Erythropoietin and fibrinolysis effects on platelet activity.
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Blood Platelets↗
Biomedical subjects
J Mehlsen
Publications and source records attributed to J Mehlsen.
Differential effects of beta-adrenoceptor partial agonists in patients with postural hypotension.
The central haemodynamic effects of pindolol and xamoterol have been investigated in patients with postural hypotension. Pindolol is a non-selective beta-adrenoceptor partial agonist, whereas xamoterol is beta 1-selective and possesses a higher degree of agonist activity. The study comprised 16 patients with postural hypotension of different aetiologies. Blood pressure, heart rate and stroke volume were measured in the supine and head-up tilted positions. Left ventricular ejection fraction (LVEF) was measured in the supine position, and vascular resistance, left ventricular volume, and left ventricular contractility were derived. Pindolol and xamoterol were administered intravenously in incremental doses to reach total doses of 0.02 and 0.20 mg.kg-1, respectively. Pindolol showed beta-adrenoceptor antagonistic effects in the supine position through decrements in heart rate from 70 to 66 beats.min-1 and LVEF from 0.57 to 0.52, and reduced mean arterial blood pressure from 103 mm Hg to 93 mm Hg. Xamoterol showed beta-adrenoceptor agonistic effects in the supine position through increments in heart rate from 72 to 90 beats.min-1 and LVEF from 0.58 to 0.66, and raised mean arterial blood pressure from 108 to 123 mm Hg. It is concluded that the degree of agonist activity of a beta-adrenergic agent is of importance if it is given to a patient with postural hypotension.
Adult↗
Twitch interpolation technique in testing of maximal muscle strength: influence of potentiation, force level, stimulus intensity and preload.
The aim was to study the methodological aspects of the muscle twitch interpolation technique in estimating the maximal force of contraction in the quadriceps muscle utilizing commercial muscle testing equipment. Six healthy subjects participated in seven sets of experiments testing the effects on twitch size of potentiation, time lag after potentiation, magnitude of voluntary force, stimulus amplitude, stimulus duration, angle of the knee, and angle of the hip. In addition, the consequences of submaximal potentiation on the estimation of maximal force from twitch sizes were studied in five healthy subjects. We found an increase in twitch size with increasing levels of potentiation and twitch size decreased exponentially following potentiation. We found a curvilinear relationship between twitch size and voluntary force, and these properties were more obvious when the stimulation intensity of the preload was reduced. The relationship between twitch size and force was only linear, for force levels greater than 25% of maximum. It was concluded that to achieve an accurate estimate of true maximal force of muscle contraction, it would be necessary for the subject to be able to perform at least 75% of the true maximal force.
Adult↗
Beneficial effect of isradipine on the development of left ventricular hypertrophy in mild hypertension.
The objective of this study was to analyze the long-term hemodynamic effects of the calcium antagonist isradipine in mild hypertension compared with those of the beta 1-selective adrenoceptor antagonist atenolol, focusing in particular on the development of cardiac hypertrophy. Ten male patients with mild essential hypertension were entered into a double-blind crossover study. Examinations were carried out after 2 weeks of placebo run-in, and after 6 and 12 months of active treatment. Mean resting blood pressure was reduced from 115 +/- 12 mm Hg to 106 +/- 12 mm Hg with atenolol, and to 107 +/- 8 mm Hg with isradipine. The increase in the product of heart rate times blood pressure was significantly greater during isradipine treatment, as was the maximum exercise capacity. Left ventricular mass was increased from 228 +/- 36 g to 305 +/- 68 g with atenolol whereas it remained unchanged with isradipine (254 +/- 55 g). The results indicate that antihypertensive treatment with isradipine as monotherapy may prevent the development of left ventricular hypertrophy whereas treatment with atenolol as monotherapy does not appear to offer this possibility.
Aged↗
Beneficial effects of intermittent suction and pressure treatment in intermittent claudication.
