Effects of hyperventilation, hypothermia, and altered blood viscosity on cerebral blood flow, cross-brain oxygen extraction, and cerebral metabolic rate for oxygen in cats

The interaction between vasopressinergic and prostanoid mechanisms in the control of cerebral hemodynamics in the conscious hypotensive newborn pig was investigated. Indomethacin treatment (5 mg/kg) of hypotensive piglets caused a significant decrease in blood flow to all brain regions within 20 min. This decrease in cerebral blood flow resulted from increased cerebral vascular resistances of 52 and 198% 20 and 40 min after treatment, respectively. Cerebral oxygen consumption was reduced from 2.58 +/- 0.32 ml.100 g-1.min-1 to 1.01 +/- 0.12 and 0.29 +/- 0.08 ml.100 g-1.min-1 20 and 40 min after indomethacin, respectively, in hemorrhaged piglets. Treatment with the putative vascular (V1) receptor antagonist [1-(beta-mercapto-beta, beta-cyclopentamethylene propionic acid-2-(O-methyl)tyrosine]arginine vasopressin (MEAVP) had no effect on regional cerebral blood flow, calculated cerebral vascular resistance, or cerebral metabolic rate either before or during hemorrhagic hypotension. However, decreases in cerebral blood flow and metabolic rate and increases in vascular resistance on treatment with indomethacin were blunted markedly in animals treated with MEAVP. These data are consistent with the hypothesis that the prostanoid system contributes to the maintenance of cerebral blood flow and cerebral metabolic rate during hypotension in the newborn pig, as reported previously, and implicate removal of vasopressinergic modulation by prostanoids as a potential mechanism for indomethacin-induced cerebral vasoconstriction in hypotensive newborn piglets.

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Acute hypoxia increases the cerebral metabolic rate – a magnetic resonance imaging study

Journal of Cerebral Blood Flow & Metabolism ◽

10.1177/0271678x15606460 ◽

2015 ◽

Vol 36 (6) ◽

pp. 1046-1058 ◽

Cited By ~ 30

Author(s):

Mark B Vestergaard ◽

Ulrich Lindberg ◽

Niels Jacob Aachmann-Andersen ◽

Kristian Lisbjerg ◽

Søren Just Christensen ◽

...

Keyword(s):

Magnetic Resonance Imaging ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Magnetic Resonance ◽

Metabolic Rate ◽

Oxygen Saturation ◽

Healthy Subjects ◽

Acute Hypoxia ◽

Resonance Imaging ◽

Cerebral Metabolic Rate

The aim of the present study was to examine changes in cerebral metabolism by magnetic resonance imaging of healthy subjects during inhalation of 10% O2 hypoxic air. Hypoxic exposure elevates cerebral perfusion, but its effect on energy metabolism has been less investigated. Magnetic resonance imaging techniques were used to measure global cerebral blood flow and the venous oxygen saturation in the sagittal sinus. Global cerebral metabolic rate of oxygen was quantified from cerebral blood flow and arteriovenous oxygen saturation difference. Concentrations of lactate, glutamate, N-acetylaspartate, creatine and phosphocreatine were measured in the visual cortex by magnetic resonance spectroscopy. Twenty-three young healthy males were scanned for 60 min during normoxia, followed by 40 min of breathing hypoxic air. Inhalation of hypoxic air resulted in an increase in cerebral blood flow of 15.5% ( p = 0.058), and an increase in cerebral metabolic rate of oxygen of 8.5% ( p = 0.035). Cerebral lactate concentration increased by 180.3% ([Formula: see text]), glutamate increased by 4.7% ([Formula: see text]) and creatine and phosphocreatine decreased by 15.2% ( p[Formula: see text]). The N-acetylaspartate concentration was unchanged ( p = 0.36). In conclusion, acute hypoxia in healthy subjects increased perfusion and metabolic rate, which could represent an increase in neuronal activity. We conclude that marked changes in brain homeostasis occur in the healthy human brain during exposure to acute hypoxia.

