Arterial Pressure and Cerebral Blood Flow Variability: Friend or Foe? A Review

Variability in arterial pressure and cerebral blood flow has
traditionally been interpreted as a marker of cardiovascular
decompensation, and has been associated with negative clinical outcomes
across varying time scales, from impending orthostatic syncope to an
increased risk of stroke. Emerging evidence, however, suggests that
increased hemodynamic variability may, in fact, be protective in the
face of acute challenges to perfusion, including significant central hypovolemia and hypotension (including hemorrhage), and during cardiac bypass surgery.
This review presents the dichotomous views on the role of hemodynamic
variability on clinical outcome, including the physiological mechanisms
underlying these patterns, and the potential impact of increased and
decreased variability on cerebral perfusion
and oxygenation. We suggest that reconciliation of these two apparently
discrepant views may lie in the time scale of hemodynamic variability;
short time scale variability appears to be cerebroprotective, while mid
to longer term fluctuations are associated with primary and secondary
end-organ dysfunction.