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Biomedical subjects

S N Hunyor

Publications and source records attributed to S N Hunyor.

At least 55 records · Page 3Linked to original sources
PubMed1983

Magnitude and mechanisms of the antihypertensive action of labetalol, including ambulatory assessment.

The blood pressure (BP) effect and modes of action of a twice daily regimen of labetalol (mean 450 mg/day) were assessed in ten mild to moderate hypertensives using continuous ambulatory BP monitoring. The reflex control of BP during physiological interventions was examined just prior to the next dose of medication to estimate the residual alpha- and beta-adrenoceptor blockade. Global 24 h BP was reduced by 15/9 mm Hg, and home pressures by 13/11 mm Hg. The predominant antihypertensive effect was noted during the waking hours. During dynamic exercise significant inhibition of the heart rate and blood pressure rise occurred. Coupled with a reduction of the post-release BP 'overshoot' in Valsalva's manoeuvre, the response resembles that seen with beta-adrenoceptor blockade. A small alpha-adrenoceptor blocking action was evident in one patient's response to the Valsalva manoeuvre.

Adult↗
PubMed1982

Anti-hypertensive action of labetalol: a detailed profile.

Continuous, ambulatory blood pressure (BP) and self measured home recordings were used to study the response of ten mild to moderate hypertensives taking a twice daily labetalol dosage. Testing of cardiovascular reflexes was carried out 12 hours after a dose of drug. The mean 24 hour BP was reduced from 145/80 +/- 14/7 (SD) mmHg to 130/71 +/- 11/6 (p less than 0.001) and home BP from 147/96 +/- 15/9 to 134/84 +/- 10/9 (p less than 0.01). The predominant effect of labetalol was evident during the waking hours. A residual 9.5% BP reduction was seen 12 hours after a dose compared to an 11% lowering effect over the entire 24 hours (NS). No symptomatic hypotensive episodes were noted. Significant inhibition of heart rate and BP rise during dynamic exercise (p less than 0.01) and reduction of post-release BP "overshoot" (p less than 0.01) in Valsalva's manoeuvre indicated a beta adrenoceptor blocking effect. There was however a reduction in the rate of rise of BP during static handgrip (p less than 0.01) indicating a small alpha adrenoceptor blocking component. This study has demonstrated the efficacy of a twice daily regimen of labetalol in continuously lowering BP. The mode of action of the drug during exercise (static and dynamic) and Valsalva's manoeuvre would indicate a predominant beta adrenoceptor blocking action.

Adult↗
PubMed1980

Precordial voltage variation in the normal electrocardiogram.

Intra-individual precordial voltage variation was examined in serial 12 lead electrocardiograms (ECGs) performed at 10 minute and 24 hour intervals in sixteen young, healthy males forming two age matched groups. Significant variation was found in repeat ECGs at both periods. When precordial electrodes remained in situ between serial 10 minute recordings variation was reduced by approximately 60% We conclude that significant precordial voltage variation is present in serial electrocardiography, even when performed over the short term. Alteration in precordial electrode placement accounts for the major proportion of variation and this may be sufficiently large to interfere with the accurate interpretation of serial precordial voltage changes in an individual subject.

Adolescent↗
PubMed1980

Cardiac and haemodynamic measurements in hypertensive pregnancy.

1. Haemodynamic and left ventricular variables were determined by M-mode echocardiography in 21 normotensive and 36 hypertensive patients during the last trimester of pregnancy. 2. Blood pressure of hypertensive patients was lowered by bed rest only, or by oxprenolol or methyldopa, but remained elevated. 3. Cardiac output was raised in the last trimester of pregnancy in both normotensive and hypertensive patients. 4. Left ventricular mass was increased in normal pregnancy, but displayed an exaggerated increase in hypertensive patients. 5. Total peripheral resistance was inappropriately elevated in hypertensive pregnancy, except in the oxprenolol-treated group. 6. There ws no reduction in heart rate or cardiac output in the group treated with beta-adrenoreceptor blocking agents. These factors, in combination with normal peripheral resistance, may contribute to the improvement in foetal outcome described in maternal hypertension of pregnancy treated with oxprenolol.

