scholarly journals The Effects of Capillary Transit Time Heterogeneity (CTH) on Brain Oxygenation

2015 ◽  
Vol 35 (5) ◽  
pp. 806-817 ◽  
Author(s):  
Hugo Angleys ◽  
Leif Østergaard ◽  
Sune N Jespersen
Keyword(s):  
Blood Flow ◽  
Diffusion Equation ◽  
Oxygen Tension ◽  
Transit Time ◽  
Time Distribution ◽  
Ischemia Reperfusion ◽  
Oxygen Metabolism ◽  
Tissue Oxygen Tension ◽  
Tissue Oxygen ◽  
Transit Time Distribution

We recently extended the classic flow–diffusion equation, which relates blood flow to tissue oxygenation, to take capillary transit time heterogeneity ( CTH) into account. Realizing that cerebral oxygen availability depends on both cerebral blood flow ( CBF) and capillary flow patterns, we have speculated that CTH may be actively regulated and that changes in the capillary morphology and function, as well as in blood rheology, may be involved in the pathogenesis of conditions such as dementia and ischemia-reperfusion injury. The first extended flow–diffusion equation involved simplifying assumptions which may not hold in tissue. Here, we explicitly incorporate the effects of oxygen metabolism on tissue oxygen tension and extraction efficacy, and assess the extent to which the type of capillary transit time distribution affects the overall effects of CTH on flow–metabolism coupling reported earlier. After incorporating tissue oxygen metabolism, our model predicts changes in oxygen consumption and tissue oxygen tension during functional activation in accordance with literature reports. We find that, for large CTH values, a blood flow increase fails to cause significant improvements in oxygen delivery, and can even decrease it; a condition of malignant CTH. These results are found to be largely insensitive to the choice of the transit time distribution.

scholarly journals The Roles of Cerebral Blood Flow, Capillary Transit Time Heterogeneity, and Oxygen Tension in Brain Oxygenation and Metabolism

2011 ◽  
Vol 32 (2) ◽  
pp. 264-277 ◽  
Author(s):  
Sune N Jespersen ◽  
Leif Østergaard
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Oxygen Tension ◽  
Transit Time ◽  
Tissue Oxygenation ◽  
Ischemia Reperfusion ◽  
Cortical Activation ◽  
Oxygen Extraction Fraction ◽  
Normal Brain ◽  
Lower Oxygen

Normal brain function depends critically on moment-to-moment regulation of oxygen supply by the bloodstream to meet changing metabolic needs. Neurovascular coupling, a range of mechanisms that converge on arterioles to adjust local cerebral blood flow ( CBF), represents our current framework for understanding this regulation. We modeled the combined effects of CBF and capillary transit time heterogeneity (CTTH) on the maximum oxygen extraction fraction ( OEFmax) and metabolic rate of oxygen that can biophysically be supported, for a given tissue oxygen tension. Red blood cell velocity recordings in rat brain support close hemodynamic—metabolic coupling by means of CBF and CTTH across a range of physiological conditions. The CTTH reduction improves tissue oxygenation by counteracting inherent reductions in OEFmax as CBF increases, and seemingly secures sufficient oxygenation during episodes of hyperemia resulting from cortical activation or hypoxemia. In hypoperfusion and states of blocked CBF, both lower oxygen tension and CTTH may secure tissue oxygenation. Our model predicts that disturbed capillary flows may cause a condition of malignant CTTH, in which states of higher CBF display lower oxygen availability. We propose that conditions with altered capillary morphology, such as amyloid, diabetic or hypertensive microangiopathy, and ischemia—reperfusion, may disturb CTTH and thereby flow-metabolism coupling and cerebral oxygen metabolism.

