Computerized Analysis of Cerebral Blood Flow Autoregulation in Humans

Schmidt, J. F.; Waldemar, Gunhild; Vorstrup, Sissel; Andersen, Andreas; Gjerris, F.; Paulson, Olaf B.

doi:10.1097/00005344-199006000-00017

Cited by 80 publications

(54 citation statements)

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“…CBF Fick and V,,,^ were plotted against the corresponding MAP, and the lower limit of autoregulation was computed by the least-squares method by repeatedly fitting the data to two linear regression lines: a horizontal and an oblique line where the crossover point defines the lower limit. 22 The following criteria had to be fulfilled to establish the lower limit of the autoregulation: (1) The squared sum of differences between the calculated autoregulation curve and the measured points should not exceed that of a straight line and (2) the calculated lower limit should be within physiologically meaningful limits, ie, between 50 mm Hg and 110 mm Hg, and it should be determined with a mean error of less than 25% of the calculated value.…”

Section: Discussionmentioning

confidence: 99%

Transcranial Doppler is valid for determination of the lower limit of cerebral blood flow autoregulation.

Larsen

Olsen

Hansen

et al. 1994

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261

152

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Background and Purpose This study validates transcranial Doppler sonography (TCD) for determination of the lower limit of cerebral blood flow (CBF) autoregulation and establishes a relation between global CBF and mean flow velocity (V mean ) in the middle cerebral artery.Methods Relative changes in CBF and in V mean were compared in 12 normal volunteers (2 women and 10 men; median age, 30 years [range, 21 to 61 years]). Catheters was placed in the left radial artery and in the bulb of the right internal jugular vein, respectively. Baseline CBF was measured by single-photon emission computed tomography scanning; concomitantly, blood samples were drawn for calculation of the cerebral arteriovenous oxygen difference. Then changes in mean arterial pressure (MAP) were induced, and relative changes in global CBF were calculated according to Fick's principle assuming a constant cerebral oxygen metabolism. MAP was increased 30 mm Hg by norepinephrine infusion and was decreased by lower body negative pressure. V raean was

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Section: Discussionmentioning

confidence: 99%

Transcranial Doppler is valid for determination of the lower limit of cerebral blood flow autoregulation.

Larsen

Olsen

Hansen

et al. 1994

Stroke

261

152

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“…In normotensive humans, the lower limit of sCA is located Ϸ60 mm Hg. 12,30,31 For obvious reasons, the upper limit of sCA cannot be studied in (normotensive) humans, but in normotensive baboons, it ranges between 120 and 150 mm Hg. 13 In humans with untreated severe chronic hypertension, the lower limit of sCA is shifted rightward to Ϸ115 mm Hg.…”

Section: Study Limitationsmentioning

confidence: 99%

“…13 In humans with untreated severe chronic hypertension, the lower limit of sCA is shifted rightward to Ϸ115 mm Hg. 11,12 Data on the upper limit of sCA are limited in that it was determined in only 3 hypertensive baboons and was found to be shifted rightward (between 155 and 169 mm Hg). 14 We assume, with MAP Ϸ165 mm Hg at admission in this study, that the pressure level was located around the upper limit of sCA with dCA impaired before treatment with SNP.…”

Section: Study Limitationsmentioning

confidence: 99%

“…Most patients suffering from malignant hypertension have a history of chronic hypertension, 10 and in those patients, the lower limit of CA has been shifted in proportion toward higher pressures. 11,12 For obvious reasons, the upper limit of CA has not been determined in normotensive or hypertensive humans. It was located between 120 and 150 mm Hg 13 in normotensive baboons and between 155 and 170 mm Hg in chronic hypertensive baboons.…”

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Impaired Cerebral Autoregulation in Patients With Malignant Hypertension

et al. 2004

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Background-In patients with a malignant hypertension, immediate parenteral treatment with blood pressure-lowering agents such as intravenous sodium nitroprusside (SNP) is indicated. In this study, we evaluated static and dynamic cerebral autoregulation (CA) during acute blood pressure lowering with SNP in these patients. Methods and Results-In 8 patients with mean arterial pressure (MAP) Ͼ140 mm Hg and grade III or IV hypertensive retinopathy at hospital admission, middle cerebral artery blood velocity (MCA V) and blood pressure were monitored. Dynamic CA was expressed as the 0.1-Hz MCA V mean to MAP phase lead and static CA as the MCA V mean to MAP relationship during SNP treatment. Eight normotensive subjects served as a reference group. In the patients, the MCA V mean to MAP phase lead was lower (30Ϯ8°versus 58Ϯ5°, meanϮSEM; PϽ0.05), whereas the transfer gain tended to be higher. During SNP treatment, target MAP was reached within 90 minutes in all patients. The MCA V mean decrease was 22Ϯ4%, along with a 27Ϯ3% reduction in MAP (from 166Ϯ4 to 121Ϯ6 mm Hg; PϽ0.05) in a linear fashion (averaged slope, 0.82Ϯ0.15% cm · s Ϫ1 · % mm Hg

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“…4-6). The autoregulation curves were determinated as de scribed by Schmidt et al (1990) by repetitive fitting of two regression lines: one sloped regression line through the CPP/CBF points below a given CPP value and one hori zontal line through the CPP/CBF points above the given CPP value. One set of these regression lines was calcu lated for every I-mm Hg increment of CPP, and the cor responding sum of squares was calculated.…”

Section: Datum Analysismentioning

confidence: 99%

Cerebral Blood Flow Autoregulation in Acute Intracranial Hypertension

Hauerberg

Juhler

1994

J Cereb Blood Flow Metab

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Summary: The present series of experiments was carried out to investigate CBP autoregulation during fixed levels of acute increased intracranial pressure (ICP). Three groups of six rats each, one with normal ICP (8 mm Hg), one with moderately increased ICP (30 mm Hg), and one with severely increased ICP (50 mm Hg), were investi gated. ICP was maintained by continuous infusion of lac tated Ringer solution into the cisterna magna. Cerebral perfusion pressure (CPP), calculated as mean arterial blood pressure -ICP, was increased by intravenously infused norepinephrine and decreased by controlled bleeding. In all groups the corresponding autoregulation curve included a plateau where CBP was independent of Abbreviations used: CPP, cerebral perfusion pressure; CVR, cerebrovascular resistance; ICP, intracranial pressure; JVP, jug ular venous pressure; LL, lower limit of autoregulation; MABP, mean arterial blood pressure. 519changes in CPP, demonstrating intact autoregulation. However, a significant shift of the lower limit of autoreg ulation (LL) toward lower CPP levels during severe in tracranial hypertension was observed (p < 0.006). In the controls the LL was found at CPP = 73 ± 6 mm Hg, in moderately increased ICP the LL was 59 ± 4 mm Hg, and in severely increased ICP the LL was 51 ± 4 mm Hg. These results indicate that an acute elevation of ICP ac tivates a reserve capacity of cerebral resistance vessels that dilate further below the normal physiological LL to maintain CBP at low levels of CPP.

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Computerized Analysis of Cerebral Blood Flow Autoregulation in Humans

Cited by 80 publications

References 0 publications

Transcranial Doppler is valid for determination of the lower limit of cerebral blood flow autoregulation.

Transcranial Doppler is valid for determination of the lower limit of cerebral blood flow autoregulation.

Impaired Cerebral Autoregulation in Patients With Malignant Hypertension

Cerebral Blood Flow Autoregulation in Acute Intracranial Hypertension

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