The present study reports on the effects of a physical treatment modality in patients with intermittent claudication. During this treatment a major part of the skin surface is subjected to intermittent suction and pressure. In a previous, preliminary study the authors found a beneficial effect of this treatment in intermittent claudication. The study included 34 patients with moderate, stable intermittent claudication. Twenty-two patients participated in a double-blinded, randomized trial comparing the effects of 25 treatments to 25 placebo applications given over a period of two months. Twelve patients participated in an open trial investigating the possible effects of the treatment on platelet aggregation and fibrinolysis. Pain-free and maximal walking distances were measured on a treadmill, and systolic blood pressure was measured on the upper limb, the ankle, and the first toe bilaterally. The threshold for adenosine diphosphate (ADP)-induced platelet aggregation was tested, and the fibrinolytic activity was estimated from the euglobulin clot lysis time. Active treatment resulted in significant improvements in pain-free and maximal walking distances, whereas no changes could be found during placebo administration. The treatment caused significant increments in the ADP thresholds for platelet aggregation, while the effects on fibrinolysis were uncertain. It is concluded that intermittent suction and pressure treatment offers a new approach for conservative treatment of intermittent claudication.
Aged↗
A botanical compound, Padma 28, increases walking distance in stable intermittent claudication.
Thirty-six patients with a median age of sixty-seven years and a median duration of intermittent claudication of five years were randomized to either active treatment with Padma 28 or placebo. The effect of treatment was quantified by measurements of systemic and peripheral systolic blood pressures and by measurements of the pain-free and the maximal walking distance on a treadmill. The ankle pressure index (ankle systolic pressure/arm systolic pressure) was calculated. The group randomized to active treatment received two tablets bid containing 340 mg of a dried herbal mixture composed according to an ancient lamaistic preparation (Padma 28). After active treatments, administered over a period of four months in a double-blinded, randomized design, the patients allocated to this group attained a significant increase in the pain-free walking distance from 52 m (20-106) to 86 m (24-164; P < 0.05) and in the maximal walking distance from 115 m (72-218) to 227 m (73- > 1,000; P < 0.05). The patient-group receiving placebo treatments did not show any significant changes in either the painfree or the maximal walking distance. The authors could not demonstrate any significant changes in the ankle pressure index either during active or during placebo treatment. In conclusion, this study has shown that treatment with Padma 28 over a period of four months significantly increased the walking distance in patients with stable, intermittent claudication of long duration.
Aged↗
Xamoterol in severe congestive heart failure: long-term oral treatment, a double-blind randomised study.
Twelve patients in severe congestive heart failure were given placebo, 100 mg xamoterol (Corwin) twice daily and 200 mg xamoterol twice daily, respectively, in 3 two-week periods in a double-blind randomised study. At the end of each treatment period the patients were evaluated. No differences were found between placebo and xamoterol in the following parameters: New York Heart Association function group index, heart volume, body weight, exercise duration on bicycle and treadmill, heart rate and systolic and diastolic blood pressure at rest. However, during exercise we found significantly lower heart rate and rate-pressure product during xamoterol treatment. This reduction is probably indicating occupation of beta-adrenoreceptors with concomitant reduced oxygen consumption during exercise.
Administration, Oral↗
Effects of vacusac in intermittent claudication: a controlled cross-over study.
The effect of a new physical treatment modality, Vacusac, was tested on a group of patients with stable intermittent claudication. Twenty-two patients with a median age of 65 years and a median duration of intermittent claudication of 5 years were randomized to either active or placebo treatments. Seventeen patients completed the study. The effect of treatment was quantified by measurements of systemic and peripheral systolic blood pressures and by measurements of the pain-free and the maximal walking distance on a treadmill. The ankle pressure index (ankle systolic pressure/arm systolic pressure) and toe pressure index (toe systolic pressure/arm systolic pressure) were calculated. After 25 active treatments, administered over a period of 2 months, the patients allocated to this group attained a significant increase in the pain-free walking distance from 54 m (24-107 m) to 99 m (30-420 m) (P less than 0.05) and in the maximal walking distance from 99 m (36-182 m) to 185 m (68-591 m) (P less than 0.05). The patient group receiving 25 placebo treatments did not show any significant changes in either the pain-free or the maximal walking distance. This group then received 25 active treatments over a period of 2 months. This active treatment resulted in a significant increase in the pain-free walking distance from 51 m (14-100 m) to 86 m (18-1000 m) (P less than 0.05) and in the maximal walking distance from 98 m (40-199 m) to 175 m (51-1000 m) (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
Reliability of impedance cardiography in measuring central haemodynamics.
