Search PubMed⌕ Search

Biomedical subjects

P Sleight

Publications and source records attributed to P Sleight.

At least 181 records · Page 10Linked to original sources
PubMed1986

Evaluation of antiplatelet agents in the prevention of aorto-coronary bypass occlusion.

The cumulative occlusion rates of aorto-coronary artery venous bypass grafts average from 16 to 26% per distal anastomosis within 12 months and about 2% per following year. The potential benefit of oral anticoagulants and platelet inhibitor drugs has been tested to prevent graft occlusion and to retard the atherosclerotic process. Oral anticoagulants started on the third postoperative day do not significantly reduce graft occlusion after 6 months. Among the platelet inhibitor drugs, dipyridamole started before surgery, followed by dipyridamole and aspirin soon after surgery, was the drug regimen with the best results. More randomised double-blind clinical trials are highly desirable to confirm these findings and to resolve the question of relative efficacy and safety for the various drugs reported to have shown benefit when used in combination.

Administration, Oral↗
PubMed1986

Use of beta adrenoceptor blockade during and after acute myocardial infarction.

In the last year, two large randomized controlled trials of metoprolol (MIAMI, almost 6,000 patients) and atenolol (ISIS 1, over 16,000 patients) given intravenously within 12 hours of the onset of acute myocardial infarction reduced mortality by about 15% in low-risk subjects. The reduction was significant for atenolol (2P = 0.04) but not for metoprolol, probably because of the smaller size of that trial. The reduction in mortality in both trials was nearly all in the first 36 hours, a finding that reduced the fears that the treatment might produce irreversible failure, shock, or heart block. Tolerance in these relatively low-risk subjects (control mortality about 5%) was good. Inotropes were used in 1-2% more subjects in the beta-blocked group but were effective in reversing the side effects without increasing mortality. No clear subgroups (age, sex, site, time from onset, initial blood pressure or heart rate) were found in which treatment was more beneficial. In the ISIS study, patients with higher heart rates were more likely to need inotropes after beta blockade and patients with long PR intervals at entry were more likely to develop block. Neither of these complications resulted in excess mortality in the blocked group, which suggests that these adverse effects were largely reversible.

Adrenergic beta-Antagonists↗
PubMed1986

Failure of plasma norepinephrine to consistently reflect sympathetic activity in humans.

To determine whether venous plasma norepinephrine concentrations consistently reflect changes in sympathetic nervous activity, the influence of mental arithmetic, static handgrip, and submaximal bicycle exercise on intra-arterial blood pressure, heart rate, and plasma norepinephrine was studied in 51 subjects with untreated essential hypertension (mean age, 46 years; range, 16-69 years). At rest, plasma norepinephrine was unrelated to age or blood pressure. Mental arithmetic increased mean arterial pressure from 108 +/- 18 to 127 +/- 18 mm Hg (mean +/- S.D.; p less than 0.001) and heart rate from 69 +/- 7 to 93 +/- 13 beats/min (p less than 0.001) but not plasma norepinephrine (547 +/- 297 to 518 +/- 250 pg/ml). Isometric exercise raised mean arterial pressure from 115 +/- 18 to 148 +/- 21 mm Hg (p less than 0.001) and heart rate from 76 +/- 9 to 95 +/- 13 beats/min (p less than 0.001) but not plasma norepinephrine (683 +/- 253 to 741 +/- 253 pg/ml). Bicycle exercise increased mean arterial pressure from 114 +/- 20 to 146 +/- 26 mm Hg (p less than 0.001), heart rate from 77 +/- 9 to 128 +/- 19 beats/min (p less than 0.001), and plasma norepinephrine from 645 +/- 228 to 1151 +/- 462 pg/ml (p less than 0.001). Both the maximum mean arterial pressure and the peak heart rate attained during bicycle exercise were related to the exercise plasma norepinephrine level (r = 0.33, p less than 0.02 and r = 0.28, p less than 0.03, respectively). Increases in plasma norepinephrine with exercise were not greater in older or more hypertensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Cardioselective and nonselective beta-adrenoceptor blocking drugs in hypertension: a comparison of their effect on blood pressure during mental and physical activity.

The ability of cardioselective and nonselective beta-adrenoceptor blocking drugs, with and without partial agonist activity, to control increases in blood pressure associated with mental and physical activity was compared in 35 subjects with hypertension. Direct measurements of blood pressure and radioenzymatic determinations of plasma norepinephrine were obtained before, during and after four activities, and were repeated after random allocation to treatment with atenolol, metoprolol, pindolol or propranolol. Cardioselective and nonselective drugs modestly reduced the pressor response to reaction time testing, but not to mental arithmetic or isometric exercise. The increase in systolic blood pressure during bicycling was attenuated significantly by the cardioselective drugs atenolol (by 23 mm Hg, or 38%) and metoprolol (21 mm Hg, or 41%), but not by the nonselective agents pindolol (with partial agonist activity) (13 mm Hg, or 20%) and propranolol (10 mm Hg, or 17%) (p less than 0.02 cardioselective versus nonselective; p = NS pindolol versus propranolol). Only bicycle exercise increased plasma norepinephrine concentrations (by 80%). These results suggest that beta-adrenoceptor blocking drugs will not attenuate increases in blood pressure during mental or physical activities unless intense sympathoadrenal activation also occurs. Marked elevations in circulating epinephrine, with or without norepinephrine, and peripheral beta 2-blockade appear necessary for alpha-mediated vasoconstriction to predominate and for the contrasting effects of cardioselective and nonselective drugs to be appreciated.

