Biomedical subjects

A C Simon

Publications and source records attributed to A C Simon.

101 records · Page 6Linked to original sources

PubMedDate not supplied

Effects of chronic administration of enalapril and propranolol on the large arteries in essential hypertension.

The forearm arterial effects of enalapril and propranolol were compared by means of pulsed Doppler velocimetry in 28 patients with hypertension after treatment for 3-6 months. Enalapril decreased blood pressure, increased both brachial artery diameter and blood flow, decreased vascular resistance, and increased the arterial compliance of the forearm. Propranolol also decreased blood pressure but did not produce any other changes. It may be concluded that the treatment of hypertension with enalapril, but not propranolol, is associated with dilatation effects on the arterial circulation of the forearm.

Adult↗

PubMedDate not supplied

Systemic arterial compliance in patients with arteriosclerosis obliterans of the lower limbs. Observations on the effect of intravenous propranolol.

Hemodynamic parameters and systemic arterial compliance were measured in patients with arteriosclerosis obliterans of the lower limbs before and after acute administration of propranolol. Arterial compliance was evaluated from a simple viscoelastic model, enabling the calculation of diastolic drainage and diastolic blood flow as indices of the reservoir role of the larger arteries in overall circulation. In comparing basal conditions with normal subjects of the same age, patients with arteriosclerosis obliterans exhibited a significant decrease in arterial compliance (p less than 0.01) and heart rate (p less than 0.02) with a significant increase in systolic pressure (p less than 0.001). Diastolic drainage was increased (p less than 0.01) and was positively correlated with diastolic time (r = 0.73, p less than 0.001). Diastolic blood flow remained within normal ranges (52 +/- 2 vs 49 +/- 3 ml/m2/sec). After acute propranolol intravenous administration, heart rate and stroke volume decreased (p less than 0.001), while total peripheral resistance increased (p less than 0.001). Systemic arterial compliance and diastolic blood flow significantly decreased (p less than 0.01). The study provided evidence that in patients with arteriosclerosis obliterans, the diastolic blood flow was maintained in basal conditions despite the observed reduction in arterial compliance, and that intravenous propranolol administration decreased systemic arterial compliance and diastolic blood flow.

Adult↗

PubMedDate not supplied

Regional compliance of brachial artery and saline infusion in patients with arteriosclerosis obliterans.

Simultaneous brachial artery pressure and blood flow measurements were made in 15 patients with arteriosclerosis of the lower limbs (AOLL) and in controls of the same age and sex. Blood flow was evaluated by a pulsed Doppler device with a double-transducer probe. From analysis of the pressure-flow curves during diastole, regional arterial compliance (RAC) was determined by using as a model of the forearm arterial tree a system of tubes, each with a storage capacity, in series with the arteriolar resistance vessels. In AOLL patients, RAC was significantly reduced (102 +/- 13 vs 173 +/- 14.10(-4) ml/mm Hg, p less than 0.01), and systolic pressure was significantly increased. After saline infusion, systolic pressure continued to increase and arterial compliance, to decrease; brachial blood flow did not change. Study of the baroreflex sensitivity in AOLL patients under basal conditions indicated that a higher pulse pressure was required to obtain the same heart rate as in the controls. The study provided evidence that in AOLL patients: 1) compliance was reduced in the brachial artery (a regional circulation with no clinical evidence of arterial occlusion); 2) an increase in systolic pressure resulted from the decreased arterial compliance; and 3) saline infusion exaggerated the observed reduction in arterial compliance and increase in systolic pressure.

Aged↗

PubMedDate not supplied

Cigarette smoking and hypertension. Factors independently associated with blood hyperviscosity and arterial rigidity.

