Biomedical subjects

A Groppelli

Publications and source records attributed to A Groppelli.

25 records · Page 2Linked to original sources

PubMed1988

Evaluation of the baroreceptor-heart rate reflex by 24-hour intra-arterial blood pressure monitoring in humans.

The baroreceptor control of the sinus node was evaluated in 10 normotensive and 10 age-matched essential hypertensive subjects in whom ambulatory blood pressure was recorded intra-arterially for 24 hours and scanned by a computer to identify the sequences of three or more consecutive beats in which systolic blood pressure (SBP) and pulse interval (PI) progressively rose (+PI/+SBP) or fell (-PI/-SBP) in a linear fashion, according to a method validated in cats. In normotensive subjects, several hundred +PI/+SBP and -PI/-SBP sequences of 3 beats were found whereas the number of sequences of 4, 5, and more than 5 beats showed a progressive drastic reduction. The mean slopes of +PI/+SBP (7.6 +/- 2.0 msec/mm Hg) and -PI/-SBP (6.4 +/- 1.5 msec/mm Hg) sequences were similar, but in both instances there was a large scattering of the values around the mean (variation coefficients: 64.2 +/- 4.7 and 62.6 +/- 2.4%). The slopes decreased as a function of the sequence length and baseline heart rate and increased to a marked extent during the night as compared with daytime values. All sequences were more rare (-33.2% for +PI/+SBP and -31.7% for -PI/-SBP) and less steep in hypertensive subjects (-40.3 and -36.2%, respectively), who failed to show the marked nighttime increase in slope observed in normotensive subjects. To our knowledge, these observations provide the first description in humans of the baroreceptor-heart rate reflex in daily life. This reflex is characterized by marked within-subject variations in sensitivity due in part to hemodynamic, temporal, and behavioral factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Neural control of circulation before and after intravenous urapidil in essential hypertension.

Drugs interfering with sympathetic influences on the cardiovascular system have been shown to effectively lower blood pressure in hypertension. However, sympathetic cardiovascular control is involved in blood pressure homeostasis, which means that these drugs may produce potential adverse haemodynamic effects that may reduce the benefit of their antihypertensive action. This paper summarises the results of a study in which we examined the effects of urapidil on the arterial baroreflex and the cardiopulmonary reflex in 6 essential hypertensive patients given 25 mg of the drug intravenously. The dose of the drug used caused a marked reduction in arterial blood pressure (direct measurement). However, pressor and depressor responses to carotid baroreceptor deactivation and stimulation (neck chamber device), respectively, were not modified when compared with those observed in the placebo period. This was also the case for increases and reductions in both forearm vascular resistance and plasma noradrenaline (norepinephrine) concentrations induced by deactivating and stimulating cardiopulmonary receptors, respectively. The pressor and tachycardic responses to handgrip and cold exposure were also unaffected by the drug. It is concluded that when administered at a clinically effective dose urapidil does not adversely affect major reflex mechanisms involved in neural cardiovascular regulation. This has favourable implications for the use of the drug in clinical practice.

Antihypertensive Agents↗

PubMed1988

24-hour blood pressure monitoring: evaluation of Spacelabs 5300 monitor by comparison with intra-arterial blood pressure recording in ambulant subjects.

The accuracy of 24-h blood pressure values obtained by ambulatory monitoring via the Spacelabs 5300 device was evaluated by comparison with simultaneous 24-h intra-arterial blood pressure recording from the contralateral arm. The comparison was made in eight essential hypertensive subjects in whom non-invasive blood pressure was measured every 15 (day) or 30 min (night). The measurements were automatically and visually edited to eliminate artefactual readings and hourly and 24-h means were calculated separately for systolic and diastolic blood pressure. The corresponding intra-arterial blood pressure means were also calculated. In the group as a whole, hourly means obtained by the non-invasive device were similar or only slightly different from those recorded intra-arterially. The 24-h systolic blood pressure mean obtained non-invasively was not significantly different from that obtained intra-arterially (138.4 +/- 9.1 and 142.9 +/- 9.2 mmHg, respectively), nor were the corresponding 24-h diastolic blood pressure means significantly different (83.5 +/- 4.5 and 80.6 +/- 3.5 mmHg, respectively). However, in spite of these similarities, there were contrasting and often large discrepancies between non-invasive and intra-arterial values in individual subjects. For the 24-h systolic blood pressure mean the discrepancies ranged from 7.6 +/- 1.1 to 16.1 +/- 2.2 mmHg and for the 24-h diastolic blood pressure mean, from 3.5 to 13.2 mmHg. Thus, the Spacelabs 5300 device has a limited ability to correctly estimate ambulatory blood pressure in individual subjects. It may be better suited for the estimation of group blood pressures, but only because errors are smoothed by the summation of individual errors of opposing signs.

