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Biomedical subjects

M Safar

Publications and source records attributed to M Safar.

At least 127 records · Page 7Linked to original sources
PubMed1995

Aortic distensibility in normotensive, untreated and treated hypertensive patients.

BACKGROUND: Compared with normotensive subjects, untreated hypertensive patients show a decrease of their aortic distensibility. Whether antihypertensive treatment, by reducing blood pressure and changing functional and/or structural abnormalities of the arterial wall, may prevent or reverse the arterial damage due to the accelerated ageing process remains unclear. The objective of the present study was to determine, using a cross-sectional approach, whether aortic distensibility as measured by pulse wave velocity, in treated hypertensive patients whose diastolic blood pressure had been normalised for several months, was significantly improved over that of untreated hypertensive patients. METHODS: Carotid femoral pulse wave velocity was measured in 124 normotensive subjects and 388 hypertensive patients. The latter group included 164 treated patients with well controlled diastolic blood pressure and 224 untreated hypertensive subjects. The three groups did not differ in other cardiovascular risk factors. RESULTS: In each group there was a significant relationship between age and pulse wave velocity. When compared with untreated hypertensives, treated hypertensives with well controlled diastolic blood pressure had significantly lower blood pressure and pulse wave velocity according to age. However, although diastolic blood pressure of well controlled hypertensives was not significantly different from that of normotensive subjects, the aortic distensibility of the controlled hypertensives remained reduced showing two characteristics: a faster increase in pulse wave velocity with age and a negative relationship with HDL-cholesterol. CONCLUSION: These results suggest that long-term antihypertensive treatment and control of blood pressure using only diastolic blood pressure criteria may not fully reverse arterial alteration associated with hypertensive vascular disease.

Adolescent↗
PubMed1994

Mortality attributable to nosocomial infections in the ICU.

Although a direct relationship between nosocomial infection and mortality in intensive care unit (ICU) patients has not always been demonstrated formally, it is possible to conclude that nosocomial infections increase the risk of death in critically ill patients. A more precise analysis indicates that: 1) this effect is highly probable for pneumonia, doubtful for bacteremia, and uncertain for urinary tract infection; 2) risk increases with duration of stay in the ICU; 3) bacterial etiology modifies the risk; and 4) this effect is stronger in less severely ill patients, probably because the severity of underlying disease remains the most significant factor.

Bacteremia↗
PubMed1994

Noninvasive detection of an increased vascular mass in untreated hypertensive patients.

Structural changes of the arterial vasculature are of major pathophysiologic and prognostic significance in human hypertension. A high-resolution ultrasonic echotracking device was used to measure internal diameter and intima-media thickness of the radial artery, a medium-sized muscular conduit artery, in 60 hypertensive patients and in 40 age-matched control subjects. Of the 60 hypertensives, 33 were never treated and 27 were well-controlled by antihypertensive therapy. Radial artery mass and thickness/radius ratio were used to describe the radial artery structure. Radial artery mass was validated in vitro by comparing the weight of arterial segments to the ultrasonographic determination of their mass, calculated as: rho L(pi Re2-pi Ri2), where rho is the arterial wall density, L the length of the arterial segment, and Re and Ri the ultrasonic values of internal and external radii, respectively. Diastolic internal diameter did not differ among the three groups, but wall thickness, radial artery mass, and thickness/radius ratio were significantly higher in the untreated hypertensive group than in the control group. In treated well-controlled hypertensive subjects, radial artery mass and thickness/radius ratio were not different from that of control subjects. Among the population of untreated patients, significant univariate relations existed between radial artery mass and blood pressure and radial artery mass and age. In multivariate analysis, radial artery mass was independently predicted by mean blood pressure, age, and sex. Circumferential wall stress, calculated from diastolic internal diameter, wall thickness, and diastolic blood pressure, was not different in the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Plasma erythrocyte relationship of catecholamines in human blood.

