Cerebrovascular physiology – article alert #24

Exercise and the brain

102- Life-long aerobic exercise preserved baseline cerebral blood flow but reduced vascular reactivity to CO2 – Thomas et al.

Anti-hypertensive treatment and the brain

103- Intensive blood pressure lowering increases cerebral blood flow in older subjects with hypertension – Tryambake et al.

Diabetes and the brain

104- Positron emission tomography measured cerebral blood flow and glucose metabolism are decreased in human type 1 diabetes – van Golen et al.

Hemodialysis and the brain

105–Cerebrovascular autoregulation in critically ill patients during continuous hemodialysis – Schramm et al.

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Crosspost: It’s not a new breakdance move, it’s muscle tensing !

(This entry is cross-posted from Pat on The Boundary Layer)

I’m sure that you’ve all felt dizzy at least once in your life when standing up from a supine position. This sudden change in position is associated with a lowering in the amount of blood returning to your heart (venous return), the amount of blood going out of your heart (cardiac output) and blood pressure. Although the reduction in blood flow to your brain (and thus oxygen level) is limited because of its capacity of autoregulation, orthostatic intolerance with associated symptoms such as dizziness is not uncommon in healthy individuals like you and me. However, in healthy individuals, postural hypotension rarely leads to a loss of consciousness (syncope).

This being said, its not the same ball game for individuals prone to syncope. In these subjects, prolonged standing is associated with vasodilatation and a reduction heart rate (vasovagal reaction). These changes are triggered, in most part, by a lowering in central blood volume, a consequence of the pooling of blood in their legs. These individuals may experience numerous losses of consciousness, from several times a year to several times a day !

Are these individuals sentenced to lose consciousness their entire life? Is there a way to attenuate orthostatic intolerance? Some researchers have been interested in that issue and found that, in healthy volunteers, the reduction in brain blood flow (and oxygen level) is attenuated by muscle tensing (that is pressing the legs against each other). Interestingly, leg crossing and muscle tensing are also associated with increased orthostatic tolerance in individuals prone to syncope. So, a simple movement can delay, or even prevent, a loss of consciousness in these individuals.

So, next time you see a move like this…

breakdance(source)

and there is no boom box nearby, it’s not a new breakdance move, it’s most likely muscle tensing!

Cerebrovascular physiology – article alert #22

Carbon dioxide and the brain

95- Dynamic cerebral autoregulation during and following acute hypoxia: role of carbon dioxide – Querido et al.

96- One size does not fit all: regional cerebral blood flow and arterial carbon dioxide tension – Secher

Cardiorespiratory fitness and the brain

97- Cerebrovascular reactivity is associated with maximal aerobic capacity in healthy older adults – Barnes et al.

Anesthesia and the brain

98- Effects of sevoflurane and propofol anaesthesia on cerebral oxygenation during normocapnia and mild hypercapnia: a pilot study – Sen et al.

Vasopressors and the brain

99- The anesthetic effects on vasopressor modulation of cerebral blood flow in an immature swine model – Bruins et al.

Cerebrovascular physiology – article alert #21

Brain monitoring

85- Feasibility of absolute cerebral tissue oxygen saturation during cardiopulmonary resuscitation – Meex et al.

86- Intra- and extra-cranial effects of transient blood pressure changes on brain near-infrared spectroscopy (NIRS) measurements – Minati et al.

Exercise training and the brain

87- The brain-in-motion study: effect of a 6-month aerobic exercise intervention on cerebrovascular regulation and cognitive function in older adults – Tyndall et al.

Sleep apnea and the brain

88- Worsening of central sleep apnea at high altitude – a role for cerebrovascular function – Burgess et al.

89- Relation between arterial blood pressure and cerebral blood flow velocity in simulated sleep apnea – Hassan et al.

90- An investigation of simultaneous variations in cerebral blood flow velocity and arterial blood pressure during sleep apnea – Alex et al.

Cardiopulmonary bypass and the brain

91- Normothermic cardiopulmonary bypass increases cerebral tissue oxygenation during combined valve surgery: a signle-centre, randomized trial – Lenkin et al.

Brain blood flow

92- The vascular conducted response in cerebral blood flow regulation – Jorn Jensen et al.

Pregnancy and the brain

93- Effect of pregnancy and nitric oxide on the myogenic vasodilation of posterior cerebral arteries and the lower limit of cerebral blood flow autoregulation – Chapman et al.

Vasopressors and the brain

94- Phenylephrine versus ephedrine on cerebral perfusion during carotid endarterectomy (PEPPER): study protocol for a randomized controlled trial – Pennekamp et al.

Open letter to the editors of my favorite exercise physiology textbooks

Dear editors of my favorite exercise physiology textbooks,

I really enjoy reading your textbooks. The information is clear and concise, the chapters are usually well-written with abundant beautiful figures.

This being said, two things really annoy me. First, the section related to cerebrovascular physiology is usually really small microscopic. When there is one, the usual sentence appears: “there is no change in brain blood flow during exercise”. Dude, this.is.not.true!!!1!! There is now plenty of evidence in the literature describing changes in brain blood flow during exercise.

Please, you need to update my favorite exercise physiology textbooks so I will stop hyperventilating when reading the section related to cerebrovascular physiology, which will preclude a reduction in PaCO2 and the subsequent lowering in brain blood flow…

I hope that you will consider my request,

Regards,

p