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Cerebral blood flow, metabolic rate, and cross-brain oxygen consumption in brain injury

Journal of Critical Care ◽

10.1016/0883-9441(87)90133-x ◽

1987 ◽

Vol 2 (1) ◽

pp. 77

Author(s):

T.C. Frewen ◽

W.O. Sumabat ◽

R.F. Del Maestro

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Oxygen Consumption ◽

Brain Injury ◽

Metabolic Rate ◽

Brain Oxygen

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Adenosine Mediates Decreased Cerebral Metabolic Rate and Increased Cerebral Blood Flow During Acute Moderate Hypoxia in the Near‐Term Fetal Sheep

The Journal of Physiology ◽

10.1113/jphysiol.2003.047928 ◽

2003 ◽

Vol 553 (3) ◽

pp. 935-945 ◽

Cited By ~ 44

Author(s):

Arlin B. Blood ◽

Christian J. Hunter ◽

Gordon G. Power

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Metabolic Rate ◽

Fetal Sheep ◽

Moderate Hypoxia ◽

Cerebral Metabolic Rate ◽

Near Term

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Effect of ephedrine and phenylephrine on brain oxygenation and microcirculation in anaesthetised patients with cerebral tumours: study protocol for a randomised controlled trial

BMJ Open ◽

10.1136/bmjopen-2017-018560 ◽

2017 ◽

Vol 7 (11) ◽

pp. e018560 ◽

Cited By ~ 2

Author(s):

Klaus Ulrik Koch ◽

Anna Tietze ◽

Joel Aanerud ◽

Gorm von Öettingen ◽

Niels Juul ◽

...

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Metabolic Rate ◽

Transit Time ◽

Oxygen Extraction Fraction ◽

Oxygen Extraction ◽

Brain Oxygenation ◽

Cerebral Metabolic Rate ◽

Arterial Blood ◽

Extraction Fraction

IntroductionDuring brain tumour surgery, vasopressor drugs are commonly administered to increase mean arterial blood pressure with the aim of maintaining sufficient cerebral perfusion pressure. Studies of the commonly used vasopressors show that brain oxygen saturation is reduced after phenylephrine administration, but unaltered by ephedrine administration. These findings may be explained by different effects of phenylephrine and ephedrine on the cerebral microcirculation, in particular the capillary transit-time heterogeneity, which determines oxygen extraction efficacy. We hypothesised that phenylephrine is associated with an increase in capillary transit-time heterogeneity and a reduction in cerebral metabolic rate of oxygen compared with ephedrine. Using MRI and positron emission tomography (PET) as measurements in anaesthetised patients with brain tumours, this study will examine whether phenylephrine administration elevates capillary transit-time heterogeneity more than ephedrine, thereby reducing brain oxygenation.Methods and analysisThis is a double-blind, randomised clinical trial including 48 patients scheduled for surgical brain tumour removal. Prior to imaging and surgery, anaesthetised patients will be randomised to receive either phenylephrine or ephedrine infusion until mean arterial blood pressure increases to above 60 mm Hg or 20% above baseline. Twenty-four patients were allocated to MRI and another 24 patients to PET examination. MRI measurements include cerebral blood flow, capillary transit-time heterogeneity, cerebral blood volume, blood mean transit time, and calculated oxygen extraction fraction and cerebral metabolic rate of oxygen for negligible tissue oxygen extraction. PET measurements include cerebral metabolic rate of oxygen, cerebral blood flow and oxygen extraction fraction. Surgery is initiated after MRI/PET measurements and subdural intracranial pressure is measured.Ethics and disseminationThis study was approved by the Central Denmark Region Committee on Health Research Ethics (12 June 2015; 1-10-72-116-15). Results will be disseminated via peer-reviewed publication and presentation at international conferences.Trial registration numberNCT02713087; Pre-results. 2015-001359-60; Pre-results.

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