The purpose of the study described here was to investigate the reliability of impedance cardiography (IC) in measuring cardiac output (CO) and central blood volume. Absolute values and changes in these variables obtained by impedance cardiography and by isotope- or thermodilution techniques were compared. The reproducibility of IC within the same day was compared with that of isotope dilution and the reproducibility in IC from day to day was derived. Finally, the effects of the readings of impedance tracings by different observers were quantified. The results are based on 270 measurements in 37 healthy subjects and in 25 unmedicated patients with ischaemic heart disease. We obtained significant correlations between absolute values (y = 0.68x + 1.48) and changes (y = 1.00x + 0.0003) in CO measured by IC and isotope- or thermodilution. IC significantly overestimated absolute values of CO (P less than 0.001). We found a qualitative but no quantitative correlation between thoracic fluid volume measured by IC and central blood volume measured by isotope dilution. IC was highly reproducible both when studies were repeated within the same day (SD on differences in CO = 0.36 1 min-1 for IC; SD on differences in CO = 0.30 1 min-1 for isotope dilution) and on different days (SD on differences in CO = 0.45 1 min-1). A low intra-observer variability was found (SD on differences in CO = 0.12 1 min-1). We conclude that impedance cardiography is reliable in measuring changes in cardiac output and thus suitable for repeated measurements in studies on the haemodynamic effects of physiological or pharmacological intervention. Impedance cardiography is sufficiently reliable for comparison of absolute values of CO between different groups of patients. We cannot recommend impedance cardiography for quantitative studies of central blood volume.
Blood Volume↗
Central haemodynamics in patients with severe postural hypotension.
Central haemodynamics in the supine and head-up tilted positions were studied in 24 patients with severe postural hypotension with and without supine hypertension. Results were compared with those obtained in eight normotensive and eight untreated hypertensive controls. In the supine position the patients had higher vascular resistances, lower stroke volumes and longer left ventricular ejection time indexes compared to controls, whereas left ventricular ejection fractions did not differ significantly. The patients with supine hypertension had significantly higher vascular resistance compared to those with supine normotension. The highest supine blood pressure levels were found in patients with multiple system atrophy. During tilt, vascular resistance and heart rates were increased and stroke volumes and left ventricular ejection time indexes were decreased in the controls. The patients were unable to increase their vascular resistance, but increased their heart rate and decreased their left ventricular ejection time indexes to a degree similar to the controls. The reductions in stroke volume were smaller in the patients compared to the controls. Changes in haemodynamics in response to head-up tilting did not differ significantly between patients with supine hypertension and supine normotension. It is concluded that patients with postural hypotension have higher supine vascular resistance and are unable to contract peripheral arteries and arterioles during head-up tilting. Contractility of the left ventricle is preserved and the baroreceptors are partially intact. Postural hypotensive patients with supine hypertension differ from those with supine normotension only with respect to supine vascular resistances.
Adult↗
Haemodynamics in postural hypotension--effects of the beta-adrenoceptor partial agonist xamoterol, and pindolol.
Beta-andrenoceptor agents have been used in the treatment of postural hypotension and agonist activity found to be important. The effects of xamoterol and pindolol on standing haemodynamics were compared in this study. Xamoterol was found to be of significant benefit, but pindolol was ineffective. Xamoterol may therefore be useful in the treatment of postural hypotension.
Adrenergic beta-Agonists↗
Influence of the renin-angiotensin system on human forearm blood flow.
