100 g per minute in the ipsilateral middle cerebral artery (MCA) territory of the patients and the controls. Arterial spin labeling CVR was 44 ± 20 and 53 ± 10% per 10 mm Hg ΔEtCO 2 in patients and controls. The BOLD CVR was lower in the patients compared with the controls (1.3 ± 0.8 versus 2.2 ± 0.4% per 10 mm Hg ΔEtCO 2 , P o 0.01). The OEF was 41 ± 8% and 38 ± 6%, and the CMRO 2 was 116 ± 39 and 111 ± 40 μmol/100 g per minute in the patients and the controls. The BOLD CVR was lower in the ipsilateral than in the contralateral MCA territory of the patients (1.2 ± 0.6 versus 1.6 ± 0.5% per 10 mmHg ΔEtCO 2 , P o 0.01). Analysis was hampered in three patients due to delayed arrival time. Thus, regional hemodynamic impairment was identified with calibrated MRI. Delayed arrival artifacts limited the interpretation of the images in some patients.

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“…This has been observed repeatedly by measuring the re maining margin of vasodilation (i.e., vasodilatory capacity) (Novack et al, 1953;Harper, 1965;Sha piro et al, 1966;Ackerman et al, 1973;Norrving et al, 1982;Vorstrup et al, 1986). Since autoregula tion is commonly accepted as being essentially a regional function of the vasculature (Skinhj21j and Paulson, 1969;Paulson et al, 1972;Strandgaard and Paulson, 1984), examination of the regional re lationship between OEF and the vascular respon siveness to vasodilator should allow us to delineate the critical border at which the resistance vessels may reach maximum vasodilation (Fazekas and Alman, 1964;MacKenzie et al, 1979) and its OEF value.…”

Section: Discussionmentioning

confidence: 99%

Oxygen Extraction Fraction at Maximally Vasodilated Tissue in the Ischemic Brain Estimated from the Regional CO₂ Responsiveness Measured by Positron Emission Tomography

Kanno

Uemura

Higano

et al. 1988

J Cereb Blood Flow Metab

105

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The oxygen extraction fraction (OEF) at maximally vasodilated tissue in patients with chronic cerebrovascular disease was evaluated using positron emission tomography. The vascular responsiveness to changes in PaCO2 was measured by the H215O autoradiographic method. It was correlated with the resting-state OEF, as estimated using the 15O steady-state method. The subjects comprised 15 patients with unilateral or bilateral occlusion and stenosis of the internal carotid artery or middle cerebral artery or moyamoya disease. In hypercapnia, the scattergram between the OEF and the vascular responsiveness to changes in PaCO2 revealed a significant negative correlation in 11 of 19 studies on these patients, and the OEF at the zero cross point of the regression line with a vascular responsiveness of 0 was 0.53 ± 0.08 (n = 11). This OEF in the resting state corresponds to exhaustion of the capacity for vasodilation. The vasodilatory capacity is discussed in relation to the lower limit of autoregulation.

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Effects of hemorrhagic hypotension on the cerebral circulation. I. Cerebral blood flow and pial arteriolar caliber.

Cited by 168 publications

References 37 publications

Theoretical model of blood flow autoregulation: roles of myogenic, shear-dependent, and metabolic responses

Theoretical model of blood flow autoregulation: roles of myogenic, shear-dependent, and metabolic responses

Calibrated MRI to Evaluate Cerebral Hemodynamics in Patients with an Internal Carotid Artery Occlusion

Oxygen Extraction Fraction at Maximally Vasodilated Tissue in the Ischemic Brain Estimated from the Regional CO₂ Responsiveness Measured by Positron Emission Tomography

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Effects of hemorrhagic hypotension on the cerebral circulation. I. Cerebral blood flow and pial arteriolar caliber.

Cited by 168 publications

References 37 publications

Theoretical model of blood flow autoregulation: roles of myogenic, shear-dependent, and metabolic responses

Theoretical model of blood flow autoregulation: roles of myogenic, shear-dependent, and metabolic responses

Calibrated MRI to Evaluate Cerebral Hemodynamics in Patients with an Internal Carotid Artery Occlusion

Oxygen Extraction Fraction at Maximally Vasodilated Tissue in the Ischemic Brain Estimated from the Regional CO2 Responsiveness Measured by Positron Emission Tomography

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Product

Resources

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Oxygen Extraction Fraction at Maximally Vasodilated Tissue in the Ischemic Brain Estimated from the Regional CO₂ Responsiveness Measured by Positron Emission Tomography