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Biomedical subjects

G Parati

Publications and source records attributed to G Parati.

At least 199 records · Page 11Linked to original sources
PubMed1985

Doctor-elicited blood pressure rises at the time of sphygmomanometric blood pressure assessment persist over repeated visits.

Blood pressure assessment by a doctor triggers an alerting reaction which may raise patients' blood pressure to a marked degree. Because this may lead to an overestimation of the prevalence of hypertension, it is important to determine whether attenuation of this blood pressure rise occurs with repetition of the doctor's visit. In 16 ambulant inpatients with mild essential hypertension, blood pressure was recorded intra-arterially for 2 days, using the Oxford method. During the recording the patients had four 10-min visits during which blood pressure was repeatedly measured by a sphygmomanometer. The visits to each patient were made by a doctor who had never seen him or her before and were regularly distributed over the total daytime available. In nearly all patients intra-arterial blood pressure and heart rate were elevated throughout the 10 min of each visit, with a peak during the first 4 min and a subsequent decline. The peak mean blood pressure rises were 22.6 +/- 1.8, 20.3 +/- 2.4, 19.3 +/- 2.4 and 21.4 +/- 3.1 mmHg (means +/- s.e.m.) in the four visits. Respective peak heart rate rises were 17.7 +/- 1.7, 20.7 +/- 2.4, 19.8 +/- 2.2 and 17.0 +/- 1.9 beats/min. The reduced pressor and tachycardic responses observed at the 10th min of the visit were also similar in the four visits (blood pressure: 19, 15, 28 and 24% of the peak response; heart rate 21, 13, 24 and 9% of the peak response, respectively). These findings show that the blood pressure rise often accompanying sphygmomanometric blood pressure assessment by the doctor persists after several visits spaced at close time intervals.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Ambulatory blood pressure monitoring does not interfere with the haemodynamic effects of sleep.

Automatic or semi-automatic blood pressure (BP) monitoring is a widely used method for assessing 24-h BP profile. However, the ability to achieve this goal depends on several factors that have not yet been controlled. The present study examined the possibility that cuff inflations disturb the sleep of patients and prevent the nocturnal fall in BP. This issue was investigated in 10 hospitalized subjects in whom BP was recorded intra-arterially for 48 h using the Oxford method. During the first or the second 24 h BP was also monitored non-invasively (Squibb ICR portable device), the cuff inflations being performed at 15 min intervals during the day and at 30 min intervals during the night. The computer analysis of the two different 24-h intra-arterial tracings showed that the addition of automatic BP monitoring had not caused any alteration in the day and night intra-arterial BP and heart rate profiles. Thus, disturbances of the haemodynamic effects of sleep do not characterize 24-h automatic BP recording, at least when made with the device employed in the present study. This removes an important objection against the ability of this approach to evaluate the patients' BP profiles properly.

Adult↗
PubMed1985

Validity and usefulness of non-invasive ambulatory blood pressure monitoring.

In the past few years non-invasive blood pressure monitoring has become increasingly popular in the belief that this approach: can provide accurate mean blood pressure values over a 24-h period or through the day and these values may define better than the casual values the severity of hypertension and its related risk of developing cardiovascular morbidity and mortality. In this paper a number of problems concerning non-invasive ambulatory blood pressure monitoring in hypertension will be reviewed. First, evidence will be shown that blood pressure measurements at intervals up to 30 min can provide a 24-h blood pressure mean similar to that obtained by continuous analysis of the blood pressure tracing, which demonstrates that intermittent readings do not represent a limitation of automatic blood pressure monitoring. Then, it will be shown that the periodical cuff inflations of automatic or semi-automatic blood pressure monitoring may not trigger an alarm reaction or disturb patients' sleep. However, these advantages must be balanced against other still unverified aspects of these new techniques: the inability of intermittent blood pressure readings to evaluate accurately blood pressure variability, which may be a determinant of the overall risk profile, the error inherent in non-invasive measurements of blood pressure and the limited prospective evidence that average 24-h or daytime blood pressure values indeed correlate with the development of target organ damage better than casual blood pressure values do.

Ambulatory Care↗
PubMed1984

Twenty-four-hour blood pressure profile and blood pressure variability in untreated hypertension and during antihypertensive treatment by once-a-day nadolol.