Although angiotensin II is a potent vasoconstrictor agent in all tissues, including the human forearm, equivocal effects on forearm blood flow (FBF) have been found after angiotensin blockade. In 13 healthy Na(+)-depleted subjects FBF was measured by the 133Xe washout technique; subcutaneous and muscle blood flows were determined separately. FBF was measured during supine rest, after the arm was lowered, and during lower body negative pressure (LBNP). The measurements were repeated during intra-arterial saralasin infusion in six subjects and after intravenous administration of enalapril in seven subjects. FBF decreased and forearm vascular resistance (FVR) increased during arm lowering and LBNP, as the result of local and central adrenergic reflexes, respectively. We observed similar FBF and FVR values after both saralasin and enalapril, except for a decrease in FVR at rest after enalapril. It is concluded that, in the human forearm, angiotensin II is not necessary for sympathetic vasoconstrictor reflexes but may, through a central effect, have some influence on arteriolar tone at rest.
Adult↗
A comparison of systolic time intervals measured by impedance cardiography and carotid pulse tracing.
The purpose of this study was to compare the systolic time intervals (STI) obtained by impedance cardiography and by the conventional carotid technique. This comparison was done with respect to: 1) correlations between variables obtained by the two methods, 2) ability to reflect drug-induced changes, 3) reliability in terms of reproducibility and 4) heart rate dependency of the variables measured. The study included 25 unmedicated patients with ischaemic heart disease and 36 healthy subjects. We obtained significant correlations between STI-variables measured by the two methods (p less than 0.001) and found that left ventricular ejection times were longer when determined by the carotid technique (p less than 0.01). We found a significant correlation between drug-induced changes in STI-variables measured by the two methods (p less than 0.001). Both methods had a high degree of reproducibility and this parameter was significantly better within the same day, when impedance cardiography was used (p less than 0.01). The error due to the reading of STI-tracings obtained by impedance cardiography was very small when performed by the same observer. We found the pre-ejection period to be independent upon heart rate, while the left ventricular ejection time depended upon this parameter. We conclude that impedance cardiography and carotid technique differ with respect to the measurement of left ventricular ejection times, but not with respect to the measurement of other STI-variables. We furthermore conclude that both methods are reliable, but we recommend the use of impedance cardiography because it is easier to apply, it may be more precise and it can be used for simultaneous measurements of other haemodynamic variables.
Cardiac Output↗
Effects of angiotensin blockade on the splanchnic circulation in normotensive humans.
The effects of angiotensin-converting enzyme inhibition (ACE-I) by enalapril on splanchnic (n = 10) and central hemodynamics (n = 9) were examined in moderately salt-depleted healthy volunteers, at rest and during 15-20 min of lower body negative pressure (LBNP), reducing mean arterial pressure by 10 mmHg. During LBNP before ACE-I, both splanchnic and total peripheral vascular resistances increased. During ACE-I, splanchnic and total peripheral vascular resistances decreased. After enalapril administration, splanchnic vascular resistance did not increase during LBNP. Total peripheral vascular resistance still increased but not to the same extent as during LBNP before ACE-I. The increases in heart rate and plasma norepinephrine during LBNP were attenuated after ACE-I compared with LBNP before ACE-I. The effectiveness of the ACE-I was clearly demonstrated by unchanged and low plasma angiotensin II levels during ACE-I. We conclude that, in normal sodium-depleted humans, acute ACE-I decreases splanchnic vascular resistance at rest and abolishes splanchnic vasoconstriction during LBNP. Furthermore, it may interfere with autonomic nervous system control of the circulation.
Adult↗
Altered balance in the autonomic nervous system in schizophrenic patients.
The aim of the present study was to evaluate the autonomic nervous function in schizophrenic patients. Twenty-eight patients (29 +/- 6 years) diagnosed as schizophrenics and in stable medication were included, together with ten schizophrenic patients (25 +/- 5 years) who were unmedicated. Eleven healthy subjects (32 +/- 7 years) served as controls. Immediate heart-rate responses to a single deep inspiration was used as a measure of parasympathetic function. Heart-rate response to standing was used as a measure of sympathetic function. Supine blood pressure, heart-rate and orthostatic changes in blood pressure did not differ between groups. Heart-rate response to standing was greater in both medicated and non-medicated schizophrenics compared to normal subjects (P less than 0.01). Heart-rate response to standing was greater in non-medicated compared to medicated schizophrenics (P less than 0.05). Heart-rate response to inspiration was greater in non-medicated schizophrenics compared to normal subjects (P less than 0.05), whereas no difference was found between medicated and non-medicated schizophrenics. The results show that the balance in the autonomic nervous system is altered in schizophrenic patients with a hyperexcitability in both the sympathetic and the parasympathetic division. Our study has thus indicated a dysfunction in the autonomic nervous system per se and the previous interpretations of attentional orienting responses in schizophrenia is questioned. Medication with neuroleptics seems to partly normalize the autonomic reactivity rather than being the cause of autonomic dysfunction.
