Quantification and Distribution of Cerebral Emboli during Cardiopulmonary Bypass in the Swine 

1999 ◽  
Vol 90 (1) ◽  
pp. 183-190 ◽  
Author(s):  
Walter Plochl ◽  
David J. Cook
Keyword(s):  
Blood Flow ◽  
Cardiopulmonary Bypass ◽  
Ocular Blood Flow ◽  
Fluorescent Microspheres ◽  
Tissue Samples ◽  
Blood Flows ◽  
Cerebral Embolization ◽  
Before And After ◽  
Aortic Cannula ◽  
The Brain

Background Patients undergoing cardiac surgery have a substantial incidence of neurologic complications related to cerebral embolization during cardiopulmonary bypass. The purpose of this study was to determine if adjustments in the arterial carbon dioxide (PaCO2) level can reduce cerebral and ocular embolization. Methods Twenty pigs underwent cardiopulmonary bypass at 38 degrees C. At either hypercarbia (PaCO2 = 50-55 mmHg, group H, n = 10) or hypocarbia (PaCO2 = 25-30 mmHg, group L, n = 10), an embolic load of 1.2 x 10(50 67-microm orange fluorescent microspheres was injected into the aortic cannula. Before and after embolization, cerebral and ocular blood flows were determined at normocapnia using 15-microm fluorescent microspheres. After cardiopulmonary bypass was completed, the eyes were enucleated and brain tissue samples were collected. Microspheres were isolated and the fluorescence was measured. Results In groups H and L, the mean PaCO2 values at embolization were 52+/-3 mmHg and 27+/-2 mmHg, respectively (P < 0.0001). Total and regional embolization were significantly less in hypocapnia than in hypercapnic animals: 142% more emboli were detected in the brain in group H than in group L (P < 0.0001). Cerebral blood flow after embolization was unchanged in both groups. Similarly, fewer ocular emboli occurred in hypocapnic animals than in hypercapnic animals (P = 0.044), but in contrast to the brain, ocular blood flow decreased significantly in both groups after embolization. Conclusions Cerebral embolization is determined by the PaCO2 at the time of embolization. In cardiopulmonary bypass practice, reductions in PaCO2 during periods of embolic risk may reduce the risk for brain injury.

Relationship between Cardiopulmonary Bypass Flow Rate and Cerebral Embolization in Dogs 

1999 ◽  
Vol 91 (5) ◽  
pp. 1387-1387 ◽  
Author(s):  
Hulya Sungurtekin ◽  
Walter Plöchl ◽  
David J. Cook
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cardiopulmonary Bypass ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Rank Order ◽  
Brain Regions ◽  
Pump Flow ◽  
Cerebral Embolization ◽  
The Brain

Background Cerebral embolization is a primary cause of cardiac surgical neurologic morbidity. During cardiopulmonary bypass (CPB), there are well-defined periods of embolic risk. In theory, cerebral embolization might be reduced by an increase in pump flow during these periods. The purpose of this study was to determine the CPB flow-embolization relation in a canine model. Methods Twenty mongrel dogs underwent CPB at 35 degrees C with alpha-stat management and a fentanyl-midazolam anesthetic. In each animal, CPB flow was adjusted to achieve a mean arterial pressure of 65-75 mmHg. During CPB, an embolic load of 1.2 x 10(5) 67 microm fluorescent microspheres was injected into the arterial inflow line. Before and after embolization, cerebral blood flow was determined using 15-microm microspheres. Tissue was taken from 12 brain regions and microspheres were recovered. The relation between pump flow and embolization/g of brain was determined. Results The mean arterial pressure at embolization was 67 +/-4 mmHg, and the range of pump flow was 0.9-3.5 l x min(-1)x m(-2). Cerebral blood flow was independent of pump flow. At lower pump flow, the percentage of that flow delivered to the brain increased. There was a strong inverse relation between pump flow and cerebral embolization (r = -0.708, P < 0.000 by Spearman rank order correlation). Conclusions Cerebral embolization is determined by the CPB flow. At an unchanged mean arterial pressure, as pump flow is reduced, a progressively greater proportion of that flow is delivered to the brain.

