Is cerebrovascular autoregulation impaired during neurally-mediated syncope?

Cerebral autoregulation is temporarily disturbed in the early recovery phase after dynamic resistance exercise

“…However, so far only little is known about changes in CBF and dynamic CA in the early recovery period directly after exercise, when BP and heart rate (HR) decrease rapidly, down to resting levels [1,35,36]. Edwards [12] has recently shown that in the early recovery period after a maximum leg press exercise, mean cerebral blood flow velocity (Vm) increases despite the parallel rapid decreases in BP and HR. This behavior in cerebral blood flow velocity (CBFV) corresponded to an increased end-tidal CO 2 , but parameters of dynamic CA were not addressed in that paper.…”

Cerebral autoregulation is preserved in postural tachycardia syndrome

“…Cerebral autoregulation has been modeled as both a static and a dynamic process (35,42,44), with the latter being a somewhat more sensitive index of a threatened cerebral circulation (9). Reduced cerebral perfusion during orthostatic stress will occur if cerebral autoregulation is overwhelmed or impaired (12). Normal individuals subjected to high levels of orthostatic stress simulated by lower body negative pressure (LBNP) have reduced cerebral perfusion and impaired dynamic cerebral autoregulation (4,54).…”

Maintaining cerebral oxygen homeostasis: a serious business

“…During strenuous muscular work, cerebral blood flow increases ~ 15% and stabilizes, whereas blood pressure and heart rate show the typical pattern during exercise regulation. Right after stopping, however, a sudden autonomic reaction brings cerebral blood flow immediately back to the previous working state, before it slowly downregulates back to normal values within the next 2 min, similar to what happens after a typical vasovagal syncope [6,7]. Cerebral blood flow regulation is a key mechanism to maintain oxygen homeostasis, both during acute conditions (e.g., to stabilize cerebral perfusion during hypotension), and to ensure adequate oxygen delivery for a longer period of time at high altitude during acclimatization as elegantly illustrated by Hoiland and colleagues in their model about the opposing influences of ventilation and cerebral blood flow on the central chemoreceptors, which are decisively involved in the regulatory process.…”

“…In the case of vasovagal syncope, the autonomic nervous system not only attempts to rapidly stabilize cerebral perfusion (as measured by transcranial Doppler ultrasound) after the syncopal event, but even increases cerebral blood flow dramatically as to temporarily exceed resting values [6,7]. A very similar reaction can be observed after stopping a hard muscular effort This is a comment on an article available at: https ://link.sprin ger.…”

“…com/artic le/10.1007/s1028 6-018-0522-2. Institute of Physiology, Christian-Albrechts-University, Kiel, Germany without proper cooling down, when blood pressure and heart rate rapidly drop down to normal resting levels, without decreasing further as to reach hypotension or bradycardia [6]. During strenuous muscular work, cerebral blood flow increases ~ 15% and stabilizes, whereas blood pressure and heart rate show the typical pattern during exercise regulation.…”