Haemoconcentration, shear-stress increase and carotid artery diameter regulation after furosemide administration in older hypertensives

The aim of the present study was to determine whether changes of carotid wa ll shear stress induced by changes in blood viscosity after diuretic admini stration cause carotid arterial dilatation in elderly hypertensives, as rep orted in the cat. Arterial wall shear rate (ultrasound technique, profilmet er FRP III), the systo-diastolic diameter (echotracking technique) and the mean blood flow velocity and volume of the common carotid artery, the blood viscosity (rotational viscometer) and the finger arterial blood pressure ( Finapress Ohmeda) were measured in 12 young volunteers (aged 25 +/- 2 years ) and in 12 elderly hypertensives (aged 80 +/- 4 years) treated with short- acting calcium antagonists up to 24 h before the study, both at baseline an d after intravenous furosemide infusion (0.5 mg/min), when the haematocrit had increased by at least two percentage points. After furosemide administration the mean arterial blood pressure decreased and blood viscosity and carotid systolic shear stress increased in both gro ups. However, common carotid artery diameter increased only in the young co ntrols but not in the elderly hypertensives. These data show that an increa se in carotid shear stress caused by haemoconcentration induces carotid vas odilatation only in young healthy subjects, and not in elderly hypertensive s. This effect may be related to impaired endothelium function and/or arter ial wall mechanics. (C) 2001 Elsevier Science Inc. All rights reserved.