In Reply: Cerebral Blood Flow

PEDIATRICS ◽  
1982 ◽  
Vol 70 (6) ◽  
pp. 1013-1014
Author(s):  
RAUL BEJAR
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Gastrointestinal Tract ◽  
Ductus Arteriosus ◽  
Left Ventricular ◽  
Blood Flows ◽  
Before And After ◽  
Regional Blood Flows ◽  
Left Ventricular Output ◽  
Patent Ductus

Baylen and Emmanouilides give the impression that their abstract was misquoted in our commentary. We would like to explain our interpretation of their data. In the abstract, Baylen et al indicate that they measured regional blood flows (RBF) in premature fetal lambs, expressing them as a percentage of the left ventricular output (LVO) before and after patent ductus arteriosus (PDA) closure. Their results (percent of LVO) before and after PDA closure were: lung, 42.7% vs 8.4% (P < .01); carcass, 35% vs 55% (P < .01); heart, 5.5% vs 10.2% (P < .05); gastrointestinal tract, 5.1% vs 9.3% (P < .05); brain, 2.7% vs 3.4% (P = NS); kidney, 2.2% vs 3.3% (P = NS); liver, 3.2% vs 5.7% (P = NS).

Continuous Airway Pressure Breathing With the Head-Box in the Newborn Lamb: Effects on Regional Blood Flows

PEDIATRICS ◽  
1977 ◽  
Vol 59 (6) ◽  
pp. 858-864
Author(s):  
G. Gabriele ◽  
C. R. Rosenfeld ◽  
D. E. Fixler ◽  
J. M. Wheeler
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Airway Pressure ◽  
Left Ventricular Pressure ◽  
Blood Gases ◽  
Ocular Blood Flow ◽  
Left Ventricular ◽  
Positive Pressure ◽  
Blood Flows ◽  
Arterial Blood

Continuous airway pressure delivered by a head-box is an accepted means of treating clinical hyaline membrane disease. To investigate hemodynamic alterations resulting from its use, eight newborn lambs, 1 to 6 days of age, were studied at 6 and 11 mm Hg of positive pressure, while spontaneously breathing room air. Organ blood flows and cardiac output were measured with 25 µ-diameter radioactive microspheres. Heart rate, left ventricular pressure, and arterial blood gases did not change during the study. Jugular venous pressures increased from 6.4 mm Hg to 18.6 and 24.2 mm Hg at 6 and 11 mm Hg, respectively (P < .005). Cardiac output decreased approximately 20% at either intrachamber pressure setting. Renal blood flow fell 21% at 11 mm Hg. No significant changes in blood flow were found in the brain, gastrointestinal tract, spleen, heart, or liver when compared to control flows. Of particular interest was the finding of a 28% reduction in ocular blood flow at 6 mm Hg and 52% at 11 mm Hg. From these results, we conclude that substantial cardiovascular alterations may occur during the application of head-box continuous airway pressure breathing, including a significant reduction in ocular blood flow.

Use of [3H]methylglucose and [14C]iodoantipyrine to determine kinetic parameters of glucose transport in rat brain

1997 ◽  
Vol 272 (1) ◽  
pp. R163-R171
Author(s):  
K. Mori ◽  
M. Maeda
Keyword(s):  
Blood Flow ◽  
Surface Area ◽  
Glucose Transport ◽  
Tissue Samples ◽  
Arterial Blood ◽  
Permeability Surface ◽  
Time Courses ◽  
Area Product ◽  
Menten Kinetic ◽  
The Brain

Local maximal velocities of transport (Tmax) and the half-maximum transport constants (KT) for glucose transport across the blood-brain barrier have been determined in local regions of the brain in normal conscious rats. [14C]iodoantipyrine and [3H]methylglucose were infused together intravenously for 2 min in rats with plasma glucose concentrations maintained at different levels, and the time courses of the tracer levels in arterial blood were measured. Local 14C and 3H concentrations were then measured in tissue samples dissected from the frozen brains. By comparing the transport-limited uptake of [3H]methylglucose with the blood flow-limited uptake of [14C]iodoantipyrine, the value of m, a factor between 0 and 10 that accounts for diffusion and/or transport limitations, was derived, and from the equation, m = 1 - PS/F (where PS is capillary permeability-surface area product and F is cerebral blood flow), the permeability-capillary surface area for methylglucose was calculated (S. S. Kety. Pharmacol. Rev. 3: 1-41, 1951). Values for Tmax and KT for glucose were calculated by application of Michaelis-Menten kinetic relationships adapted for the competition for transport between glucose and methylglucose. Tmax was determined in three representative gray structures and one white structure of the brain: Tmax was 5.3 +/- 0.3 (SD) mumol.g-1.min-1 in the gray structures and 4.3 mumol.g-1.min-1 in the white structure. KT was 3.6 +/- 0.4 (SD) mM in the gray structures and 5.9 mM in the white structure. This approach allows the simultaneous determination of local values of Tmax and KT for glucose and the rates of blood flow in various regions of the brain in conscious animals.