First, blood pressure and heart rate variability was studied in 89 normotensive and hypertensive ambulatory subjects with the use of an intra-arterial monitoring device. Short- and long-term variabilities were analyzed by computer. Absolute variabilities (standard deviations) were greatest in patients with hypertension, but relative variabilities (variation coefficients, i.e., standard deviations as percent of means) were slightly lower in the subjects with more severe hypertension. Second, the effect of nadolol on 24-hour blood pressure and heart rate values and on their variability was assessed in seven ambulatory patients with essential hypertension by means of the same intra-arterial device and computer analysis. Two recording sessions were performed (1) without treatment and (2) after 10 days' administration of nadolol once a day (dose range, 80 to 320 mg). Nadolol, given once a day, was shown to reduce blood pressure uniformly throughout the 24-hour period without loss of activity in the hours farthest from administration. The lack of alteration in relative blood pressure variability suggests that nadolol lowers blood pressure without interfering with the mechanisms involved in cardiovascular homeostasis. Reduction in heart rate variability after nadolol suggests less chance of tachycardia episodes in patients with angina and/or arrhythmias receiving nadolol.

Adrenergic beta-Antagonists↗
PubMed1984

Hemodynamic effects of once a day administration of combined chlorthalidone and metoprolol slow-release in essential hypertension.

The effects of a fixed combination of chlorthalidone (25 mg) and metoprolol slow-release (200 mg) (CM) on 24 hour blood pressure (BP) and heart rate (HR) values and their variabilities were evaluated in 6 ambulant hypertensives by the Oxford method, to obtain continuous intra-arterial recording and by computer to have a beat-to-beat analysis of the data. Compared to pre-treatment values, average 24 hour HR and mean BP recorded after 7-10 days of once daily CM orally administration were reduced by 18.4 +/- 3.1 and 14.7 +/- 3.0%, respectively. The effects of CM were also evident during isometric and dynamic exercise, whose pressor and tachycardic responses were left unimpaired (BP) or were only slightly reduced (HR) by CM. The long- and short-term BP and HR variabilities (calculated as variation coefficients among and within half hours, and within minutes) were also left unaffected by CM. These findings indicate that once a day administration of CM effectively reduces BP and HR over the 24 hours, without interfering with cardiovascular homeostasis. The effective and persistent reduction in both these variables (as well as their occurrence during exercise) suggests that the antihypertensive action of this treatment is accompanied by a clear-cut reduction in cardiac work.

Administration, Oral↗
PubMed1983

Effects of blood-pressure measurement by the doctor on patient's blood pressure and heart rate.

Changes in blood pressure in 10 or 15 min periods during which a doctor repeatedly measured blood pressure by the cuff method were monitored by a continuous intra-arterial recorder. In almost all the 48 normotensive and hypertensive subjects tested the doctor's arrival at the bedside induced immediate rises in systolic and diastolic blood pressures peaking within 1 to 4 min (mean 26.7 +/- 2.3 mm Hg and 14.9 +/- 1.6 mm Hg above pre-visit values). There were large differences between individuals in the peak response (range, 4--75 mm Hg systolic and 1--36 mm Hg diastolic) unrelated to age, sex, baseline blood pressure, or blood-pressure variability. There was concomitant tachycardia (average peak response 15.9 +/- 1.5 beats/min, range 4--45 beats/min) which was only slightly correlated with the blood-pressure rise. After the peak response blood pressure declined and at the end of the visit was only slightly above the pre-visit level. A second visit by the same doctor did not change the average size of the early pressor response or the slope of its subsequent decline.

Adolescent↗
PubMed1983

Plasma catecholamines do not invariably reflect sympathetically induced changes in blood pressure in man.

Plasma concentrations of noradrenaline and adrenaline were measured radioenzymatically in nine subjects during 4 min pressor and depressor responses (intra-arterial measurements) induced by increasing and reducing sympathetic vasoconstrictor tone via carotid baroreceptor deactivation and stimulation (neck chamber technique). During the pressor response (15 +/- 3 mmHg, mean +/- SE) plasma noradrenaline and adrenaline showed various changes in the different subjects and on average were not significantly increased above control. During the depressor response (-9 +/- 2 mmHg) plasma noradrenaline and adrenaline also showed various changes in the subjects and were on average not significantly reduced below control. In contrast the same subjects all showed an increase in noradrenaline and adrenaline (average 76 and 117%) at the fourth minute of a tilting manoeuvre with a return to pretilting values no more than 4 min after resumption of the supine position. These results suggest that the moderate and/or restricted alterations in sympathetic tone produced by manipulating a single baroreflex, though capable of affecting blood pressure, are not reflected by alterations in plasma catecholamines. To modify these humoral indices significantly, the more drastic or more diffuse alterations in sympathetic activity that may be produced by manipulating low as well as high pressure reflexogenic areas are needed.

