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Biomedical subjects

E O'Brien

Publications and source records attributed to E O'Brien.

At least 199 records · Page 11Linked to original sources
PubMed1991

Clinical benefits of structural and functional changes with calcium antagonists.

Calcium antagonists have a large variety of pharmacologic effects in addition to those exploited clinically. All drugs used in the management of hypertension, including calcium antagonists, are coming under increasing scrutiny for the possible beneficial and adverse effects they may have on the circulation and risk factor profile. This is particularly because of concern about the relative resistance of coronary heart disease to antihypertensive drug treatment and the increasing interest in evaluating the impact of blood pressure-lowering drugs on surrogate endpoints such as left ventricular hypertrophy. Given the pharmacokinetic and pharmacodynamic heterogeneity of calcium antagonists, it may be wise to keep in mind the subtypes as exemplified by the prototypes nifedipine, diltiazem, and verapamil and to extrapolate from one type to another with great caution. The increased understanding of the diversity among calcium antagonists as well as the pathophysiology of hypertension and other vascular diseases promises an exciting future for calcium antagonists in cardiovascular therapeutics.

Calcium Channel Blockers↗
PubMed1991

Choice of drug treatment for elderly hypertensive patients.

It is generally agreed that moderate and severe hypertension in the elderly should be treated, but it is not clear which drug or drugs are most appropriate. Thiazide diuretics are inexpensive and effective, but they are associated with metabolic side effects that are becoming less acceptable as newer agents become available. Beta blockers are effective, but can be associated with central nervous system side effects and are often contraindicated by coexisting disease. Recently, attention has been focused on the newer agents, including calcium antagonists and angiotensin-converting enzyme inhibitors. The advantage of calcium antagonists is that they do not produce metabolic side effects. However, they are expensive and may cause vasodilatory side effects. The angiotensin-converting enzyme inhibitors are effective and relatively free of side effects and may be particularly useful for elderly hypertensive patients with congestive heart failure.

Aged↗
PubMed1991

Plasma atrial natriuretic peptide concentration and platelet atrial natriuretic peptide binding site density in ageing and hypertension.

1. Ageing and hypertension are associated with changes in the way in which the body handles sodium. This may involve changes in plasma atrial natriuretic peptide concentration, since atrial natriuretic peptide is a regulator of sodium handling by the kidney and the plasma atrial natriuretic peptide concentration is increased in both ageing and hypertension. An increase in the plasma atrial natriuretic peptide concentration could also be associated with a change in atrial natriuretic peptide receptor density, possibly involving down-regulation. 2. To investigate these possibilities plasma atrial natriuretic peptide concentration and platelet atrial natriuretic peptide binding site density were measured in 18 young, 11 middle-aged and 12 elderly healthy subjects and in 23 patients with mild to moderate essential hypertension. 3. In normotensive subjects, the plasma atrial natriuretic peptide concentration increased with age (r = 0.49, P less than 0.01) and was significantly higher in elderly than young subjects (mean +/- SEM, 31.9 +/- 4.5 versus 18.3 +/- 2.0 pmol/l, P less than 0.05). The plasma atrial natriuretic peptide concentration increased with the mean arterial pressure in normotensive subjects (r = 0.47, P less than 0.01). Multiple regression analysis did not show independent relationships between the plasma atrial natriuretic peptide concentration and either age or mean arterial pressure in normotensive subjects alone. However, when normotensive subjects and hypertensive patients were considered together, multiple regression revealed both age and mean arterial pressure as independent predictors of the plasma atrial natriuretic peptide concentration (P less than 0.05, P less than 0.01, respectively). In normotensive subjects, the platelet atrial natriuretic peptide binding site density did not change with age (r = 0.19, P = 0.27).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Twenty-four-hour ambulatory blood pressure in men and women aged 17 to 80 years: the Allied Irish Bank Study.

In order to determine reference values for ambulatory blood pressure, a sample of 815 healthy bank employees (399 men and 416 women), aged 17-79 years, were investigated. Ambulatory blood pressure was recorded over 24 h, taking measurements at 30-min intervals. Blood pressure was also measured by trained observers in the clinic. Ambulatory blood pressure in the 815 subjects averaged 118/72 mmHg over 24 h, 124/78 mmHg during the day (1000-2259 h) and 106/61 mmHg at night (0100-0659 h). Office blood pressure, measured by an observer, was 4/2 mmHg lower (p less than 0.0001) than daytime ambulatory pressure. The 95th centiles for the daytime ambulatory pressure in men were: 114/88 mmHg for the age group 17-29 years (n = 107); 143/91 mmHg from 30-39 years (n = 123); 150/98 mmHg from 40-49 years (n = 109); and 155/103 mmHg in 50-79 year old men (n = 60); for the corresponding age groups in women, the 95th centiles of the daytime pressure were: 131/83 mmHg (n = 174); 132/85 mmHg (n = 149); 150/94 mmHg (n = 55); and 177/97 mmHg (n = 38).

Adult↗
PubMed1991

The effects of age on platelet intracellular free calcium concentrations in normotensives and hypertensives.

We have investigated relationships between age, blood pressure and intracellular calcium concentration in platelets from normotensives and hypertensives. In normotensives, there were positive correlations between age and platelet intracellular calcium concentration (r = 0.76, P less than 0.001), age and mean arterial pressure (MAP; r = 0.55, P less than 0.01) and MAP and platelet intracellular calcium concentration (r = 0.45, P less than 0.01). Multiple regression analysis revealed that age was the primary determinant of platelet intracellular calcium concentration in normotensives. The effect of MAP on platelet intracellular calcium concentration when adjusted for age was not significant (P = 0.73). In hypertensives, there was no significant relationship between age and platelet intracellular calcium concentration (r = 0.15, P = 0.43), age and MAP (r = 0.17, P = 0.37) or MAP and platelet intracellular calcium concentration (r = -0.27, P = 0.15). Overall, platelet intracellular calcium concentration was significantly higher in hypertensives than in age-matched normotensives (P less than 0.05). Within the age groups examined, platelet intracellular calcium concentration was significantly higher only in younger hypertensives when compared with controls of a similar mean age (P less than 0.001). Thus, age, in addition to hypertension, is an important determinant of platelet intracellular calcium concentration.