Hemodynamic effects of leukotriene C4 in ovine fetus

1990 ◽  
Vol 259 (6) ◽  
pp. E851-E855
Author(s):  
B. A. Meyer ◽  
S. W. Walsh ◽  
V. M. Parisi
Keyword(s):  
Blood Flow ◽  
Vena Cava ◽  
Cardiovascular Effects ◽  
In Vivo Studies ◽  
Leukotriene C4 ◽  
Blood Flows ◽  
Before And After ◽  
Placental Blood ◽  
Near Term

Leukotrienes are synthesized during pregnancy and produce cardiovascular effects in adults. We hypothesized that leukotriene C4 would cause vasoconstriction in the fetus and placenta. Eight near-term, unanesthetized ovine fetuses were studied before and after infusion of 10 micrograms leukotriene C4 (LTC4) into the fetal vena cava. Cardiovascular monitoring of maternal and fetal arterial pressures and heart rates was performed. Fetal blood flows were measured by the radioactive-microsphere technique. Sustained elevations in systolic and diastolic blood pressure and decreased fetal heart rate began by 1 min and returned to baseline by 30 min. Arterial pH fell from 7.33 +/- 0.01 to 7.29 +/- 0.01 at 15 min (P less than 0.05) and to 7.29 +/- 0.01 at 30 min (P less than 0.05), with a significant increase in base deficit from 0.7 +/- 0.7 to 3.5 +/- 0.7 at 15 min (P less than 0.05) and to 2.9 +/- 1.0 at 30 min (P less than 0.05). Fetal PO2 and PCO2 were unchanged. Significant decreases in blood flow and resistance were seen in the umbilical placental circulation as well as in fetal skeletal muscle and intestine. Blood flow and resistance were unchanged in the renal and adrenal vascular beds. Fetal administration of LTC4 caused no changes in maternal cardiovascular parameters. These findings represent the first in vivo studies of the effects of a lipoxygenase metabolite on fetal-placental blood flow.

Cerebrovascular effects of hypocapnia during adenosine-induced arterial hypotension

1985 ◽  
Vol 63 (6) ◽  
pp. 937-943 ◽  
Author(s):  
David J. Boarini ◽  
Neal F. Kassell ◽  
James A. Sprowell ◽  
Julie J. Olin ◽  
Hans C. Coester
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Arterial Hypotension ◽  
Content Type ◽  
Blood Flows ◽  
Before And After ◽  
Regional Blood Flows ◽  
Fine Print

✓ Profound arterial hypotension is à commonly used adjunct in surgery for aneurysms and arteriovenous malformations. Hyperventilation with hypocapnia is also used in these patients to increase brain slackness. Both measures reduce cerebral blood flow (CBF). Of concern is whether CBF is reduced below ischemic thresholds when both techniques are employed together. To determine this, 12 mongrel dogs were anesthetized with morphine, nitrous oxide, and oxygen, and then paralyzed with pancuronium and hyperventilated. Arterial pCO2 was controlled by adding CO2 to the inspired gas mixture. Cerebral blood flow was measured at arterial pCO2 levels of 40 and 20 mm Hg both before and after mean arterial pressure was lowered to 40 mm Hg with adenosine enhanced by dipyridamole. In animals where PaCO2 was reduced to 20 mm Hg and mean arterial pressure was reduced to 40 mm Hg, cardiac index decreased 42% from control and total brain blood flow decreased 45% from control while the cerebral metabolic rate of oxygen was unchanged. Hypocapnia with hypotension resulted in small but statistically significant reductions in all regional blood flows, most notably in the brain stem. The reported effects of hypocapnia on CBF during arterial hypotension vary depending on the hypotensive agents used. Profound hypotension induced with adenosine does not eliminate CO2 reactivity, nor does it lower blood flow to ischemic levels in this model, even in the presence of severe hypocapnia.

scholarly journals Fold-Over Oversampling Effects in the Measurements of Cerebral Cerebrospinal Fluid and Blood Flows with 2D Cine Phase-Contrast MRI

Diagnostics ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 387
Author(s):  
Fadoua Saadani-Makki ◽  
Serge Metanbou ◽  
Garance Arbeaumont-Trocme ◽  
Julien Van Gysel ◽  
Malek I. Makki
Keyword(s):  
Blood Flow ◽  
Cerebrospinal Fluid ◽  
Stroke Volume ◽  
Phase Contrast ◽  
Blood Flows ◽  
Phase Offset ◽  
Section Area ◽  
Significant Difference ◽  
Before And After ◽  
Cine Phase Contrast

