One important issue regarding the classical model of cerebral autoregulation

I just read a very interesting, and provocative, review on cerebral autoregulation written by Shieak Tzeng and Phil Ainslie. These authors challenged existing paradigms regarding how brain perfusion pressure and brain blood flow are related. I definitely encourage you to read it (open access paper !).

In the first section of the review, they are presenting the original description of cerebral autoregulation from Lassen’s work, that has dominated cerebrovascular physiologists’ thinking on the association between blood pressure and brain perfusion:

CBF* is maintained at a constant level across a wide range of mean arterial blood pressure (60-150 mmHg)

In two previous posts (here and here), I’ve provided some information regarding static and dynamic cerebral autoregulation, skipping one important issue. As highlighted by Tzeng and Ainslie in this review:

Although Lassen’s diagram is widely cited as the “autoregulation curve” describing the pressure-flow relations within an individual, it must be acknowledged that each data point on the curve derives from independent subjects, and therefore represents inter- (not intra-) individual relationships.

Indeed,

In a review paper, Lassen constructed a plot of average pressure and flow from 7 studies involving 11 different patient groups with varying drug and pathology induced blood pressure levels.

So, one need to remember that piece of information from the original review paper when discussing their results related to static cerebral autoregulation !

________________________

* CBF: Cerebral blood flow

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Cerebrovascular physiology – article alert #37

Blood pressure and the brain

161- Defining the characteristic relationship between arterial pressure and cerebral blood flow – Tan

Aging and the brain

162- Endothelium-dependent control of cerebrovascular functions through age: exercise for healthy cerebrovascular aging – Bolduc et al.

Sympathetic activity and the brain

163- Autonomic blockade during sinusoidal baroreflex activation proves sympathetic modulation of cerebral blood flow velocity – Hilz et al.

Regulation of brain blood flow

164- Astrocyte regulation of cerebral vascular tone – Filosa and Iddings

Brain circulation

165- Differential cerebrovascular CO2 reactivity in anterior and posterior cerebral circulations – Skow et al.

Cerebrovascular physiology – article alert #36

Exercise and the brain

155- Cognitive functions in middle aged individuals are related to metabolic disturbances and aerobic capacity: a cross-sectional study – Pedersen et al.

Altitude and the brain

156- The Young Everest Study: preliminary report of changes in sleep and cerebral blood flow velocity during slow ascent to altitude in unacclimatised children – Gavlak et al.

Spinal cord injury and the brain

157- Regulation of cerebral blood flow after spinal cord injury – Phillips et al.

Multiple sclerosis and the brain

158- Cerebrovascular hemodynamic changes in multiple sclerosis patients during head-up tilt table test: effect of high-dose intravenous steroid treatment – Mezei et al.

Glaucoma and the brain

159- Cerebral blood flow in glaucoma patients – Harris and Wirostko

Hypercapnia and the brain

160- Does hypercapnia-induced impairment of cerebral autoregulation affect neurovascular coupling? A functional TCD study – Maggio et al.

Cerebrovascular physiology – article alert #35

Brain autoregulation

150- Blood pressure regulation IX: cerebral autoregulation under blood pressure challenges – Tzeng and Ainslie

Mental work and the brain

151- Cortical oxygen consumption in mental arithmetic as a function of task difficulty: a near-infrared spectroscopy approach – Verner et al.

Brain monitoring

152- Pro: cerebral oximetry should be a routine monitor during cardiac surgery – Wernick and Gutsche

153- Con: near-infrared spectroscopy has not proven its clinical utility as a standard monitor in cardiac surgery – Gregory and Kohl

Cardiopulmonary bypass and the brain

154- Influence of variations in systemic blood flow and pressure on cerebral and systemic oxygen saturation in cardiopulmonary bypass patients – Moerman et al.

Cerebrovascular physiology – article alert #34

Skin blood flow and the brain

146- Human skin hypoxia modulates cerebrovascular and autonomic functions – Pucci et al.

Anxiety and the brain

147- Anxiety, pCO2 and cerebral blood flow – Van den Bergh et al.

High altitude and the brain

148- Breathing and sleep at high altitude – Ainslie et al.

Cardiac arrest and the brain

149- Effect of moderate hyperventilation and induced hypertension on cerebral tissue oxygenation after cardiac arrest and therapeutic hypothermia – Bouzet et al.