scholarly journals Effects of Hematocrit Variations on Cerebral Blood Flow and Oxygen Transport in Ischemic Cerebrovascular Disease

1981 ◽  
Vol 1 (4) ◽  
pp. 413-417 ◽  
Author(s):  
Masahito Kusunoki ◽  
Kazufumi Kimura ◽  
Masaichi Nakamura ◽  
Yoshinari Isaka ◽  
Shotaro Yoneda ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cerebrovascular Disease ◽  
Oxygen Transport ◽  
Oxygen Delivery ◽  
Inverse Correlation ◽  
Arterial Oxygen ◽  
Brain Oxygenation ◽  
Arterial Oxygen Content ◽  
Ischemic Cerebrovascular Disease

The contribution of hematocrit (Ht) changes on cerebral blood flow (CBF) and brain oxygenation in ischemic cerebrovascular disease is still controversial. In the present study, effects of Ht variations on CBF and oxygen delivery were investigated in patients with ischemic cerebrovascular disease. CBF was measured by the Xe-133 intracarotid injection method in 27 patients, whose diagnoses included completed stroke, reversible ischemic neurological deficit, and transient ischemic attack. Ht values in the patients ranged from 31 to 53%. There was a significant inverse correlation between CBF and Ht in these Ht ranges. Oxygen delivery, i.e., the product of arterial oxygen content and CBF, increased with Ht elevation and reached the maximum level in the Ht range of 40–45% and then declined. The CBF-Ht and oxygen transport-Ht relations observed in our study were similar to those in the glass-tube model studies by other workers rather than to those in intact animal experiments. From these results, it is conceivable that in ischemic cerebrovascular disease, the vasomotor adjustment was impaired in such a manner that the relations among Ht, CBF, and oxygen delivery were different from those in healthy subjects. Further, an “optimal hematocrit” for brain oxygenation was also discussed.

Oxygen delivery at high blood viscosity and decreased arterial oxygen content to brains of conscious rats

2001 ◽  
Vol 280 (6) ◽  
pp. H2591-H2597 ◽  
Author(s):  
A. Rebel ◽  
C. Lenz ◽  
H. Krieter ◽  
K. F. Waschke ◽  
K. Van Ackern ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Oxygen Content ◽  
Blood Viscosity ◽  
Oxygen Delivery ◽  
Brain Structures ◽  
Arterial Oxygen ◽  
Cerebral Oxygen ◽  
Compensatory Mechanisms ◽  
Arterial Oxygen Content

We addressed the question to which extent cerebral blood flow (CBF) is maintained when, in addition to a high blood viscosity (Bvis) arterial oxygen content (CaO2 ) is gradually decreased. CaO2 was decreased by hemodilution to hematocrits (Hct) of 30, 22, 19, and 15% in two groups. One group received blood replacement (BR) only and served as the control. The second group received an additional high viscosity solution of polyvinylpyrrolidone (BR/PVP). Bvis was reduced in the BR group and was doubled in the BR/PVP. Despite different Bvis, CBF did not differ between BR and BR/PVP rats at Hct values of 30 and 22%, indicating a complete vascular compensation of the increased Bvis at decreased CaO2 . At an Hct of 19%, local cerebral blood flow (LCBF) in some brain structures was lower in BR/PVP rats than in BR rats. At the lowest Hct of 15%, LCBF of 15 brain structures and mean CBF were reduced in BR/PVP. The resulting decrease in cerebral oxygen delivery in the BR/PVP group indicates a global loss of vascular compensation. We concluded that vasodilating mechanisms compensated for Bvis increases thereby maintaining constant cerebral oxygen delivery. Compensatory mechanisms were exhausted at a Hct of 19% and lower as indicated by the reduction of CBF and cerebral oxygen delivery.

scholarly journals The Effect of Hematocrit and Systolic Blood Pressure on Cerebral Blood Flow in Newborn Infants

1987 ◽  
Vol 7 (3) ◽  
pp. 295-299 ◽  
Author(s):  
D. P. Younkin ◽  
M. Reivich ◽  
J. L. Jaggi ◽  
W. D. Obrist ◽  
M. Delivoria-Papadopoulos
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Systolic Blood Pressure ◽  
Newborn Infants ◽  
Inverse Correlation ◽  
Compartmental Analysis ◽  
Arterial Oxygen ◽  
Newborn Animal ◽  
Arterial Oxygen Content

The effects of hematocrit and systolic blood pressure on cerebral blood flow were measured in 15 stable, low birth weight babies. CBF was measured with a modification of the xenon-133 (133Xe) clearance technique, which uses an intravenous bolus of 133Xe, an external chest detector to estimate arterial 133Xe concentration, eight external cranial detectors to measure cephalic 133Xe clearance curves, and a two-compartmental analysis of the cephalic 133Xe clearance curves to estimate CBF. There was a significant inverse correlation between hematocrit and CBF, presumably due to alterations in arterial oxygen content and blood viscosity. Newborn CBF varied independently of systolic blood pressure between 60 and 84 mm Hg, suggesting an intact cerebrovascular autoregulatory mechanism. These results indicate that at least two of the factors that affect newborn animal CBF are operational in human newborns and may have important clinical implications.