Adult↗
PubMed1980

Labetalol and propranolol in mild hypertensives: comparison of blood pressure and plasma volume effects.

Labetalol administered in a small to moderate dose (first month 400 mg/day, second month average 585 mg/day) was effective in lowering blood pressure (BP) (-21/-18 mmHg, recumbent) in 11 of 13 mild essential hypertensives over an eight-week period, despite a significant (+294 ml) increase in plasma volume. The effect of propranolol (first month 160 mg/day, second month average 234 mg/day) was significantly less on both blood pressure (-9/-9 mmHg) and plasma volume (+98 ml), although the pre-propranolol BP was lower and the final BP achieved on the two medications was comparable (labetalol 147/89 mmHg, propranolol 145/89). Six patients who continued labetalol for periods of up to 14 months had persistent plasma volume expansion. Three of these, taking a higher dose of labetalol, developed resistance to the drug's antihypertensive effect. Addition of a diuretic restored antihypertensive efficacy and led to a fall in plasma volume. No such plasma volume expansion was seen in six patients who were followed on long term propranolol therapy. Some plasma volume expansion with the combined alpha- beta-adrenoceptor blocker labetalol may be appropriate to its vasodilator action. Provided this effect is not excessive, it appears not to lead to resistance to its antihypertensive action. Small to moderate doses of labetalol would, therefore, seem effective without concomitant diuretic. Such sole use of labetalol could help minimise orthostatic symptoms which can be a major side effect of combination therapy.

Adult↗
PubMed1979

Randomised comparison of methyldopa and oxprenolol for treatment of hypertension in pregnancy.

Fifty-three pregnant women with moderately severe hypertension were randomly allocated to treatment with methyldopa or oxprenolol. There were no significant differences between the groups in age, height, weight, parity, or stage of gestation at the start of treatment. The outcome of pregnancy was better in the group treated with oxprenolol, with greater maternal plasma volume expansion and placental and fetal growth. No intrauterine deaths occurred in either group, and antepartum fetal distress, detected by oxytocin challenge testing, was evident in only one patient, who received methyldopa. This infant, and one other in the methyldopa group, died in the neonatal period. No neonatal deaths occurred in the oxprenolol-treated group. Even in this small number of patients these results were considerably better than those in untreated women with hypertension of similar severity. Apgar scores in both groups were equivalent at birth, while blood sugar concentrations were higher in the oxprenolol group. Oxprenolol appears to be safe and effective in controlling hypertension during pregnancy. There was no evidence of harmful effects on the fetus, and oxprenolol may offer a selective advantage over methyldopa for fetal growth and wellbeing in utero.

Adult↗
PubMed1979

Anatomical accuracy of echocardiographically assessed left ventricular wall thickness.

1. A comparison of direct measurement and M-mode echocardiography in the determination of posterior left ventricular wall thickness was performed in 26 subjects, of whom 21 underwent cardiac bypass surgery; the remainder came to necropsy. 2. In the surgical group a close correlation was demonstrated between direct measurement of posterior wall thickness and the echocardiographic end-diastolic dimension (r = 0.76, P less than 0.001). 3. The necropsy measurement of posterior wall thickness correlated with the echocardiographic end-systolic dimension (r = 0.99, P less than 0.001). 4. These findings confirm that the echocardiographic measurement of posterior wall thickness accurately reflects the anatomical dimension.

Blood Pressure↗
PubMed1979

Haemodynamic profile of angiotensin II antagonism in essential hypertensive patients.