Adult↗
Increase in vagal activity during hypotensive lower-body negative pressure in humans.
Progressive central hypovolemia is characterized by a normotensive, tachycardic stage followed by a reversible, hypotensive stage with slowing of the heart rate (HR). We investigated circulatory changes and arterial hormone concentrations in response to lower-body negative pressure (LBNP) in six volunteers before and after atropine administration. LBNP of 55 mmHg initially resulted in an increase in HR from 55 +/- 4 to 90 +/- 5 beats/min and decreases in mean arterial pressure (MAP) from 94 +/- 4 to 81 +/- 5 mmHg, in central venous pressure from 7 +/- 1 to -3 +/- 1 mmHg, and in cardiac output from 6.1 +/- 0.5 to 3.7 +/- 0.11/min. Concomitantly, epinephrine and norepinephrine levels increased. After 8.2 +/- 2.3 min of LBNP, the MAP had decreased to 41 +/- 7 mmHg and HR had decreased to 57 +/- 3 beats/min. Vasopressin increased from 1.2 +/- 0.3 to 137 +/- 45 pg/ml and renin activity increased from 1.45 +/- 4.0 to 3.80 +/- 1.0 ng.ml-1.h-1 with no further changes in epinephrine, norepinephrine, and vasoactive intestinal polypeptide. A tardy rise in pancreatic polypeptide indicated increased vagal activity. After atropine. LBNP also caused an initial increase in HR, which, however, remained elevated during the subsequent decrease in MAP to 45 +/- 6 mmHg occurring after 8.1 +/- 2.4 min.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
[The effect of natural medicine and vacuum therapy (Vacusac) in patients with stable intermittent claudication].
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Aged↗
Immediate haemodynamic effects of a novel partial agonist, beta 1-adrenoceptor blocking drug ICI 141,292 after intravenous administration to healthy young volunteers and patients with ischaemic heart disease.
ICI 141,292 is a new beta 1-adrenoceptor blocking drug. The beta 1-adrenoceptor antagonistic effect of ICI 141,292 was examined in a double-blind, randomised crossover study in eight healthy young volunteers and compared with atenolol. Three doses of ICI 141,292 (1, 2 and 4 mg) and atenolol 5 mg were administered intravenously. The attenuation in exercise induced tachycardia varied between 16.0 and 21.2% (P less than 0.01). A significant reduction in blood pressure could be demonstrated following all three doses of ICI 141,292 and atenolol during exercise. At rest in the sitting position HR decreased approximately 8% following all three doses of ICI 141,292 and 14.9% after atenolol 5 mg. No changes in blood pressure were observed under resting conditions after any of the drugs. In six patients with ischaemic heart disease the intrinsic sympathomimetic activity following intravenous administration of four sequential doses (0.5, 0.5, 1.0 and 2.0 mg) of ICI 141,292 was examined. HR decreased 7% (P less than 0.05) following ICI 141,292 1 mg with no further decrease following the succeeding doses. Cardiac output decreased 5.2% (P less than 0.05) following a cumulative dose of 4 mg. No significant changes were observed in mean arterial blood pressure, stroke volume or total peripheral resistance whereas an increase in supine resting mean pulmonary arterial pressure of 3.4 mm Hg (P less than 0.05) could be demonstrated. ICI 141,292 seems to be a potent (at least five times as potent as atenolol) beta 1-adrenoceptor blocking agent possessing moderate intrinsic sympathomimetic activity.
Adrenergic beta-Antagonists↗