Heliox increases quadriceps muscle oxygen delivery during exercise in COPD patients with and without dynamic hyperinflation

2012 ◽  
Vol 113 (7) ◽  
pp. 1012-1023 ◽  
Author(s):  
Zafeiris Louvaris ◽  
Spyros Zakynthinos ◽  
Andrea Aliverti ◽  
Helmut Habazettl ◽  
Maroula Vasilopoulou ◽  
...  
Keyword(s):  
Blood Flow ◽  
Oxygen Content ◽  
Oxygen Delivery ◽  
Quadriceps Muscle ◽  
Arterial Oxygen ◽  
Arterial Oxygen Content ◽  
Muscle Oxygen ◽  
Peripheral Muscle ◽  
Copd Patients ◽  
Gastric Pressure

Some reports suggest that heliox breathing during exercise may improve peripheral muscle oxygen availability in patients with chronic obstructive pulmonary disease (COPD). Besides COPD patients who dynamically hyperinflate during exercise (hyperinflators), there are patients who do not hyperinflate (non-hyperinflators). As heliox breathing may differently affect cardiac output in hyperinflators (by increasing preload and decreasing afterload of both ventricles) and non-hyperinflators (by increasing venous return) during exercise, it was reasoned that heliox administration would improve peripheral muscle oxygen delivery possibly by different mechanisms in those two COPD categories. Chest wall volume and respiratory muscle activity were determined during constant-load exercise at 75% peak capacity to exhaustion, while breathing room air or normoxic heliox in 17 COPD patients: 9 hyperinflators (forced expiratory volume in 1 s = 39 ± 5% predicted), and 8 non-hyperinflators (forced expiratory volume in 1 s = 48 ± 5% predicted). Quadriceps muscle blood flow was measured by near-infrared spectroscopy using indocyanine green dye. Hyperinflators and non-hyperinflators demonstrated comparable improvements in endurance time during heliox (231 ± 23 and 257 ± 28 s, respectively). At exhaustion in room air, expiratory muscle activity (expressed by peak-expiratory gastric pressure) was lower in hyperinflators than in non-hyperinflators. In hyperinflators, heliox reduced end-expiratory chest wall volume and diaphragmatic activity, and increased arterial oxygen content (by 17.8 ± 2.5 ml/l), whereas, in non-hyperinflators, heliox reduced peak-expiratory gastric pressure and increased systemic vascular conductance (by 11.0 ± 2.8 ml·min−1·mmHg−1). Quadriceps muscle blood flow and oxygen delivery significantly improved during heliox compared with room air by a comparable magnitude (in hyperinflators by 6.1 ± 1.3 ml·min−1·100 g−1 and 1.3 ± 0.3 ml O2·min−1·100 g−1, and in non-hyperinflators by 7.2 ± 1.6 ml·min−1·100 g−1 and 1.6 ± 0.3 ml O2·min−1·100 g−1, respectively). Despite similar increase in locomotor muscle oxygen delivery with heliox in both groups, the mechanisms of such improvements were different: 1) in hyperinflators, heliox increased arterial oxygen content and quadriceps blood flow at similar cardiac output, whereas 2) in non-hyperinflators, heliox improved central hemodynamics and increased systemic vascular conductance and quadriceps blood flow at similar arterial oxygen content.

