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Biomedical subjects

A E Russell

Publications and source records attributed to A E Russell.

At least 19 recordsLinked to original sources
PubMed1995

Effect of indomethacin on blood pressure control during treatment with nitrendipine.

This study tested the hypothesis that treatment with a nonsteroidal anti-inflammatory drug will not alter the hypotensive effect of a dihydropyridine calcium channel antagonist. Fifteen essential hypertensives (ages 58-80 years) had a supine diastolic blood pressure (DBP) < 100 mmHg after 4 weeks monotherapy with nitrendipine 5-20 mg twice daily. They entered a double-blind randomised crossover study in which the addition of indomethacin 25 mg three times daily was compared with placebo in treatment phases each of 4 weeks duration. Subjects were seen weekly and measurements in the last 2 weeks of each phase were compared. Supine blood pressure (mean +/- SE) was higher in the indomethacin phase (158 +/- 4/80 +/- 2) than in the placebo phase (154 +/- 4/76 +/- 3) (p < 0.01 for DBP). In 6/15 (40%) of subjects the increase in supine diastolic blood pressure with indomethacin was > 5 mmHg. Plasma urea was also increased in the indomethacin phase: 7.6 +/- 0.6 mmol/l compared with placebo: 6.3 +/- 0.5 mmol/l (p < 0.001). The study has demonstrated that concurrent treatment with the NSAID indomethacin impairs the blood pressure lowering effect of the dihydropyridine calcium channel antagonist nitrendipine. This increase in blood pressure with indomethacin in subjects treated with nitrendipine may represent either an independent pressor effect of indomethacin or a reduced vasodilator prostanoid contribution to the hypotensive effect of nitrendipine. This blood pressure increase may be sufficient to interfere significantly with clinical blood pressure control in some subjects.

Aged↗
PubMed1994

Felodipine, metoprolol and their combination compared with placebo in isolated systolic hypertension in the elderly.

This study compared with placebo the efficacy and tolerability of optimised doses of felodipine 5-20 mg daily, metoprolol 50-200 mg daily and their combination in subjects 60 years or over with isolated systolic hypertension. The study employed a randomised double-blind crossover design with allocation of treatment order within subjects by Latin squares. For each subject, after a single-blind run-in placebo phase, there were four randomised treatment phases each of six weeks duration, with a dose titration step at three weeks if necessary. Twenty-eight subjects entered the randomised phases of the study and twenty-one completed all four phases--13 male, 8 female (ages: median 71, range 59-85 years). At the end of both the felodipine and metoprolol phases systolic and diastolic pressure were reduced at 2 hours postdose compared with the placebo phase (p < 0.001), the blood pressure reduction with felodipine (-40/-20 mmHg) being greater than that with metoprolol (-15/-9 mmHg) (p < 0.01). Immediately predose (12 hours postdose) there was a persisting reduction of supine systolic blood pressure (-17 mmHg) with felodipine (p < 0.001), but there was no significant effect of metoprolol. At both measurement times the two drugs when in combination had an additive effect on blood pressure. There was a 20% increase in reported symptoms during each of the active treatment phases. Four subjects withdrew during the randomised phases because of probable drug-related adverse events and six subjects required dosage reductions during the felodipine or combination phases.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Mono- and combination therapy with felodipine or enalapril in elderly patients with systolic hypertension.

Using a randomised double-blind crossover design with Latin square allocation of treatments in 20 subjects (7 male, 13 female-ages: 61-87 years) with systolic hypertension, we investigated the efficacy and tolerability of once daily felodipine (extended release) 5-20 mg, enalapril 5-20 mg and their combination compared with placebo in four treatment phases each of 6 weeks duration. During each phase, doses were titrated to achieve a predose clinic supine systolic blood pressure of 140 mmHg or to a predetermined maximum dose. In both the felodipine and combination phases, predose supine and standing systolic and diastolic pressures were significantly reduced compared with the placebo phase (decrease in supine pressure: -13/-5 and -18/-7, respectively). Only predose supine diastolic pressure was significantly reduced (-3 mmHg) compared to placebo in the enalapril phase. In combination the effects of the two drugs on predose blood pressure were additive. There was a 40-60% increase in reported symptoms in the felodipine and combination phases compared with the placebo and enalapril phases. Thus, in elderly subjects with systolic hypertension, felodipine effectively reduces blood pressure throughout the dose interval but with vasodilator adverse effects. In contrast, enalapril is well tolerated but is less effective in reducing blood pressure throughout the whole dose interval.