Adolescent↗
PubMed1985

Mechanisms concerned with blood pressure variability throughout the day.

Blood pressure variability throughout the day has been found to be inversely related to baroreflex sensitivity, as is the response to injected phenylephrine, mental stress and sleep. It is concluded that variability in blood pressure results in some degree from defective buffering of blood pressure by the baroreceptors.

Blood Pressure↗
PubMed1985

High blood pressure: what level to treat?

Recent trials of the treatment of mild hypertension have suggested that there may be benefit from drug treatment of quite modest or borderline levels of pressure. Drug treatment of subjects with diastolic pressures over 95 mm Hg would pose a major problem in the efficient organization of such a long-term program and would also be costly. Perhaps about 350 patient years of treatment might be necessary to prolong one patient's life by 1 year. The side effects as well as the costs of such a program should make us cautious about offering such treatment solely on the results of measurement of arterial pressure. In people with diastolic pressures in the range of 90-100 mm Hg we should carefully consider several factors such as age, sex, cholesterol concentrations, diabetes, family history, and smoking habit which might also interact to identify particularly high risks and exclude those individuals with a particularly benign prognosis. The results of the more recent trials can give very little information about such subgroup analysis, which would be possible only with much larger samples. The untreated subjects with raised pressure should be carefully followed and offered advice on nondrug strategies such as weight reduction, treatment of lipid abnormalities, and reduction in dietary salt intake. This type of program demands careful, possibly computerized, records and follow-up.

Aging↗
PubMed1985

The role of baroreflex sensitivity in post-exercise hypotension.

We investigated whether changes in baroreflex sensitivity could explain the drop in blood pressure after exercise in 12 borderline hypertensive subjects. Intra-arterial blood pressure and baroreflex sensitivity (phenylephrine method) were measured before and 10, 20, 40 and 60 min after maximal exercise. Systolic blood pressure was lower at all stages after exercise. Baroreflex sensitivity was reduced at 10 min, recovered at 20 min and rose above control values at 40 and 60 min. Although the baroreflex sensitivity recovers slowly after exercise, at 40 and 60 min it is higher than the control value and could therefore contribute to the sustained reduction in blood pressure after a period of heavy exercise.

Blood Pressure↗
PubMed1985

Differences between casual and 24-h blood pressures.

Casual (office) blood pressure measurements using the conventional cuff method are open to a number of errors which are well recognized, e.g. errors due to large arm size, small cuff bladder, digit preference, variations in environmental temperature, smoking and/or coffee ingestion and lastly the 'defence' or alerting reaction. Although the latter error may be reduced by the habituation induced by repeated measures, it may not be so extinguished in some subjects. As an incidental finding in a trial of four different beta-blocking agents we were surprised to find how common this was. We had to reject about one-third of the subjects recruited as hypertensive on the basis of at least three cuff readings, when we found their intra-arterial pressures were normal away from hospital. Raftery and his colleagues in London have claimed that intra-arterial recordings eliminate the common placebo induced fall in blood pressure, which would greatly simplify the testing of new hypotensive drugs, particularly if it could be shown that ambulatory recordings made by non-invasive methods also removed this artefact. Others have used multiple non-invasive methods of blood pressure measurement with the Remler device and found similar results. In general the pressures taken at home are less than office pressures. Pickering and his colleagues in New York have found this discrepancy is particularly large in subjects with borderline hypertension. Littler et al. were one of the few groups to record higher pressures at home compared with hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Ambulatory Care↗
PubMed1984

The entry ECG in the early diagnosis and prognostic stratification of patients with suspected acute myocardial infarction.

475 patients with suspected uncomplicated myocardial infarction (MI) were divided into 3 groups based on their entry ECG: group 1--significant ST elevation; group 2a--ST depression or T inversion; group 2b--normal ECG. Infarction was confirmed in 99.7% of group 1, 68.5% of group 2a and 39.7% of group 2b patients. Despite similar clinical, haemodynamic and historical variables at presentation, group 1 patients had significantly larger MI, more in-hospital complications and a higher short-term and long-term mortality (P less than 0.005) than group 2 patients. The entry ECG of patients with suspected MI is an excellent and simple predictor of those who are most likely to have an MI confirmed and identifies a group of patients at high risk of death or developing complications.