This prospective study investigated the effects of fold-over oversampling on phase-offset background errors with 2D-Cine phase contrast (Cine-PC) magnetic resonance imaging (MRI). It was performed on brain MRI and compared to conventional Full-field of view FOV coverage and it was tested with two different velocity encoding (Venc) values. We chose Venc = 100 mm/s to encode cerebrospinal fluid (CSF) flows in the aqueduct and 600 mm/s to encode blood flow in the carotid artery. Cine-PC was carried out on 10 healthy adult volunteers followed simultaneously by an acquisition on static agar-gel phantom to measure the phase-offset background errors. Pixel-wise correction of both the CSF and the blood flows was calculated through 32 points of the cardiac-cycle. We compared the velocity-to-noise ratio, the section area, the absolute and the corrected velocity (peak; mean and minimum), the net flow, and the stroke volume before and after correction. We performed the statistical T-test to compare Full-FOV and fold-over and Bland–Altman plots to analyze their differences. Our results showed that following phase-offset error correction, the blood stroke-volume was significantly higher with Full-FOV compared to fold-over. We observed a significantly higher CSF mean velocity and net flow values in the fold-over option. Compared to Full-FOV, fold-over provides a significantly larger section area and significantly lower peak velocity-offset in the aqueduct. No significant difference between the two coverages was reported before and after phase-offset in blood flow measurements. In conclusion, fold-over oversampling can be chosen as an alternative to increase spatial resolution and accurate cerebral flow quantification in Cine-PC.

Effects of hematocrit variations on regional hemodynamics and oxygen transport in the dog

1980 ◽  
Vol 238 (4) ◽  
pp. H545-H522 ◽  
Author(s):  
F. C. Fan ◽  
R. Y. Chen ◽  
G. B. Schuessler ◽  
S. Chien
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Blood Vessels ◽  
Oxygen Transport ◽  
Oxygen Supply ◽  
Blood Flows ◽  
Regional Hemodynamics ◽  
Regional Blood Flows ◽  
Splenic Vessels ◽  
The Brain

The responses of alterations in regional hemodynamics and oxygen transport rate to hematocrit (Hct) were studied in 20 pentobarbitalized dogs. Hemodilution was carried out by isovolemic exchange with plasma in 12 dogs and the hemoconcentration with packed cells in 8 dogs. The cardiac output and regional blood flows were determined with the microsphere technique. In hemodilution, the increases of blood flow to the myocardium and the brain were out of proportion to the increase of cardiac output; the oxygen supply to the myocardium remained unchanged while that to the brain decreased only slightly. In hemoconcentration, vasodilation occurred in the myocardium and the brain to maintain constant oxygen supply. Splenic vessels had marked vasoconstriction with Hct alteration in either direction. Blood vessels in the liver, intestine, and kidney responded with a milder vasoconstriction and maintained a constant oxygen supply between Hct of 30-55%. Therefore, during Hct alteration, redistribution of blood flow to myocardium and brain occurred. The optimal Hct range for constant oxygen supply was different among various organs.

The Effect of Altered Cerebral Blood Flow on the Cerebral Kinetics of Thiopental and Propofol in Sheep

2000 ◽  
Vol 93 (4) ◽  
pp. 1085-1094 ◽  
Author(s):  
Richard N. Upton ◽  
Guy L. Ludbrook ◽  
Cliff Grant ◽  
David J. Doolette
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Random Order ◽  
High Flow ◽  
Low Flow ◽  
Flow State ◽  
Concentration Difference ◽  
Blood Flows ◽  
Kinetics Of ◽  
The Brain

Background Thiopental and propofol are highly lipid-soluble, and their entry into the brain often is assumed to be limited by cerebral blood flow rather than by a diffusion barrier. However, there is little direct experimental evidence for this assumption. Methods The cerebral kinetics of thiopental and propofol were examined over a range of cerebral blood flows using five and six chronically instrumented sheep, respectively. Using anesthesia (2.0% halothane), three steady state levels of cerebral blood flow (low, medium, and high) were achieved in random order by altering arterial carbon dioxide tension. For each flow state, 250 mg thiopental or 100 mg propofol was infused intravenously over 2 min. To quantify cerebral kinetics, arterial and sagittal sinus blood was sampled rapidly for 20 min from the start of the infusion, and 1.5 h was allowed between consecutive infusions. Various models of cerebral kinetics were examined for their ability to account for the data. Results The mean baseline cerebral blood flows for the "high" flow state were over threefold greater than those for the low. For the high-flow state the normalized arteriovenous concentration difference across the brain was smaller than for the low-flow state, for both drugs. The data were better described by a model with partial membrane limitation than those with only flow limitation or dispersion. Conclusions The cerebral kinetics of thiopental and propofol after bolus injection were dependent on cerebral blood flow, despite partial diffusion limitation. Higher flows produce higher peak cerebral concentrations.

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