Aged↗
PubMed1993

Cheap thrills.

Explore the source record for details and available documents.

Auscultation↗
PubMed1990

Lack of effect of fish oil supplementation on blood pressure in treated hypertensives.

Fish and fish oils have been reported to reduce blood pressure in normotensives and untreated hypertensives. The present study examined the effect of dietary supplementation with fish oil on blood pressure in 20 treated hypertensives with controlled blood pressures who continued their usual antihypertensive drug treatment throughout. A double-blind, randomized crossover design was used, with two phases, each of 8 weeks' duration. In one phase, subjects took fifteen 1 g fish oil capsules (Lipitac; Reckitt and Colman Pharmaceuticals, Sydney, Australia) daily, and in the other, 15 capsules of identical appearance containing 1 g olive oil daily. There was no difference between the treatment phases for any blood pressure parameter, heart rate or body weight, but blood pressure was lower in both phases compared with pretreatment values. The fasting plasma triglyceride concentration was 30% lower in the fish oil phase (P less than 0.001), but there was no difference between the phases for plasma concentrations of total or high-density lipoprotein (HDL) cholesterol. We conclude that, in treated hypertensives with controlled blood pressures, any additional fall in blood pressure produced by dietary supplementation with fish oil is so small that the requirement for antihypertensive drug therapy is unlikely to be reduced.

Adult↗
PubMed1990

Diltiazem and atenolol in essential hypertension: additivity of effects on blood pressure and cardiac conduction with combination therapy.

In 15 patients with mild to moderate essential hypertension, the effects of diltiazem (120 mg twice daily) were compared with those of atenolol (50 mg once daily), the two drugs in combination, and placebo in a randomized double-blind cross-over study with treatment phases of 4 weeks duration. Blood pressure was reduced in the active treatment phases (supine blood pressure: diltiazem, 172/92 mmHg; atenolol, 172/92 mmHg; diltiazem plus atenolol, 164/88 mmHg; pooled estimate of s.e.m. by analysis of variance = 3/1) compared with placebo (180/101 mmHg). Factorial analysis confirmed fully additive antihypertensive effects of the drugs in combination. The time interval from the beginning of the P wave to the beginning of the QRS complex (P-R interval) was longer during combination therapy (0.184s) compared with either diltiazem (0.175s) or atenolol (0.174s) alone, or placebo (0.164s); s.e.m. by analysis of variance = 0.003. No clinically significant conduction disturbances occurred. Plasma atrial natriuretic peptide was elevated by atenolol but not diltiazem. Thus, in subjects with uncomplicated essential hypertension, diltiazem and atenolol had equal antihypertensive efficacy when used alone, and fully additive effects in combination, on both blood pressure and cardiac conduction.

Atenolol↗
PubMed1990

Automated non-invasive measurement of cardiac output by the carbon dioxide rebreathing method: comparisons with dye dilution and thermodilution.

The accuracy and reproducibility of indirect measurement of cardiac output at rest by the carbon dioxide rebreathing (indirect Fick) method with an automated respiratory analysis system (Gould 9000IV) were compared with simultaneous measurements made in duplicate by dye dilution and thermodilution in 25 patients having cardiac catheterisation studies. Measurements of cardiac output by the carbon dioxide rebreathing method were not significantly different from those obtained with dye dilution (mean difference -0.3 l/min, SD 0.76, 95% confidence interval -0.7 to 0.1). Thermodilution significantly over-estimated cardiac output by a mean of 2.2 l/min or 39% (SD 1.5, 95% confidence interval 1.6 to 2.8) compared with the carbon dioxide rebreathing method and significantly overestimated cardiac output by 1.9 l/min or 31% (SD 1.2, 95% confidence interval 1.2 to 2.5) compared with dye dilution. The reproducibility of measurements of cardiac output in individual patients was satisfactory with the dye dilution method but was poor with carbon dioxide rebreathing and thermodilution. Indirect measurement of resting cardiac output by the Gould 9000IV automated carbon dioxide rebreathing method is more accurate but the variability inherent with this method requires that multiple measurements be taken for each determination. Measurement of cardiac output by the thermodilution method by a commercially available cardiac output computer was not satisfactory because not only was there considerable variability between repeat measurements but the method also consistently overestimated cardiac output compared with the dye dilution method.