Arrhythmias, Cardiac↗
PubMed1984

Neural and humoral mechanisms involved in blood pressure variability.

In order to study blood pressure variability we have measured blood pressure, heart rate, plasma noradrenaline and adrenaline concentration and plasma renin activity during sleep and during the waking process in 20 subjects with borderline hypertension. The responses to a number of standardized tests were also measured. These were reading, mental arithmetic, change in posture, physical exercise and the response to intravenously injected phenylephrine and noradrenaline. The sensitivity of the baroreflex for heart rate control was also determined from the relationship between heart period (R-R interval) and change in systolic pressure after the injection of phenylephrine. Blood pressure was also recorded continuously for 24 hours. From the lowest levels achieved during sleep, blood pressure rose as the subjects regained consciousness but was not restored to its baseline value until mental activity was also restored by reading. Blood pressure rose further with mental arithmetic. These changes were accompanied by a greater proportional rise in plasma adrenaline than in plasma noradrenaline concentrations. Plasma renin activity changed little. The pressor responses to phenylephrine and noradrenaline were inversely related to baroreceptor sensitivity. The fall in blood pressure with sleep and the rise with mental arithmetic was also inversely related to the sensitivity of the reflex. Systolic pressure recorded throughout the day was inversely related to the R-R interval in each subject. The slope of this relationship and range of R-R interval was greatest in the subjects with the most sensitive baroreflexes.

Adolescent↗
PubMed1984

Impaired control of heart rate leads to increased blood pressure variability.

Blood pressure variability has been studied from 24-h direct arterial pressure recordings in 109 subjects (36 normals and 73 hypertensives). Baroreflex sensitivity was also measured. From the 24-h record a linear relationship was found between systolic pressure and heart period. The slope was related to baroreflex sensitivity (r = 0.66, P less than 0.001). Those with shallow slopes had a high systolic pressure level and greater variability, thus efficient control of heart rate limits blood pressure variability.

Blood Pressure↗
PubMed1983

Reduction of ventricular arrhythmias by early intravenous atenolol in suspected acute myocardial infarction.

The effect of intravenous atenolol on ventricular arrhythmias in acute myocardial infarction was assessed in 182 patients admitted within 12 hours of the onset of chest pain. Ninety-five patients were randomised to receive 5 mg intravenous atenolol followed immediately by 50 mg by mouth and 50 mg 12 hours later, then 100 mg daily for 10 days; 87 patients served as controls. The treated patients had significantly fewer ventricular extrasystoles; 58 control patients (67%) had R-on-T extrasystoles compared with only 25 treated patients (26%) (2p less than 0.0001); repetitive ventricular arrhythmias were detected in 64 control patients (74%) and 55 treated patients (58%) (2p less than 0.05). Heart rate was significantly reduced from 77 +/- 1 beats/min at entry to 65 +/- 1 beats/min (2p less than 0.001) in the first hour after intravenous atenolol, and in addition the rate was significantly different from that in the control group. There was no difference in the incidence of heart failure, but fewer patients in the treated group received other antiarrhythmic agents or digoxin. These results show that early intravenous atenolol prevents ventricular arrhythmias in suspected acute myocardial infarction.

Adult↗
PubMed1983

The effect of phenylephrine upon arterial pressure, carotid sinus radius and baroreflex sensitivity in the conscious greyhound.

1. A method for recording carotid sinus diameter in conscious dogs has been developed, using an ultrasound transit time technique. We have used this method to measure the distensibility of the carotid sinus in resting animals, and we have investigated the effect of injecting the vasoactive drug phenylephrine on the mechanical behaviour of the sinus wall. 2. Baroreflex sensitivity was measured in the dogs by the usual method of relating the slowing of the heart to the transient pressure rise induced by the injections of phenylephrine. 3. We have shown that phenylephrine directly reduces the radius of the carotid sinus during the measurements of baroreflex sensitivity. At a dose of 2-4 micrograms/kg, phenylephrine has an enhancing effect on the baroreflex response, possibly resulting from a modification of baroreceptor output.

Animals↗
PubMed1983

The influence of arterial baroreceptors in man on the variability of blood pressure and plasma catecholamines in man.

The variability of intra-arterial blood pressure, recorded over the waking hours in free-ranging subjects away from the hospital, was expressed as the SD of the mean of all recorded beats. This variability was found to be related to age, the individual's level of arterial pressure, and his baroreflex sensitivity using the Oxford phenylephrine method. Multiple regression analysis showed that baroreflex sensitivity was the only independent influence on variability. Baroreflex sensitivity also strongly determined the level of pressure rise in response to a number of different stimuli, including bicycling exercise, isometric exercise, mental arithmetic, a reaction time test, and the response to injected phenylephrine or noradrenaline. Plasma noradrenaline proved a poor index of sympathetic nervous activity, except with bicycle exercise.

Adolescent↗