Adult↗

PubMed1987

Role of heart rate variability in the production of blood pressure variability in man.

In both normotensive and hypertensive subjects blood pressure (BP) and heart rate (HR) show concordant changes over 24 h. This may depend on a central factor exerting influences of the same nature on cardiac and vascular targets. An alternative explanation, however, is that a cause-effect relationship links these variabilities, i.e. that HR variations induce BP changes [presumably via variations in cardiac output (CO)]. Blood pressure was recorded intra-arterially in five supine and five exercising (walking) essential hypertensive subjects during a control period of 1 h and during an additional hour in which atropine, 0.04 mg/kg body weight, was injected intravenously (i.v.). The same recordings were performed in seven other subjects, in which saline rather than atropine was employed. One-hour BP and HR variabilities (variation coefficients, VC) were computer analysed. In both the supine and the exercising subjects atropine caused a marked reduction in HR VC (-65.3 and -48.4%, respectively). In the supine subjects this reduction was accompanied by only a modest reduction in BP VC whereas in the exercising subjects the BP VC increased by 30.4%. In the seven subjects in which saline was injected no change in BP and HR VC occurred. Thus a marked reduction in HR variability is not accompanied by a comparable attenuation in BP variability, which rules out a cause-effect link between these two phenomena. Indeed, during physical exercise HR stabilization is followed by an increase rather than a reduction in BP variation, which supports the conclusion that under some circumstances HR plays an anti-oscillatory role.

Activity Cycles↗

PubMed1987

Calcium antagonists and neural control of circulation in essential hypertension.

Data from animals and from man suggest that calcium antagonists interfere with alpha-adrenergic receptors and that this mechanism may be responsible for some of the vasodilation induced by these drugs. However, alpha-adrenergic receptors play a primary role in baroreceptor regulation of the cardiovascular system and blood pressure homeostasis, which might therefore be adversely affected by calcium antagonist treatment. We addressed this question in 14 essential hypertensives studied before treatment, 1 h after 20 mg oral nitrendipine and 5-7 days after daily administration of 20 mg oral nitrendipine. Blood pressure was measured by an intra-arterial catheter, heart rate by an electrocardiogram, cardiac output by thermodilution and forearm blood flow by venous occlusion plethysmography. Total peripheral and forearm vascular resistances were calculated by dividing mean blood pressure by blood flow values. Plasma norepinephrine was also measured (high performance liquid chromatography) in blood taken from the right atrium. Compared with the pretreatment values, acute nitrendipine administration caused a fall in resting blood pressure, an increase in the resting heart rate and cardiac output, and a fall in resting peripheral and forearm vascular resistance. The resting hypotension and vasodilation were also evident during the prolonged nitrendipine administration, which was, however, accompanied by much less resting cardiac stimulation than that observed in the acute condition. Baroreceptor control of the heart rate (vasoactive drug method) was similar before and after acute and prolonged nitrendipine treatment. This was also the case for carotid baroreceptor control of blood pressure (neck chamber technique) and for control of forearm vascular resistance as exerted by receptors in the cardiopulmonary region (lower-body negative-pressure and passive leg-raising techniques).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Evaluation of the antihypertensive effect of TTS clonidine by multiple 24-hour automatic blood pressure monitoring.

Transdermal clonidine (TTSC) has been proposed as a means to improve compliance to treatment of hypertensive patients because of the reported 7-day duration of its antihypertensive effect. However, no detailed information is available on the onset, the time course, and the day and night distribution of this effect throughout the 7 days of the drug skin application. In 12 hospital in-patients with mild or moderate untreated essential hypertension, 24-h blood pressure (BP) was measured at 10-20 min intervals via a noninvasive automatic device (Spacelabs 5300 M) in a no-drug condition, on the 2nd, 4th, and 7th day of the arm application of a 7.0 or 10.5 cm2 patch of TTS clonidine, and on the 2nd and 4th day after substitution of the TTS clonidine patch with an identical patch containing an inert substance (placebo). In nine out of 12 patients, TTS clonidine reduced 24-h systolic and diastolic blood pressure at the 2nd day and even more so on the 4th and 7th day of its application. The reduced blood pressure values observed on the 7th day increased progressively on the 2nd and 4th day after TTS clonidine removal with no rebound over the pre-drug values. The hypotensive effects observed during TTS clonidine were evident throughout the day and night. Thus TTS clonidine exerts a hypotensive effect that starts early and is maintained throughout the 7 days and nights of its application. The discontinuation of this treatment is associated with a smooth return of blood pressure values towards the pre-treatment levels.

Administration, Cutaneous↗

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↗