Adult↗
PubMed1983

Mechanisms of antihypertensive action of beta-adrenergic blocking drugs: evidence against potentiation of baroreflexes.

A possibility that can be advanced to explain the antihypertensive effect of beta-blocking drugs is that they act through the baroreflex control of the cardiovascular system. In 38 essential hypertensive patients we measured 1) The lengthening and shortening in R-R interval caused by stimulation or deactivation of arterial baroreceptors (vasoactive drug technique); 2) The fall and rise in blood pressure caused by stimulation and deactivation of carotid baroreceptors (neck chamber); 3) The rise in forearm vascular resistance caused by deactivation of cardiopulmonary receptors (lower body suction). The study was made before and after 6-10 days' administration of nadolol (80-360 mg once a day) or acebutolol (200-600 mg t.i.d.). Nadolol and acebutolol similarly reduced blood pressure and heart rate. Either drug increased heart rate responses to arterial baroreceptor manipulation but the increase fell short of statistical significance. Blood pressure and vasomotor responses to carotid baroreceptor and cardiopulmonary receptor manipulation were also not significantly modified by beta blockade. The baroreceptor control of heart rate and blood pressure showed a modification, however, insofar as a resetting towards the lower blood pressure values occurred. These findings demonstrate that arterial baroreceptor and cardiopulmonary receptor control of circulation is not potentiated by beta-blocking drugs, and that therefore this mechanism cannot account for their antihypertensive effect. The resetting of the baroreflex that occurs during beta blockade may, however, contribute to maintain the hypotension obtained.

Adrenergic beta-Antagonists↗
PubMed1983

Reproducibility of laboratory tests evaluating neural cardiovascular regulation in man.

In 31 normotensive and hypertensive subjects with continuous intra-arterial blood pressure (BP) and heart rate (HR) monitoring, we examined the short term reproducibility of the haemodynamic responses to a number of tests commonly employed in studies on neural cardiovascular regulation: (1) hand-grip exercise and cold pressor tests that increase BP and HR through central and reflex mechanisms; (2) bolus injections of phenylephrine and trinitroglycerine that reflexly reduce and increase HR through stimulation and inhibition of arterial baroreceptors; (3) negative and positive pressure alterations within a neck chamber that reflexly reduce and increase BP through stimulation and inhibition of carotid baroreceptors. Each test was standardized and repeated at 30 min intervals six times in each subject. In the group as a whole the BP and HR responses to hand-grip showed a variability (mean variation coefficient, VC) of 22 and 25% respectively. BP and HR responses to cold pressor test showed a VC of 17 and 44% and HR responses to trinitroglycerine showed a VC of 28%. HR responses to phenylephrine were slightly less (19%) and BP responses to neck chamber considerably less variable (14 and 10%). The variability of the responses was not related to basal BP or HR or to the time sequence of the tests. Thus, tests commonly employed for studying neural cardiovascular control in man have a limited short-term reproducibility. This implies that caution should be used in interpreting results obtained by a single performance of any given test, and in comparing results in different states or groups such as normotensive and hypertensive subjects, unless a relatively large number of responses is available.

Adult↗
PubMed1982

Modification of arterial baroreflexes by captopril in essential hypertension.

Captopril lowers blood pressure without increasing heart rate and plasma norepinephrine, which suggests that this drug may potentiate arterial baroreflexes. In eight subjects with untreated essential hypertension, blood pressure was monitored intraarterially and the effects of baroreceptor stimulation or deactivation were assessed by measuring (1) the slopes of the relations between increase or reduction in systolic pressure (intravenous phenylephrine or nitroglycerin) and the resulting lengthening or shortening in R-R interval, and (2) the increase or decrease in mean arterial pressure induced by increasing and decreasing carotid transmural pressure (neck chamber). The measurements were made before and after a hypotensive oral dose of captopril (50 mg). Before captopril, the slopes of the R-R interval changes with increase and reduction in systolic pressure were 8 and 4 ms/mm Hg, respectively. The slopes of the mean arterial pressure changes with increase and reduction in carotid transmural pressure were 0.51 and 0.40 mm Hg, respectively. After captopril, the responses to baroreceptor stimulation were unaltered but those to baroreceptor deactivation were augmented. The pressor and heart rate responses to hand-grip and cold exposure were unchanged by captopril. Administration of captopril is accompanied by a baroreflex potentiation which involves the lower portion of the stimulus-response curve of the reflex. This phenomenon (which may originate at the afferent baroreceptor fibers or centrally) may avoid a reduction in the tonic baroreflex influence during captopril-induced hypotension, thus contributing to the hemodynamic effects of the drug.