1. The haemodynamic response to antagonistic (10 microgram min-1 kg-1) and agonistic (40 microgram min-1 kg-1) doses of saralasin was studied in young essential hypertensive patients. Blood pressure behaviour alone was thought to be inadequate to describe the response pattern. 2. Pre-saralasin setting of the renin-angiotensin axis was varied with salt intake (15 and 290 mmol of Na+/day) each for 10 days. This failed to influence blood pressure or plasma volume. 3. Antagonist blockade after low salt lowered blood pressure in three patients with the highest plasma renin values. Cardiac output rose in two of these, but it dropped in all others. 4. Decreases in cardiac output occurred with both doses of saralasin and even with suppression of the renin-angiotensin axis. This response is therefore unlikely to be due to removal of myocardial or venous angiotensin effects. 5. The renin-angiotensin system played a part in maintenance of blood pressure only with severe salt restriction and in a small proportion of cases. 6. No heart rate effect was seen with sarcalasin. 7. Blood pressure and total peripheral resistance responses were dependent on pre-(antagonist/agonist) setting, but heart rate and cardiac output were not influenced by this factor.

Adult↗
PubMed1979

Plasma volume contraction: a significant factor in both pregnancy-associated hypertension (pre-eclampsia) and chronic hypertension in pregnancy.

The role of plasma volume in hypertension in pregnancy (pre-eclampsia) was investigated. Significant volume expansion from non-pregnant levels (16.5 +/- 1.60 ml/cm height) was present throughout pregnancy in 189 normal women, reaching 23.1 +/- 1.21 ml/cm at 33-36 weeks amenorrhoea. In another 40 initially normotensive pregnant women who developed hypertension, similar early volume expansion was followed by significant volume contraction in the third trimester, before evaluation of blood pressure in 29 (20.6 +/- 1.26 ml/cm), after it in 11 (18.6 +/- 1.27 ml/cm). Equivalent volume contraction was present in another 44 women studied only after hypertension developed in the third trimester. Oedema had no value as a clinical sign. In another 30 women with chronic hypertension, blood pressure was inversely related to plasma volume (r = 0.822) and to fetal growth (r = -0.710), which was directly related to plasma volume (r = 0.701). Plasma volume depletion plays a significant role in hypertension in pregnancy.

Blood Pressure↗
PubMed1978

Comparison of performance of various sphygmomanometers with intra-arterial blood-pressure readings.

Seven types of sphygmomanometer were used in random order on each of nine hypertensive patients and the readings compared with simultaneous intra-arterial blood-pressure recordings. All the devices gave significantly different values for systolic pressure, and only two measured diastolic pressure without significant error. Systolic pressure was consistently underestimated (range 31-7 mm Hg), and all but one instrument overestimated diastolic pressure (range 10-2 mm Hg). The variability of readings was least with the standard mercury sphygmomanometer and the random-zero machine, while with some of the more automated devices single readings were in error up to -68/33 mm Hg. The strong correlations found between intra-arterial and cuff systolic pressures with all devices tested and significant correlations for diastolic pressure with all but one device indicate that, with one possible exception, the sphygmomanometers would give accurate results where a change in blood pressure was the main concern.

Adult↗
PubMed1978

Side-effects of antihypertensive treatment: a placebo-controlled study.

1. A questionnaire, modified from Bulpitt & Dollery (1973), inquired about 20 symptoms commonly associated with hypertension or its drug therapy in 1017 subjects (age 30--69 years). Groups consisted of (a) active therapy, (b) placebo, (c) no tablets, and (d) a non-study control group. The response rate was 96% in the first three groups and 92% in group (d). 2. The subjects in groups (a), (b) and (c) constituted part of a placebo-controlled, patient-blind intervention study in the treatment of mild hypertension (The Australian National Blood Pressure Study). 3. After age/sex adjustment of the data, only sleepiness and self-assessed depression were found to be more common in the actively treated group. Impotence, failure of ejaculation and nocturia were age-related symptoms. Generally, complaint rate was higher in females. 4. The knowledge of a mild hypertensive condition or its modern drug therapy lead to very few symptoms in a non-hospital population who already have a fairly high 'complaint level'.

Adult↗