Adult↗
PubMed1989

Neuropeptide Y-like immunoreactivity of plasma during hypoglycaemia in man.

Previous studies have demonstrated that plasma Neuropeptide Y-like immunoreactivity (NPY-LI) increases after activation of sympathetic nerves. To test the hypothesis that the adrenal medulla may also be a significant source of circulating plasma NPY-LI and to determine if NPY is co-released with adrenal catecholamines, we have measured the peripheral venous concentrations of NPY-LI, adrenaline and noradrenaline in six patients, before and after induction of hypoglycaemia as part of pituitary function tests that also tested gonadotrophin and thyroid stimulating hormone release. The plasma adrenaline concentration was increased approximately 15 times (p less than 0.05) relative to baseline at 30 mins and remained elevated for the 90 minutes of the study. The plasma concentration of both noradrenaline and NPY-LI remained unchanged. These results failed to demonstrate an increase in the amount of NPY-LI released into the plasma during stimulation of the adrenal medulla with hypoglycaemic stress in man. They do not support significant co-release of NPY with adrenaline from the adrenal medulla in man, nor a physiological role for NPY as an adrenal hormone in human subjects in this situation.

Adult↗
PubMed1989

Optimal size of cuff bladder for indirect measurement of arterial pressure in adults.

This study tested the hypothesis that a sphygmomanometer cuff bladder long enough to encircle the arm in most adults ('obese cuff') would provide a more accurate and precise estimate of intra-arterial pressure than the usual 'standard' cuff bladder. In 53 patients undergoing diagnostic coronary angiography (35 males, 18 females, aged 36-79 years), indirect blood pressure, measured in the left arm with a random-zero sphygmomanometer, was compared with simultaneously measured femoral intra-arterial pressure. Duplicate indirect measurements were made with each of two cuffs containing bladders measuring 39 x 15 cm ('obese') and 23 x 12 cm ('standard'). The obese cuff bladder encircled 80% or more of the arm circumference in all subjects, whereas the standard cuff bladder met this requirement in only 19% of the subjects. For both systolic and diastolic pressure there was marked interindividual variability in the differences between indirect and direct measurements with both cuffs. With the obese cuff there was no systematic error in the diastolic blood pressure measurement. The standard cuff consistently overestimated diastolic pressure by 7.7 +/- 8.3 mmHg (mean +/- s.d.). For both cuffs, the difference between indirect and direct diastolic pressure increased with arm size (P less than 0.05). Both cuffs underestimated systolic blood pressure, the obese cuff by 15.5 +/- 11.7 mmHg and the standard cuff by 7.6 +/- 12.1 mmHg. These systolic blood pressure underestimates were greater at higher blood pressures (P less than 0.01) and with smaller arms (P less than 0.05). Age was not related to measurement error with either cuff.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Accuracy of the Takeda TM-2420 ambulatory blood pressure monitor.

1. The accuracy of blood pressure measurement with the Takeda TM-2420 ambulatory blood pressure monitor and the TM-2020 data recorder have been assessed by comparison with simultaneous measurements taken using auscultation and direct femoral artery measurements. 2. Systolic blood pressure was underestimated by the TM-2420 by a mean of 10 mmHg (s.d. = 6, 95% confidence interval (CI) = -13 to -7) over the range of pressures measured by auscultation. It was underestimated by 23 mmHg (s.d. = 12, 95% CI = -28 to -18) compared with direct femoral artery measurements. 3. Diastolic pressure measurements were similar to those obtained by auscultation. When compared with direct femoral artery recordings, diastolic pressure was overestimated by about 5 mmHg (s.d. = 4, 95% CI = 3.4-6.6), which is consistent with indirect readings, taken with a 'standard' cuff (inflatable bladder 23 cm X 12 cm). 4. The TM-2420/2020 is thus suitable for ambulatory measurements of blood pressure when diastolic pressure is the criterion of interest.

