Measurement of blood flow, oxygen utilisation, oxygen extraction ratio, and fractional blood volume in human brain tumours and surrounding oedematous tissue

Background Calcium produces constriction in isolated coronary vessels and in the coronary circulation of isolated hearts, but the importance of this mechanism in vivo remains controversial. Methods The left anterior descending coronary arteries of 20 anesthetized dogs whose chests had been opened were perfused at 80 mmHg. Myocardial segmental shortening was measured with ultrasonic crystals and coronary blood flow with a Doppler flow transducer. The coronary arteriovenous oxygen difference was determined and used to calculate myocardial oxygen consumption and the myocardial oxygen extraction ratio. The myocardial oxygen extraction ratio served as an index of effectiveness of metabolic vasodilation. Data were obtained during intracoronary infusions of CaCl2 (5, 10, and 15 mg/min) and compared with those during intracoronary infusions of dobutamine (2.5, 5.0, and 10.0 microg/min). Results CaCl2 caused dose-dependent increases in segmental shortening, accompanied by proportional increases in myocardial oxygen consumption. Although CaCl2 also increased coronary blood flow, these increases were less than proportional to those in myocardial oxygen consumption, and therefore the myocardial oxygen extraction ratio increased. Dobutamine caused dose-dependent increases in segmental shortening and myocardial oxygen consumption that were similar in magnitude to those caused by CaCl2. In contrast to CaCl2, however, the accompanying increases in coronary blood flow were proportional to the increases in myocardial oxygen consumption, with the result that the myocardial oxygen extraction ratio remained constant. Conclusions Calcium has a coronary vasoconstricting effect and a positive inotropic effect in vivo. This vasoconstricting effect impairs coupling of coronary blood flow to the augmented myocardial oxygen demand by metabolic vascular control mechanisms. Dobutamine is an inotropic agent with no apparent direct action on coronary resistance vessels in vivo.

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The physiologic reserve in oxygen carrying capacity: studies in experimental hemodilution

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y86-002 ◽

1986 ◽

Vol 64 (1) ◽

pp. 7-12 ◽

Cited By ~ 107

Author(s):

C. K. Chapler ◽

S. M. Cain

Keyword(s):

Blood Flow ◽

Cardiac Output ◽

Oxygen Supply ◽

The Body ◽

Extraction Ratio ◽

Oxygen Extraction ◽

Whole Body ◽

Oxygen Extraction Ratio ◽

Acute Anemia ◽

Total Body Oxygen

The mechanisms by which the body attempts to avoid tissue hypoxia when total body oxygen delivery is compromised during acute anemia are reviewed. When the hematocrit is reduced by isovolemic hemodilution the compensatory adjustments include an increase in cardiac output, redistribution of blood flow to some tissues, and an increase in the whole body oxygen extraction ratio. These responses permit whole body oxygen uptake to be maintained until the hematocrit has been lowered to about 10%. Several factors are discussed which contribute to the increase in cardiac output during acute anemia including the reduction in blood viscosity, sympathetic innervation of the heart, and increased venomotor tone. The latter has been shown to be dependent on intact aortic chemoreceptors. With respect to peripheral vascular responses, the rise in coronary and cerebral blood flows which occur following hemodilution is proportionally greater than the increase in cardiac output while the opposite is true for kidney, liver, spleen, and intestine. Skeletal muscle does not contribute to a redistribution of blood flow to more vital areas during acute anemia despite its relatively large anaerobic capacity. Overall, peripheral compensatory adjustments result in an increased oxygen extraction ratio during acute anemia which reflects a better matching of the limited oxygen supply to tissue oxygen demands. However, some areas such as muscle are relatively overperfused which limits an even more efficient utilization of the reduced oxygen supply. Studies of the response of the microcirculation and the extent to which sympathetic vascular controls are involved in peripheral blood flow regulation are necessary to further appreciate the complex pattern of physiological responses which help ensure survival of the organism during acute anemia.

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HEPATIC BLOOD FLOW AND OXYGEN EXTRACTION RATIO DURING NORMOTHERMIC RECIRCULATION AND TOTAL BODY COOLING AS VIABILITY PREDICTORS IN NON-HEART-BEATING DONOR PIGS1

Transplantation Journal ◽

10.1097/00007890-199807270-00005 ◽

1998 ◽

Vol 66 (2) ◽

pp. 170-176 ◽

Cited By ~ 43

Author(s):

Ricard Valero ◽

Juan C. Garc??a-Valdecasas ◽

Jeanine Tabet ◽

Pilar Taur?? ◽

Ram??n Rull ◽

...

Keyword(s):

Blood Flow ◽

Hepatic Blood Flow ◽

Extraction Ratio ◽

Oxygen Extraction ◽

Oxygen Extraction Ratio ◽

Heart Beating ◽

Body Cooling ◽

Total Body ◽

Normothermic Recirculation ◽

Total Body Cooling

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Correction for the Presence of Intravascular Oxygen-15 in the Steady-State Technique for Measuring Regional Oxygen Extraction Ratio in the Brain: 2. Results in Normal Subjects and Brain Tumour and Stroke Patients

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.1983.68 ◽

1983 ◽

Vol 3 (4) ◽

pp. 425-431 ◽

Cited By ~ 100

Author(s):

Adriaan A. Lammertsma ◽

Richard J. S. Wise ◽

Jon D. Heather ◽

Jeremy M. Gibbs ◽

Klaus L. Leenders ◽

...