Regulation of cerebral blood flow in the ovine fetus

1978 ◽  
Vol 235 (2) ◽  
pp. H162-H166 ◽  
Author(s):  
M. D. Jones ◽  
R. E. Sheldon ◽  
L. L. Peeters ◽  
E. L. Makowski ◽  
G. Meschia
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Oxygen Content ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Arterial Oxygen ◽  
Flow Measurements ◽  
Arterial Oxygen Content ◽  
Sagittal Sinus ◽  
Ovine Fetus

The effects on fetal cerebral blood flow (Qc) of changes in the carotid arterial and sagittal sinus venous PO2, PCO2, and oxygen content were studied in the chronically catheterized ovine fetus in utero at 130–140 days of gestation. Forty-seven measurements of Qc were made in 20 fetuses with radioactive microspheres. In 11 of these animals, 84 measurements of cerebral arteriovenous differences of oxygen content were performed, permitting an indirect measurement of cerebral blood flow (Qc*), assuming a constant cerebral metabolic rate. Arterial and, in 11 animals, sagittal sinus blood was withdrawn for analysis of PO2, PCO2, oxygen content, and pH at the time of the flow measurements. Preliminary analysis showed the best predictor of Qc and Qc* to be the reciprocal of the arterial oxygen content (1/CaO2). Multiple linear regression analysis combining the effects of 1/CaO2 with arterial PCO2 (PaCO2) gave the following equations: Qc = 458.8 (1/CaO2) + 2.68 PaCO2 - 107.93 (R2 = 0.68); Qc* = 435.54 (1CaO2) + 2.20 PaCO2 - 75.03 (R2 = 0.86). As a result of the hyperbolic relationship between Qc (and Qc*) and CaO2, changes in CaO2 at the low levels found during intrauterine life exert an important influence on the fetal cerebral circulation.

scholarly journals Regional Cerebral Blood Flow in Patients with Ischemic Cerebrovascular Disease

1985 ◽  
Vol 25 (5) ◽  
pp. 340-347
Author(s):  
Shigeki KAMEYAMA ◽  
Ken-ichi TANIMURA ◽  
Hiroshige ODA ◽  
Yoshiho HONDA
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cerebrovascular Disease ◽  
Regional Cerebral Blood Flow ◽  
Regional Cerebral Blood ◽  
Ischemic Cerebrovascular Disease

Long-term prognosis in ischemic cerebrovascular disease in relation to cerebral blood flow and metabolism

1982 ◽  
Vol 56 (2-3) ◽  
pp. 357-364 ◽  
Author(s):  
Hisao Tachibana ◽  
Fumio Gotoh ◽  
Shin-Ichiro Ebihara ◽  
Hiroyuki Okayasu ◽  
Yasuhisa Kitagawa ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cerebrovascular Disease ◽  
Ischemic Cerebrovascular Disease ◽  
Long Term Prognosis

scholarly journals Modulation of Myocardial Oxygen Delivery in Response to Isovolemic Hemodilution

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Blake R. Simon ◽  
Hana E. Baker ◽  
Conner C. Earl ◽  
Adam G. Goodwill ◽  
Sam Luebbe ◽  
...  
Keyword(s):  
Blood Flow ◽  
Coronary Blood Flow ◽  
Oxygen Delivery ◽  
Venous Blood ◽  
Blood Gases ◽  
Arterial Oxygen ◽  
Neural Pathways ◽  
Isovolemic Hemodilution ◽  
Arterial Oxygen Content ◽  
Arterial Blood

Background and Hypothesis: Prior studies have established that progressive increases in coronary blood flow are sufficient to maintain myocardial oxygen delivery in response to reductions in arterial oxygenation. However, the precise mechanisms responsible for anemic coronary vasodilation remain poorly understood. This investigation tested the hypothesis that autonomic neural pathways contribute to the maintenance of myocardial oxygen delivery in response to graded reductions in arterial hematocrit.  Experimental Design: Experiments were conducted in open-chest anesthetized swine while assessing coronary blood flow and coronary arterial and venous blood gases in response to progressive hemodilution. Isovolemic hemodilution was achieved via simultaneous removal of 250mL of arterial blood and addition of 250mL of a synthetic plasma expander (Hespan) in swine that received either vehicle or a combination of atropine (0.5mg/kg) and propranolol (1mg/kg) (Atro/Pro).  Results: Relative to vehicle control swine, treatment with Atro/Pro increased heart rate by ~50±4 beats/min and arterial pressure by ~10±1 mmHg.  However, Atro/Pro did not significantly alter increases in coronary blood flow in response to isovolemic hemodilution (hematocrits ranging from ~35±1% to ~15±1%). Coronary venous PO2, an index of myocardial oxygenation, was also unchanged by hemodilution in both vehicle and Atro/Pro treated swine.   Conclusion and Potential Impact: These data suggest that autonomic neural pathways do not play a significant role in the maintenance of myocardial oxygen delivery in response to graded reduction in arterial oxygen content. Understanding of how myocardial oxygen supply is ultimately sensed and regulated in response to reductions in tissue oxygenation remains elusive.  

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