Adult↗
PubMed1982

Blood pressure response to labetalol in twice and three times daily administration during a 24-hour period.

1 The anti-hypertensive effect of labetalol given twice or three times daily was evaluated in ambulant subjects with essential hypertension by recording blood pressure directly for 24 h before and after 15 d of labetalol administration (daily dose 600-1800 mg). 2 Labetalol reduced 24 h systolic and diastolic blood pressures by about 20%. The reduction was evident throughout the whole 24 h period, although it was less marked during sleep. The hypotensive effect was similar when the drug was given twice or three times daily. 3 The 24 h heart rate was reduced during labetalol treatment. However, this effect was less marked than the hypotensive effect and was not present in all subjects. 4 There was a reduction in the standard deviations of blood pressure and heart rate values. However, in neither case was the coefficient of variation altered, indicating that labetalol did not have any significant effect on the shape of the 24 h blood pressure measurements.

Adult↗
PubMed1981

Carotid sinus reflex control of renin release in hypertensive subjects with high renin secretion.

1. Carotid baroreceptor manipulation (neck-chamber technique) and passive head-up tilting were used in ten patients with renovascular hypertension and in five subjects with essential hypertension under diuretic treatment to study reflex control of renin secretion at high basal-renin production rates. 2. Reflex effects of carotid baroreceptor manipulation on renin secretion were only minor. During baroreceptor deactivation there was a moderate increase in mean arterial pressure, but an inconsistent change in the renal venous--arterial difference in plasma renin activity (PRA). 3. During baroreceptor stimulation there was a modest fall in mean arterial pressure and a marked rise in the renal venous--arterial difference in PRA. This was opposite to the fall which might have been predicted as a result of the sympathetic depressor influence of the baroreceptor stimulus. Conversely, tilting increased the venous--arterial PRA difference by about 200%. 4. It is concluded that when renin production rate is high carotid baroreceptors exert little control over renin release, just as when renin production is low. Reflex control of renin, however, is very active in subjects with a high renin production, probably due to receptors in the cardiopulmonary region.

Adult↗
PubMed1980

Blood pressure variability in man: its relation to high blood pressure, age and baroreflex sensitivity.

1. Intra-arterial blood pressure and heart rate were recorded for 24 h in ambulant hospitalized patients of variable age who had normal blood pressure or essential hypertension. Mean 24 h values, standard deviations and variation coefficient were obtained as the averages of values separately analysed for 48 consecutive half-hour periods. 2. In older subjects standard deviation and variation coefficient for mean arterial pressure were greater than in younger subjects with similar pressure values, whereas standard deviation and variation coefficient for mean arterial pressure were greater than in younger subjects with similar pressure values, whereas standard deviation aations and variation coefficient were obtained as the averages of values separately analysed for 48 consecurive half-hour periods. 2. In older subjects standard deviation and variation coefficient for mean arterial pressure were greater than in younger subjects with similar pressure values, whereas standard deviation and variation coefficient for heart rate were smaller. 3. In hypertensive subjects standard deviation for mean arterial pressure was greater than in normotensive subjects of similar ages, but this was not the case for variation coefficient, which was slightly smaller in the former than in the latter group. Normotensive and hypertensive subjects showed no difference in standard deviation and variation coefficient for heart rate. 4. In both normotensive and hypertensive subjects standard deviation and even more so variation coefficient were slightly or not related to arterial baroreflex sensitivity as measured by various methods (phenylephrine, neck suction etc.). 5. It is concluded that blood pressure variability increases and heart rate variability decreases with age, but that changes in variability are not so obvious in hypertension. Also, differences in variability among subjects are only marginally explained by differences in baroreflex function.

Adult↗