Angiocardiography↗
PubMed1989

Transmitral velocities measured by pulsed Doppler in healthy volunteers: effects of acute changes in blood pressure and heart rate.

The effect of a two minute cold pressor test on transmitral velocities measured by pulsed Doppler was studied in 11 healthy volunteers. Blood pressure increased significantly during cold immersion but peak atrial and peak early diastolic transmitral velocities and their ratio (A:E) were unchanged. There was no correlation between changes in Doppler variables and changes in calculated mean arterial blood pressure during the test. Heart rate changes were variable and not related to changes in blood pressure. In individual people the change in pulse interval during cold immersion was significantly and inversely correlated with the change in the A:E ratio. The large acute increase in arterial pressure seen during the cold pressor test in normal volunteers had no consistent effect on the transmitral velocity profile although small changes in heart rate were associated with large changes in A:E ratio. The effect of small changes in heart rate may be of considerable importance in determining transmitral velocity profiles. Thus in clinical and experimental studies in which the heart rate is not controlled, Doppler data on transmitral flow should be interpreted with caution.

Adult↗
PubMed1988

Plasma neuropeptide Y and atrial natriuretic peptide concentrations in man.

1. In order to examine the concentration of neuropeptide Y-like immunoreactivity (NPY-LI) and atrial natriuretic peptide (ANP) in the circulation in man, blood was sampled from the iliac vein, the inferior vena cava, the superior vena cava, the pulmonary artery and the femoral artery in 13 patients undergoing cardiac catheterization. 2. Plasma NPY-LI levels were similar at all points sampled and no arteriovenous differences were found. Plasma ANP concentration in the pulmonary artery was greater than in peripheral venous blood but there was a strong correlation between the two. 3. The concentration of NPY-LI and ANP in peripheral venous blood reflects central venous and arterial concentrations.

Adult↗
PubMed1988

Automated non-invasive measurement of cardiac output: comparison of electrical bioimpedance and carbon dioxide rebreathing techniques.

Two commercial automated, non-invasive systems for estimation of cardiac output were evaluated. Values of cardiac output obtained by electrical bioimpedance cardiography (BoMed NCCOM3 machine) were compared with values derived from an indirect Fick technique that uses carbon dioxide rebreathing (Gould 9000 IV system) during 103 simultaneous measurements made at rest in 19 randomly selected subjects and on exercise in 11 subjects. Cardiac output values obtained with impedance cardiography were significantly correlated with those measured by the indirect Fick method, although there was a wide scatter with over 73% of the readings lying outside the limits defined by the line of identity +/- 20%. This correlation was greatly reduced when stroke volume index was used instead of cardiac output. Indirect Fick results were linearly related to oxygen uptake both at rest and on exercise, while impedance cardiography results did not correlate with oxygen uptake. Impedance cardiography gave consistently lower results for cardiac output than indirect Fick at all levels of exercise. Both machines were easy to use and produced acceptable mean (SE) coefficients of variation (BoMed NCCOM3 7.7 (1.0)%, Gould 9000 IV 10.6 (1.4)%). Further validation is required before either of these machines can be recommended as an alternative to invasive monitoring in clinical practice.

Adolescent↗
PubMed1988

Enalapril and atenolol in essential hypertension: attenuation of hypotensive effects in combination.