Keyword(s):

Steady State ◽

Brain Tumour ◽

Normal Subjects ◽

Extraction Ratio ◽

Oxygen Extraction ◽

Inhalation Technique ◽

Cerebral Oxygen ◽

Stroke Patients ◽

Oxygen Extraction Ratio ◽

Oxygen Utilisation

Values of regional cerebral oxygen extraction ratio and oxygen utilisation obtained with the oxygen-15 steady-state inhalation technique have been found to be overestimated due to the signal from intravascular oxygen-15. A previously described method to correct for this intravascular component has been applied to a series of studies on normal subjects, and on brain tumour and stroke patients. With this correction the regional cerebral oxygen extraction ratio in normals becomes comparable to the global values previously reported with arteriovenous sampling techniques. Within the lesions of brain tumour and stroke patients, the corrections have been found to be variable and often substantial. It is concluded that failure to apply this correction may result in major errors in the values for regional oxygen extraction ratio and oxygen utilisation. This is especially true when the regional blood flow and oxygen extraction ratio of a tissue is low and regional blood volume is high.

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Myocardial oxygen extraction ratio is decreased during endotoxemia in pigs

Journal of Applied Physiology ◽

10.1152/jappl.1995.79.2.479 ◽

1995 ◽

Vol 79 (2) ◽

pp. 479-486 ◽

Cited By ~ 38

Author(s):

M. J. Herbertson ◽

H. A. Werner ◽

J. A. Russell ◽

K. Iversen ◽

K. R. Walley

Keyword(s):

Blood Flow ◽

Myocardial Blood Flow ◽

Left Ventricular ◽

Extraction Ratio ◽

Oxygen Extraction ◽

Ventricular Contractility ◽

Oxygen Extraction Ratio ◽

Extraction Capacity ◽

Myocardial Oxygen Extraction ◽

Increased Blood Flow

Why the myocardial oxygen extraction ratio (ERm) is decreased during septic shock in humans is unknown. Therefore, we calculated ERm in 15 anesthetized pigs by measuring arterial and coronary venous oxygen content. We measured myocardial lactate flux, myocardial contractility, and global myocardial blood flow and its distribution. After baseline measurements, animals received either saline (n = 6) or 50 micrograms/kg of endotoxin (n = 9). Measurements were repeated for 4 h. After endotoxin, ERm decreased from 67 +/- 12% at baseline to 36 +/- 10% (P < 0.01) at 1 h and 54 +/- 10% (P < 0.05) at 4 h, associated with an increased myocardial blood flow that was heterogeneous. Neither myocardial oxygen nor lactate consumption decreased in the endotoxin group, and changes in left ventricular contractility were not correlated with changes in ERm. We conclude that the decrease in ERm after endotoxin infusion is due to both increased blood flow and mismatching between myocardial oxygen delivery and demand. Impaired myocardial oxygen extraction capacity during sepsis did not cause global myocardial tissue hypoxia.

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Cerebral blood flow and oxygen delivery during hypoxemia and hemodilution: role of arterial oxygen content

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1994.267.5.h2025 ◽

1994 ◽

Vol 267 (5) ◽

pp. H2025-H2031 ◽

Cited By ~ 15

Author(s):

M. M. Todd ◽

B. Wu ◽

M. Maktabi ◽

B. J. Hindman ◽

D. S. Warner

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Extraction Ratio ◽

Oxygen Extraction ◽

Arterial Oxygen ◽

Adaptive Responses ◽

Oxygen Extraction Ratio ◽

Arterial Oxygen Content ◽

O2 Delivery

To determine the role of arterial O2 content (CaO2) in the cerebral blood flow (CBF) responses to hypoxemia and hemodilution, CaO2 was progressively reduced from approximately 18 to approximately 6 ml O2/dl in normocapnic, normothermic, pentobarbital-anesthetized rabbits. This was done either by reducing PaO2 (hypoxemia, minimum PaO2 approximately 26 mmHg) or arterial hematocrit (isovolemic hemodilution with hetastarch, minimum hematocrit approximately 14%) while CBF was measured with radioactive microspheres. As CaO2 decreased, CBF increased in both groups but was greater in hypoxemic animals at CaO2 values < or = 9 ml O2/dl. For example, at a CaO2 approximately 6 ml O2/dl, CBF in hypoxemic animals was 110 +/- 38 ml.100 g-1.min-1 (means +/- SD) compared with 82 +/- 22 ml.100 g-1.min-1 in hemodiluted animals (means +/- SD). While calculated cerebral O2 delivery (cerebral DO2) was well maintained in hypoxemic animals, it decreased significantly during hemodilution (from 7.95 +/- 2.92 baseline to 5.08 +/- 1.10 ml O2/dl.100 g-1.min-1 at the lowest CaO2 value). This decrease in cerebral DO2 was offset by an increase in oxygen extraction ratio during hemodilution. By contrast, the small increase in oxygen extraction ratio seen with hypoxemia did not achieve significance. These results suggest that there are different adaptive responses to acute hypoxemia or hemodilution . They also imply that at similar CBF and CaO2 values, tissue O2 availability may be greater during hemodilution than during hypoxemia.

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