The equilibrating process of catecholamines (CAs) between plasma and red blood cells (RBC) was studied by measuring their erythrocyte/plasma concentration gradient (E/P ratio); ratio of E/P > 1 for a given amine was considered the consequence of its accumulation in or on RBC. We studied in vitro human blood obtained from 9 polycythemic patients from whom blood was drawn in control condition and in response to loading with exogenous CAs. Preliminary study showed a lack of difference in results obtained in these patients from those in 9 healthy volunteers and confirmed that RBC accumulate dopamine (DA) and epinephrine (EPI) but not norepinephrine (NE). When a moderate amount of exogenous CAs was added, plasma and RBC concentrations were increased, with a delay between the two compartments indicated by a decrease in the E/P ratio of DA and EPI. When a large amount of exogenous CAs was added, their RBC concentrations were in direct proportion to their plasma concentrations. Thus, the kinetics of CA equilibration between plasma and RBC appears to be dependent on their chemical structure (DA is more easily accumulated than NE) and their plasma concentrations. Physiologically, the E/P ratio of DA was significantly greater than 1, suggesting that RBC maintained their capacity to accumulate DA even when DA plasma concentration was very high. Additional studies demonstrated that accumulation of CAs in or on RBC is a reversible process, inhibited by cold temperature and increased when blood pO2 is drastically reduced.(ABSTRACT TRUNCATED AT 250 WORDS)

Catecholamines↗
PubMed1994

Effects of bradykinin B2 receptor antagonism on the hypotensive effects of ACE inhibition.

1. The aim of this study was to determine the participation of endogenous bradykinin (BK) in the antihypertensive effects of the angiotensin converting enzyme inhibitor (ACEI), perindoprilat, in the spontaneously hypertensive rat (SHR) on different salt diets. 2. Conscious SHRs receiving either a low or a high NaCl diet were used in order to evaluate the respective roles of angiotensin II suppression and bradykinin stimulation in the acute hypotensive effects of perindoprilat. Two different B2 receptor antagonists (B 4146 and Hoe 140) were used after bolus administration of 7 mg kg-1 of the ACEI, perindoprilat. In separate animals, Hoe 140 was administered before the injection of perindoprilat. In other experiments, the effects of Hoe 140 on the hypotensive effects of the calcium antagonist, nicardipine, were tested. 3. The different NaCl diets had no effect on baseline blood pressure. Hoe 140 injection before ACE inhibition did not modify blood pressure. Perindoprilat caused more marked hypotension in the low salt-fed rats than in the high salt animals (P < 0.01). Administration of Hoe 140 or B4146 after perindoprilat significantly reduced the antihypertensive effects of perindoprilat in the different groups, but this effect was more pronounced in high salt-fed rats. However, in SHRs receiving Hoe 140 before perindoprilat, the antihypertensive effect of perindoprilat was completely abolished in both high or low salt diet rats. In separate experiments we confirmed that Hoe 140 did not affect the hypotensive efficacy of the calcium antagonist, nicardipine. 4. Our study shows that inhibition of endogenous bradykinin degradation participates in the acute antihypertensive effects of perindoprilat in SHRs. The role of bradykinin is more pronounced following exposure to a high salt diet i.e., when the renin-angiotensin system is suppressed. Blockade of bradykinin B2 receptors by Hoe 140 before administration of perindoprilat completely abolished the hypotensive effect of perindoprilat suggesting an increased role of bradykinin in the onset of hypotensive action of ACE inhibitors. However, the exact mechanism of this interaction remains unclear.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1994

Sympathetic activation decreases medium-sized arterial compliance in humans.

This study used a precise noninvasive method in normotensive humans to determine the effects of sympathetic activation on arterial compliance. A recently developed, high-resolution echo-tracking system capable of measuring systolic/diastolic variations of arterial diameter was coupled to a Finapres system and used to calculate instantaneous systolic/diastolic pressure-diameter and compliance-pressure curves for a muscular medium-sized artery, the radial artery. Two standardized tests of sympathetic system activation, a cold pressor test (2 min) and a mental stress test (2 min of mental arithmetic), were performed at an interval of 8 days in random order in nine healthy volunteers [30 +/- 9 (SD) yr]. Radial arterial parameters were recorded every 30 s for 9 min, which included 2 min of cold pressor test or mental stress test. During both tests, radial arterial mean diameter did not change despite t he increase in mean arterial pressure (P < 0.001); stroke change in diameter decreased (P < 0.01), whereas pulse pressure increased (P < 0.01). Arterial compliance, calculated for the instantaneous level of mean arterial pressure, decreased significantly (P < 0.01). Compliance (C) calculated at 100 mmHg (C100) was arbitrarily chosen as a reference point for comparing compliance among the different periods of the test. C100 decreased significant (P < 0.05) during both tests (from 2.93 +/- 1.27 to 2.04 +/- 0.94 and from 3.29 +/- 1.73 to 2.63 +/- 1.55 mm2.mmHg-1.10(-3) during mental stress and the cold pressor test, respectively). These results indicate that sympathetic activation is able to decrease radial arterial compliance in healthy subjects. The reduction in arterial compliance probably resulted from complex interactions between changes in distending blood pressure and changes in radial arterial smooth muscle tone.