Tissue oxygen tension and blood-flow changes in rat incisor pulp with graded systemic hyperoxia

2002 ◽  
Vol 47 (3) ◽  
pp. 239-246 ◽  
Author(s):  
Christine Y Yu ◽  
Nick M Boyd ◽  
Stephen J Cringle ◽  
Valerie A Alder ◽  
Dao-Yi Yu
Keyword(s):  
Blood Flow ◽  
Oxygen Tension ◽  
Tissue Oxygen Tension ◽  
Tissue Oxygen ◽  
Rat Incisor ◽  
Flow Changes

scholarly journals Metoprolol Reduces Cerebral Tissue Oxygen Tension after Acute Hemodilution in Rats

2009 ◽  
Vol 111 (5) ◽  
pp. 988-1000 ◽  
Author(s):  
Tenille E. Ragoonanan ◽  
W Scott Beattie ◽  
C David Mazer ◽  
Albert K.Y. Tsui ◽  
Howard Leong-Poi ◽  
...  
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Cerebral Blood Flow ◽  
Oxygen Tension ◽  
Tissue Oxygen Tension ◽  
Beta Blockade ◽  
Tissue Oxygen ◽  
Cerebral Tissue ◽  
Protein Levels

Background Perioperative beta-blockade and anemia are independent predictors of increased stroke and mortality by undefined mechanisms. This study investigated the effect of beta-blockade on cerebral tissue oxygen delivery in an experimental model of blood loss and fluid resuscitation (hemodilution). Methods Anesthetized rats were treated with metoprolol (3 mg x kg) or saline before undergoing hemodilution with pentastarch (1:1 blood volume exchange, 30 ml x kg). Outcomes included cardiac output, cerebral blood flow, and brain (PBrO2) and kidney (PKO2) tissue oxygen tension. Hypoxia inducible factor-1alpha (HIF-1alpha) protein levels were assessed by Western blot. Systemic catecholamines, erythropoietin, and angiotensin II levels were measured. Results Hemodilution increased heart rate, stroke volume, cardiac output (60%), and cerebral blood flow (50%), thereby maintaining PBrO2 despite an approximately 50% reduction in blood oxygen content (P < 0.05 for all). By contrast, PKO2 decreased (50%) under the same conditions (P < 0.05). Beta-blockade reduced baseline heart rate (20%) and abolished the compensatory increase in cardiac output after hemodilution (P < 0.05). This attenuated the cerebral blood flow response and reduced PBrO2 (50%), without further decreasing PKO2. Cerebral HIF-1alpha protein levels were increased in beta-blocked hemodiluted rats relative to hemodiluted controls (P < 0.05). Systemic catecholamine and erythropoietin levels increased comparably after hemodilution in both groups, whereas angiotensin II levels increased only after beta-blockade and hemodilution. Conclusions Cerebral tissue oxygen tension is preferentially maintained during hemodilution, relative to the kidney, despite elevated systemic catecholamines. Acute beta-blockade impaired the compensatory cardiac output response to hemodilution, resulting in a reduction in cerebral tissue oxygen tension and increased expression of HIF-1alpha.

scholarly journals Hypotension during Fluid-restricted Abdominal Surgery

2011 ◽  
Vol 114 (3) ◽  
pp. 557-564 ◽  
Author(s):  
Luzius B. Hiltebrand ◽  
Eliana Koepfli ◽  
Oliver Kimberger ◽  
Gisli H. Sigurdsson ◽  
Sebastian Brandt
Keyword(s):  
Blood Flow ◽  
Abdominal Surgery ◽  
Oxygen Tension ◽  
Intestinal Tract ◽  
Tissue Oxygen Tension ◽  
Control Group ◽  
Tissue Oxygen ◽  
Microcirculatory Blood Flow ◽  
Intestinal Tissue ◽  
Doppler Flowmetry

