title: Cerebral autoregulation of blood velocity and volumetric flow during steady-state changes in arterial pressure.
abstract: The validity of using transcranial Doppler measurement of cerebral blood flow velocity (CBFV) to assess cerebral autoregulation (CA) still is a concern. This study measured CBFV in the middle cerebral artery using transcranial Doppler and volumetric cerebral blood flow (CBF) in the internal carotid artery (ICA) using color-coded duplex ultrasonography to assess CA during steady-state changes in mean arterial pressure (MAP). Twenty-one healthy adults participated. MAP was changed stepwise by intravenous infusion of sodium nitroprusside and phenylephrine. Changes in CBFV, CBF, cerebrovascular resistance (CVR=MAP/CBF), or cerebrovascular resistance index (CVRi=MAP/CBFV) were measured to assess CA by linear regression analysis. The relationship between changes in ICA diameter and MAP was assessed. All values were normalized as percentage changes from baseline. Drug-induced changes in MAP were from -26% to 31%. Changes in CBFV and CVRi in response to MAP were linear, and the regression slopes were similar between middle cerebral artery and ICA. However, CBF in ICA remained unchanged despite large changes in MAP. Consistently, a steeper slope of changes in CVR relative to CVRi was observed (0.991 versus 0.804; P<0.05). The ICA diameter changed inversely in response to MAP (r=-0.418; P<0.05). These findings indicate that CA can be assessed with transcranial Doppler measurements of CBFV and CVRi in middle cerebral artery. However, it is likely to be underestimated when compared with the measurements of CBF and CVR in ICA. The inverse relationship between changes in ICA diameter and MAP suggests that large cerebral arteries are involved in CA.
authors.affiliation: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Ave, Dallas, TX 75231. RongZhang@texashealth.org.
authors.forename: Jie
authors.initials: J
authors.lastname: Liu
authors.forename: Yong-Sheng
authors.initials: YS
authors.lastname: Zhu
authors.forename: Candace
authors.initials: C
authors.lastname: Hill
authors.forename: Kyle
authors.initials: K
authors.lastname: Armstrong
authors.forename: Takashi
authors.initials: T
authors.lastname: Tarumi
authors.forename: Timea
authors.initials: T
authors.lastname: Hodics
authors.forename: Linda S
authors.initials: LS
authors.lastname: Hynan
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000328:Adult; D062186:Arterial Pressure / Q000187:drug effects / Q000502:physiology*; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology*; D002536:Cerebral Arteries / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D017585:Ultrasonography, Doppler, Transcranial; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine
keywords: blood pressure; carotid artery, internal; middle cerebral artery; ultrasonography, Doppler, transcranial
references.citation: Stroke. 1989 Jan;20(1):1-3
references.pmid: 2911822
references.citation: Stroke. 1989 Dec;20(12):1733-6
references.pmid: 2512693
references.citation: Stroke. 1999 Feb;30(2):398-401
references.pmid: 9933278
references.citation: Stroke. 2000 Jan;31(1):147-50
references.pmid: 10625730
references.citation: Stroke. 2005 Sep;36(9):e83-99
references.pmid: 16100027
references.citation: Stroke. 1997 Jun;28(6):1115-22
references.pmid: 9183335
references.citation: Stroke. 1996 Oct;27(10):1829-34
references.pmid: 8841340
references.citation: J Clin Invest. 1978 Oct;62(4):761-8
references.pmid: 701475
references.citation: J Physiol. 2012 Jul 15;590(14):3261-75
references.pmid: 22495584
references.citation: J Physiol. 2007 Oct 1;584(Pt 1):347-57
references.pmid: 17690148
references.citation: Stroke. 1989 Jan;20(1):45-52
references.pmid: 2492126
references.citation: Neurology. 1972 Sep;22(9):978-87
references.pmid: 4343348
references.citation: J Cereb Blood Flow Metab. 2011 Oct;31(10):2019-29
references.pmid: 21654697
references.citation: Neurosurgery. 1993 May;32(5):737-41; discussion 741-2
references.pmid: 8492848
references.citation: Stroke. 2004 Apr;35(4):843-7
references.pmid: 14976327
references.citation: Am J Physiol. 1998 Jan;274(1 Pt 2):H233-41
references.pmid: 9458872
references.citation: Alzheimers Dement. 2014 Mar;10(2):162-70
references.pmid: 23871763
references.citation: Pediatr Res. 1993 Aug;34(2):173-7
references.pmid: 8233721
references.citation: Am J Physiol Heart Circ Physiol. 2011 Apr;300(4):H1492-500
references.pmid: 21317304
references.citation: Anesthesiology. 1995 Jul;83(1):66-76
references.pmid: 7605020
references.citation: Stroke. 1994 Apr;25(4):793-7
references.pmid: 7909175
references.citation: Stroke. 1994 Oct;25(10):1985-8
references.pmid: 7916502
references.citation: Stroke. 1998 Jan;29(1):212-21
references.pmid: 9445353
references.citation: Physiol Rev. 1998 Jan;78(1):53-97
references.pmid: 9457169
references.citation: Stroke. 2000 Jul;31(7):1672-8
references.pmid: 10884472
references.citation: J Cereb Blood Flow Metab. 2013 Aug;33(8):1190-6
references.pmid: 23591649
references.citation: Stroke. 1984 May-Jun;15(3):413-6
references.pmid: 6374982
references.citation: J Appl Physiol (1985). 2009 Aug;107(2):506-17
references.pmid: 19541730
references.citation: Am J Physiol Heart Circ Physiol. 2000 Jun;278(6):H1848-55
references.pmid: 10843881
references.citation: Hypertension. 2007 May;49(5):1149-55
references.pmid: 17353511
references.citation: J Neurosurg. 1982 Dec;57(6):769-74
references.pmid: 7143059
references.citation: Circ Res. 1990 Jan;66(1):8-17
references.pmid: 2403863
references.citation: Hypertension. 2010 Mar;55(3):698-705
references.pmid: 20083726