Impaired Cerebral Autoregulation in Patients With Malignant Hypertension

Abstract

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

Anoxic Injury-Associated Cerebral Hyperperfusion Identified with Arterial Spin-Labeled MR Imaging

“…17,27,28 Little human research exists regarding the effect of global anoxia on autoregulation. 4,20,[29][30][31][32][33][34][35][36][37] Animal models have shown a loss of cerebral vascular resistance in the postanoxic state resulting in uncontrolled hyperperfusion. [38][39][40][41][42] Cerebral blood volume has been shown to increase with loss of autoregulation secondary to ischemia, but no large studies have demonstrated a similar relationship for CBF.…”

Dynamic cerebral autoregulation during and following acute hypoxia: role of carbon dioxide

“…The mechanisms of CA are complex and incompletely understood, but likely rely on a combination and interaction of myogenic, neural, endothelial, and metabolic factors (1,32). Although recently challenged in both healthy humans (18) and patients (13), the conventional model of static CA proposes that cerebral blood flow (CBF) is independent of steady-state changes in mean arterial pressure (MAP) between ϳ50 and 160 mmHg (17). In contrast, dCA responds to sudden changes in blood pressure and is frequently active throughout a typical day, such as during rapid adjustments in posture.…”

Age-Related Changes of Cerebral Autoregulation: New Insights with Quantitative T2′-Mapping and Pulsed Arterial Spin-Labeling MR Imaging

“…Chronic arterial hypertension is one of the most important factors affecting cerebrovascular autoregulation. 2 Furthermore, alterations in CBF or in cerebrovascular autoregulation are discussed in neurodegeneration. 3,4 An acute breakthrough of autoregulation may play an important role in acute hypertensive encephalopathy, eclampsia, and in acute brain injury.…”