Background Vasopressors, such as norepinephrine, are frequently used to treat perioperative hypotension. Increasing perfusion pressure with norepinephrine may increase blood flow in regions at risk. However, the resulting vasoconstriction could deteriorate microcirculatory blood flow in the intestinal tract and kidneys. This animal study was designed to investigate the effects of treating perioperative hypotension with norepinephrine during laparotomy with low fluid volume replacement. Methods Twenty anesthetized and ventilated pigs were randomly assigned to a control or treatment (norepinephrine) group. Both groups received 3 ml · kg⁻¹ · h⁻¹ Ringer's lactate solution. In addition, the norepinephrine group received norepinephrine to stepwise increase blood pressure to 65 and 75 mmHg. Regional blood flow was measured in the splanchnic arteries. In the small bowel and colon, microcirculatory blood flow was measured using laser Doppler flowmetry. Intestinal tissue oxygen tension was measured with intramural Clark-type electrodes. Results Hepatosplanchnic and kidney blood flow remained unchanged after reversal of arterial hypotension to a mean arterial pressure of 75 mmHg with norepinephrine. For the norepinephrine group versus the control group, the mean ± SD microcirculatory blood flow in the jejunum (96 ± 41% vs. 93 ± 18%) and colon (98 ± 19% vs. 97 ± 28%) and intestinal tissue oxygen tension (jejunum, 45 ± 13 vs. 43 ± 5 mmHg; colon, 50 ± 10 vs. 45 ± 8 mmHg) were comparable. Conclusions In this model of abdominal surgery in which clinical conditions were imitated as close as possible, treatment of perioperative hypotension with norepinephrine had no adverse effects on microcirculatory blood flow or tissue oxygen tension in the intestinal tract.

scholarly journals Goal-directed Colloid Administration Improves the Microcirculation of Healthy and Perianastomotic Colon

2009 ◽  
Vol 110 (3) ◽  
pp. 496-504 ◽  
Author(s):  
Oliver Kimberger ◽  
Michael Arnberger ◽  
Sebastian Brandt ◽  
Jan Plock ◽  
Gisli H. Sigurdsson ◽  
...  
Keyword(s):  
Blood Flow ◽  
Oxygen Tension ◽  
Fluid Therapy ◽  
Group Versus ◽  
Tissue Oxygen Tension ◽  
Colon Anastomosis ◽  
Tissue Oxygen ◽  
Microcirculatory Blood Flow ◽  
Crystalloid Fluid ◽  
Group 3

Background The aim of this study was to compare the effects of goal-directed colloid fluid therapy with goal-directed crystalloid and restricted crystalloid fluid therapy on healthy and perianastomotic colon tissue in a pig model of colon anastomosis surgery. Methods Pigs (n = 27, 9 per group) were anesthetized and mechanically ventilated. A hand-sewn colon anastomosis was performed. The animals were subsequently randomized to one of the following treatments: R-RL group, 3 ml x kg(-1) x h(-1) Ringer lactate (RL); GD-RL group, 3 ml x kg(-1) x h(-1) RL + bolus 250 ml of RL; GD-C group, 3 ml x kg(-1) x h(-1) RL + bolus 250 ml of hydroxyethyl starch (HES 6%, 130/0.4). A fluid bolus was administered when mixed venous oxygen saturation dropped below 60%. Intestinal tissue oxygen tension and microcirculatory blood flow were measured continuously. Results After 4 h of treatment, tissue oxygen tension in healthy colon increased to 150 +/- 31% in group GD-C versus 123 +/- 40% in group GD-RL versus 94 +/- 23% in group R-RL (percent of postoperative baseline values, mean +/- SD; P < 0.01). Similarly perianastomotic tissue oxygen tension increased to 245 +/- 93% in the GD-C group versus 147 +/- 58% in the GD-RL group and 116 +/- 22% in the R-RL group (P < 0.01). Microcirculatory flow was higher in group GD-C in healthy colon. Conclusions Goal-directed colloid fluid therapy significantly increased microcirculatory blood flow and tissue oxygen tension in healthy and injured colon compared to goal-directed or restricted crystalloid fluid therapy.

Decreases in Oral Tissue Blood Flow Induced by Remifentanil Are Not Accompanied by Deterioration of Oral Tissue Oxygen Tension in Rabbits

2019 ◽  
Vol 77 (5) ◽  
pp. 965-970
Author(s):  
Sayaka Kobayashi ◽  
Masataka Kasahara ◽  
Yui Akiike ◽  
Nobuyuki Matsuura ◽  
Tatsuya Ichinohe
Keyword(s):  
Blood Flow ◽  
Oxygen Tension ◽  
Tissue Oxygen Tension ◽  
Tissue Blood Flow ◽  
Tissue Oxygen ◽  
Oral Tissue
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