title: Cerebrovascular effects of the thigh cuff maneuver.
abstract: Arterial hypotension can be induced by sudden release of inflated thigh cuffs (THC), but its effects on the cerebral circulation have not been fully described. In nine healthy subjects [aged 59 (9) yr], bilateral cerebral blood flow velocity (CBFV) was recorded in the middle cerebral artery (MCA), noninvasive arterial blood pressure (BP) in the finger, and end-tidal CO2 (ETCO2) with nasal capnography. Three THC maneuvers were performed in each subject with cuff inflation 20 mmHg above systolic BP for 3 min before release. Beat-to-beat values were extracted for mean CBFV, BP, ETCO2 , critical closing pressure (CrCP), resistance-area product (RAP), and heart rate (HR). Time-varying estimates of the autoregulation index [ARI(t)] were also obtained using an autoregressive-moving average model. Coherent averages synchronized by the instant of cuff release showed significant drops in mean BP, CBFV, and RAP with rapid return of CBFV to baseline. HR, ETCO2 , and ARI(t) were transiently increased, but CrCP remained relatively constant. Mean values of ARI(t) for the 30 s following cuff release were not significantly different from the classical ARI [right MCA 5.9 (1.1) vs. 5.1 (1.6); left MCA 5.5 (1.4) vs. 4.9 (1.7)]. HR was strongly correlated with the ARI(t) peak after THC release (in 17/22 and 21/24 recordings), and ETCO2 was correlated with the subsequent drop in ARI(t) (19/22 and 20/24 recordings). These results suggest a complex cerebral autoregulatory response to the THC maneuver, dominated by myogenic mechanisms and influenced by concurrent changes in ETCO2 and possible involvement of the autonomic nervous system and baroreflex.
authors: University of Leicester, Department of Cardiovascular Sciences, Leicester Royal Infirmary, Leicester, United Kingdom; and National Institutes for Health Research, Biomedical Research Unit in Cardiovascular Science, Glenfield Hospital, Leicester, United Kingdom rp9@le.ac.uk.
authors: R B
authors: RB
authors: Panerai
authors: University of Leicester, Department of Cardiovascular Sciences, Leicester Royal Infirmary, Leicester, United Kingdom; and.
authors: N P
authors: NP
authors: Saeed
authors: University of Leicester, Department of Cardiovascular Sciences, Leicester Royal Infirmary, Leicester, United Kingdom; and National Institutes for Health Research, Biomedical Research Unit in Cardiovascular Science, Glenfield Hospital, Leicester, United Kingdom.
authors: T G
authors: TG
authors: Robinson
mesh_terms: D000328:Adult; D000368:Aged; D062186:Arterial Pressure; D002560:Cerebrovascular Circulation; D005260:Female; D005385:Fingers / Q000098:blood supply*; D064368:Healthy Volunteers; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D007022:Hypotension / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply*; D020127:Recovery of Function; D012039:Regional Blood Flow; D013848:Thigh; D013997:Time Factors; D014111:Tourniquets
keywords: arterial hypotension; autonomic nervous system; cerebral autoregulation; cerebral blood flow; cerebrovascular resistance; critical closing pressure