Adult↗
PubMed1991

Ambulatory blood pressure measurement in the diagnosis and management of hypertension.

Before the diagnostic potential of 24-hour non-invasive BP measurement can be assessed, the accuracy of ambulatory recorders must be established, and normal reference values determined. The accuracy criteria of four ambulatory BP measuring systems (the SpaceLabs 90207, the Novecor DIASYS 200, the Takeda TM-2420 and the Del Mar Avionics Pressurometer IV) have been assessed according to the British Hypertension Society (BHS) protocol, and the Medilog, Suntech Accutracker II and the SpaceLabs 90202 according to the standard of the Association for the Advancement of Medical Instrumentation (AAMI). The SpaceLabs 90202 and 90207, the DIASYS 200 and the Medilog fulfilled the AAMI criteria. The best devices with the BHS grading system are the SpaceLabs 90207 and the DIASYS 200. Normal reference values for daytime, night-time and 24-hour ambulatory BP have been provided by the Allied Irish Bank study of 815 healthy individuals, which showed clear age and sex differences. The mean 24-hour ambulatory pressure for the entire group was 118/72 mm Hg. 24-hour ambulatory BP measurement possesses clear advantages over conventional clinic measurement in evaluating drug efficacy, as it provides many more readings, allowing for the possibility of reducing the number of patients in antihypertensive drug studies and eliminating the need for a placebo-controlled crossover design. It allows assessment of night-time BP, which is important in view of the fact that excessive BP reduction may put patients at risk of myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Validation requirements for ambulatory blood pressure measuring systems.

The increasing application of ambulatory blood pressure measurement in clinical practice has stimulated the manufacture of a large number of ambulatory systems which must be independently validated. The British Hypertension Society protocol for the evaluation of blood pressure measuring devices has now been used to evaluate eight ambulatory systems. Based on this experience recommendations are made for improving validation techniques for the evaluation of ambulatory devices.

Blood Pressure Monitors↗
PubMed1991

The role of twenty-four-hour ambulatory blood pressure measurement in clinical practice.

Twenty-four-hour ambulatory blood pressure monitoring is passing from research into clinical practice and it is necessary to clarify circumstances for which 24-h ambulatory measurement will be most beneficial. Devices should be accurate and reasonably priced. The operator should be able to interpret 24-h recordings and be familiar with the operation of the equipment. The subject must be capable of complying with the instructions necessary for successful use of the device. In diagnosis, 24-h ambulatory blood pressure measurement is particularly useful in deciding whether subjects with borderline hypertension have a genuinely elevated blood pressure, in identifying white-coat hypertension, in determining dipper status and in diagnosing symptomatic hypotension. In the management of antihypertensive drug treatment, the technique helps the clinician to select the drug best suited to the individual patient in terms of duration of action and suitability for the individual 24-h profile; the technique also identifies any excessive reduction in blood pressure and provides a means of assessing resistant cases of hypertension.

Antihypertensive Agents↗
PubMed1991

Clinical application of ambulatory blood pressure measurement in pregnancy.

Eclampsia and pre-eclampsia are the most important obstetric causes of maternal mortality in the Western world. The current definitions of hypertensive disorders in pregnancy rely on arbitrary blood pressure limits based on intermittent clinic readings which are subject to bias and error. Twenty-four-hour ambulatory blood pressure monitoring can overcome many of these deficiencies but has only recently been introduced into antenatal care. Five pregnancy studies using ambulatory blood pressure monitoring are currently underway in Birmingham, Glasgow, Grenoble, Oxford and Dublin. The results so far indicate that ambulatory blood pressure monitoring is an acceptable method of measuring blood pressure in pregnancy. It is also concluded that ambulatory blood pressure monitoring may have several roles in the future antenatal management of hypertension, including modification of existing classification systems, a clinical confirmatory role and a possible predictive role for pre-eclampsia.

Blood Pressure↗
PubMed1991

Ambulatory blood pressure measurement in the elderly.

A number of problems relating to clinic measurements of blood pressure may be particularly relevant to elderly patients with isolated systolic hypertension. First, there are large discrepancies in the blood pressure levels measured by these two techniques in the elderly population. Second, while blood pressure is universally accepted as one of the most important risk factors for the development of cardiovascular morbidity, its predictive value in the individual is relatively poor. Clinic and 24-h ambulatory recordings from 318 patients aged 17-80 years, diagnosed as having isolated systolic hypertension on clinic measurement, were compared with reference values determined from 815 healthy bank employees. In the isolated systolic hypertension group, mean systolic blood pressure by daytime ambulatory measurement was 27 mmHg lower than that recorded in the clinic, while diastolic pressure was similar (151 +/- 17/87 +/- 11 versus 178 +/- 28/84 +/- 9 mmHg). This discrepancy was greater in women than men, increased slightly but significantly with age (r = 0.12, P less than 0.05) and raised the crucial question as to which of the two measurements might best predict prognosis in this population. In a further study of the association between electrocardiographic (ECG) voltages and blood pressure measured in the clinic and by ambulatory monitoring in 216 patients with isolated systolic hypertension, the sum of SV1 + RV5 and the sum of SV1 + RV6 were significantly and positively related to systolic pressure both in the clinic and with daytime and night-time ambulatory measurement.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