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Biomedical subjects

J Levenson

Publications and source records attributed to J Levenson.

194 records · Page 11Linked to original sources
PubMed1976

Screening and supportive techniques for home dialysis in the treatment of renal failure.

Patients with end-stage renal disease are being kept alive by dialysis treatment which may be provided either in an institution or in the patient's home. However, medical advancements have outstripped the ability of the treatment team to insure the quality of life for these long-term patients. Although the predominant pattern of care continues to be the hospital- or institution-based unit, an attempt is being made by both patients and physicians to make home dialysis a more viable alternative. There are two major barriers to the large-scale effectiveness of treatment by home dialysis: 1) lack of criteria for the selection of candidates, and 2) lack of a continuing supportive service system. Home care requires a total understanding of the psychosocial functioning of the patient and the family.

Costs and Cost Analysis↗
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

Enhanced constriction of the peripheral large artery in response to acute induction of a low-flow state in human hypercholesterolemia.

The diameter, blood velocity, and blood flow of the brachial artery were evaluated with a pulsed-Doppler apparatus before and after wrist occlusion in 16 normocholesterolemic and 27 hypercholesterolemic male subjects of similar age and body mass index. Before occlusion, no hemodynamic differences were observed between the two groups. Occlusion significantly reduced blood velocity and blood flow in the two groups (p less than 0.001), but such reductions were not different between hypercholesterolemic and normocholesterolemic groups. Occlusion decreased the arterial diameter in the hypercholesterolemic group only (p less than 0.001), and absolute diameter changes after occlusion were significantly different between the two groups (p less than 0.001). No correlation was found between the change in arterial diameter after occlusion and the baseline diameter before occlusion in the normocholesterolemic and hypercholesterolemic population overall. Absolute and percent diameter changes after occlusion were correlated with total cholesterol (r = -0.73, r = -0.72; p less than 0.001) and with low density lipoprotein (LDL) cholesterol (r = -0.68, r = -0.69; p less than 0.001) in the normocholesterolemic and hypercholesterolemic population overall, respectively. These findings indicate that the low-flow state induces a reduction in large-artery diameter in the hypercholesterolemic but not in the normocholesterolemic state and is closely related to the degree of elevation of blood cholesterol and of its LDL fraction.

Adult↗
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

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

Pulsed Doppler: an evaluation of diameter, blood velocity and blood flow of the common carotid artery in patients with isolated unilateral stenosis of the internal carotid artery.

Arterial diameter, blood velocity and blood flow of both common carotid arteries were studied in 24 patients with isolated unilateral internal carotid artery stenosis, without any other significant lesion of the carotid system. The methodology used a pulsed Doppler system with two original characteristics: an adjustable range-gated system and a double transducer probe enabling both the arterial diameter and blood velocity to be evaluated. On the involved side, the diameter, the blood velocity and the blood flow were significantly reduced (p less than 0.001) in comparison with the opposite side. The degree of the internal carotid artery stenosis judged on arteriography was negatively correlated with (i) the blood flow of the common carotid artery homolateral to the stenosis (r = -0.78, p less than 0.001); and (ii) the ratio of the common carotid artery blood flow between the involved and the opposite side (r = -0.80, p less than 0.001). The proposed quantitative evaluation can be suitable for the detection and for the follow up of patients with stenosis of the internal carotid artery who do not have any other lesion of the carotid system.

Aged↗
PubMedDate not supplied

[Role of prostaglandins and the beta-adrenergic system in central and peripheral hyperkinesia in borderline hypertension].

The effects of short-term administration of indomethacin and propranolol were studied in two groups of patients with borderline hypertension and both central and peripheral hyperkinesia. Indomethacin and propranolol both significantly increased total peripheral resistance (respectively +32 +/- 3%, +59 +/- 7%, p less than 0.001). The increase in blood pressure after administrating propranolol was not significant (+3 +/- 2%), as opposed to what was obtained with indomethacin, (+5 +/- 2%, p less than 0.02). On the brachial artery, Indomethacin had no effect on blood flow and local resistance, on the other hand propranolol induced a decrease in blood flow in the brachial artery (-43 +/- 3%, p less than 0.001) and an elevation of local resistance (+105 +/- 18%, p less than 0.01). While central hyperkinesia depends on both prostaglandins and on the beta-adrenergic system, high muscle blood flow seems to be regulated by the beta-adrenergic system alone, without participation of prostaglandins.

Hemodynamics↗
PubMedDate not supplied

Antihypertensive and vasodilating effects of acute medroxalol, a new beta-blocker with beta-2-adrenergic receptor stimulation.

The effects of medroxalol, a new beta-blocking drug, were simultaneously studied on the brachial artery, the arterioles and the veins of the forearm in 15 patients with mild to moderate essential hypertension after administration of a single oral dose of 200 mg, by means of pulsed Doppler velocimetry of the brachial artery and strain gauge mercury-in silastic plethysmography of the forearm. In addition the systolic time intervals including preejection period (PEP) and left ventricular time (LVET) were also measured after drug administration. Acute oral medroxalol produced a rapid and significant decrease in systolic and diastolic blood pressure and in heart rate. Concomitantly a significant increase was observed in brachial artery diameter (p less than 0.05), blood velocity and flow (p less than 0.01); forearm vascular resistance decreased (p less than 0.001) but forearm venous tone was unchanged. Lastly medroxalol prolonged PEP but shortened LVET corrected for heart rate. These results demonstrate a rapid antihypertensive action of a single dose of medroxalol with a dilation of the arteries but not of the veins of the forearm and a discrepant effect on the systolic time intervals.

Adult↗