Short-term blood pressure variability and predictability of dynamic cerebral autoregulation in acute stroke patients

Blood pressure (BP) management in acute ischaemic stroke presents uncertainties regarding whether systolic BP (sys), mean BP (mean), or diastolic BP (dia) should be used for therapeutic guidance. Repeated assessments of BP-dependent cerebral autoregulation (CA) could help identify a suitable BP modality for this purpose. Forty-nine patients (median age 75 [62-81] years; 13 women) with unilateral acute ischemic stroke (NIHSS 5 [1.75-15.0]), underwent stroke center care and dynamic cerebral autoregulation (dCA) assessments on days 1 to 3 after the stroke event. Using frequency-dependent transfer function analysis between BP and cerebral blood flow velocity (CBFV), gain indicates the amplitude transmission, and phase shift represents the phase difference between the two. CA failure is typically indicated by a low or absent phase shift in the very low (0.02-0.07 Hz) or low frequencies (0.07-0.20 Hz) ranges, leading to a direct transmission of BP changes to CBFV changes. BP values were averaged, with their standard deviation indicating BP variability (BPV). Averaged sys, mean, or dia BP did not predict gain or phase, but BPV did. In the stroke-affected hemisphere (AH), sys, mean and dia BPV on day 1 predicted low frequency gain on days 1 and 2 (p < 0.02 - p < 0.001). On day 2, dia more than mean BPV predicted linearly (p < 0.001) very low frequency phase with small phase values associated with a low BPV and large phase values with high BPV values. In acute stroke, dia BPV predicts best phase shift, and could be a promising candidate for BP guidance.