The effects of cigarette smoking and hypertension on hemorheological variables (blood viscosity over a wide range of shear rates, plasma viscosity, microhematocrit, and plasma protein concentration) and on arterial stiffness (pulse wave velocity) were investigated in 33 normotensive men and 81 mild to moderately hypertensive men. Of these, 22 normotensive and 24 hypertensive subjects were cigarette smokers. Cigarette smoking and hypertension were independently associated with higher blood viscosity at all studied shear rates (from 0.2 to 241 sec-1) as well as with higher plasma viscosity, hematocrit, and pulse wave velocity. At constant hematocrit levels, hypertension remained associated with a higher blood viscosity, while the association with cigarette smoking disappeared. Normotensive smokers had the same increase of blood and plasma viscosity and pulse wave velocity as hypertensive nonsmokers. No interactive effects of hypertension or cigarette smoking on blood or arterial variables were observed, suggesting that the effect of these two factors on blood and vascular rheology are cumulative. Smoking and hypertension may change the flow properties of the blood and the behavior of the arterial wall and this may explain the arterial damage observed in cigarette smokers and hypertensive patients.

Adult↗

PubMedDate not supplied

Rapid dextran infusion in essential hypertension.

Hemodynamic parameters were studied before and after rapid dextran infusion in 34 men including 17 patients with sustained essential hypertension and 17 normotensive controls. In both groups of patients, dextran infusion induced a significant increase (p less than 0.001) in central venous pressure (CVP), cardiac output (CO), and stroke volume. The percent change in stroke volume was significantly higher in hypertensives (p less than 0.001) than in controls. Three indices of volume expansion were calculated: 1) the ratio between the change in CO and the change in volume, which was significantly higher in hypertensives (p less than 0.025), 2) the ratio between the change in CO and the change in CVP, which was similar in both groups, and 3) the ratio between the change in volume and the change in CVP, which was significantly reduced in hypertensives (p less than 0.001). In the overall population, the latter ratio was negatively correlated with the change in CO (or in stroke volume) induced by expansion ( r = -0.75). The results provided evidence that: 1) the slope of the relationship between CO and blood volume was steeper in hypertensives than in normotensives, and 2) the steeper slope was due to a reduction in the effective compliance of the vascular bed, causing a greater elevation in CO per unit rise in volume.

Adult↗

PubMedDate not supplied

Peripheral large arteries and the response to antihypertensive treatment.

Since systolic pressure is governed by the rate of ventricular ejection and the rigidity of the aortic wall, antihypertensive agents may have different effects on systolic and diastolic pressure. Despite an adequate decrease in diastolic pressure, systolic pressure may remain elevated due to structural alterations of large arteries. In the present study, a procedure is described to distinguish the dilation of small and large arteries. The former is evaluated from the calculation of forearm resistance and the latter from the determination of the arterial diameter of the brachial artery, using a bidimensional pulsed Doppler system. Nitroglycerin dilates the brachial artery, with no change in forearm resistance. Dihydralazine reduces the diameter of the brachial artery but decreases forearm resistance. Only calcium and converting-enzyme inhibitors dilate both small and large arteries and cause an increase in brachial blood flow.

Antihypertensive Agents↗

PubMedDate not supplied

Systemic and arterial hemodynamic effects of nifedipine (20 mg) in mild-to-moderate hypertension.

Systemic and arterial hemodynamic effects of the new 20 mg tablet of nifedipine were studied in seven patients with mild-to-moderate essential hypertension. Hemodynamics of the forearm arterial circulation were investigated using a new pulsed Doppler system, enabling the simultaneous determination of the brachial artery diameter and the arterial blood flow velocity. After nifedipine administration, blood pressure decreased significantly, due to a fall in total peripheral resistance. Simultaneously, brachial blood flow increased significantly, due both to an increase in arterial diameter and blood flow velocity. The study provided evidence that, with nifedipine, there is both 1) a dilation of small arteries, causing a decrease in blood pressure; and 2) a dilation of peripheral large arteries, leading to an increase in peripheral blood flow.

Adult↗

PubMedDate not supplied

Renal and systemic hemodynamics in sustained essential hypertension.

