Cerebral autoregulation indices are unimpaired by hypertension in middle aged and older people.
BACKGROUND
Hypertension is known to increase the limits of static cerebral autoregulation (CA) but its effects on other aspects of CA such as efficiency and latency are unknown. In this study we test the hypothesis that dynamic cerebral autoregulation and the efficiency of static cerebral autoregulation are impaired by untreated hypertension.


METHODS
Cerebral blood flow velocity was recorded using transcranial Doppler ultrasound, along with noninvasive beat-to-beat blood pressure (BP), electrocardiogram, and transcutaneous carbon dioxide levels, with subjects at rest and during isometric hand grip, thigh cuff, and the Valsalva maneuver. Static and dynamic CA indices were calculated.


RESULTS
No significant difference was seen in static or dynamic CA indices between normotensive and hypertensive groups for any pressor or depressor stimulus. Spearman's rank correlation showed no relation between static or dynamic CA indices and systemic BP levels for all maneuvers, but a significant relationship between age and static CA index, determined using isometric handgrip (P =.002), was found.


CONCLUSIONS
In middle-aged and older people, sustained untreated hypertension does not alter dynamic CA or the efficiency of static CA within the BP limits studied.
Eames
Penelope J
PJ
Division of Medicine for the Elderly, University of Leicester, Glenfield Hospital, Leicester LE3 9QP, UK. penny.eames@UHL-tr.nhs.uk
Blake
Melanie J
MJ
Panerai
Ronney B
RB
Potter
John F
JF
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D017704:Baroreflex / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D018660:Blood Pressure Monitoring, Ambulatory; D002302:Cardiac Output / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D007537:Isometric Contraction / Q000502:physiology; D008150:Lower Body Negative Pressure; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology; D013223:Statistics as Topic; D013599:Systole / Q000502:physiology; D013687:Telencephalon / Q000000981:diagnostic imaging / Q000503:physiopathology*; D017585:Ultrasonography, Doppler, Transcranial; D006113:United Kingdom; D014636:Valsalva Maneuver / Q000502:physiology