Adult↗
PubMed1994

Elastic modulus of the radial artery wall material is not increased in patients with essential hypertension.

Hypertension is known to decrease arterial distensibility and systemic compliance. However, the arterial tree is not homogeneous, and it has been shown that the medium-size radial artery does not behave like the proximal, elastic, large, common carotid artery. Indeed, radial artery compliance in hypertensive patients (HTs) has been shown to be paradoxically increased when compared with that in normotensive control subjects (NTs) at the same blood pressure level. To determine whether this increase was due to hypertension-related hypertrophy of the arterial wall, radial artery functional and geometric parameters from 22 NTs (mean +/- SD, 44 +/- 11 years) were compared with those from 25 age- and sex-matched never-treated essential HTs (48 +/- 12 years) by using a high-precision ultrasonic, echo-tracking system coupled to a photoplethysmograph (Finapres system), which allows simultaneous arterial internal diameter, intima-media thickness, and finger blood pressure measurements. When the values for HTs were compared with those of NTs at their respective mean arterial pressures, HTs had similar internal diameter (2.50 +/- 0.56 versus 2.53 +/- 0.32 mm, mean +/- SD) and greater intima-media thickness (0.40 +/- 0.06 versus 0.28 +/- 0.05 mm, P < .001) measurements and increased arterial wall cross-sectional areas (3.79 +/- 1.14 versus 2.45 +/- 0.57 mm2, P < .001). Circumferential wall stress was not significantly different between the two groups. Compliance calculated for a given blood pressure, ie, 100 mm Hg (C100), was greater in HTs than NTs (3.46 +/- 2.41 versus 2.10 +/- 1.55 m2.kPa-1 x 10(-8), P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Carotid artery distensibility and distending pressure in hypertensive humans.

Whether the decrease in large-artery distensibility observed in hypertensive patients is due primarily to an increase in distending pressure or to hypertension-induced changes in structural properties has been much debated. We determined noninvasively the diameter-pressure curve of the common carotid artery over the systolic-diastolic range by continuously recording both the pulsatile changes in internal diameter (high-resolution echo-tracking system) and, simultaneously on the contralateral artery, the pressure waveform (high-fidelity applanation tonometry). We then derived the distensibility/pressure curve and compared arterial distensibility in 14 normotensive subjects and 15 age- and sex-matched hypertensive subjects at their respective mean arterial pressures (MAP) and at a common distending pressure: 100 mm Hg. Distensibility decreased as blood pressure increased, and distensibility at MAP was significantly lower in hypertensive than in normotensive subjects (7.8 +/- 0.7 versus 11.7 +/- 1.7 kPa-1.10(-3), mean +/- SEM; P < .05). In hypertensive subjects, the distensibility-pressure curve was shifted toward higher levels of blood pressure, and a large part of the curve overlapped that of normotensive subjects. No significant downward shift of the distensibility-pressure curve was observed in hypertensive subjects, and distensibility at 100 mm Hg was not significantly different from that of normotensive subjects (10.0 +/- 1.0 versus 9.0 +/- 1.1 kPa-1.10(-3)). Distensibility at 100 mm Hg decreased with aging (P < .05) and was not reduced in hypertensive subjects compared with normotensive subjects after adjustment for age.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Systemic and regional haemodynamic effects of 1-(2,5-dimethoxy-4-iodo-phenyl)-2-aminopropane (DOI) and alpha-methyl-5-HT, in the anaesthetised rat.