Cardiac output (CO), renal blood flow (RBF), calf blood flow (CBF), and hepatic blood flow (HBF), glomerular filtration rate (GFR), and dopamine beta hydroxylase (D beta H) activity were studied in 198 men (67 normotensive controls and 131 hypertensive patients) of the same age with sustained uncomplicated essential hypertension. In the hypertensive men, the RBF and the RBF/CO ratio were significantly decreased (p less than 0.001). The RBF and RBF/CO ratio were negatively correlated with age (p less than 0.01), blood pressure (p less than 0.01), and D beta H activity (p less than 0.01). None of these relationships were observed with CBF and HBF. The observed decreases in RBF and the RBF/CO ratio in hypertensive men were reversed after administration of clonidine and alpha-methyldopa (p less than 0.01), but not after administration of propranolol. The study provides evidence that the reduction of renal perfusion in essential hypertension is partly reversible and related to an abnormality in the adrenergic system control.

Adult↗

PubMedDate not supplied

Structural changes of large arteries in sustained essential hypertension.

The physical properties of intact superficial arteries can be studied in humans by using original pulsed Doppler systems. Measurements of the diameter, blood flow velocity, volumic flow, and compliance of the brachial artery can be obtained in hypertensive humans in comparison with controls of the same age. In sustained essential hypertension, arterial compliance is decreased, in a manner that is not related exclusively to age and to the level of blood pressure. On the basis of pharmacological studies, the predominant role of activation of the autonomic nervous system can be excluded. As observed in isolated systolic hypertension and in arteriosclerosis obliterans of the lower limbs, the reduction in arterial compliance is probably due to structural alterations of the arterial wall, which produce a disproportionate increase in systolic pressure. Nitroglycerine is able to reverse both the decreased compliance and the increased systolic pressure. The conclusion follows that adaptive changes of large arteries participate in the structural autoregulation of blood flow in hypertension and lead to a predominant elevation of systolic pressure in older subjects.

Adult↗

PubMedDate not supplied

Evidence of early degenerative changes in large arteries in human essential hypertension.

Noninvasive evaluation of brachial artery diameter (pulsed Doppler velocimetry) and pulse wave velocity (strain gauge mechanography) was performed in 23 normal subjects and 49 patients with uncomplicated essential hypertension. Pulsatile arterial function was described in terms of derived characteristic impedance and arterial compliance. Compared with normal controls, hypertensive patients had greater arterial diameter (p less than 0.01) and pulse wave velocity (p less than 0.001). Two nomograms obtained from normal subjects relating the product of age and diastolic pressure to diameter and pulse wave velocity were used for analysis of the hypertensive group; 35 patients were inside the 95% confidence limits of the diameter and pulse wave velocity nomograms (Group 1), while 14 patients were outside the pulse wave velocity nomogram (Group 2). Age and mean pressure were similar, but pulse wave velocity was higher (p less than 0.001), arterial compliance lower (p less than 0.001), and characteristic impedance higher (p less than 0.001) in Group 2 than in Group 1. The amplitude of pulse pressure was higher in Group 2 than in Group 1 (p less than 0.001), and a negative correlation was found between pulse pressure and arterial compliance in Group 2, but not in Group 1. Thus, in the majority of hypertensive patients, arterial modifications could be related to the normal influence of age and pressure. In contrast, other patients exhibited features suggesting excessive arterial stiffness, manifested by abnormally high pulse wave velocity, decreased arterial compliance, and increased characteristic impedance.

Adolescent↗

PubMedDate not supplied

Hand hygiene, the crusade of the infection control specialist. Alcohol-based handrub: the solution!

Hands of healthcare workers are the main route of transmission of microorganisms responsible for nosocomial infections. Compliance with hand hygiene procedures however is still grossly insufficient. Rubbing hands with alcohol-based solutions in order to decontaminate hands instead of handwashing, as proposed in new recommendations is one way of solving the problem. Alcohol is more efficient and faster acting than antiseptic soaps and takes care of the real or perceived constraints of healthcare workers against hand hygiene. The pocketsize bottle version of the alcohol-based solution significantly improves doctors' compliance with hand hygiene.

Alcohols↗