In 16 patients with essential hypertension the effects of enalapril 20 mg once daily were compared with those of atenolol 50 mg once daily, with the two drugs in combination and with placebo using a double-blind cross-over design with allocation of treatment order by randomised Latin squares. For each patient there were four treatment phases, each of four weeks duration, which together comprised a 2 x 2 factorial experiment. All blood pressure parameters were reduced in the three active treatment phases compared to placebo (p less than 0.001). Supine blood pressures (group means) were 171/97 (placebo), 147/85 (enalapril), 154/84 (atenolol) and 144/78 (enalapril plus atenolol) (S.E.M. +/- 2/+/- 1-ANOVA), and standing blood pressures were 170/105 (placebo), 146/92 (enalapril), 154/92 (atenolol) and 147/86 (enalapril plus atenolol) (S.E.M. +/- 3/+/- 1). In the combination phase there was an additional hypotensive response but the potential fully additive effects of the two agents were attenuated by 30-50%. The mechanism of the attenuated hypotensive effect of the combined agents has not been determined. Plasma atrial natriuretic peptide (ANP) concentration was doubled in the presence of atenolol (P less than 0.01) suggesting that ANP may contribute to the hypotensive effect of the beta-blocker.

Aldosterone↗
PubMed1987

Treatment of hypertension with enalapril and hydrochlorothiazide or enalapril and atenolol: contrasts in hypotensive interactions.

To determine the nature of the resultant effect on blood pressure when angiotensin converting enzyme (ACE) inhibitors are combined with other hypotensive agents in the treatment of uncomplicated essential hypertension, two randomized, double-blind, crossover trials were conducted. In each trial there were four treatment phases, each 4 weeks in duration, comprising a 2 X 2 factorial experiment. Twenty-one patients completed the first study in which the effects of enalapril (10 mg twice daily) were compared with hydrochlorothiazide (25 mg twice daily), with the two drugs in combination and with placebo. All blood pressure parameters were reduced in the three active treatment phases compared with placebo (P less than 0.001). Enalapril and hydrochlorothiazide were equally effective and in combination their hypotensive effects were fully additive. Sixteen patients completed the second study which compared the effects of enalapril (20 mg daily), atenolol (50 mg daily), the two drugs in combination and placebo. All blood pressure parameters were again reduced in all phases compared with placebo (P less than 0.001). Enalapril and atenolol were also equally effective, but in combination their hypotensive effects were less than fully additive, with attenuation of the potential additive response by 30-50%. These results indicate that a diuretic-ACE inhibitor combination can be expected to have a greater hypotensive effect than a beta-blocker-ACE inhibitor combination. Both hydrochlorothiazide and atenolol increased plasma atrial natriuretic peptide (ANP) concentrations (P less than 0.01), suggesting that ANP could contribute to the hypotensive effects of these two drug classes.

Angiotensin II↗
PubMed1986

Increases in plasma neuropeptide Y concentrations during sympathetic activation in man.

Neuropeptide Y (NPY) coexists with noradrenaline in postganglionic sympathetic neurons. In order to test the hypothesis that NPY may be released along with catecholamines by activation of the sympathoadrenal system we measured plasma NPY-like immunoreactivity (NPY-LI) concentrations during cold pressor test, head up tilt and bicycle exercise in healthy volunteers. All 3 manoeuvres resulted in elevation of blood pressure, heart rate and plasma noradrenaline and adrenaline concentrations. These were accompanied by increases in plasma NPY-LI concentrations on cold pressor test and exercise, but not with head up tilt. The increases in both NPY-LI and catecholamines were greatest with exercise. These findings suggest that NPY is released at the same time as noradrenaline when sympathetic noradrenergic nerves are activated.

Adult↗
PubMed1986

Binding isotherms by continuous-flow dynamic dialysis.

The classical dynamic dialysis technique for the determination of a protein-ligand binding isotherm has been modified by the introduction of a flow cell in which the dialysate on the sink side of the membrane is continuously eluted with a constant flow of eluting buffer and its ligand concentration measured. This new experimental method is termed continuous-flow dynamic dialysis (CFDD). A transfer function procedure for extracting the binding isotherm from the dialysis data is described. This is a more general technique (requiring only a verifiable assumption of linearity) than that previously used, in which the system was modelled using Fick's first law and which relied on the establishment of quasi-steady state conditions across the membrane. The present analysis uses the Laplace transform to effect deconvolution of the impulse response function of the cell from the dialysis data and, using a Fourier series approach, directly yields numerical data representing the free ligand concentration in equilibrium with the protein-ligand complex. The protein-ligand binding isotherm is obtained in parametric form, with time as the parameter.

Journal Article↗