The present experiment was performed to investigate the haemodynamic effects of 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and alpha-methyl-5-hydroxytryptamine (alpha-methyl-5-HT) in the anaesthetised normotensive rat. DOI (1-300 micrograms/kg i.v.) increased mean arterial pressure (MAP), total peripheral resistance (TPR) and decreased cardiac output (CO) and heart rate (HR). DOI increased all vascular resistances investigated (hindquarters, mesenteric and renal). Alpha-methyl-5-HT (10-300 micrograms/kg i.v.) dose-dependently increased MAP, TPR, all regional vascular resistances and decreased CO and HR. The bradycardia induced by alpha-methyl-5-HT was suppressed by bivagotomy. Both DOI and alpha-methyl-5-HT were more effective on renal vascular bed than hindquarters and mesenteric vascular beds. The effects of DOI and alpha-methyl-5-HT were antagonised by spiperone (10 or 100 micrograms/kg i.v.) and LY 53857 (10 micrograms/kg i.v.). Intracerebroventricular administration of DOI (100 micrograms/kg) increased MAP, TPR, regional vascular resistances and did not change HR and CO. Pretreatment with xylamidine (10 micrograms/kg i.v.), a selective peripheral 5-HT2 receptor antagonist, blocked i.v. and i.c.v. effects of DOI. These results suggest that: 1) the increase in MAP induced by DOI and alpha-methyl-5-HT is due to an increase in TPR. All regional vascular beds and in particular the renal vascular bed participate in the increase of TPR. 2) Peripheral--and may be--central 5-HT2 receptors seem to be implicated in the control of regional vascular resistances. 3) Cardiac effects of alpha-methyl-5-HT are baroreflexly-mediated whereas those of DOI are--at least in part--centrally mediated.

Amphetamines↗
PubMed1994

[Measurement of the vascular mass of the human radial artery by ultrasonics].

OBJECTIVE: To determine the reproducibility of radial artery mass (RAM), in hypertensive patients. DESIGN AND METHODS: In 49 patients, RAM was measured using a high resolution echotracking device (Nius-02) which allows noninvasive measurement of diameter and wall thickness of the radial artery. RAM was validated in vitro by comparing weight of arterial segments to ultrasonographic measurement and determined as RAM = r (pi Re2-pi Ri2) where r is the arterial wall density (1.06 g/cm3), and Re and Ri are values of internal and external radii, respectively. Repeatability coefficient (RC2 = SDi2/n) was 1.3 mg. RESULTS: Blood pressure was (mean +/- SD) 146 +/- 19/85 +/- 15 mmHg, radial arterial diameter was 2,449 +/- 376 microns, radial wall thickness was 302 +/- 68 microns, RAM was 28 +/- 9 mg (range 13-43 mg). CONCLUSION: These results indicate that radial artery mass can be measured using a high resolution echotracking device.

Humans↗
PubMed1994

[Arterial compliance is not diminished in hypertensive patients when compared at the same level of blood pressure].

Whether the decrease in large artery compliance, observed in hypertensive patients (HT), is due to an increase in distending pressure or to intrinsic alterations of the vascular wall remains much debated. We determined the diameter-pressure curve of the common carotid artery over the systolic-diastolic range, then derived the compliance-pressure curve, in order to compare arterial compliance in normotensive subject (NT) and in HT, for a common level of distending blood pressure: 100 mmHg (isobaric compliance). Fourteen NT and 15 never treated essential HT were included in the study. The diameter-pressure curve of the common carotid artery was determined non-invasively by simultaneously and continuously recording the systolic-diastolic changes in internal diameter (using a high resolution echotracking system) and pressure waveform (using high fidelity applanation tonometry on the contralateral artery) over 4-6 cardiac cycles. The level of MAP of the carotid pressure waveform was determined electronically and set equal to mean brachial pressure. Compliance-pressure curve was then derived from the pressure-diameter curve in order to determine compliance (C) for any given level of blood pressure, particularly MAP (CMAP) and 100 mmHg (C100). Despite the considerable differences in blood pressure, the compliance-pressure curve of HT was not different from that of NT. CMAP decreased with aging (p < 0.001) and MAP (p < 0.001). According to age, CMAP was reduced in HT as compared to NT (84 +/- 49 vs 116 +/- 52 mm2.mmHg.10(-3) p < 0.01). C100 decreased with aging (p < 0.05) but not with MAP. According to age, C100 was not reduced in hypertensives.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Heterogeneity of the arterial tree in essential hypertension: a noninvasive study of the terminal aorta and the common carotid artery.

The diameter and the stiffness of the distal portion of the abdominal aorta and of the common carotid artery were evaluated noninvasively in 72 subjects with mild to moderate hypertension by comparing 39 normotensive controls of same age and sex distribution. For each arterial segment, pulsatile changes of diameter were determined by a newly described echotracking technique and pulse pressure was evaluated by applanation tonometry and oscillometric methods. In both territories, distensibility of hypertensive subjects was significantly reduced but compliance was reduced only at the aortic level. Diastolic diameter was increased at the carotid but not at the aortic site. Multiple regression analysis indicated that whereas compliance and distensibility were strongly influenced by BP in the terminal aorta, age was the predominant factor influencing carotid arterial stiffness. Following 30 days of converting enzyme inhibition, the decrease of BP was associated with a normalisation of aortic compliance and distensibility whereas no change was observed at the site of the carotid artery. The study provides evidence that the response of the arteries to the changes of BP differ in the various parts of the arterial tree. This factor may influence the drug effect produced by chronic converting enzyme inhibition.

Adult↗
PubMed1994

[Current status on the treatment of arterial hypertension in the elderly].

Hypertension in the elderly is a frequently encountered problem. When the permanent nature of such hypertension is confirmed, its treatment is justified. All types of drug can be used in the elderly but treatment must be started gradually and on an individual basis. In the majority of cases, one drug only should be sufficient to control hypertension in an elderly individual.

Aged↗
PubMed1993

Vascular and cardiac effects of alpha-methyl-5-HT and DOI are mediated by different 5-HT receptors in the pithed rat.

In pithed rats, alpha-methyl-5-hydroxytryptamine (alpha-methyl-5-HT) increased blood pressure and heart rate, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) almost exclusively increased blood pressure and 1-(3-chlorophenyl)piperazine (mCPP), heart rate. The maximal responses relative to 5-HT indicate that alpha-methyl-5-HT may be a full agonist at vascular and cardiac 5-HT receptors, DOI a partial agonist at both receptors and mCPP a full agonist at cardiac 5-HT receptors but a partial agonist at vascular 5-HT receptors. The alpha 1-adrenoceptor antagonist, 2-[2-[4(o-methoxyphenyl)-piperazine-1-yl]-ethyl]4,4-dimethyl -1,3(2H-4H) isoquinolinedione (AR-C 239), did not change the pressor and tachycardiac effects of alpha-methyl-5-HT and DOI, excluding the participation of alpha 1-adrenoceptors. 4-Isopropyl-7-methyl-9-(2-hydroxy-1-methylpropoxycarbonyl) 4,6,6a,7,8,9,10,10a-octahydroindolo[4,3-fg]quinoline (LY 53857), spiperone and ketanserin but not propranolol antagonised the pressor effect of alpha-methyl-5-HT, indicating a preferential participation of 5-HT2 receptors although an implication of 5-HT1C receptors could not be ruled out. Spiperone, spiperone plus propranolol, LY 53857, ketanserin and propranolol antagonised the pressor effects of DOI suggesting the stimulation of both 5-HT2 and 5-HT1C receptors. Propranolol and spiperone plus propranolol suppressed the weak increase in heart rate induced by DOI, indicating the stimulation of 5-HT1C receptors. However, propranolol and LY 53857 only antagonised the tachycardiac effects of a high dose of alpha-methyl-5-HT. We hypothesised that the pressor and tachycardiac effects of these agonists may be mediated by 5-HT2 and 5-HT1C receptors, respectively. However, the availability of specific 5-HT1C and/or 5-HT2 receptor antagonists is necessary to verify our hypothesis and before a clear-cut conclusion can be drawn.

Adrenergic alpha-Antagonists↗